Dissertations / Theses on the topic 'Sports science and exercise'

Current research ideologies in sport science allow for the possibility of investigators producing statistically significant results to help fit the outcome into a predetermined theory. Additionally, under the current Neyman-Pearson statistical structure, some argue that null hypothesis significant testing (NHST) under the frequentist approach is flawed, regardless. For example, a p-value is unable to measure the probability that the studied hypothesis is true, unable to measure the size of an effect or the importance of a result, and unable to provide a good measure of evidence regarding a model or hypothesis. Many of these downfalls are key questions researchers strive to answer following an investigation. Therefore, a shift towards a magnitude-based inference model, and eventually a fully Bayesian framework, is thought to be a better fit from a statistical standpoint and may be an improved way to address biases within the literature. The goal of this article is to shed light on the current research and statistical shortcomings the field of sport science faces today, and offer potential solutions to help guide future research practices.

The aim of this thesis was to develop our understanding of the Functional Re-adaptive Exercise Device (FRED): a novel prototype exercise device proposed to facilitate the activation the deep paraspinal and anterolateral abdominal wall musculature in a manner consistent with the requirements of motor control training in people with low back pain. Firstly, the intra- and interday reliability and precision of measurement of ultrasound imaging of the lumbar multifidus (LM) and transversus abdominis (TrA) were established. LM and TrA demonstrated good (ICC ≥ 0.75) to excellent (ICC ≥ 0.9) intrarater reliability for both intra- and interday measurements of absolute linear muscle thickness across all conditions. Normalised thickness change, expressed relative to resting values, also demonstrated good reliability between days, with ICCs in excess of 0.75 across all conditions. Secondly, the typical nature of LM and TrA function during this mode of exercise was evaluated in relation to commonly used assessment techniques such as the abdominal drawing-in manoeuvre, active straight-leg raise, and contralateral arm-lift. All contraction conditions successfully resulted in active relative thickness change of LM and TrA. Relative thickness change of the LM when using the FRED was favourable in that it was lower than that observed in loaded contralateral arm raise and walking conditions, suggesting that one of the key features of specific motor control training (contraction intensity of 30-40 % MVC) has been met. Thirdly, activity of the LM and TrA during this mode of exercise and other commonly used corrective/rehabilitative techniques based on relatively static challenges to stability was compared (gym ball, balance board). All stability challenges successfully induced non-volitional concomitant activation of both the LM and TrA. Additionally, it was observed that the LM followed a pattern where all standing conditions elicited greater recruitment than seated conditions, with no additional effect of surface lability. Contrastingly, the TrA only demonstrated an effect of surface instability during FRED conditions. The preferential contraction ratio of the TrA in comparison to IO and EO was greatest during use of the exercise device in the standing position. Fourthly, the intrinsic kinematic stability of the lumbopelvic region whilst using the exercise device was examined, revealing further evidence of the underlying mechanisms facilitating LM and TrA contraction. Key differences between FRED exercise and overground walking included reduced axial rotation of the trunk with respect to the pelvis (i.e. increased lumbopelvic stability) and a more anteriorly tilted pelvis. FRED exercise potentially moved the pelvis into a more advantageous position for the recruitment of TrA and LM. However, the unstable base of support afforded by FRED exercise would seem to add a challenge to movement control that could result in greater TrA and LM activity than overground walking. Finally, the pattern of global muscle activation during this exercise was examined, and provided evidence as to the tonic nature of FRED mediated muscle activity of the lumbar paraspinal and anterolateral abdominal muscles. FRED exercise a) promoted more tonic activity of the lumbopelvic musculature compared to overground walking, b) resulted in greater spinal extensor activity than spinal flexor muscles compared with overground walking, and c) resulted in greater knee extensor activity compared with overground walking.

Interleukin-6 (IL-6) is a pluripotent cytokine which has inflammatory properties. It is suggested to mediate a variety of processes including increased perception of fatigue during inflammatory states. In addition, prolonged exercise can cause a marked increase in circulating IL-6, and although there is a widely reported association between plasma IL-6 and fatigue in disease and inflammatory conditions, this relationship has remained relatively unexplored in healthy individuals during exercise. Therefore, the aims of this thesis were firstly, to develop a repeatable preload time trial in order to examine the variability of circulating IL-6 and other signalling molecules in response to an exercise challenge; secondly, to investigate the effect of plasma IL-6 and signalling molecules on fatigue and performance during a pre-loaded time trial; and thirdly, to evaluate the impact of nutritional interventions (glutamine intake during exercise, manipulation of pre-exercise diet and carbohydrate intake during exercise) on the response of circulating IL-6, IL-6 signalling molecules and biomarkers associated with IL-6 during exercise and their effect on preload time trial performance. Results from the studies determined that there was large variability in the plasma IL-6 and signalling receptors response to the pre-loaded time trial (8-20%) but that the exercise protocol was repeatable. Nutritional interventions did not alter the signalling receptor response, nor biomarkers associated with IL-6, including hepcidin. However, carbohydrate intake during exercise attenuated the circulating IL-6 response to exercise by 49% which correlated well with an improved time trial performance. Regardless of the intervention, a consistent finding in all studies indicated that a greater plasma IL-6 response to the preload exercise bout correlated well with a reduced relative exercise performance as a percentage of velocity at VO 2max during the subsequent time trial. To summarise, the findings from this thesis indicate that elevated levels of plasma IL-6 are associated with a decrement in exercise performance. Associated IL-6 signalling molecules are elevated in response to exercise but are not associated with performance and are unaltered by nutritional interventions.

Fatigue is a universal phenomenon with functional and perceptual consequences. The study of fatigue in the exercise sciences has historically focussed on factors that limit performance during exercise. More recent proposals have shifted the focus of this understanding to examine how intensity is regulated during exercise through the study of the pacing strategy, which has both physiological and practical consequences. The aim of this thesis was to investigate the biological basis of self-pacing and the optimum pacing strategy for endurance time-trial events. Study 1 assessed the reproducibility of the pacing strategy and the consistency of the performance, perceptual and physiological response during self-paced time-trial exercise in well-trained cyclists. This study demonstrated the existence of a global pacing strategy that was reproducible on repeat 20 km cycling time-trials (TTs), and consistent between 4, 20 and 40 km TTs. The performance, perceptual and physiological response was also reproducible, confirming the feasibility of studying manipulations of the self-pacing strategy and the subsequent impact on these variables. Studies 2 and 3 adopted a model whereby participant’s best self-paced TT performance was used to set time- and work-matched exercise bouts to study the effect of even- and variable-pacing. These studies revealed that a variable-pacing strategy that contains frequent periods of high-intensity exercise resulted in an augmented physiological response and higher perception of exertion compared to time- and work-matched even- and self-paced exercise. Conversely, even-pacing resulted in attenuation in the metabolic and perceptual cost of the bout, but only when the self-selected pacing strategy was sub-optimal. When self-pacing was optimal, time- and work-matched even-pacing resulted in cumulative metabolic stress that caused early exercise termination. In study 4 the biological basis to fatigue during 4, 20 and 40 km TTs was assessed. This study demonstrated that the contribution of central and peripheral mechanisms of fatigue during self-paced exercise is task-dependent. Specifically, the shorter, higher intensity 4 km time-trials were characterised by a greater degree of peripheral fatigue and less central fatigue compared to longer, lower intensity 20 and 40 km time-trials where less peripheral and more central fatigue was observed. The supraspinal contribution to fatigue was alsomgreater during longer TT exercise. These studies have provided novel insight in to the biological factors that underpin the regulation of self-paced exercise, and the optimum pacing strategy for endurance TT events.

Raised postprandial triglycerides (TG) is an independent risk factor for cardio-metabolic disorders. This is due, in part, to the increases in circulating remnant lipoproteins after TG have been transported for storage or hydrolysis. Raised TG, are also associated with an atherogenic lipoprotein phenotype (High TG, low high-density lipoprotein cholesterol (HDL-c) and small, dense low-density lipoprotein (LDL) particles). In addition, elevated TG contribute to ectopic storage of fatty acids in liver, adipose and muscle tissues, contributing to insulin resistance in all three tissues and consequent metabolic dysregulation. It is therefore paramount to prevent frequent and prolonged exposure to raised TG in the postprandial period, particularly in groups who are at increased risk of cardio-metabolic disease. The dyslipidaemic component of cardio-metabolic health can be inferred by assessing the capacity to breakdown and clear TG from circulation after high fat ingestion using an oral fat tolerance test (OFTT). The OFTT can also be used to assess the efficacy of interventions targeting reductions in postprandial TG. Exercise and nutritional interventions have been shown to alter postprandial TG excursions and provide insight in to underlying mechanisms of postprandial lipid metabolism. However, there are several topics within this area of research that require further clarification. These topics have been addressed within this thesis. The first experimental chapter of this thesis (chapter 3) aimed to investigate the repeatability of an OFTT (75g fat, 22g carbohydrate, 14g protein) designed to meet recommendations from an expert panel statement. This study also aimed to evaluate the repeatability of the postprandial response to an OFTT preceded by 1 hour of acute moderate intensity exercise (cycling at a work rate eliciting 90% oxygen consumption anaerobic threshold). After an overnight fast, 11 healthy adult male participants consumed OFTT meals on 4 separate occasions; 2 preceded by rest and 2 preceded by exercise. TG area under the curve (AUC) was calculated for each test and compared to the repeat condition using non-parametric Bland-Altman analysis. The 4-hour OFTT was repeatable in the rest condition, with 9 of 10 repeat measurements falling within ±15% of the median TG AUC (predefined as the upper limit of acceptable error). However, in the exercise condition repeatability was poor with only 2 of 11 repeat measurements falling within 15% of the median TG AUC. Adult offspring of type 2 diabetics (OT2D) show irregular TG responses to OFTT with high or low carbohydrate content, compared to healthy controls. Prior acute aerobic exercise may favourably influence these postprandial responses in OT2D. This feasibility study (Chapter 4) aimed to investigate the effects of carbohydrate content and acute exercise on TG AUC after OFTT in OT2D. On 4 separate days, 8 adult male OT2D ingested OFTTs with low (HFLC; 75g fat, 22g carbohydrate, 14g protein) or high (HFHC; 75g fat, 95g carbohydrate, 14 g protein) carbohydrate content. Participants rested or exercised (1-hour moderate intensity; 90% oxygen consumption at anaerobic threshold) the day before each OFTT. Recruitment to the single centre was slow, but participant adherence to the study was good. There were large effect sizes for lower TG AUC and incremental AUC (iAUC) in the HFHC with prior exercise. Insulin AUC was higher in HFHC conditions and there was a large effect size for lower insulin AUC in the exercise conditions. Given the large effect sizes observed for the effects of prior acute exercise on postprandial TGs, an adequately powered multi-centre study was deemed to be relevant and feasible. Consumption of strawberries appears to be beneficial in attenuating the postprandial lipaemic response to OFTT due to the high polyphenol content within strawberries. The mechanisms of this attenuation in postprandial lipaemia appear to be different from the mechanisms involved in exercise induced reductions in postprandial lipaemia. However, the combined effects of exercise and strawberry interventions in reducing postprandial lipaemic responses to OFTT has not been investigated. The final experimental chapter (Chapter 5) aimed to evaluate the combined effects of acute exercise and strawberry consumption on postprandial responses to OFTT (73g to 74g fat, 32g to 33g carbohydrate, 11g to 12g protein). On 4 separate days, ten overweight/obese males ingested OFTTs with 25g freeze dried strawberries or a placebo. Participants rested or exercised (40 minutes submaximal high intensity exercise, HIIE) the day before each OFTT. There was a 20% reduction in TG AUC in the exercise conditions and no differences in TG AUC in the strawberry conditions. This thesis offers key contributions to postprandial lipid metabolism research. First, the OFTT recommended by an expert panel statement is repeatable. Second, the variability observed in postprandial responses to OFTT with immediate prior exercise may explain the inconsistencies within the literature. Third, acute exercise showed a substantive effect in reducing TG AUC and iAUC with high carbohydrate OFTT in adult OT2D. These improvements could be explained by acute improvements in insulin sensitivity, however, a further adequately powered study is required to support the findings of this feasibility study. Finally, acute HIIE appears to be an effective strategy to reduce postprandial TG, but strawberry intake does not appear to improve postprandial TG.

The aim of this series of studies was to investigate the effects of oral caffeine ingestion (5 mg . kg-1) on whole-body, short-term, high-intensity exercise (ST; representing an exercise intensity of between 100% -150% V02 max), an area that has received scant attention in the past. It was found that, in common with other 'open-ended' tests, one ST assessment, the maximal accumulated oxygen deficit (MAOD), appeared to lack both validity and reliability. Although traditional reliability markers of MAOD were favourable, the 95% limits of agreement were unacceptably large. In addition, the validity of MAOD was also found to be questionable because a study of elite runners revealed that a large proportion were unable to accomplish a plateau in the V02 -exercise intensity relationship. A follow-up study developed an original bespoke 'preloaded' ST cycling protocol that combined constant-rate exercise with an 'all-out' effort. This protocol appears to have several features that make it a more appropriate assessment to use in ergogenic studies than the MAOD. The work also considered the original, and as yet, undeveloped potential, for the assessment of rating of perceived exertion (RPE) during ST. It was shown for the first time that RPE (Borg scale; 6-20) could be used reliably during constant-rate ST. Three of the ten studies demonstrated that caffeine can be ergogenic during ST, with improvements averaging 11 % (95% GI, 7.4% -14.5%) above placebo treatment. In addition, the caffeine studies contributed to a meta-analysis of the effects of caffeine on test outcome that resulted in an effect size greater than zero, with 95% confidence intervals not crossing zero. The studies have examined potential physiological and metabolic mechanisms of action that may help explain caffeine's impact on ST. These suggest that there is some evidence that caffeine both stimulates anaerobic glycolysis and reduces electrolyte disturbance during ST. Finally this work has demonstrated for the first time that the perceptual response during constant-rate ST, as measured by RPE, is blunted following caffeine ingestion. It is concluded that caffeine is ergogenic during ST, and that while the exact mechanism(s) of action remains unknown, one consistent test outcome is a reduction in RPE during constant-rate ST.

This thesis comprises a series of independent investigations examining rugby injuries occurring to players from under 14 to senior provincial level in the Cape Province (now the Western Cape). The first two studies report data aimed at gaining a more detailed understanding of rugby injuries in specific populations or under specific conditions, whilst the remainder of the thesis reports injury data from both a retrospective and a prospective epidemiological survey involving the same 3990 boys from 25 high schools. Following publication of data showing a progressive rise in the number of spinal cord injuries in the Western Cape, coupled with a sustained media attack on the attitudes of the (then) South African Rugby Board, certain experimental law changes were introduced to South African schoolboy rugby in 1990 and 1991. The purpose of the law changes was either to make the game safer or to make it more open and flowing, or both. Accordingly, the studies described in chapters 4 -8 set out to analyse the effects of these law changes on the incidence and nature of rugby injuries. This was accomplished by comparing data with a similar study conducted in 1983 and 1984 in the same 25 schools (Roux, 1992). The study reported in chapter 2 determined whether the use of neoprene (thermal) pants might reduce the risk of hamstring injury amongst 60 senior club rugby players, all of whom had previously sustained a hamstring muscle tear. The rationale was that the few seasons prior to this 1992 study had been characterised by an increasing use by rugby players of thermal or neoprene pants; a practice which seemed to have evolved spontaneously and without any scientific assessment of its value. We concluded that the wearing of thermal pants can reduce the risk of hamstring injury during rugby. However, other risk factors for injury are probably more important. These include levels of preseason physical fitness, correct warm up and stretching procedures before activity and adequate rehabilitation before returning to activity following injury. The objective of the study reported in chapter 3 was to determine the influence of preseason strength and endurance training on risk of injury in rugby players from two South African provincial teams during the 1992 rugby season. Players from one province followed a supervised scientifically-designed physical training programme, while those from the other did not follow a structured programme. The findings of the study, the first study to prove the relationship between pre-season preparation and early season injury, showed that inadequate pre-season endurance training is a major contributor to the high injury rate at the beginning of the season amongst provincial rugby players. Further, strength and endurance training are interrelated as risk factors. Thus, compared to players with adequate strength and endurance training, those with adequate strength training and insufficient endurance training are at greatest risk of injury, followed by players with insufficient strength and endurance training. It was also shown that contact practices 2 days after inter-provincial match contributed more to an increased number of injuries than to success; that "niggling" injuries may develop into more serious injury if players attempt to "play through" them; and that the lack of structured treatment and rehabilitation of an injury places players at risk of being re-injured.

The effect of the long acting dihydropyridine calcium channel antagonist, amlodipine, on the exercise performance of hypertensive patients is not known. The aim of this study was to determine the effects of amlodipine on maximal (MAX), prolonged submaximal (PSX) and on skeletal muscle function (SMF) in patients with mild hypertension. In a double-blind randomised crossover trial, ten physically active hypertensive patients performed i) graded exercise to exhaustion for determination of maximal oxygen consumption (VO₂ₘₐₓ), peak heart rate (HR) and systolic blood pressure (SBP); ii) PSX at 75% VO₂ₘₐₓ to determine, cardiorespiratory responses, cardiac output (Q), blood lactate [La], free fatty acid [FFA], glucose [G] concentrations and ratings of perceived exertion (RPE), and iii) tests of isometric SMF including maximal voluntary contraction (MVC) and time to fatigue (TTF) during repetitve isometric MVC's. Tests were performed following two week ingestion of amlodipine (5 mg daily) or placebo seperated by a two week washout period. Resting SBP was decreased following ingestion of amlodipine (142 ± 13 vs l33 ± 12 mmHg; vs placebo: [mean± SD]; P<0.05). However, VO₂ₘₐₓ ( 31 ± 5 vs 33 ± 5 mlO₂.kg.min⁻¹ ; amlodipine vs placebo), peak heart rate ( 167 ± 12 vs 165 ± l6b.min⁻¹;amlodipine vs placebo)and peak SBP(l8l ±21 vs 170± 16mmHg; amlodipine vs placebo) were not reduced following ingestion of amlodipine. Submaximal cycling time. VO₂, Q, BP, HR, ventilation, RPE, [FFA], [La] and [G] during PSX were unaltered following ingestion of amlodipine. Similarly ingestion of amlodipine did not alter tests of isometric SMF. These data suggest that: i) ingestion of amlodipine lowers resting SBP but does not alter the normal haemodynamic response during exercise; ii) MAX, PSX exercise performance and SMF are unaltered following ingestion of amlodipine in athletic hypertensive patients. These findings suggest that the regulatory mechanisms which maintain haemodynamic homeostasis during maximal and submaximal exercise are not influenced by ingestion of amlodipine in athletic hypertensive patients.

There are evidence that high-intensity acute exercise can promote oxidative stress. High-intensity intermittent exercise (HIIE) is a type of structured physical training characterised by repeated bouts of high-intensity exercise interspersed by recovery periods. As the impact of intermittency during acute HIIE has not been extensively studied, it is possible that the repeated intensive bouts within HIIE could induce oxidative stress levels. Plasma biomarkers, including lipid hydroperoxides and markers of DNA damage, have been increasingly applied within acute exercise physiology research to measure oxidative stress. This thesis presents the experimental outcomes of research into the effect of different forms of HIIE on established and novel biomarkers of oxidative stress. For the 1st study (chapter 3) a liquid chromatography-mass spectrometry (LCMS) method was developed and optimised to measure DNA oxidation in plasma samples. Implementing a range of progressive analytical techniques, the method developed had a sensitivity to detect 8-hydroxy-2'-deoxyguanosine (8-Oxo-dG) in human plasma samples in the range of 5 – 500 nM. The implementation of this LC-MS method along with other oxidative stress biomarkers was thereafter applied to a randomised investigation of different high-intensity intermittent exercise protocols. The 2nd (chapter 4) and 3rd (chapter 5) studies considered the effect of different forms of intermittent exercise undertaken by 9 healthy, regularly active male participants (aged 21.0 ± 3.0 years). Each intermittent exercise session was performed for a total duration of 45 minutes. Each 45 minute exercise protocol consisted of 4 minute stages of high-intensity intermittent running at a mean 75% v!O2max, followed by 1 minute of passive recovery (halt of running). The experimental protocol was specifically designed to match for average speed, duration and distance but varied in either the intermittency (chapter 4) or the acceleration/deceleration (chapter 5). The effects of different forms of intermittent exercise (high, moderate, low) or different acceleration/deceleration components (high, moderate, low) in relation to oxidative stress biomarkers were determined. Results showed the absence of significant increases in all the biomarkers examined. However, significant variation in individual oxidative stress responses was observed. Within a final study, the 8-Oxo-dG method developed was compared to a widely used ELISA method, as there are indications in the literature that ELISA may overestimate 8-Oxo-dG. Determination of 8-Oxo-dG was undertaken on blood plasma samples from 30 chronic heart failure patients (males = 23, females = 7) recruited from the Academic Cardiology department at Castle Hill hospital, Hull, UK, as previous studies have characterised the heart failure syndrome to be associated with higher levels of oxidative stress. Results showed that the LC-MS method developed found no detectable levels of 8-Oxo-dG in plasma samples whereas ELISA showed quantifiable amounts of 8-Oxo-dG. Thus, this thesis presented that the impact of intermittency or acceleration/deceleration following acute HIIE does not induce significant oxidative stress as determined by plasma and serum biomarkers, including plasma 8-Oxo-dG.

African runners dominate distance running both in South Africa and internationally. Therefore, the aim of this thesis was to compare selected exercise and skeletal muscle characteristics in well-trained African and Caucasian 10 km runners to determine if evidence exists of differences between these groups with respect to these physiological and biochemical characteristics. Furthermore, the relationship between exercise and skeletal muscle characteristics was investigated. Sedentary individuals from each population group were also studied to determine if differences existed in untrained skeletal muscle between groups. Maximal oxygen consumption and peak treadmill speed were measured using an incremental treadmill protocol whilst submaximal exercise characteristics were measured during a specifically designed protocol consisting of four sequential submaximal workloads relative to the peak treadmill speed of the individual. The final workload was maintained until fatigue with resistance to fatigue defined as total test time. Running economy was measured at a treadmill speed of 16.1 km/hr. Race pace characteristics were measured directly at race pace. Characteristics measured during exercise tests were oxygen uptake, minute ventilation, respiratory exchange ratio and heart rate whilst plasma lactate concentration was determined immediately after exercise. Skeletal muscle characteristics were determined by needle biopsy of the vastus lateralis muscle. Skeletal muscle enzymes citrate synthase, phosphofructokinase, 3-hydroxyacyl CoA dehydrogenase, hexokinase and carnitine palmityl transferase were assayed spectrophotometrically. Skeletal muscle buffering capacity was measured using by titration and fibre type proportions were analysed histochemically. Comparisons between groups were made with the Student's t-test for unpaired data whilst the relationships between variables were analysed using the Pearson's correlation coefficient. The first major finding was that when exercising at the same relative percentage of individual maximal treadmill velocity, African distance runners were able to exercise for longer than the Caucasians (1376±227 vs 1137±126 sec, p<0.01) with lower plasma lactate accumulation (4.8±3.2 vs 7.7±2.8 mmol/l,p<0.05). Time to fatigue was significantly related to a lower plasma lactate concentration (r=-0.63) and a lower respiratory exchange ratio (r=-0.53). The second major finding indicated that African runners were able to race 10 km at a higher percentage of their maximal oxygen uptake (93.5 vs 86.0%, p<0.005), whilst eliciting only a comparable plasma lactate concentration and respiratory exchange ratio. The third main finding was that the African runners were more economical than the Caucasian runners (p<0.05). The fourth main finding is that the African runners had a 50% greater activity of citrate synthase (p<0.005) and 3-hydroxyacyl CoA dehydrogenase (p<0.01) in the vastus lateralis than the Caucasians and this could not be explained by fibre type proportions, because the proportion of type I fibres was lower in the African runners (p<0.05). Citrate synthase activity, was related to the runners' ability to resist fatigue at high intensity relative to their individual peak treadmill velocity (r=0.70, p<0.05). A higher CS activity was related to a lower plasma lactate concentration and a lower RER. The sixth main finding of this thesis was that skeletal muscle buffering capacity of the Caucasian runners was higher than that of the African runners (p<0.05). A methodological study of buffering capacity in rats showed the buffering capacity was largely dependent upon fibre type and protein concentration, however these parameters could not explain the difference observed between the African and Caucasian runners. Furthermore, despite the differences in skeletal muscle characteristics observed between African and Caucasian runners in the current thesis, there was no evidence of these differences being inherently present in sedentary African and Caucasian individuals. In conclusion, the current series of studies do provide evidence of differences in selected exercise and skeletal muscle characteristics between African and Caucasian distance runners, with the African runners possessing exercise and skeletal muscle profiles that are considered to be more advantageous for endurance performance.

For patients with type 1 diabetes, a fear of hypoglycaemia and a concern over a loss of control with wider diabetes management are the most salient barriers to exercise participation and adherence. A large proportion of patients report a lack of advice for preventing post-exercise hypoglycaemia, and many feel largely uninformed about insulin administration and carbohydrate intake around aerobic-based exercise. Presently, recommendations within the literature are based predominantly on anecdotal and observational, but not empirical or interventional data. Therefore, this thesis aimed to develop a strategy that enables patients to effectively self-manage glycaemia following exercise, supported by evidence pertaining to the deeper physiological implications and consequences. Study one (chapter 3) revealed that under conditions of reduced pre-exercise rapid-acting insulin dose, it is also necessary to reduce post-exercise rapid-acting insulin administration by 50% to prevent early-onset hypoglycaemia (≤ 8 hours post-exercise). Consequently, some patients experienced post-prandial hyperglycaemia with this intervention, although this was not associated with any other metabolic, counter-regulatory hormonal, or inflammatory disturbances. The results of study two (chapter 4) demonstrate that post-exercise meal composition, under conditions of reduced pre- and post-exercise rapid-acting insulin dose, carry important implications for post-prandial glycaemia. Specifically, consumption of low GI post-exercise carbohydrates normalise post-prandial hyperglycaemia, whilst protection from early onset hypoglycaemia is maintained. In addition, post-exercise meal composition heavily influences inflammatory markers; a high GI meal results in a pronounced inflammatory response, but a low GI meal completely prevented any rise in measured inflammatory markers. Lastly, study three (chapter 5) assessed the efficacy of a combined basal-bolus insulin reduction and low GI carbohydrate post-exercise feeding strategy. A 20% reduction in basal insulin provided full protection from hypoglycaemia for a total of 24 hours after exercise. Furthermore, ketonaemia did not increase to clinically meaningful levels, nor did inflammatory markers rise above concentrations seen at rest or when exercising under usual basal dose. No other metabolic or counter-regulatory hormonal disturbances were observed following a combined dose reduction to basal-bolus insulin and low GI carbohydrate post-exercise feeding. Collectively, this thesis has shown that acute prandial adjustments in rapid-acting insulin and carbohydrate feeding, in combination with alterations in basal dose, are effective for managing post-exercise glycaemia and protecting patients from hypoglycaemia for a total of 24 hours after exercise. Moreover, this strategy aims to maintain euglycaemia by reducing post-prandial hyperglycaemia. This is not associated with clinically significant rises in ketonaemia, nor does it induce inflammatory, counter-regulatory hormonal, or other metabolic disturbances. Clinicians are advised to tailor these recommendations to a patient’s individual exercise preferences, fitness and exercise ability, level of diabetes management, and treatment regimen.

The aim of the first experiment of this thesis was to determine whether the ingestion of a concentrated sodium chloride solution (100mEq/1) during exercise would expand the plasma volume when fluid was ingested at approximately half the rate at which it was being lost as sweat. Six male cyclists exercised for 90 minutes in the heat (32 ± 1 °C, 55 ± 5% RH) at 66 ± 1 % of VO₂ₘₐₓ while ingesting either no fluid CNF), water (W), or a saline CS) solution (100mEq/1). In the Wand S trials, subjects drank 400ml of the fluid immediately prior to commencing exercise, and 100ml of fluid every 10 minutes during exercise until 80 minutes. In the S trial sodium chloride was ingested in capsules. One capsule containing 0.585g of sodium chloride was ingested with every 100ml of water. At the end of the 90 minute exercise bout they rested in a sitting position for one hour in cool conditions (22 ± 1 °C and 70 ± 5% RH). After the initial drop in plasma volume due to the onset of exercise. plasma volume decreased progressively during the NF trial and was significantly less than the 10 minute value at 80 and 90 minutes (p<0.0033). At 40, 60, 80 and 90 minutes of exercise, the plasma volume in the NF trial was significantly less than in the W and the S trials (p<0.05). There was no significant difference between the W and the S trials at any time. Further, after the initial drop in plasma volume due to the onset of exercise. plasma volume did not decrease any further in either the W or the S trial. Plasma sodium concentrations in the NF and the S trial were significantly elevated at 40, 60, 80 and 90 minutes (p<0.0033). Plasma sodium concentration in the NF and the S trials were also significantly higher than in the W trial at 80 and 90 minutes of exercise (p<0.05). Since the ingestion of a sodium chloride solution containing 100mEq/1 did not have a beneficial effect on plasma volume and plasma sodium concentration, when fluid ingestion rates were approximately half of the rate of sweat loss, it is concluded the under these conditions, the ingestion of a concentrated sodium chloride beverage has no advantage over the ingestion of water. The aim of the second experiment of this thesis was to determine the effect of varying concentrations of sodium chloride ingestion on fluid balance, when the rate of fluid ingestion matched the sweat rate. Six male cyclists cycled for 4 hours at 55% of VO₂ₘₐₓ in mild conditions (20 ± 1°c and 70 ± 5% RH), while ingesting either a low salt (LS) (4.6 mEq/1), a medium salt (MS) (50 mEq/1) or a high salt (HS) (100 mEq/1) beverage. Each beverage also contained a glucose polymer in an 8% concentration (8g/100ml). The subjects ingested 400ml of beverage immediately prior to commencement of exercise, and 150ml of fluid every 10 minutes during exercise until 220 minutes. Sodium chloride in the MS and HS trials was given to the subjects as supplemental gel capsules so that the drink was palatable. At the end of exercise, subjects recovered in a sitting position for 30 minutes. At the end of the 4 hours of exercise, fluid loss via the urine was significantly greater in the LS and the MS trials than in the HS trial (p<0.05). As a result, the fluid deficits in the LS and the MS trials were significantly greater than the fluid deficit in the HS trial. There was no significant difference between the MS and the LS trials for urinary fluid loss. During the 4 hour exercise bout, plasma sodium concentrations in the LS, the MS and the HS trials were not significantly different from one another, nor were they significantly different from resting values. There was no significant difference in the rectal temperature response to exercise in the three trials. It can therefore be concluded that in conditions where fluid ingestion matches sweat rate, attenuation of urinary fluid loss to optimise fluid replacement, relies on the ingestion of sodium chloride in quantities greater than that lost in the sweat. Therefore, for the ingestion of sodium chloride in excess of that which is currently available in sports drinks to beneficial, fluid must be ingested in volumes matching sweat loss.

Bone health is known to deteriorate with age, which can increase the risk of osteoporotic fractures and subsequently all-cause mortality. Current life expectancies are higher than ever before and with our ageing population, osteoporosis and low bone density levels are an ever growing problem that command a lot of medical attention and resources. Women are at a greater risk than men due to increased rates of bone loss that occur in the early years following the menopause. Mechanical loading in the form of exercise is known to reduce the rates of postmenopausal bone loss although an optimal exercise programme is yet to be established. Furthermore, investigations conducted with animals have found intermittent mechanical loading to provide a greater stimulus for bone adaptation than continuous mechanical loading, this has not been investigated in human populations to date. The aim of this thesis was to establish a sufficient exercise mode for stimulating bone adaptation in postmenopausal women and investigate the effects of continuous and intermittent exercise on postmenopausal bone loss. This was attempted with a 12 month randomised controlled trial with postmenopausal women. The first study gave a systematic review of the current literature that investigated continuous or intermittent exercise. The review found that as the studies were not designed to specifically analyse continuous or intermittent exercise, there were numerous problems regarding the control of previous exercise programmes with regards to defined exercise and rest intervals. This was due to the design of the included studies, as many of them were not specifically designed to analyse the different effects of continuous and intermittent exercise on bone mineral density (BMD). In addition, BMD outcomes were not reported in a standardized manner, which complicated the comparisons drawn. From this investigation, it was evident that well-controlled exercise interventions (using a single exercise), are required for the comparison of the effect of continuous and intermittent exercise on BMD in human populations. The second study investigated the feasibility of developing a non-motorised treadmill exercise intervention that included both continuous and intermittent exercise groups. Non-motorised treadmill (NMT) locomotion allows for the instantaneous quantification of ground reaction forces (GRF) and is well suited to both continuous exercise and intermittent exercise with the potential for the use of a range of intermittent running based protocols. In order to establish the osteogenic potential of this mode of exercise, it was necessary to quantify the mechanical loading parameters. This study found that loading parameters showed large reductions during NMT locomotion when compared to overground or motorised treadmill locomotion (24 to 29 %), which could potentially compromise the level of bone adaptation if this mode of exercise was used for intervention purposes. The third study investigated the loading parameters of more traditional high impact exercises in a population of postmenopausal women. All exercises were performed under both continuous and intermittent conditions to assess for consistency during the two conditions. This project showed that countermovement jumps (CMJ) and box drops (BD) produced the highest loading parameters when compared to heel drops (HD) and stamping (STP) (d = 0.83 – 2.38), along with no statistical differences between continuous and intermittent conditions (continuous: 10.7 ± 4.8 g for CMJ, 9.6 ± 4.1 g for BD; intermittent 10.0 ± 5.0 g for CMJ, 9.5 ± 4.0 g for BD). CMJ, BD and HD exercises all appeared to generate a sufficient level of peak acceleration and acceleration gradient for osteogenic adaptation however. For consistency purposes and the fact that no equipment was required, CMJs were selected as the most appropriate home-based exercise for use in a 12 month intervention to reduce postmenopausal bone loss. The fourth study investigated the effects of continuous and intermittent exercise on BMD in early postmenopausal women over the course of a 12 month randomised control trial. Unfortunately the study was underpowered and in addition, the findings showed no statistically significant differences in the bone response between groups. Only the control group experienced a statistically significant loss in both lumbar spine (-2.7% [95%CI: -3.9 to -1.4]) and femoral neck (-3.0% [95%CI: -5.1 to -0.8]) BMD, which exceeded the 95% least significant change at the lumbar spine and femoral neck in 57% of control group participants. There appeared to be no beneficial effect of continuous or intermittent exercise on BMD, hip structural analysis (HSA) parameters or muscular force characteristics when compared to a control group however. In conclusion, this thesis has identified that future research should further investigate the effects of continuous and intermittent exercise on BMD with appropriately controlled randomised control trials, with greater participant numbers. Whilst CMJ and BD provide adequate loading parameters, this does not translate into BMD adaptations. Continuous and intermittent CMJ exercises had no effect on reducing postmenopausal BMD loss at the lumbar spine and the femoral neck, although further investigation is required in an adequately powered study.

Background: Long distance road running is continually growing as competitive and recreational sport, globally. Despite its popularity, a high burden of incidence of injury exists among runners. Previous research has focussed on specific injuries, whereas others have investigated isolated risk factors that may contribute to running related injuries. The purpose of the study is to determine possible internal and external screening variables that may predict the incidence of running-related injuries in general. Methods: Forty one recreational runners participated in an observational study over the course of 12 weeks. Screening assessments consisted of injury history, training history, and anthropometric measurements. Functional and performance assessments included the Foot Posture Index (FPI), the Functional Movement Screen (FMS), vertical jump, single leg hop and sit-and-reach tests. Participants were monitored over a period of 12 weeks by completing a weekly online logbook regarding their training and possible incidence of injury. Monitoring was terminated after 12 weeks of observation. Differences between injured and non-injured runners were determined using Independent -T-tests for mean differences, or Mann-Whitney U Test for distributional differences (non-parametric data). Binomial Logistic regression models were used to determine the influence of internal, external functional and external behavioural factors on the risk for running injury, respectively. Results: The total group revealed a cumulative incidence of injury of 63% over the 12 weeks of observation. There was no gender difference between incidences of injuries over the 12 week observation training period (OTP). Injured runners achieved a higher total FMS score (median = 16, Interquartile Range = 3) compared to uninjured runners (median = 15, Interquartile range = 3; p = 0.006). Binomial logistic regression models of external functional (FMS, Vertical Jump, Sit-and-Reach scores) factors [X² (3) = 9.764, p = 0.021] were statistically significant. Only the FMS score contributed significantly to the incidence of injury (p = 0.013) of the three external functional factors in the Regression Model. Discussion and Conclusion: The study adds to current evidence that the assessment of the Functional Movement Screen is important in predicting injury, however, the present study shows that a higher score obtained during the FMS increase your odds to sustain an injury. The study is in contrast with the body of evidence that the incidence of previous injury is the strongest predictor of the incidence of a current injury. The study concluded that the Functional Movement Screen is a useful screening tool to determine a long distance runner's risk for running-related injuries and should be included in health-injury risk assessments of recreational runners.

In spite of the well-known physical and psychological benefits of exercise roughly 50% of people who start an exercise program will have dropped out within six months. Therefore, it is important to examine the determinants of exercise adherence. Past research has shown that enjoyment is an essential factor in exercise adherence. Additionally, music has been shown to influence exercise enjoyment. The music and enjoyment literature has generally included most preferred and no music conditions, yet no one has considered a least preferred music condition. Therefore, the purpose of this study is to examine the effects of music preference and exercise intensity on exercise enjoyment and perceived exertion. Participants (N=200) began by completing a music preference questionnaire. Each participant was randomly assigned to one of three music preference conditions (most preferred, least preferred, or no music). Next, they were asked to walk/run on a treadmill at one of three randomly assigned exercise intensities (low, moderate, or high) for 20 min. Following the exercise, participants completed an exercise enjoyment scale and a music satisfaction scale. Participants completed a measure of attentional focus (AFQ) as a trait measure before the exercise and as a state measure following the exercise. Perceived exertion was measured using Borg's RPE scale at the 10 and 20- min mark. A 3 (Music Condition) X 3 (Exercise Intensity) ANCOVA was conducted on enjoyment levels. There were no significant main effects and no significant interactions for music or intensity. A 3 (Music Condition) X 3 (Exercise Intensity) ANCOVA conducted on RPE scores revealed a significant main effect for intensity, F(2, 166) = 99.60, p <.01, r| = .55. There was no main effect for the music conditions and no significant interaction. A one-way ANOVA conducted on the music satisfaction questionnaire was significant, F(l, 130) =67.56, p <.00, r| = .34, with those in the most preferred music condition reporting higher levels of satisfaction with music choice than those in the least preferred music condition. An exploratory analysis, a 3 (Music) X 3 (Intensity) ANOVA conducted on enjoyment using participants that had paid attention to the music revealed a significant main effect for music, F(l,86) = 4.18, p = .044, accounting for roughly 5% of the variance in exercise enjoyment. Results of the study indicated that music preference does matter, as long as one pays attention to the music. If one pays attention to the music being played during exercise, then that person will enjoy that exercise significantly more than if she is listening to music she likes compared to music she does not like. Music preference does not appear to affect one's perceived effort during exercise. Results also revealed that the higher intensity at which a person is exercising, the more effort she will feel like she has to put forth. The results of the current study question the financial worth of health exercise facilities making music individualized for their patrons. Individualized music stations will be beneficial only to those patrons who pay attention to the music.

Introduction: Recent data suggests that UK cardiac rehabilitation (CR) programmes do not substantially improve cardiorespiratory fitness (CRF) or patient survival. The exercise dose prescribed as part of a routine CR programme may be insufficient. The aims of the thesis were to (i) investigate whether a routine UK CR exercise training programme could improve peak oxygen consumption (VO₂peak) and, (ii) reduce carotid intima-media thickness (CIMT) progression in patients with coronary heart disease (CHD) and, (iii) determine whether higher exercise training doses prescribed to patients with CHD through a tele-monitoring system elicit superior VO₂peak improvements compared to routine CR alone. Study One: We recruited n=34 patients (85.3% male; age 62.1 ± 8.8 years; body mass index [BMI] 29.5 ± 4.5 Kg·m⁻²) who had recently been diagnosed with CHD. n=22 patients formed an exercise training group (TG) and undertook an eight week (16 session) low to moderate intensity (40-70% peak heart rate reserve), routine CR exercise training programme. n=12 patients declined routine CR and were assigned to a non- exercise control group (CG). Patients in the training group were followed up after completing their exercise training programme. Controls were followed up approximately 8 to 10 weeks after their initial visit (visit 2). Both groups were followed up 12 months later. VO₂peak change was determined in all patients via “gold standard” maximal cardiopulmonary exercise testing (CPET) using the modified Bruce treadmill protocol. C-IMT progression was also determined using B-mode ultrasound. In the UK, submaximal exercise tests such as cycle ergometry are typically used to assess CRF change following CR. Submaximal cycle ergometry (intensities up to 70% heart rate reserve) was used to estimate changes in CRF. Submaximal cycle ergometry showed a mean improvement of 1.64 METs (95% CI 1.20 to 2.09 METs; p<0.001). However, “gold standard” maximal CPET showed that this equated to no significant change in VO₂peak (Δ change: 0.12 ml·kg⁻¹·min-1; 95% CI -1.00 to 1.24 ml·kg⁻¹·min⁻¹). No VO₂peak improvement was detected in controls (Δ change: 0.15ml·kg⁻¹·min⁻¹; 95% CI -1.37 to 1.66 ml·kg⁻¹·min⁻¹; p=0.978). VO₂peak remained unchanged after 12 months amongst patients in the TG (Δ -0.94 ml·kg⁻¹·min⁻¹; range -6.09 to 2.10 ml·kg⁻¹·min⁻¹; p=0.846). Controls experienced C-IMT progression in the right lateral aspect of their common carotid artery (CCA) at the end of the eight week CR period (Δ change: 0.070 mm; range -0.060 to 0.200 mm; p=0.038). Patients in the TG experienced C-IMT reduction in the left lateral aspect of their CCA between CR programme completion and their 12 month follow-up (Δ change: 0.054 mm; range -0.160 to 0.020 mm; p=0.015). Study Two: We recruited n=50 healthy volunteers (60% male; age 26.2 ± 5.0 years; BMI 24.6 kg·m⁻² ) to examine the intra and inter-operator variability of automated c-IMT measurements when taken by novice operators. Two novice operators performed serial bilateral C-IMT ultrasound measurements using the CardioHealth Station (Panasonic Biomedical Sales Europe BV, Leicestershire, UK). Immediate inter-operator variability was determined by comparing operators’ initial measurements. Immediate retest variability was determined by comparing consecutive measurements (<10 minutes apart). Longer-term variability was determined by comparing operators’ initial measurements to a third set of measurements conducted one week later. Bland-Altman analysis and intraclass correlations were conducted. The limits of agreement (LoA) for immediate inter-operator variability were -0.063 to 0.056 mm (mean bias -0.003 mm). Operator 1’s immediate retest intra-operator LoA were -0.057 to 0.046 mm (mean bias was -0.005 mm). Operator 1’s intra-operator LoA at one week were -0.057 to 0.050 mm (mean bias -0.003 mm). Operator 2’s LoA were similar to those of operator 1. Novice operators produce acceptable short-term and one week inter- and intra-operator C-IMT measurement variability in healthy, young to middle aged adults using the Panasonic CardioHealth Station. Study Three: We recruited n=27 patients with a diagnosis of CHD (88.9% male; age 59.5 ± 10.0 years; BMI 29.6 ± 3.8 kg·m⁻²). VO₂peak change was quantified in n=10 patients receiving routine CR plus personalised exercise training based on maximal CPET data delivered via a bespoke tele-monitoring device. VO₂peak change was also determined in n=17 patients receiving routine CR only. CPET was performed using a 25W stepped cycle ergometry protocol. The combination of routine CR and a bespoke exercise training programme significantly increase VO₂peak (Δ change: 2.08 ml·kg⁻¹·min⁻¹; 95% CI 1.88 to 3.97 ml·kg⁻¹·min⁻¹; p=0.014) compared to routine CR alone (Δ change: -0.29 ml·kg⁻¹·min⁻¹; 95% CI -1.75 to 1.16 ml·kg⁻¹·min⁻¹; p=0.841). Conclusions: An eight week (16 session) low to moderate intensity (40-70% peak heart rate reserve) CR exercise training programme, typical of many programmes in the UK, does not improve direct measurements of VO₂peak on treadmill or cycle ergometer protocols. Current assessment methods utilising submaximal exercise testing may be overstating the effect of CR exercise interventions on CRF. Current UK recommendations for exercise training doses may also be inadequate. Data within study three indicates that a minimum of 13 sessions over a 12 week period may be required to improve VO₂peak. Limited evidence indicates that routine CR with structured exercise training may attenuate C-IMT progression compared with usual care control participants. This anti-atherosclerotic effect may be related to lower coronary risk factors and better adherence to other secondary prevention measures. Overall, higher exercise training doses and personalised exercise prescription derived from maximal CPET data appeared necessary for attaining significant CRF improvements in patients with CHD.

Movement disorders are the hallmark of Parkinson’s disease (PD) and can severely compromise an individual’s ability to perform well-learned motor skills such as walking, writing, turning around and transferring in and out of bed. The first symptoms of PD typically do not appear until a critical threshold of 70-80% loss of the striatal neurotransmitter called Dopamine (DA) is exceeded. The loss of DA compromises the connection between the striatum and the Substania Nigra (SN); this connection is essential for the control of body movement. The lifelong management of individuals with PD needs a multidisciplinary approach, which includes coordination of pharmacological and non-pharmacological interventions. The use of prescribed exercise as a non-invasive PD symptom management tool is well recognized. What needs further research and development is an evidence-base for the type, frequency, intensity, duration etc. of exercise bouts. It is however ethically, socially and morally challenging to put unknown physical demands on PD sufferers, therefore in vivo and in vitro studies will be essential in delineating and targeting appropriate interventions. Additionally, in order to establish whether the various interventions are effective will also require a simple measure, preferably one that can be detected following exercise. Ca2+ plays an important role in the synthesis of DA via the Ca2+ calmodulin system and its increase in exercise coincidences with the reported positive effects of exercise on dopamenirgic neuron activity. The aim of this thesis was therefore to use in vivo, in vitro and human methodologies to establish a role for physical exercise in the amelioration of the symptoms of PD. The in vivo study comprised of four groups of experimental animals (rats): a control group (C), a training exercise group (E), a group in which Parkinson’s was induced via systemic injections of PD toxin MPTP (PD) and a group where PD-induced animals were trained/exercised (PDE). (E) and (PDE) groups were trained with 8 weeks of endurance exercise at 90% of the lactate threshold (LT), 5 times a week with each bout lasting for 45 min using a custom-built rodent treadmill. After 8 weeks, all animals were sacrificed and brain samples were collected for immunohistochemistry and western blot analysis. Ca2+ calmodulin kinases I (CaMK-1) and IV (CaMK-4) were investigated as indicators of the activity of the Ca2+ calmodulin pathway. Immunohistochemical analysis of SN region indicated that in the PD group, CaMK-1 and CaMK-4 expression was suppressed when compared with control (C) animals. This phenotype was apparently rescued by endurance exercise as those animals. The western blot results also showed quantitative differences in CaMK-1 and CaMK-4 proteins in the studied brain regions in the (PDE) and (E) groups compared with the PD group. It was concluded from this data that endurance exercise could up regulate the expression of both CaMK-1 and CaMK-4 in the brain of PD sufferers. It was postulated that changes in Ca2+ levels might therefore drive the neuroprotective effect of exercise. The in vitro study was designed to test the hypothesis generated from the in vivo work that Ca2+ is a main effector of the neuroprotective effect of exercise. The SH-SY5Y human neuroblastoma cell line is used as a model of DA neurons as it has DA activity and can synthesize DA. PD was simulated in these cells by exposure to the toxin 6-OHDA whilst addition of Ca2+ was used as an “exercise mimic”. Results showed differences in the survival of SH-SY5Y cells after exposure to specific concentration of Ca2+ following treatment with 6-OHDA. Finally, in order to assess the importance of this data to the clinical population and to further develop the concept that Ca2+ is a major effector of the positive effect of exercise, the effect of moderate-level exercise on the levels of blood Ca2+ in subjects with PD was investigated. Measures of cardiovascular physiology and blood biochemistry (total blood Ca2+) were obtained during cycling exercise at an intensity of 90% of the lactate threshold. Results indicated exercise to be beneficial in alleviating motor symptoms of PD.

Includes bibliographical references
Elite kayakers are required to perform repetitive movements that create strength and flexibility asymmetries in their bodies, making them susceptible to injury. The first portion of this thesis is dedicated to investigating whether a supervised, corrective pre-habilitation programme of the kinetic chain, conducted twice a week for 10 weeks, would reduce these predisposing factors. A group of 19 marathon paddlers were assessed before and after the intervention, with nine of them receiving the intervention. The 10-week intervention programme was found to significantly improve scapular position and kinesis, thoracic spine extension and single arm pulling ability, thus suggesting improved shoulder function and reduced risk of injury. The second portion of the thesis involved novel biomechanical analysis of kayaking on the water and on a kayaking-ergometer. It is the first objective description of the three dimensional movements of the kayak in the literature. Sprint and marathon paddlers performed a 180 metre time trial using an instrumented paddle with an accelerometer and gyroscope attached to the boat for analysis of boat movement characteristics and paddler-generated forces. Similar patterns for paddle torque, boat acceleration and pitch were observed between male sprint paddlers and male marathon paddlers. However, the direction and timing of the roll and the yaw of the boat during the water phase of the kayak stroke differed between these groups of paddlers. In addition, substantial individual variation existed within the group of male marathon paddlers. On the kayaking ergometer, activation patterns of the trunk and pelvic muscles were measured using electromyography during a maximal 200 metre time trial. Gluteus medius, lower trapezius and erector spinae were measured for the first time in maximal kayaking. The latissimus dorsi, pectoralis major and external oblique muscles were more active during the contralateral phase than has previously been reported. When these paddlers performed a single arm pull test on the same day, the muscle activation patterns changed, and muscle groups were active according to their anatomical function and what has previously been described. First, variation of movement, flexibility and segmental training of the kinetic chain may be advantageous when incorporated with kayaking training to prevent shoulder injury risk factors in paddlers. Second, individual evaluation of three-dimensional boat kinematics and muscle recruitment timing provides objective insight into an individual's kayak technique, with potential benefits for improving technical performance and mechanical efficiency.

Whilst the benefits of physical activity have been well documented, many in the UK population remain insufficiently active to substantively benefit their health, placing individuals at greater risk of developing a range of non-communicable diseases and conditions. As a large percentage of the population accesses primary care, at least on an annual basis, the use of this health care sector to advocate increased physical activity has become widespread. Exercise referral schemes (ERSs) have enabled primary care professionals to refer their patients, typically to a local leisure facility, for supervised exercise. ERSs have seen prolific growth across the UK since their conception in the 1990s and yet their effectiveness has remained in question. Despite a variety of research designs being employed, evidence regarding schemes’ effectiveness continues to be inconclusive. Within the existing research literature, the complexity of context within which ERSs operate has remained largely overlooked; specifically, how individual interpretations of ERSs might be co-produced according to the interactions between those central to the service, and how this might influence both service delivery and impact. This study, therefore, aimed to address these lacunae by exploring participants’ understanding of ERSs, and how these perceptions contoured ERS service provision. The research focused on one case-study ERS in the East of England. Semi-structured interviews were employed through a combination of group and one-to-one interviews, with 27 participants (15 patients, 7 exercise practitioners, 5 health professionals) who were central to the ERS at a delivery level, and a further 5 (1 ii district manager, 2 representatives from the County Sports Partnership and 2 representatives from Public Health) one-to-one interviews were conducted with individuals who represented the strategic management of ERSs. A process sociological lens was adopted to provide novel insights into participants’ perceptions of ERSs, their role and their ability to influence ERS service provision. Data were also supported by self-elicited reflections born from the researcher’s ‘insider’ position to the County’s ERS. Thematic analysis generated salient themes that showed conflicting interpretations of ERS service provision, and perceptions of scheme receipt and impact. Data highlighted that the networks of relationships in which individuals were situated not only contoured participant experiences but shaped the delivery processes of ERSs. Individual ‘I’ identities were situated within interdependent networks of ‘we’ and ‘they’ relationships, where identifiable groups were formed according to individuals’ perceived role within the scheme. Relationships between individuals and groups were in a tensile state, marked by power balances that had impacted on service provision but also the associated meaning of ERSs, producing interesting, yet unexpected and unintended outcomes. Such findings could prove useful to policy-makers, those responsible for commissioning ERSs, and practitioners, as well as those in similar roles for other multi-agency interventions. By facilitating enhanced understanding of the complexities of this physical activity intervention, findings suggest how the actions and interpretations of those central to a service can fundamentally alter delivery mechanisms and receipt, potentially influencing the very existence of the intervention, or in this case ERSs.

The physiological responses to upper-body exercise (UBE) are well established. Few published studies, however, have attempted to elucidate the mechanical ventilatory responses to UBE. There is empirical evidence that respiratory function may be compromised by UBE during which the ventilatory and postural functions of the ‘respiratory’ muscles may be exacerbated. Therefore, the aims of this thesis were: 1) to characterise the mechanical-ventilatory responses to UBE in healthy subjects; 2) to explore the putative mechanisms that underpin the respiratory responses to UBE; and 3) to assess whether the mechanical-ventilatory stress imposed by UBE induces contractile fatigue of the respiratory muscles. Compared to lower-body exercise (LBE; leg cycling) at ventilation-matched work rates, UBE (arm-cranking) resulted in constraint of tidal volume, higher respiratory frequency, and greater neural drive to the respiratory muscles. Furthermore, end-expiratory lung volume was significantly elevated during peak UBE compared to LBE (39 ± 8 vs. 29 ± 8% vital capacity, p < 0.05) and was independent of expiratory flow limitation. In assessing the influence of cadence on cardiorespiratory function and respiratory mechanics, submaximal arm-cranking at high cadence (90 rev.min-1) induced significantly greater cardiorespiratory stress, a trend towards elevated intra-thoracic pressures and significantly greater perceptions of dyspnoea than at low cadence (50 rev.min-1). Furthermore, there was a greater prevalence of locomotor-respiratory coupling at high cadences (p < 0.05), suggestive of greater antagonistic loading of the thoracic muscles, likely the result of static postural contractions. Finally, there was objective evidence of abdominal muscle contractile fatigue in response to severe- but not heavy-intensity UBE. Specifically, there was a 22% decrease in gastric twitch pressure from pre- to post-exercise in response to magnetic stimulation of the thoracic nerves (p < 0.05). However, there was limited evidence of exercise-induced diaphragm fatigue, as assessed using magnetic stimulation of the phrenic nerves (p > 0.05). In conclusion, mechanical-ventilatory function may be compromised during UBE due to complex interactions between thoracic muscle recruitment, central neural drive and thoracic volume displacement. This thesis presents novel findings which may have important functional implications for clinical populations who report breathlessness during activities of daily living that involve the upper-body, as well as for athletes engaged in upper-body sports.

The main focus of this thesis was to develop an accessible home-based isometric exercise training (IET) protocol for the reduction of resting blood pressure (BP). Hypertension is estimated to affect nearly 30% of the world’s population (WHO, 2012) and represents an inordinate health and economic burden worldwide. A growing body of research suggests that IET can lower resting BP. However, the majority of studies have utilised expensive and/or laboratory-based equipment, which may not be accessible to the general population. To this end, the studies within this thesis explored whether the novel isometric wall squat exercise could be prescribed for home-based training using relatively simple, inexpensive equipment. The first study determined a method for adjusting the wall squat intensity. It was found that knee joint angle reliably produced inverse relationships with heart rate (HR) and BP when individual bouts of wall squat exercise were completed (r at least -0.80; P < 0.05). Study 2 then established that these inverse relationships could be replicated from completing an incremental test (r at least -0.88; P < 0.05), from which wall squat training intensity could then be prescribed at an individualised knee joint angle (104 ± 7°) to elicit a target training HR (95% peak HR: 121 ± 14 beats∙min-1). Finally, using these methods, study 3 implemented a 4 week home-based isometric wall squat training protocol and found statistically significant and clinically relevant resting BP reductions (systolic BP: -4 mmHg; diastolic BP -3 mmHg; mean arterial pressure: -3 mmHg). These results support the majority of previous research that has found reductions in resting BP following IET. Furthermore, the primary BP control mechanisms were also explored and the results suggested that a reduction in resting BP was potentially mediated by a decrease in resting cardiac output (-0.54 ± 0.66 L∙min-1), which may have been governed by a reduction in resting HR (-5 ± 7 beats∙min-1). The novel home-based IET protocol developed within this thesis may be more time and cost effective, which may ultimately increase the adherence to and efficacy of IET for the reduction of resting BP.

The purpose of this thesis was to explore the role of exercise induced blood flow haemodynamics in the cardiovascular adaptations associated with isometric exercise training, with focus on resting blood pressure adjustment in normotensive participants. Using a cross-sectional study, it was identified that significant relationships were present between (i) blood flow, (ii) shear stress, and (iii) shear pattern responses (measured in the femoral artery), during and immediately following isometric bilateral leg extension exercise of increasing intensity. Based on these findings, it was feasible to suggest that the haemodynamic response to high intensities of acute isometric exercise might provide a physiological challenge to the cardiovascular system, that upon repeated exposure via isometric exercise training, may induce cardiovascular adaptation and resting blood pressure reductions. Subsequent to this, a randomised controlled trial established that performing isometric exercise training to a ‘high haemodynamic stimulus’ did not induce significantly greater adaptation in resting blood pressure than when performing isometric exercise training to a ‘low haemodynamic stimulus’ or control. When the training group (high and low combined) were compared to the control, significant reductions in resting blood pressure were observed. Furthermore, non-invasive cardiovascular variables that were considered as possible physiological mechanisms for resting blood pressure adaptation following isometric exercise training did not correlate with within group resting blood pressure changes. Whilst these findings suggest that a haemodynamic challenge may not be the primary stimulus responsible for inducing resting blood pressure adaptation following isometric exercise training, these results do demonstrate the effectiveness of isometric exercise training for potential health gains via reductions in resting blood pressure in normotensives. Importantly, these findings have progressed the current understanding surrounding isometric exercise training induced resting blood pressure reductions and will allow future research to narrow their focus upon other physiological variables that may be the stimuli for blood pressure adaptation.

The severe health implications associated with physical inactivity highlight the need for research aiming to elucidate mechanisms underlying individuals’ experience of exercise. Affective responses to exercise have been identified as a central factor shaping exercise behaviour (Ekkekakis, 2003; Kwan & Bryan, 2010; Williams, et al., 2008). Research identifies that external and internal factors influence affective evaluations of exercise. One external factor influencing the evaluation of affective responses is the environmental stimuli comprising the exercise setting (Antoniewicz & Brand, 2014; DaSilva, et al., 2011). Therefore, study one examined the influence of environmental cues on affective and cognitive responses to exercise in an ecologically valid setting. Results revealed significant interactions between environmental cues and affect, and motivation; this suggests that intra-individual processes may influence exercise behaviour. The thesis subsequently investigated internal processes that influence affective evaluations of exercise; in particular, processes underlying the recall of affective experience (Kahneman, et al., 1993). Study two examined individuals’ recall of exercise related affect over a period of two weeks using a randomised control crossover design. Results indicated that exercise related affect fluctuated over the two-week period with a significant drop at 24 hours post low-to-moderate and high intensity exercise trials. Additionally, recalled affect better predicted anticipatory feelings than affect recorded during exercise. The study also found partial support for the peak and end rule particularly for the high intensity exercise. Extending study two’s findings, study three explored the recall of exercise related affect and anticipatory feelings using an experimental design with a self-paced exercise protocol. The study revealed significant changes across postexercise recall with follow-up measures at 8 and 24 hours indicating a substantial decline in affect. Overall findings revealed that contextual factors promote positive affect when aligned with one’s goals; however discordant contextual cues and goals can thwart positive affective responses. Further, recall of affective experiences of exercise dynamically change over time and recalled affect can predict anticipatory feelings of exercise. Lastly, all studies’ findings emphasise on the imperative role of idiographic analysis in research on affective responses to exercise.

Training is a complex, multi-factorial process, which involves the manipulation of the duration, frequency and intensity of exercise. When quantifying the physiological and performance responses to training a large inter-individual variability in training responses is frequently observed. To date, the majority of research has examined the relationship between genetics and trainability. Another hypothesis, which has not been fully explored, is that the variability is also due to an inappropriate standardisation of exercise intensity or duration. This thesis, therefore, presents a series of studies that investigate the effects of individualised methods of prescribing exercise intensity and duration on performance and physiological responses in cycling. Study 1 compared time-to-exhaustion (TTE) to time-trial (TT) performances when the duration of the trials were matched and participants were blinded to feedback. A higher mean power output was found for TTE compared to TT at 80% (294 ± 44 W vs. 282 ± 43 W respectively, P < 0.05), but not at 100% (353 ± 62 W vs. 359 ± 74 W) and 105% (373 ± 63 W vs. 374 ± 61 W) of maximum aerobic power (MAP). Critical power (CP) calculated from the TTE trials was also higher, whereas, anaerobic work capacity (W′) was lower (P < 0.05). The findings favour TTE over TT performances for a higher mean power output and calculated CP. Study 2 compared the effects of three training intensities: moderate intensity (MOD), high intensity (HIT) and a combination of the two (MIX) when the duration of exercise was individualised. Participants were randomly assigned to one training group and trained 4 times per week for 4-weeks. Training duration was individualised to each participant’s maximum performance. All training groups increased maximal oxygen uptake (V̇O2max), MAP, TTE and gross efficiency (GE) after training (P < 0.05), but no differences were observed between groups (P > 0.05). Therefore, when the duration of training is individualised, similar improvements in performance and physiological responses are found, despite differences in exercise intensity. The CP and power law models propose power-duration relationships that describe maximum endurance capacity. Study 3 compared the predictive ability of these two models for TTE performances. It was hypothesised that the CP and power law models would reliably predict actual TTE for intensities between 80-110% MAP, but a power law model would better predict TTE for intensities outside of this range. No significant differences for parameter estimates were found between models (CP and power law) and actual TTE for intensities ranging from 80-110% MAP. Outside of this range however, the CP model over predicted actual performance at 60% and 150% MAP (P < 0.05), while there was no significant difference between the power law model and actual performance at these intensities (P > 0.05). Both models were different from actual performance at 200% MAP (P < 0.05). Therefore, a power law model can accurately predict cycling TTE for intensities ranging from 60-150% MAP. Study 4 tested the hypothesis that the inter-individual variability for TTE performances is due to the methods used to standardise exercise intensity. A %V̇O2max prescription was compared with an alternative based on an individual power-duration relationship (using a power law model). A power law model predicted the intensity for TTE lasting exactly 20-min and 3-min. A corresponding intensity for TTE as a %V̇O2max was 88% and 109%. On two separate occasions participants completed two TTE trials using the power law and %V̇O2max prescriptions, with 30-min rest between trials. There was a significant reduction in the inter-individual variability for TTE when exercise was prescribed using a 20-min power law versus 88% V̇O2max prescription method (coefficient of variation = 29.7 vs. 59.9% respectively; P < 0.05). However, there was no significant difference in the inter-individual variability for TTE using a 3-min power law versus 109% V̇O2max prescription method (P > 0.05). Two main conclusions can be drawn from this thesis. Firstly, a power law model can accurately predict and describe cycling endurance performance across a wide range of intensities. Secondly, prescribing exercise intensity using a power law model reduces the variability in TTE by 50% when compared to a %V̇O2max prescription method. Therefore, the methods used to standardise exercise intensity appear to be related to the variability in TTE performances. Future research should examine whether training prescribed using a power law model reduces the variability in subsequent training responses.

Title: The Association Of Risk Markers And The Prevalence Of Exercise Associated Muscle Cramps In Distance Runners Candidate: Izaan de Jager Promoter: Prof. MP Schwellnus Co-promoter: Dr. E Korkie Degree: MSc Sports Science Background: The epidemiology, clinical characteristics, severity and the risk markers associated with exercise associated muscle cramps (EAMC) in runners participating in different race distances have not been studied. Aim of the study: To determine the lifetime prevalence, clinical characteristics, severity, preferred treatment and potential risk markers associated with EAMC in distance runners. Design: Cross-sectional study. Setting: 2012-2015 Two Oceans marathon races (21.1km and 56km), South Africa. Participants: 76654 consenting race entrants. Methods: 106743 runners completed an online pre-race medical screening questionnaire as part of the entry for the 2012-2015 races. 76654 (71.8%) consenting entrants were included in this study (21.1km=47069; 56km=29585). The lifetime prevalence (%), retrospective annual incidence (%) and clinical characteristics (main muscle groups affected, timing of occurrence during a race, severity of EAMC, frequency of complex forms of EAMC, and preferred treatment of EAMC) were compared between 21.1km vs. 56km race entrants. Data are reported as frequency (%; adjusted for sex and age groups) and Risk Ratio (RR) with 95%CIs. Secondly, we apply a multivariate model to report independent risk markers associated with a history of EAMC (hEAMC) (sex, age, training variables, history of chronic disease, allergies, prescription medication use and running injuries) in all entrants and 21.1km and 56km entrants (prevalence risk ratios of hEAMC with 95%CI). Results: The lifetime prevalence (%) of EAMC was significantly higher in the 56km (16.0; 15.5-16.5) compared to 21km race entrants (8.8; 8.5-9.1). The onset of EAMC (%) was significantly more frequent in the first quarter (4.9; 4.3-5.7), second quarter (3.7; 3.2-4.4) and after the race (29.5; 28.1-31.1) among 21.1km race entrants, while the onset in 56km race entrants was more frequent in the third (13.7; 12.7-14.8) and fourth quarter (47.2; 45.6-48.9). Serious EAMC (6.9; 6.2-7.8), EAMC associated with dark urine (2.9; 2.4-3.5) and whole body EAMC (4.1; 3.5-4.7) was reported more frequently in 56km race entrants. Specific independent risk markers associated with hEAMC in 21.1km and 56km runners were: history of GIT disease (PR; 21.1km=1.47, 56km=1.58), history of running injury in last 12 months (PR; 21.1km=1.44, 56km=1.45), history of CVD (PR; 21.1km=1.42, 56km=2.10), history of risk factor for CVD (PR; 21.1km=1.34, 56km=1.45), history of allergies (PR; 21.1km=1.21, 56km=1.40), average slower training speed in last 12 months (PR; 21.1km=1.06, 56km=1.03) and increase years of recreational running (PR; 21.1km=1.05, 56km=1.11). Conclusion: More 56km race entrants report ever suffering from EAMC compared to 21.1km race entrants. The muscle groups affected, time of onset, severity (cramp duration), severity of serious EAMC and effective treatment modalities used to relieve acute muscle cramping differed between 21.1km vs. 56km race entrants. Independent risk markers associated with hEAMC identified in this study are male sex, older age, longer race distances runners, training variables, several chronic diseases, a history of allergies and the use of prescription medications for both 21.1km and 56km race entrants.
Dissertation (MSc)--University of Pretoria, 2020.
Physiology
MSc
Restricted

Muscle cramp is a forceful, involuntary contraction of skeletal muscle, but its underlying mechanisms are not well understood. Our limited understanding of muscle cramp may be due to its unreliable occurrence. Electrical train stimulation (ETS) has been reported to induce cramp in the small flexor muscles of the foot, and a relationship exists between the threshold frequency (TF) of ETS to induce cramp and muscle cramp susceptibility. The use of ETS to induce muscle cramp in the calf muscles however may be challenging, and the test-retest reliability of this method has not been examined in the calf muscles. Since athletes can experience muscle cramp in the calf muscles, in turn affecting their athletic performance, it is necessary to establish a method to assess calf muscle cramp. The first purpose of this study therefore was to determine the usefulness of the ETS application to the calf muscles, along with its reliability. Using a Compex 2 stimulator, ETS was applied to the calf muscles of both dominant and non-dominant legs in 10 men (33.5 ± 8.4 y) who reported experiencing cramp during training or competition. Each leg was treated separately in a counterbalanced order, with subjects in the supine position and legs supported by a bench that fixed the ankle at maximal plantarflexion. ETS consisted of 2 s (including 500 ms ramp time) of 300 μs square pulsed waves followed by 30 s rest. ETS commenced with two bouts of stimulation at 10 Hz during which the stimulation intensity was increased to the maximum tolerated, with values of 46.9 ± 6.5 and 45.4 ± 7.7 mA for the dominant and non-dominant legs, respectively. Subsequent stimulation trains increased by 3 Hz until cramp occurred, as confirmed by a spontaneous electromyograph (EMG) signal. The protocol was repeated 30 min after the first test, with the entire testing procedure repeated seven days later. Muscle cramp was induced in all subjects, but the TF varied amongst subjects (13-55 Hz). Mean TF value to induce muscle camp for the dominant leg was 25.0 ± 7.6 Hz for the first test and 23.7 ± 5.0 Hz for the second test. The non-dominant leg also showed similar values. Test-retest reliability, as indicated by the intraclass correlation coefficient (ICC), limits of agreement (LOA) and coefficient of variation (CV), were 0.94, 5.4 % and 9.2 %, respectively for the dominant leg, and 0.72, 9.8 % and 15.4 %, respectively for the non-dominant leg. These results show that ETS can induce muscle cramp in the calf muscles and that the TF of ETS was a reliable measure to assess the calf muscle cramp susceptibility. The second purpose of this thesis was to examine the influence of fatigue on the TF of ETS-induced muscle cramp in the calf muscles of 10 men (35.8 ± 9.2 y) who reported experiencing cramp during sporting activity. The previously described methods were used to assess muscle cramp in the calf muscles of the subject’s dominant leg with a stimulation intensity of 49.3 ± 4.9 mA before, immediately after, and 30 min after exercise. Exercise consisted of uphill treadmill walking, standing calf raises, skipping, drop jumps and cycling to fatigue, which was completed in 82.9 ± 2.0 min at an average heart rate of 141.7 ± 6.0 bpm. An isokinetic dynamometer was used to measure plantarflexor muscle torque of the dominant leg before and immediately after exercise, and following 30 mins of passive recovery. Blood and urine samples were obtained to assess electrolyte concentrations and hydration status before and immediately after exercise. Plantarflexor muscle torque decreased significantly (p < 0.05) approximately 20 % from the baseline (42.4 ± 17.1 Nm) immediately post exercise (34.6 ± 14.9 Nm), and was still significantly lower at 30 min post-exercise (37.4 ± 15.9 Nm). Serum (4.32 ± 0.35 vs 4.66 ± 0.38 mmol/L) and urine (56.3 ± 38.6 vs 87.2 ± 40.8 mmol/L) potassium concentrations, urine osmolality (551.1 ± 306.6 vs 683.9± 236.6 mmol/L), and urine specific gravity (1.014 ± 0.008 vs 1.022 ± 0.009) changed significantly from pre to post exercise, but serum osmolality, serum sodium and urine sodium concentrations remained unchanged. No significant changes in TF were evident before (23.2 ± 6.0 Hz), immediately after (22.6 ± 5.1 Hz) and 30 min post-exercise (25.3 ± 7.4 Hz). These results suggest that neither fatigue nor mild changes in hydration status affect the TF. Nevertheless, the duration of exercise used in this study might not have been sufficient to cause the physiological changes that may occur during training or racing. As muscle cramp can reliably be assessed by ETS, future investigations should use this method to uncover potential mechanisms related to muscle cramp, such as body temperature, hydration status and electrolyte concentrations.

Within Exercise Science, there are ongoing debates among health and fitness professionals over exercise related health questions. It can be difficult to discern myth from science when there are poorly designed research studies or limited evidence to unequivocally answer the question. Therefore, the purpose of this symposium is-to have a panel of experts provide research-based evidence related to three controversial topics often posed to exercise science professionals. First, within the weight loss community there is frequent debate over the role of exercising in the fat burning zone for weight loss. Dr. Ed Howley will address the questions: what is the fat burning zone, and what is its significance for those trying to lose fat? Secondly, there has been an interest in the concept of a runner's high and some early research linked this phenomenon to brain endorphins. Dr. Pat O'Connor will address the questions: is there a physiological basis for euphoria associated with exercise and what role do endorphins play in this phenomenon? Lastly, the health related benefits of cardiovascular and resistance training are well documented, but the importance of stretching for health and sports performance is less clear. Dr. Mike Stone will address the questions: does research support the role of stretching in enhanced health and athletic performance and are there situations in which stretching might be considered contraindicative?

Endothelial microparticles (EMP) offer an insight into the state of the endothelium and are known to be elevated in diseases characterised by endothelial dysfunction (ED) (Horstman et al., 2004; Vince et al., 2009a). EMP have also been shown to increase after exercise/endothelial stress in healthy individuals (Sossdorf et al., 2011; Vince et al, 2009) but this area remains relatively novel. The purpose of the first experiment was to quantify the effects of an acute bout of strenuous exercise on the circulating levels of EMP and to assess if this effect is different after the ingestion of an extensively researched ergogenic aid (sodium bicarbonate, NaHCO3). Seven physically active and apparently healthy males volunteered to perform 10 x 15 second (s) cycle sprints after the ingestion of either 0.03 g.kg.BW−1 NaHCO3 or 0.045 g.kg.BW−1 of a placebo (sodium chloride, NaCl) in capsules. The ingestion of NaHCO3 induced a pre exercise alkalosis as evidenced by a significantly altered resting acid base status, but had no influence on levels of EMP in healthy males. As a result, the data was combined for the two experimental groups, and the exercise produced a significantly increased level of CD105+ MP (MP; microparticles) at 90 minutes (min) and 180 min when compared with resting levels (p = 0.010, p = 0.043 respectively). The observed peak value at 90 min was also significantly greater compared to immediately post exercise (p = 0.019). CD106+ MP also increased significantly to 90 min from immediately post exercise (p = 0.020) and this was still greater at 180 min compared to post exercise (p = 0.015). It was concluded that exercise of this nature was sufficient to elicit ED, although the endothelium shows signs of endothelial repair within a matter of hours (hr). Also, it appears that pre exercise alkalosis has no effect on the attenuation of EMP quantity. Additional work was completed to verify the novel finding that CD105+ MP and CD106+ MP appear markers of endothelial function (EF), and to further examine the quantification of EMP, this time in healthy females. There was also an additional blood draw in order to assess where the maximum level of endothelial stress was occurring post exercise. In the second experiment, 10 healthy females completed the identical repeated sprints protocol as the first experiment, this time without the ingestion of NaHCO3. CD105+ MP were increased 90 min post exercise compared to immediately after exercise (p = 0.042). There was again a decline in both markers from 90 min to 180 min, although this was not significant. Furthermore, with the addition of a blood draw at 45 min post exercise, it was suggested that EMP levels appear to be rising between 45 min and 90 min post exercise, speculating this is the time point of greatest endothelial damage. Finally, shear stress was suggested as a key reason behind the increase in endothelial damage as a result of exercise, as indicated by significant changes in variables such as heart rate (HR) and systolic blood pressure (SBP). The third experiment employed a longer 90 min interval cycling protocol with the purpose of quantifying EF over a greater period of time, allowing investigation into whether the markers of EF were altered in the same way as the previous two experiments. It was also an aim to further assess the possible influence of shear stress factors on ED. Fourteen healthy males completed 90 min of high intensity aerobic exercise, and there were several changes in both CD105+ MP and CD106+ MP. CD105+ MP rose significantly from rest to an observed peak at 90 min (p = 0.019). Both of these markers indicated a significant restoration of the endothelium as indicated by a fall from peak values during recovery to 180 min post exercise (CD105+ MP, p = 0.009; CD106+ MP, p = 0.022). This experiment concluded that the endothelium is greatly affected by highly intense exercise over a prolonged period of time, but is recovered fully in a time period of 3 hr. The effects of shear stress again appear to be largely influential, but future work must now be conducted in order to build on the findings from this research and examine shear stress closely during exercise and its relationship with EMP quantification. It was the aim of the next experiment to investigate two separate methods of assessing EF (EMP and EndoPAT-2000), this time in a group of sedentary, but otherwise healthy individuals, in order to monitor the changes as a result of an acute bout of moderate intensity acute exercise. There were no significant differences found in EF as a result of exercise. This was indicated by no significant changes in CD105+ MP concentrations from pre to post exercise (p = 0.84) or pre to 60 min post exercise (p = 0.612). CD106+ MP concentrations showed a decrease from resting values (2513 CD106+ MP per μl platelet free plasma; PFP) to immediately post exercise (1368 CD106+ MP per μl PFP, p = 0.09), and again at 60 min post exercise (1293 CD106+ MP per μl PFP, p = 0.073) compared to resting values. Additionally, EndoPAT scores were unaffected by exercise, with values of reactive hyperaemia index (RHI) changing from rest (2.43) to post exercise (2.57), but this was not significant (p = 0.35). Correlations were carried out in order to determine and comparisons that may have existed between EMP and EndoPAT score using RHI. Although there was a slight trend for the higher numbers of CD105+ MP to correlate with the lower scores of RHI (r = 0.327) this was not significant (p = 0.171). CD106+ MP showed no correlations with RHI (r = -0.087, p = 0.717). This chapter suggested that exercise was not strenuous enough to see any significant changes in EF, and EMP continue to appear efficient markers of EF in a population of sedentary, healthy individuals. The final experimental chapter investigated the effects of a supervised 8 week moderate intensity exercise programme on women with polycystic ovary syndrome (PCOS) and control women free from any known disease. The aim was to assess if this type of exercise could improve EF in this population, and if there was a relationship with EMP (CD105+ MP and CD106+ MP) to other factors, such as body composition and cardiorespiratory fitness. EF was improved from baseline values to post exercise programme, with CD105+ MP concentrations reducing from 2113 CD105+ MP per μl PFP to 424 CD105+ MP per μl PFP (p = 0.025). Furthermore, control women showed no significant change from pre to post exercise programme in CD105+ MP (p = 0.25), or CD106+ MP (p = 0.99). Further analysis was performed to look for any associations with the changes in EMP compared to body composition changes as a result of exercise, but no significant correlations existed. This study concluded that supervised, moderate intensity exercise independent of substantial weight loss was enough to elicit an00 improvement in EF in women with PCOS compared to healthy control women. Additionally, EMP concentrations appear to be able to effectively map changes in EF across a long period of time in diseased states, adding to the notion that EMP may account for EF. Future work must now build on these findings from this research and examine this response in a larger cohort involving PCOS women with varied phenotypes and body composition.

DNA methylation, an epigenetic modification which can regulate gene transcription independently from alterations to the nucleotide sequence, can be manipulated by lifestyle factors such as diet and exercise, hypothetically reversing aberrant DNA methylation associated with disease pathogenesis. The underlying mechanisms by which these changes occur are currently poorly characterised, however, in vitro data suggest that inflammatory mediators are involved. Furthermore, regular exercise appears to reduce inactivity-associated systemic inflammation, possibly by alterations to the methylome, thereby suggesting a cyclic relationship between exercise, inflammation, and epigenetic modification. The aims of this research programme, therefore, were to: characterise the acute changes that occur to the de novo DNA methyltransferases following exercise in peripheral blood mononuclear cells (PBMCs), and the role of exercise-induced systemic inflammation in this process; investigate how these changes then translate into functional modifications to the methylome; and to determine whether a training programme utilising sedentary individuals manipulates DNA methylation of genes involved in chronic systemic inflammation associated with physical inactivity. Pilot investigations corroborated previous in vitro data that recombinant IL-6 is able to regulate nuclear concentrations of DNMT3A and DNMT3B in PBMCs. In order to isolate the influence of circulating proteins independently from genetic polymorphisms that may influence susceptibility to epigenetic change, cells were stimulated with exercise-conditioned plasma following intense endurance exercise which elicited significant alterations in nuclear concentrations of DNMT3A and DNMT3B. Eccentric exercise, which is typically not associated with elevations in circulating cytokines, did not cause any significant changes in nuclear or cytoplasmic DNMT concentration, or global DNA methylation; this supports the hypothesis that transient systemic elevations in inflammatory cytokines are important regulators of epigenetic modifications associated with exercise. Lack of transcriptional changes in DNMT3A following both exercise training and an acute maximal bout suggests that, in line with in vitro data, that the observed elevations in nuclear DNMT concentration are largely due to cellular relocalisation and not gene expression of this enzyme. It remains to be elucidated whether the training regime, and the subsequent response to an acute maximal bout, is able to elicit differential methylation of IL6, NFκB2, and ASC, however, in vitro stimulation of PBMCs with the cytokines IL-6 and IL-1β did cause significant changes to IL6 promoter methylation, further supporting the role of these proteins in epigenetic regulation. The data presented in this thesis support the postulation that exercise-induced changes to DNA methylation in PBMCs likely occur due to systemic elevations of inflammatory proteins, in particular IL-6, which causes manipulation of de novo DNMT nuclear concentrations due to cellular translocation of the enzymes themselves. While it was not possible to determine whether exercise directly modified gene-specific methylation, in vitro experiments suggest that inflammatory cytokines are able to regulate IL6 promoter methylation in human PBMCs.

Postactivation potentiation (PAP) has been recognised as an improvement in muscle-twitch force following conditioning contractile activity. The phosphorylation of myosin regulatory light chains has been identified as the principal mechanism underlying PAP. Contractile activity has been shown to produce both PAP and fatigue, and it is the balance between the two that determines whether the response is enhanced, suppressed or unaffected. To date, the optimum time period between the heavy-resistance exercise and subsequent power performance remains to be elucidated. Similarly, many studies have been conducted on the effects of whole-body vibration (WBV) in relation to PAP with inconclusive results. The use of WBV with elite athletes has been limited, and there are no published studies focussing on WBV and its possible use in activating PAP. The purpose of the present study was to determine whether an acute enhancement of power (PAP) differs between WBV training and a heavy set of resistance exercise, and to investigate the time-course changes at 1, 3 and 5 minutes post WBV and heavy resistance exercise interventions. Fifteen male professional rugby union players (age 20.4±2.6 yrs) were recruited as participants. Using a cross-over design where participants performed all interventions, the heavy-resistance intervention consisted of a 3RM back squat, while the WBV intervention consisted of participants performing full dynamic squats whilst exposed to a vibration treatment (40 Hz, 4 mm displacement) on a VibroGym Professional vibration platform. A control condition consisting of body-weight squats only was also employed. All interventions were performed after a standardised squat warm-up. Peak power and peak displacement were measured by means of a countermovement jump. Comparison between interventions showed no statistically significant differences in peak power or peak displacement at any time point, but ES calculations indicated that moderate to large changes occurred in peak displacement (WBV - 5.9%, ES=0.60; 3RM - 10.9%, ES=1.09; Control - 8.2%, ES=1.05). The results also showed that a large effect (ES=1.16) was evident 3-5 minutes post-intervention. The results from the present study suggest that in professional rugby union players, PAP may be elicited from both WBV and heavy-resistance exercise. The large effects found post-intervention have implications for both strength and conditioning coaches and athletes in understanding potential outcomes when trying to elicit PAP using WBV or heavy-resistance exercise. Further study in this area will need to focus on the underlying mechanisms and their effects on an elite or high-performance population.

INTRODUCTION: Monitoring an athlete’s psychological, physiological, and performance level is important when preparing for a major competition. No study to date has tracked a high-level weightlifter peaking for a major competition all the way up to the day of competition. Assessing performance at a competition is vital to ascertain if the athlete has reached a peaked and if peak performance will actually be expressed during the competition. PURPOSE: Therefore, the purpose of this study was to determine when peak jumping performance was achieved and whether psychological or physiological variables explained any jump performance changes in a high-level female weightlifter preparing for a national competition. We hypothesized that jumping performance would peak on competition day corresponding with improved recovery and stress states and preserved muscle cross-sectional area (CSA) relative to baseline values. METHODS: A USA national-level female weightlifter (23.5y; 54.0±0.6kg; 155.4cm) participated in this investigation. Laboratory testing was carried out over a 7-month period as part of an ongoing long-term athlete monitoring program. At 11-weeks out, testing was administered twice a week for each week leading up to competition, at the competition, and returning from the competition. Each testing session evaluated body mass, recovery-stress inventories using the short recovery and stress scale (SRSS), and vastus lateralis CSA via ultrasonography followed by a standardized warm-up preceding unloaded squat jumps (SJ) performed on dual force plates sampling at 1kHz. Hopkin’s effects size (ES) classifications for each data point was used to determine the potential magnitude of change observed for each test relative to baseline values. The smallest worthwhile change was used to determine a meaningful change relative to baseline values. This typical error and smallest worthwhile change were used to quantify the probability (i.e., precision) of performance change that took place. Values greater or less than baseline values with precision >95% signified a very likely change for each testing session relative to the competition. RESULTS: Weightlifting performance goals were met for the national championship (snatch=67kg, clean and jerk=92kg, total=159kg). Jumping performance (precision=99%,ES=2.7) was almost certainly peaked on competition day with increased recovery (ES=0.7) and decreased stress scores (ES=0.5). However, the athlete possibly exhibited a small decrease in muscle CSA (precision=64.8%;ES=0.4) the week of competition that corresponded with very large changes in body mass (precision=99%;ES=2.8). CONCLUSIONS: The training program was effective in ensuring the athlete was peaked the day of competition based on jumping performance and recovery-stress scores despite small decreases in CSA. Thus, weightlifting coaches and sport scientists working with high-level athletes should monitor jumping performance and recovery-stress state to ensure athletes peak at an appropriate time. PRACTICAL APPLICATIONS: SRSS and SJ testing can be used as monitoring tools for high-level weightlifters preparing for important competitions.

Book Summary:It is an essential skill for any strength and conditioning coach to be able to reliably assess the physical performance of their athletes and communicate the results and their implications to performers and coaches, alike. Performance Assessment in Strength and Conditioning is the first textbook to clearly and coherently suggest the most appropriate and reliable methods for assessing and monitoring athletes’ performance, as well as including detailed sections on testing considerations and the interpretation and application of results. The book explores the full range of considerations required to reliably assess performance, including questions of ethics and safety, reliability and validity, and standardised testing, before going on to recommend (through a comparison of field- and laboratory-based techniques) the optimal methods for testing all aspects of physical performance.

Book Summary: It is an essential skill for any strength and conditioning coach to be able to reliably assess the physical performance of their athletes and communicate the results and their implications to performers and coaches, alike. Performance Assessment in Strength and Conditioning is the first textbook to clearly and coherently suggest the most appropriate and reliable methods for assessing and monitoring athletes’ performance, as well as including detailed sections on testing considerations and the interpretation and application of results. The book explores the full range of considerations required to reliably assess performance, including questions of ethics and safety, reliability and validity, and standardised testing, before going on to recommend (through a comparison of field- and laboratory-based techniques) the optimal methods for testing all aspects of physical performance.

Background: The epidemiology and risk factors associated with medical complications, including life-threatening complications during distance running events has not been well described. The aims of this research were to document the incidence of medical complications (study 1), determine risk factors associated with medical complications (studies 2 and 3), and develop and apply a pre-race medical screening tool to determine the prevalence of chronic disease in race entrants, using a risk stratification model (study 4). Design: Prospective studies Setting: Two Oceans Marathon races (2008-2011) (studies 1-3) and race entrants (2012) Participants: Studies 1-3: 65 865 race starters; 21.1 km (n =39 511), 56 km runners (n=26 354). Study 4: 15 778 race entrants Methods: Study 1: In all 4 years, race day medical complications were recorded and subdivided by severity (serious life-threatening/death), organ system and final diagnosis. Studies 2 and 3: Independent risk factors associated with all medical complications, severity and organ system involvement were determined in 21.1 and 56km runners, using multivariate modeling. Study 4: A pre-race medical screening tool was developed, based on international pre-exercise medical screening guidelines, and administered to all race entrants (2012). The prevalence (%) of runners with four risk categories was determined. Results: The incidence (per 1000 race starters) of all and serious/life-threatening medical complications was 8.27 and 0.56 respectively (study 1). Risk factors associated with medical complications were less experience (56km), slower running pace (56 km) and older females (21.1 km) (studies 2 and 3). 16.8% runners were identified as those that should undergo medical evaluation for suspected cardiac disease with 3.4% reporting existing CVD (very high risk) and 13.4% reporting multiple CVD risk factors (high risk) (study 4). Conclusion: The incidence of all and serious/life-threatening medical complications in the 21.1km and 56km race is 1/121 and 1/1786 race starters respectively. Race experience, running pace and sex are risk factors for medical complications. 16.8% runners have underlying suspected cardiovascular disease. These data formed the basis for the implementation of a pre-race medical screening and risk stratification. The research lays the foundation for a future educational intervention programme to reduce the risk of medical complications in distance running and other endurance events.

COL5A1 encodes the α1 chain of type V collagen, a minor fibrillar collagen that is an important regulator of collagen fibril assembly. A polymorphism (rs12722, C/T) within the 3'-untranslated region (UTR) of COL5A1 is associated with chronic Achilles tendinopathy (TEN) and other soft tissue injuries as well as exercise-related phenotypes. These phenotypes are directly or indirectly associated with the mechanical properties of musculoskeletal soft tissue. It has therefore been hypothesised that variants in the COL5A1 gene, specifically the 3'-UTR, regulate synthesis of the α1(V) chain and type V collagen production. Type V collagen levels in turn regulate fibril architecture and structure and, thereby, mechanical properties of musculoskeletal soft tissues. Although the 3'-UTR of many eukaryotic genes have been shown to play an important regulatory role, the function of the COL5A1 3'-UTR is currently unknown. Aim. The primary aim of this thesis was therefore to determine whether the COL5A1 3'-UTR was functional and to identify functional differences between the COL5A1 3'-UTR cloned from participants with TEN and healthy asymptomatic control individuals. The secondary aim was to start mapping the functional regions within the 3'-UTR, focusing on regions which are potentially responsible for contributing to the tendinopathic phenotype.

INTRODUCTION: Chronic diseases of lifestyle (CDL) are a major cause of global morbidity and mortality. Although CDL are largely preventable and treatable through adopting and maintaining healthy lifestyle behaviours, CDL rehabilitation programmes remain an underutilised resource. Behaviour modification is thus complex, and requires a collaborative approach between psychologists and medical clinicians involved in the management of CDL. This thesis examined the role of psychological factors in the management of patients with CDL who participated in a comprehensive lifestyle intervention (CLI) programme. METHODS: An explanatory mixed methods design was used to describe the CLI experience. These included an initial clinical audit of 308 patients commencing and completing a twelve week CLI programme to test associations of psychological, demographic, medical and diagnostic factors with physical outcomes. Two qualitative studies were subsequently conducted to further understand patient experiences of CDL and CLI programmes. The first involved interviews of 14 patients at programme commencement and completion. The second consisted of a case study of a patient participating in the programme using human centred design principles as well as ethnography.

Background: Global levels of overweight and obesity in preschool-aged children have increased dramatically in the last two decades, with most overweight and obese children younger than five years living in low- and middle-income countries (LMICs). Statistics from the 2013 South African National Health and Nutrition Examination Survey (SANHANES-1) confirm that levels of overweight and obesity are high in South African preschool-aged children, with prevalence rates of overweight and obesity up to 18.2% and 4.7%, respectively. This increasing problem of overweight and obesity in South African preschoolaged children highlights the need for intervening in this age group. Overweight and obesity interventions in preschool children typically include one or more of the following behaviours: physical activity, sedentary behaviour and screen time. Aim and objectives: The aim of this study was to characterise the preschool environment in rural South Africa, and to explore physical activity, gross motor skill proficiency, sedentary behaviour and screen time in rural South African preschool-aged children. Additionally, aims of this study were to explore the associations between gross motor skills, body composition and physical activity; and to assess compliance with current physical activity and sedentary behaviour guidelines. Methods: Preschool-aged children (3-5 years old, n=131) were recruited from three Preschools and two Grade R (reception year) settings in Agincourt, a rural village in north eastern South Africa. In order to gain an understanding of the Preschool and Grade R settings, an observation of the preschool environments was conducted using a tool adapted from the Outdoor Play Environmental Categories scoring tool, Environmental and Policy Assessment and Observation instrument, and the Early Learning Environments for Physical Activity and Nutrition Environments Telephone Survey. Each child’s height and weight was measured. Physical activity and sedentary behaviour were measured objectively using a hip-worn ActiGraph GT3X+ accelerometer for 7 days (24 hours, only removed for water-based activities). Gross motor skills were assessed using the Test for Gross Motor Development–Version 2 (TGMD-2). Physical activity and sedentary behaviour, including the contextual information for these behaviours, during the preschool day (08h00 until ±12h00) were measured using the Observational System for Recording Physical Activity in Children (Preschool Version). A separate sample of parents/caregivers were recruited (n=143) to complete a questionnaire that was adapted from the Healthy Active Preschool Years questionnaire and Preschool Physical Activity Questionnaire. Parents reported on their child’s screen time, and on factors within the home and community contexts in which physical activity and sedentary behaviours occur. Results: In terms of the environment, the Preschools and Grade R settings differed in that fixed play equipment only featured in the Preschool settings. Grade R settings had more open space in which to play. All Preschool and Grade R settings provided children with limited portable play equipment, and none of the schools had access to screens. Although all children recruited for the study were preschool-aged, the Grade R children were significantly older than the Preschool children (5.6±0.3years vs. 4.4±0.4 years, p <0.05). According to IOTF cut-offs, the prevalence of overweight/obesity was low (5.0%) in the sample, and 68.1% of children were classified as normal weight. On average, children spent 477.2±77.3 minutes in light- to vigorous-intensity physical activity (LMVPA) per day, and 93.7±52.3 minutes in moderate- to vigorous-intensity physical activity (MVPA). In terms of the new current guidelines (180min/day LMVPA, including 60min of MVPA, described as ‘energetic play’), and using average daily average of LMVPA and MVPA, 78.2% met current guidelines. Observed and objectively measured sedentary behaviour results revealed that children were more sedentary during preschool time (between 08:00 to 12:00) compared to the afternoons. Overall, boys were significantly more physically active than girls; and Preschool children did more physical activity during preschool time than Grade R children (all p< 0.05). Over 90% of the sample achieved an ‘average’ or better ranking for gross motor skill proficiency. The Grade R children were significantly more proficient than the Preschool children for all gross motor skill components (raw scores and standardised scores). Overall, boys achieved significantly better object control raw scores than the girls, and displayed greater proficiency than the girls in the strike (p=0.003), stationary dribble (p< 0.001) and kick (p< 0.001). None of the preschool or Grade R settings had access to screens such as televisions or iPads, and parent-reported screen time was low for the total sample (0.5±0.3hr/day). The majority of the sample (97.9%) met current screen time guidelines (<1 hour per day). Parents (82.5%) reported that they believed that their child did sufficient PA for their health, but 81.8% also reported believing that television time would not affect their child’s health. Parent responses revealed neighbourhood safety as a potential barrier to being physically active in the community. Conclusions: Rural preschool-aged children in South Africa appear to be engaged in adequate amounts of physical activity, particularly LMVPA, and are adequately proficient in gross motor skills. The children did not engage in excessive amounts of screen time. Overweight and obesity were not prevalent in this sample of rural preschool-aged children, and therefore it would appear that an intervention to reduce or prevent obesity by increasing physical activity, improving gross motor skills and reducing screen time is unnecessary. Rather, interventions that facilitate the increase in levels of MVPA in order to meet current physical activity guidelines are warranted. Additionally, it is essential that the high levels of physical activity (LMVPA) and good foundation of gross motor skills observed in this sample are promoted in an effort to maintain them throughout childhood. Future research may want to determine whether these activities (high levels of LMVPA, low levels of screen time) track throughout childhood and into adolescence.

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Includes bibliographical references.
The HIMS test, which consists of controlled exercise at increasing workloads, has been developed to monitor changes in training status and accumulative fatigue in athletes. As the workload can influence the day-to-day variation in heart rate, the exercise intensity which is associated with the highest sensitivity needs to be established with the goal of refining the interpretability of these heart rate measurements. The aim of the study was to determine the within subject day-to-day variation of submaximal and recovery heart rate in subjects who reached different exercise intensities.

Obesity treatment requires approaches that target the reduction of body weight and fat mass. The improvement of cardiorespiratory fitness (CRF), metabolic flexibility and insulin sensitivity also contribute towards reducing obesity-associated risk factors. While energy restriction alone results in significant weight loss, exercise-only interventions provide small amounts of weight loss and prevent weight gain, while also improving many of the other variables targeted in obesity treatment. Once achieved however, successful weight-loss maintenance is challenging, with many individuals subsequently experiencing weight regain. The main objectives of this thesis were to explore the role of metabolic rate and substrate utilization in influencing body weight, body composition and insulin sensitivity. This twopart thesis hypothesised that: 1) exercise training, without dietary intervention, will improve metabolic rate and substrate utilization in a sedentary obese population, and that this would be associated with improved body composition, insulin sensitivity and CRF; and 2) metabolic rate, substrate utilization and insulin sensitivity are altered through weight loss/regain, predisposing these individuals to weight regain and impairing successful weight-loss maintenance. In Part 1 of this thesis a 12 week exercise intervention in sedentary, obese (BMI 30-40kg.m-2 ) black South African (SA) women (aged 22, IQR 21-24 years) was completed. Previous studies have shown that black SA women present with very low CRF, a key indicator of increased risk for non-communicable disease (NCD), and have a high prevalence of obesity and insulin resistance (IR). They are thus at increased risk for developing type 2 diabetes (T2DM). Furthermore, physiologically black SA women have also been shown to have less visceral adipose tissue (VAT) and more peripheral gluteal fat mass (FM) compared to their white counterparts, but are paradoxically more IR. Despite this presentation, to date there has been no supervised exercise intervention studies undertaken in this very high risk population group. The first study of this thesis (chapter 2) aimed to assess the effects of the exercise intervention on changes in CRF, energy expenditure (EE) and substrate utilization, both at rest and during steady-state exercise compared to non-exercising controls. It also assessed baseline and changes in these measurements in relation to changes in body composition. Black SA women (BMI 30-40 kg.m-2 , 20-35 y) were recruited and randomized into control (CTL, n=15), or exercise (EXE, n=20) groups. The CTL was instructed to maintain usual activity while the EXE completed 12 weeks of combined resistance and aerobic exercise training (4d.wk-1 , 40-60min.d-1 @ >70% peak heart rate (HRpeak)). At pre-intervention, a treadmill-based CRF test, measuring peak volume of oxygen consumption (VO2peak), was carried out. Thereafter resting and steady state exercise (50% VO2peak) energy expenditure (EE) and respiratory exchange (RER) were measured along with body composition (dualenergy X-ray absorptiometry (DXA)). A frequently sampled intravenous glucose tolerance test (FSIGT) was also carried out to determine changes in insulin sensitivity. These tests were repeated at post-intervention testing with steady state testing being carried out both at the same relative intensity (50% post-testing VO2peak) and the same workload (treadmill speed and gradient) as used for pre-testing. Dietary intake (4d diary) and daily step-count (ActivPAL) data was collected at pre-testing, 4, 8 & 12 weeks. Results showed that all participants had very low baseline CRF, falling below the 20th percentile previously shown in African American women. In response to exercise training, CRF increased by ≈11% and rates of fat oxidation during steady-state exercise were improved, while in controls these remained unchanged. Compared to CTL, EXE also showed small but significant reductions, in weight, as well as BMI, waist (WC) and hip (HC) circumferences. In contrast weight, BMI and WC increased in non-exercising controls. Gynoid FM (absolute FM and as a proportion of total FM), rather than visceral adipose tissue (VAT), was reduced in exercise participants. Within the exercise group higher baseline fat oxidation rates during steady state exercise and lower resting carbohydrate oxidation rates explained 61.6% (p< 0.001) of the variability in changes in gynoid FM in response to 12 weeks of exercise training in this group. In conclusion, exercise training improved CRF and fat oxidation rates during submaximal exercise in sedentary, obese black SA women. Higher fat oxidation rates during steady state exercise and lower resting carbohydrate oxidation rates at baseline were associated with the mobilization of gynoid FM in response to exercise training, rather than VAT as is typically shown in exercise interventions. This novel finding potentially represents an ethnic/gender specific response to exercise training. Further studies are needed to confirm this. Similar exercise training programs, that are sustainable over the long term, would therefore be beneficial in achieving meaningful increases in CRF while also supporting weight management and body composition improvements in this high risk population group. Using data from the exercise intervention in obese black SA women, the second study of this thesis (chapter 3) investigated inter-individual variability in the CRF response (∆VO2peak) to exercise training. The study specifically aimed to compare changes in EE and substrate utilization at rest and during steady state exercise, body weight and composition and insulin sensitivity between high and low CRF responders to the 12 week intervention. Furthermore it aimed to explore associations between baseline metabolic rate, EE and substrate utilization and subsequent changes in CRF in response to exercise training, to determine if baseline variability in these measures contributed to inter-individual variability in the CRF outcome. Within the exercise group, high inter-individual variability in CRF response to exercise training was identified. Based on a median split in ∆VO2peak, high responders (HRS, n=10) increased CRF by 21.7 ±10.0% (p< 0.001) compared to no change in both low responders (LRS, n=10; +0.6 ±6.3%, p=0.748) and CTL (-3.2 ±10.8%, p=0.195). This occurred despite all groups having similar baseline VO2peak and the exercise group receiving the same exercise dose (number of exercise sessions attended and average intensity of the exercise sessions). At baseline, HRS derived ≈62% of energy expenditure from fat oxidation during steady-state exercise compared to just 41% in LRS, who relied to a greater extent on carbohydrate oxidation. Furthermore, HRS were ≈11 kg lighter than LRS. There was also a positive association between BMI and RER such that individuals with higher BMI showed lower fat utilization (i.e., higher RER). HRS reduced gynoid FM whereas in LRS this remained unchanged. This is in line with the findings of the previous chapter which showed that exercise-related reduction in gynoid FM was associated with greater baseline fat oxidation. LRS showed improvements in insulin sensitivity compared to CTL and HRS. Using regression analysis including the exercising participants, greater baseline carbohydrate oxidation rates both at rest and during steady state exercise predicted a poorer CRF to exercise training, explaining 37.5% of the variability in ∆VO2peak. To the best of my knowledge, this is the first study to show that baseline variability in substrate utilization among sedentary obese individuals contributes towards explaining the variability in the CRF response to exercise training. However, further studies are required to confirm these results. Together, these studies show that higher fat oxidation rates are necessary for FM mobilization, while correspondingly reduced reliance on carbohydrate oxidation both at rest and during exercise supports improvements in CRF in response to exercise training. These findings add to a growing body of research aimed at explaining inter-individual variability in exercise intervention outcomes and may contribute to individualizing the exercise prescription. Part 2 of this thesis used a cross-sectional approach and investigated firstly whether there was evidence for metabolic adaptation to weight loss/regain in response to long term weight maintenance, potentially predisposing individuals to future weight gain/regain. Secondly, I investigated whether insulin sensitivity is altered as a result of prior weight loss history, or whether successful weight loss restores insulin sensitivity to levels that are comparable to phenotypically similar controls with no weight loss history. Weight stable, BMI-matched South African women aged 20-45 years with or without a history of prior weight loss were screened and recruited. Four groups were defined as follows: Weight Reduced (RED, n=15) - lost at least 15% of body weight & maintained a reduced weight (BMI ≤ 27kg.m-2 ) for over 12 months (15% of body weight), but relapsed back to overweight or obese (BMI ≤ 27kg.m-2 ); and overweight or obese (BMI ≤ 27kg.m-2 ) stable-weight controls (OSW, n=11) - no history of significant weight loss. The first study in Part 2 (Chapter 4) compared metabolic rate and substrate utilization in RED and REL to their respective BMI-matched controls with no weight loss history, both at rest and in response to a high fat meal challenge. Metabolic rate and substrate utilization were measured both at rest, immediately after consumption of the high fat test-meal and every hour thereafter for three hours. Dietary intake (3 x 24h recalls) and physical activity (ACTi Graph GT3X accelerometer worn for 7 days) data was collected and body composition was measured (bioelectrical impedance, BIA). Questionnaires were also completed covering weight history, socio-economic status and eating behaviour. Results showed that there was no difference in either resting EE or substrate utilization between the RED and REL compared to the respective BMI-matched controls, after accounting for fat free mass (FFM). The TEF, postprandial EE (absolute and per kg FFM), post-prandial energy balance, RER, fat oxidation rate and post-prandial fat balance were similar between RED and REL compared to their respective controls, indicating that there was no evidence of metabolic adaption to weight loss. However, successful weight-loss maintainers did show behavioural strategies that may have counteracted weight-loss associated adaptive thermogenesis and supported weight-loss maintenance. These individuals had manipulated macronutrient intake (increasing protein and reducing carbohydrate intake), were more physically active, exhibiting less sedentary behaviour and increased moderate and vigorous activity, and had greater fat free soft tissue mass (FFSTM). While the presence of adaptive thermogenesis is not disputed in these results, the distinct physiological and behavioural differences together observed in the RED may have been instrumental in attenuating weight-loss associated declines in EE, shown to persist into weight-loss maintenance. Together with these lifestyle strategies, weight reduced individuals also reported greater dietary restraint in comparison to controls. This is surprising after such a significant period of weight-loss maintenance (median weight-loss maintenance: 30 months) and highlights the ongoing challenges to maintain reduced weight. These findings contribute to the relatively smaller body of research into the longer-term persistence of weight-loss associated adaptive responses in comparison to that covering the acute weight loss phase. It also highlights strategies that may be effective in counteracting metabolic adaption to weight loss. As such, these strategies may warrant inclusion as part of weight-loss maintenance programs as they potentially help to reduce the risk for weight regain as a result of weight-loss associated adaptive thermogenesis. The next study in Part 2 of the thesis (Chapter 5) aimed to examine the impact of successfully maintained weight loss and weight-loss relapse on insulin sensitivity compared to BMImatched controls without a weight loss history. Predictors of variability in insulin sensitivity were also explored. Following the measurement of resting metabolic rate and substrate utilization a 75g oral glucose tolerance test was used to determine fasting and 2hr plasma glucose and insulin. The Homeostatic Model Assessment (HOMA-IR) and insulin sensitivity index (ISI(0,120)) were used to assess insulin sensitivity. A novel finding of this study was that successfully maintained, weight-reduced individuals displayed enhanced measures of insulin sensitivity (lower HOMA-IR and higher ISI(0,120) measurements), compared to all other groups, including BMI-matched controls with no weight loss history. Previously studies have investigated changes in insulin sensitivity in response to weight loss and in weight-loss maintenance, but not necessarily in comparison to individuals without a weight loss history as defined by this study protocol. With weight regain however, insulin sensitivity measures for REL were not different compared to either LSW or OSW, showing that enhanced insulin sensitivity accompanying weight loss is likely reversed with weight regain. Prior weight history, fasting substrate utilization, measures of body weight and composition, protein intake per kilogram, physical activity and CRF were all associated with measures of insulin sensitivity. Using these variables in regression models, ≈60% of the variability in insulin sensitivity in both HOMA-IR and ISI(0,120). Weight loss and weight regain history followed by fasting RER were the most significant independent predictors of insulin sensitivity. In conclusion, a novel finding was that successfully weight-reduced individuals are more insulin sensitive than their BMI-matched controls with no weight loss history, independent of dietary intake and physical activity. This remains evident even after significant periods of maintaining the reduced weight. Weight loss maintenance programs are essential to retaining metabolic benefits acquired through weight loss. Remaining physically active by reducing sedentary behaviour and in particular including small amounts of vigorous physical activity significantly predicts improved insulin sensitivity. This thesis includes a number of novel findings. In Part 1, we showed that in response to exercise training gynoid FM, rather than VAT, was reduced in sedentary obese black SA women undergoing a 12 week exercise intervention, which may represent an important ethnic/gender specific response. We also showed that substrate utilization plays an important role in altering body composition and CRF in response to an exercise intervention. Greater fat oxidative capacity at the outset resulted in an enhanced ability to reduce gynoid FM in response to exercise training. Furthermore, a greater reliance on carbohydrate rather than fat oxidation during baseline testing predicted a poorer CRF response. Identification of individuals with a lower capacity for fat oxidation at the outset of an exercise intervention may therefore allow for a more targeted exercise prescription, which may in turn improve outcomes of exercise interventions. The lack of clinically significant weight loss suggests that future exercise interventions should prescribe exercise EE of sufficient magnitude to achieve weight loss and emphasize adherence to this prescription or include some dietary restriction. Education around the possible adaptive responses to increased EE and the imposed energy deficit, highlighting the strategies employed by weight reduced individuals from Part 2 of this thesis, may help to attenuate potential metabolic adaption to increased EE and further improve the weight loss outcomes of exercise-only interventions. It may also help to inform weight-loss maintenance programs to assist individuals to maintain the reduced weight following weight loss. The enhanced insulin sensitivity in weight reduced individuals as shown in Part 2, may potentially represent an ongoing and persistent adaptive response to weight loss that may in itself increase the risk for weight-loss relapse. Education around the physiological adaption to significant weight loss and emphasizing strategies that may counteract this metabolic adaptation may improve the efficacy of both weight-loss and weight-loss maintenance programs.

Historically, cricketing literature has explored the disciplines of bowling and batting, with fielding receiving little attention until its importance was highlighted by the introduction of T20 matches. The novelty of this research lies in its clinically meaningful contribution to understanding shoulder injury aetiology in cricketers as overhead throwing athletes. The studies included in this thesis investigate the musculoskeletal profile of a cricketer’s shoulder, as well as the intrinsic factors associated with shoulder injury risk. Further, the influence of some of these risk factors on the cricketers’ overhead throwing biomechanics is explored and intend to improve the development of cricket-specific shoulder injury prevention programmes. An overview of the literature (Chapter 2) includes the epidemiology of shoulder injuries in cricketers; as well as a description of overhead throwing kinematics and the musculoskeletal adaptations associated with overhead throwing in cricket, compared to baseball, which has the greatest volume of throwing related studies. Based on previous outdated definitions of injury and not the current consensus definitions, shoulder injuries in cricket have been reported to occur infrequently. Various injury surveillance studies have identified time-loss shoulder injuries in cricketers, yet none have considered non-time-loss shoulder injuries. Although a limited number of studies have proposed potential intrinsic risk factors to shoulder injury in cricketers, no associations have been found. However, the cricketer’s shoulder is prone to injury due to the high forces generated while repeatedly throwing overhead during fielding. While overhead throwing biomechanics has been well investigated in baseball, minimal research exists for cricket. In addition, the understanding of throwing biomechanics in cricket has relied on two-dimensional motion analysis that is known to be insufficient for the analysis of rotational kinematics and kinetics. Elite (senior national and franchise) cricketers were recruited for this study. This study consisted of two parts. During the first part of the thesis demographic, training, competition and injury history data were obtained; and a shoulder-specific functional questionnaire and pre-season shoulder screening protocol were performed, prior to annual musculoskeletal screening. The incidence of all shoulder injuries were recorded throughout a six month cricket season. A profile of pertinent risk factors was assessed. The second part of the thesis evaluated throwing biomechanics of cricketers. Upper quarter, spinal, pelvic and hip kinematics, as well as shoulder and elbow kinetics were measured during the execution of overhead throwing from a stationary position, and with a run-up. This thesis includes three original papers and two experimental Chapters. The first paper (Chapter 3) documents the incidence of non-time-loss shoulder injuries in elite South African cricketers. Overall, the incidence of shoulder injury in cricketers during the 2016/2017 season was 18%, described as 5% time-loss and 13% non-time-loss injuries. Primary skill and fielding were negatively impacted in 100% and 80% of cricketers who sustained non-time-loss shoulder injuries, respectively. The entire cricket cohort recorded low scores on the shoulderspecific questionnaire, completed pre- and post-season, irrespective of injury history or injury sustained during the 2016/2017 season indicating a generalised reduction in the level of function in overhead activity. Paper 2 (Chapter 4) provides a description of the musculoskeletal profile of a cricketer’s shoulder which is atypical to the “thrower’s paradox” described in baseball. Specifically, cricketers present with a loss in total glenohumeral (GH) rotational range of motion (ROM), GH internal rotation deficit (GIRD) in the absence of external rotation gain (ERG); and global weakness of the rotator cuff and scapula stabilising muscles. Further, dominant shoulder supraspinatus tendon (SsT) thickness ≥5.85mm (sensitivity: 72%, specificity: 63%) and nondominant pectoralis minor length (PML) ≤12.85cm (sensitivity: 83%, specificity: 55%) predicted seasonal dominant shoulder injury (p< 0.05). From the findings indicated in Papers 1 and 2 (Chapters 3 and 4) it can be postulated that cricketers are generally a high-risk population for shoulder injury, amongst overhead throwing athletes, due to the lack of shoulder-specific musculoskeletal adaptation frequently observed in other overhead throwing populations. Paper 3 (Chapter 5) and experimental Chapters 6 and 7 investigate the kinematics and kinetics of overhead throwing from a stationary position, with a run-up and the consequence of GIRD in these two throwing approaches. A kinematic description of overhead throwing in cricket is provided and compared to baseball overhead pitching, in Paper 3 (Chapter 5). Maximum external rotation (MER) was regarded as the most critical point for potential shoulder injury in cricketers when throwing overhead from a stationary position. Further, a comparison between playing levels highlighted that amateur cricketers may display an increased risk for shoulder injury at MER as these cricketers were found to have decreased elbow flexion ROM in 2-14% of the throwing cycle (p=0.01), as well as greater shoulder (p=0.021) and elbow (p=0.043) compression and increased superior shoulder force (p=0.022) at MER, when compared to elite cricketers. Findings from experimental Chapter 6 indicate that when throwing with a run-up (dynamic) increased lumbo-pelvic (p=0.02) and hip flexion (p=0.01) occur sporadically in the throwing cycle, compared to throwing from a stationary position (static). In addition, increased shoulder compression (p=0.02) and posterior force (p=0.009) occur at MER, while reduced superior shoulder force (p=0.005) and elbow compression (p=0.03), superior (p=0.002) and medial (p=0.03) forces occur at ball release (BR), when throwing dynamically versus statically. These two Chapters highlight MER as the most critical point for potential shoulder injury in cricketers, which may further be attenuated by the absence of ERG, level of play and throwing from a stationary position while fielding. Experimental Chapter 7 investigated and highlights the potential correlations between GIRD, a frequently described risk factor for overhead athletes, and the other musculoskeletal variables measured, as well as overhead throwing biomechanics from a stationary and runup approach. Greater GIRD was associated with reduced passive hip external rotation ROM on the dominant side (p< 0.03), measured by inclinometer. In addition, increased GIRD was associated with reduced dominant hip abduction ROM during 0-23% of the throwing cycle (p=0.002), and superior shoulder force (p< 0.004) and elbow compression (p< 0.009), when throwing from a stationary position. Finally, greater GIRD was associated with increased posterior shoulder force at maximum internal rotation (MIR), when throwing from a stationary position (p< 0.013) and with a run-up (p< 0.03). These findings suggest that GIRD may negatively influence ball velocity specifically when cricketers attempt to throw overhead from a stationary position. Further, it is postulated that when throwing overhead (irrespective of approach) cricketers may overcome the mechanical insufficiency of GIRD by actively engaging the dominant hip internal rotators, to prematurely rotate the pelvis forward, in order to generate sufficient ball velocity. This may result in cricketers employing a throw across the body, which when repeatedly performed may cause hypertrophy of the dominant hip internal rotators, thereby reducing passive hip external rotation ROM. This biomechanical adaptation to GIRD may contribute to the cricketer’s predisposition for shoulder injury when throwing overhead, or may occur in an attempt to protect the shoulder against further injury. In conclusion, the inherent musculoskeletal profile of this elite cricketing cohort’s shoulder increases injury risk, particularly when throwing overhead. There is a need to investigate the influence of throwing volume, duration of season and player speciality on the musculoskeletal profile of the shoulder and concomitant injury in cricket. It is suggested that modifiable intrinsic factors found to be associated with shoulder injury and the performance of overhead throwing should be appropriately incorporated into injury prevention or pre-season conditioning programmes, to reduce the occurrence of injury. Further research should determine the efficacy of these programmes on shoulder injury prevention and throwing performance, in cricketers.