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1
Jolley, Daniel. "Misconceptions and Critical Thinking Ability In Undergraduate Exercise Science Students, Vocational Fitness Students, and Exercise Professionals". Thesis, Curtin University, 2019. http://hdl.handle.net/20.500.11937/76905.
Testo completoAbstract (sommario):
This research is the first known cross-sectional and longitudinal investigation of misconceptions and critical thinking in exercise science and fitness students and professionals. Misconceptions were higher in students than degree-qualified professionals, though there was no difference between vocational graduates and vocationally-qualified personal trainers. An online, content-specific critical thinking course was effective in reducing misconceptions and improving critical thinking ability in professionals. Critical thinking appears to be more important than specific knowledge in reducing misconceptions.
2
Bush, Jeremiah G. "Post-Exercise Hypotension in Brief Exercise". TopSCHOLAR®, 2011. http://digitalcommons.wku.edu/theses/1072.
Testo completoAbstract (sommario):
The purpose of this investigation was to examine whether a single 10 minute bout of exercise, performed at multiple intervals throughout the day to equal 30 minutes, can effectively elicit post-exercise hypotension (PEH). Secondly, it is important to explore whether a light (40% VO2R) or moderate (70% VO2R) intensity is required to elicit PEH within 10 minutes. Subjects (N=11) completed a VO2max test utilizing the Bruce Treadmill protocol. Each subject returned within 3 – 5 days to complete two separate exercising trials. A counter balanced system was employed so that each subject did not perform the same intensity rotation (Counter Balance 1 = 40% VO2R and 70% VO2R for session 1 and session 2, respectively; Counter Balance 2 = 70% VO2R and 40% VO2R for session 1 and session 2). The first session consisted of 3 sessions (morning, noon, evening) separated by an average of 3.5 hours at one of two intensities (40% VO2R or 70% VO2R). The second group of sessions were performed identical to the first, however, the intensity was altered depending upon counter balance. Baseline BP was measured prior to exercising. After each session, BP was measured at 2 intervals for the morning and noon sessions (immediately following and 20 minutes post-exercise); and at 3 intervals for the evening sessions (60 minutes post-exercise added) for both intensities. At 40% VO2R, BP decreased significantly at the morning (p = 0.007), noon (p = 0.018) and evening (p = 0.010) sessions at the 20 minute post-exercise interval. Although not significantly different, BP was observed to be lower at 60 minutes post-exercise interval. During the 70% VO2R session, BP was significantly lower at the morning 20 minute (p = .029) and evening 60 minute post-exercise measurements (p = .006) when compared to baseline. There was no significant difference noted between 40% and 70% VO2R intensities at eliciting a drop in BP at any interval at any time point. Although not statistically significant, 70% VO2R appeared to produce a further decrease at the 60 minute post-exercise measurement (102 mmHg) than did the 40% session (106 mmHg). The results of this study indicate that PEH may be elicited after a single 10 minute exercise session. Furthermore, multiple bouts of 10 minutes produce an accumulated decrease in BP that can be observed at the completion of the day.
3
Aguilera, Lorri Castro. "Exercise and dietary habits of high school, health science students". CSUSB ScholarWorks, 1995. https://scholarworks.lib.csusb.edu/etd-project/997.
Testo completo
4
Nelson, William Bradley. "Exercise Induced Hypervolemia: Role of Exercise Mode". Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd2128.pdf.
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5
Stone, Michael H. "What is Sport Science?" Digital Commons @ East Tennessee State University, 2009. https://dc.etsu.edu/etsu-works/4578.
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6
Stone, Michael H. "What Is Sport Science". Digital Commons @ East Tennessee State University, 2010. https://dc.etsu.edu/etsu-works/4536.
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7
Stone, Michael H. "What Is Sport Science?" Digital Commons @ East Tennessee State University, 2011. https://dc.etsu.edu/etsu-works/4543.
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8
Walshe, Ian. "The effect of manipulating the IL-6 response to exercise on biomarkers and exercise performance". Thesis, Northumbria University, 2012. http://nrl.northumbria.ac.uk/10131/.
Testo completoAbstract (sommario):
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.
9
Jin, Wei-Hua. "Improving the environmental situation in China : an exercise in social science". Thesis, University of Lincoln, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393069.
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10
Richardson, Laura A. Ph D. "Weightism: An Exploration of University Exercise Science Students' Views of Obesity". University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1460644039.
Testo completo
11
Gibbon, Karl. "Lumbopelvic muscle function during low impact weight-bearing exercise : development of the functional re-adaptive exercise device". Thesis, Northumbria University, 2017. http://nrl.northumbria.ac.uk/32567/.
Testo completoAbstract (sommario):
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.
12
Sieracki, Joseph R. "RELATIONSHIPS BETWEEN DIET, EXERCISE, AND LEARNING IN THE REGULAR SCIENCE CLASSROOM SETTING". Cleveland State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=csu1401190547.
Testo completo
13
Mahn, Nathan A. (Nathan Aaron) 1979. "A new 6.111 laboratory exercise : Mastermind". Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/87427.
Testo completoAbstract (sommario):
Thesis (M.Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003.Includes bibliographical references (leaf 55).
by Nathan A. Mahn.
M.Eng.and S.B.
14
Mullineaux, David Ross. "Issues in the application of statistical techniques in sport and exercise science". Thesis, Sheffield Hallam University, 2002. http://shura.shu.ac.uk/20766/.
Testo completoAbstract (sommario):
The aim of this research is to demonstrate the benefits and limitations of selected techniques used to analyse data derived from , sport and exercise science research. Although statistical techniques are easy to access through software packages, supporting literature about their appropriate application is less common. Many researchers are unaware of the full benefits or potential pitfalls when using these techniques. An understanding of the appropriate use of statistics will benefit the researcher by maximising the potential for analysing, interpreting and applying data correctly. Furthermore, it will minimise wasted effort or dissemination of inaccurate information through incorrect analyses. In this thesis examples are derived from fifteen published articles based on five topics that illustrate the appropriate use of particular statistical techniques. Firstly, the use of 'agreement' and 'least-products-regression' as appropriate techniques for comparing repeated measures are demonstrated (e.g. Mullineaux et al., 1999). Both techniques revealed that over two separate days the peak-torque-extension of the knee of healthy females is unreliable. Secondly, the use of 'allometric' scaling of body size differences that should allow for meaningful comparisons between participants' measurements is explored (e.g. Batterham, George and Mullineaux, 1997). Results showed that left ventricular mass is related to fat free mass to the power of 1.07 (0.92 to 1.22; 95% Cl). Thirdly, mathematical modelling is used to explore a theory that would be difficult to test empirically (e.g. Payton, Hay and Mullineaux, 1997). Results revealed that body roll contributes substantially to the propulsive force in front crawl swimming. Fourthly, logistic regression is used to predict group membership from the combined effect of several independent variables (e.g. Mullineaux et al., 2001a). It was found that the likelihood of participation in adequate physical activity to promote health can be strongly predicted from six variables. Lastly, in an invited review paper, key features in the application of research methods and statistics in biomechanics and motor control are highlighted (e.g. Mullineaux et al., 2001b). These published papers form a body of work that will facilitate a greater and more appropriate use of selected statistical techniques in sport and exercise science.
15
Sulzer, Nicole Uschi. "Exercise associated muscle cramping : investigating a novel hypothesis". Master's thesis, University of Cape Town, 2003. http://hdl.handle.net/11427/26321.
Testo completoAbstract (sommario):
This thesis on Exercise Associated Muscle Cramping (EAMC) comprised three individual studies. The aims of this series of investigations were firstly to investigate the nature and prevalence of EAMC in a group of lronman triathletes with a past history of EAMC, secondly to compare the serum electrolyte concentrations in cramping and control Ironman triathletes as well as to record the baseline electromyography (EMG) of cramping lronman triathletes during recovery and thirdly to compare the EMG activity of cramping and control runners before, during and after a fatiguing bout of exercise.
16
Nelson, Mara Hendricks. "A pilot study to examine a therapeutic exercise intervention on fibromyalgia symptoms". BYU ScholarsArchive, 2006. https://scholarsarchive.byu.edu/etd/398.
Testo completoAbstract (sommario):
Objective. To examine the feasibility of a home-based, video therapeutic exercise program on pain, fatigue, self-efficacy, and health status in fibromyalgia patients. Methods. Nine individuals who were previously diagnosed with fibromyalgia completed the study (out of an initial pool of 31). Subjects were randomly assigned to one of two groups: a group who received a home-based therapeutic exercise video and a control group who continued to undergo their current standard of care or "treatment-as-usual." The video group was instructed to conduct the exercises as prescribed in the 42-minute video at least 3 times per week for 4 weeks. The treatment-as-usual control group was instructed to continue to undergo their current standard-of-care and to not begin any new treatments during that time. Instruments measuring self-efficacy, pain, fatigue, self-rated health status and health distress were administered at baseline and 4 weeks. Results. None of the variables analyzed showed a significant change between the treatment and control groups over the course of the 4-week study. Conclusion. This study was not sufficiently powered to detect differences between the two groups. However, several of the treatment group participants subjectively indicated that they found the exercises to be helpful in the management of their fibromyalgia symptoms and the program did not exacerbate any of their symptoms. With this information, it appears that patients are able to tolerate the treatment and are able to complete the outcome measures. Between-group clinical outcomes will now need to be assessed in a larger clinical trial.
17
Littrell, Ashley. "The Relationship Between Body Image and Exercise Type". Digital Commons @ East Tennessee State University, 2017. https://dc.etsu.edu/honors/366.
Testo completoAbstract (sommario):
Exercise can have very beneficial effects on health and body satisfaction, but sometimes a negative body image gets in the way of exercising. Modern society holds certain beauty ideals in high regard, and these standards are often unattainable and unrealistic. These outside pressures to look a certain way can have a very negative effect on an individual’s body image, or the way that a person perceives his or her own appearance. There have been many studies done that have attempted to define the relationship between body image with exercise behaviors (Burger and Diony 2002, Hall and Pearson 2013). Some studies have shown that a negative body image is related with higher prevalence of exercise, while others have shown that a negative body image is a major barrier to participation in exercise at all (Berry, McHugh, and Pankratow 2013, Burger and Diony 2002, Gammage and Lamarche 2012, Hall and Pearson 2013). While the data from these studies has shown different relationships, there is an abundance of research on the topic. There is a lack of information, however, on the relationship between body image and exercise type. This study focused on this relationship in an attempt to determine if body image, positive or negative, had any effect on what type of exercise activities an individual chose to participate in. A total of 70 undergraduate college students were surveyed using a 9 question health and exercise questionnaire and a 6 question body image survey, written and published by Thomas Cash and previously utilized in other body image survey studies (Cash, et al. 2002). The data collected was analyzed using chi-square tests and a significant correlation between body image and exercise type, as well as body image and gender. Participants with a negative body image reported a preference for aerobic exercise while those with a positive body image preferred anaerobic exercise. The analysis also found that females were more likely to have a negative body image than males, which supports previous research trends (Burger and Diony 2002). This study only surveyed 70 individuals, and so the results can not necessarily be generalized to the entire population. Further research could include a larger sample size so as to find a more generalizable relationship between body image and exercise type.
18
Van, Breda Keelyn. "The influence of methylphenidate on heart rate and brain connectivity". Doctoral thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/27818.
Testo completoAbstract (sommario):
The central governor model (CGM) proposes that muscle recruitment is regulated by the brain through subconscious homeostatic control of afferent feedback. It has been suggested that the dopaminergic system plays a key role in the CGM, with dopaminergic activation leading to lower fatigue thresholds. Key neural circuits, including the central autonomic network (CAN), may also play a role in altering thresholds by reducing conscious bodily awareness, known as interoception. However, few studies have directly examined the dopaminergic neurotransmitter system and CAN connectivity, during exercise-induced fatigue. Although there is reason to suspect that subjects with high activity (HA) and low activity (LA) levels have different fatigue thresholds, potential differences in dopaminergic function and related circuity have not been compared across these groups. In this thesis, I was therefore interested in examining the impact of a dopaminergic agent, methylphenidate (MPH) on: a) brain connectivity at rest before exercise and during exercise, b) on heart rate (HR) at rest before exercise and during exercise. Furthermore, c) I was interested in whether the effect of MPH administration (MA) on HR and functional connectivity (FC), between CAN regions, pre-exercise impacted HR and FC during exercise and whether this differed between HA and LA subjects. In order to measure the effect of MA on brain connectivity at rest and during exercise I used a functional magnetic resonance imaging (fMRI) scanner. To measure the effect of MA on fatigue thresholds, I used a MRI compatible handgrip device which recorded grip force output during a fatiguing handgrip task. To measure HR before and during handgrip exercise I used a MRI compatible electrocardiogram (ECG) machine. My first study aimed to determine the effect of MA on resting state (R-fMRI) FC between CAN regions and its correlation with HR before exercise. My second study aimed to see the effect of MA on task HR, force output and, FC and EC between CAN regions, during a fatiguing handgrip task. My third study aimed to see the effect of MA on the relationship between HR and FC pre-exercise and HR and FC during exercise and whether this differed between LA and HA subjects. I found that: 1.) MA decreased R-fMRI FC between CAN regions, and that this was associated with an increase in HR during resting state 2.) MA decreased FC between CAN regions with an associated increase in task HR and force output during a fatiguing handgrip task 3.) After MA, R-fMRI FC determines task FC independent of HR 4.) MA significantly increased task HR in LA but not HA subjects 5.) After MA, R-fMRI FC determines task FC independent of HR in LA but not HA subjects. Taken together, the functional uncoupling of CAN regions and increased HR after MA suggests that MA increases the fatigue threshold by diverting attention away from interoceptive cues, such as HR. However, this finding may be more relevant in LA subjects, where MA is also associated with increased HR during exercise.
19
Wulfsohn, Jason. "The agreement, reliability and accuracy of a subjective-rating for technique measurement in rugby union after video-based training". Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29227.
Testo completoAbstract (sommario):
Background: Rugby union is a high-intensity, intermittent sport, characterised by numerous contact events, such as rucks, mauls, scrums, and tackles. Specifically, the tackle is the most common action to occur during a rugby game. Subsequently, the tackle (tackler and ballcarrier) is responsible for the highest number of total injuries during a season. The most effective tackle technique is associated with a lower risk of injury than poorly executed tackles. Considering the prevalence of tackles, their propensity to cause injury, and the link between safety and proper tackle technique, a tool for assessing individual tackling and ball-carrying technique would be useful for rugby union researchers and practitioners. In particular, the assessment of tackling and ball-carrying technique would aid in monitoring adaptations to training, evaluating training programs and the prescription of training, assessing player qualities, and predicting performance and identifying future talent.
Objectives: The primary objectives of this study were 1) to determine if undergoing videobased training would improve the agreement, reliability, and accuracy of raters using a subjective-rating measure to assess contact technique in rugby union, and 2) to establish if a self-selected viewing pace resulted in improved agreement, reliability, and criterion-validity over a real-time pace.
Methods: Data were collected from 30 participants, with no prior experience in rugby union, who were randomly divided into training and non-training groups. After completing the training or non-training visits, all participants conducted tackling and ball-carrying technique assessments in 4 subsequent visits. Participants viewed video footage of players tackling and carrying the ball into contact during a full contact rugby drill on a laptop computer. Participants assessed tackling and ball-carrying technique using the standardised list of technical criteria. Technical proficiency scores were calculated out of 12 for tackling technique and out of 10 for ball-carrying technique, respectively. Agreement and reliability of the assessments were measured using the proportion of observed agreement (Po) and Kappa statistics (K). Criterion validity (accuracy) was measured using the proportion of observed agreement (Po) by comparing the raters’ assessments to a criterion. Between groups comparisons for technical proficiency scores and accuracy were done with hypothesis testing and effect sizes.
Results: Over the real-time and self-selected paces, the training group produced 61-73% (K=0.24-0.38, Fair) and 63-73% (K=0.12-0.17, Poor) inter-rater agreement for tackling and ball-carrying technique, respectively. The non-training group produced 61-72% (K=0.26-0.38, Fair) and 59-71% (K=0.15-0.19, Poor) inter-rater agreement for tackling and ball-carrying technique, respectively. Including both real-time and self-selected paces, the within session intra-rater agreement for the training group ranged from 71-84% (K=0.43-0.65, Moderate-Substantial) and 74-83% (K=0.39-0.48, Moderate) for tackling and ball-carrying technique assessment, respectively. Then, the intra-rater agreement for the non-training group ranged from 68-83% (K=0.40-0.62, Fair-Moderate) and 67-84% (K=0.31-0.55, Fair-Moderate) for tackling and ball-carrying technique assessment, respectively. In terms of between session reliability, over the real-time and self-selected paces, the training group achieved intra-rater reliability that ranged from 74-83% (K=0.50-0.62, Moderate-Substantial) and 72-82% (K=0.35- 0.45, Fair-Moderate) for tackling and ball-carrying technique assessment, respectively. The non-training group achieved intra-rater reliability ranging from 72-82% (K=0.46-0.59, Moderate) and 69-81% (K=0.33-0.48, Fair-Moderate) for tackling and ball-carrying technique assessment, respectively. The technical proficiency scores between the groups displayed variation, and in some cases it was statistically significant. Compared to the criterion scores, the training group produced observed agreement of 68% and 67% for real-time pace and 74% and 72% for self-selected pace on tackling and ball-carrying technique assessment, respectively. The non-training group produced observed agreement of 66% and 67% for realtime pace and 74% and 73% for self-selected pace on tackling and ball-carrying technique assessment, respectively.
Conclusion: Whether trained or untrained, the individual should be able to produce the same results if the footage is assessed within the same viewing period (agreement) or over two separate viewings (reliability). The tool is accurate for both groups when assessing at real- time or self-selected paces, with the latter being more accurate. However, it would appear that the tool is insufficiently robust when it comes to agreement between different raters. Future research should explore the inter-rater dynamics of assessing tackling and ball-carrying technique.
20
Hume, David John. "Mind the gap: brain-behaviour barriers to successful weight loss maintenance". Doctoral thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/20254.
Testo completoAbstract (sommario):
The primary objectives of this dissertation were to investigate the behavioural and neurophysiological factors related to overweight and obesity, as well as to weight loss maintenance versus weight relapse in a purposively sampled group of healthy South African women. The battery of investigations was designed to explore two central hypotheses: First, weight loss induces several behavioural compensations related to habitual eating behaviour and daily physical activity (PA) practices which facilitate the generation of a chronic positive energy balance, thereby increasing the risk of weight regain in reduced-overweight and reduced-obese women. Second, overweight and obese women as well as those at risk of undergoing relapse exhibit heightened indices of visual food cue-reactivity in various regions of the brain associated with obesogenic eating and reward-seeking tendencies. The novelty of this thesis lies in that we ascertained dietary, PA and psychobehavioural variables through both subjective accounts and objective measurement. Moreover, we employed electroencephalography to objectively evaluate high resolution temporal changes in visual food cue processing to test our second hypothesis. Overweight and obesity treatments focus, for the most part, on dietary- and/or exercise-centred interventions to facilitate weight loss. Our data suggest that certain interaction effects exist between the perception of environmental food cues and variables such as dietary restraint, habitual fat intake, body shape dissatisfaction and total body adiposity
[Note: this thesis is embargoed until 30 November 2016]
21
Taliep, Mogammad Sharhidd. "An investigation into the kinematic, cortical electrical and visual search strategies of skilled and less-skilled cricket batsmen in response to projected video footage of a medium-fast bowler". Doctoral thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/2768.
Testo completoAbstract (sommario):
Includes abstract.Includes bibliographical references (p. [212]-228).
The aim of this dissertation was to investigate various systems affecting performance in skilled and less-skilled batsmen. These systems included kinetics, visual perception, psychophysiology and visual tracking. Individual chapter abstracts have been presented because of the multifaceted nature of this dissertation.
22
Azevedo, Liane. "Risk factors for Achilles tendinopathy in runners - an investigation of selected intrinsic, kinematic, kinetic and muscle activity factors that are associated with Achilles tendinopathy". Doctoral thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/2772.
Testo completoAbstract (sommario):
The overarching purpose of this study was to investigate the multifactorial aetiology of Achilles tendinopathy. Variables such as training and injury history, lower limb alignment, running biomechanics and movement variability were investigated. This study also aims to understand how different sensory inputs, such as shoe or pain may affect biomechanics. Thirty four uninjured runners (UN) and twenty one runners with Achilles tendinopathy (AT) composed the population sample for this study. Questionnaire and lower limb measurements were used to investigate the multifactorial aetiology of the injury. Selected kinetic, kinematic and muscle activity parameters were employed to analyse the biomechanics aetiology of the injury. Runners performed 10 running trials at a self-selected speed in two running shoes with different hardness. Additionally, the UN runners ran for 10 min on the treadmill while the AT runners ran on the treadmill until they developed pain in the Achilles tendon. The results of the study showed that AT runners have a higher incidence of previous injury, run for more years, have reduced hamstring flexibility, and are heavier and taller than uninjured runners. The study also showed a reduced integrated electromyography activity (IEMG) of tibialis anterior and rectus femoris in the AT group during the running cycle. Stride to stride variability was similar between UN and AT runners but the biomechanics variability between participants were lower for the AT runners. No specific biomechanical adaptations were found between the two different shoe conditions (soft vs. hard). Similarly, biomechanics parameters were not altered at the onset of pain, but the reduced IEMG activity of tibialis anterior and rectus femoris were presented before and during the pain condition. It can, therefore, be concluded that runners with Achilles tendinopathy present reduced muscle activity during running which may be either a novel aetiological factor, or an adaptive response to the injury. The lower variability between runners with AT may indicate that these runners are less able to adjust their biomechanics according to their different functional behaviour or external input signals but this may require further investigation. Finally, it can also be concluded that the sensory inputs such as shoes and pain do not change this muscle activity pattern.
23
Runciman, Phoebe Anne. "Performance and fatigue charateristics of paralympic athletes with cerebral palsy". Doctoral thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/20269.
Testo completoAbstract (sommario):
Includes bibliographical referencesThe studies described in this thesis were the first to investigate in - depth body composition, exercise performance and neuromuscular characteristics of elite Paralympic athletes with cerebral palsy (CP). In the first study, in - depth whole body and site specific body composition was investigated in six athletes with CP using dual - energy x - ray absorptiometry. There were no differences between non - affected and affected sides with respect to bone mineral density and fat mass. Fat free soft tissue mass was lower on the affected side in bot h upper and lower limbs of the athletes. The novel findings of this study provided the first insight into anthropometric and bone physiology of elite Paralympic athletes with CP, and the possible residual effect of CP in these individuals. In the second study, five athletes with CP and 16 able - bodied (AB) age and performance matched controls performed a 30 second Wingate sprint cycle test. Power output was significantly higher in the AB group, although fatigue indices were statistically similar between groups. Muscle activity changed similarly in all muscle groups tested, in both affected and non - affected sides, in both CP and AB groups. However, certain neuromuscular irregularities were identified in the CP group. The similarity in fatigue profile was a novel finding. It was proposed that this similarity in fatigue was the result of long term high level athletic training required for Paralympic competition. Study three tested the similarity in fatigue between CP and AB athletes (that was described in the second study), using an externally paced fatiguing running trial. Six athletes with CP and 12 AB athletes performed one 40 m sprint test and vertical jump tests off both legs, the affected leg individually and the non - affected leg individually, before and after an adapted multistage shuttle run test to exhaustion. The 40 m sprint test, vertical jump off both legs and vertical jump off the affected leg were significantly compromised in the CP group, while vertical jump off the non - affected leg was similar between groups. Both groups fatigued similarly with regard to performance and muscle activity. The third study's finding s generally supported those of the second study. However, it was shown that although athletes with CP may represent a group of individuals who have achieved maximal physiological adaptation toward AB levels, the activity generated by both legs was performed towards the capacity of the affected leg. Study four attempted to elucidate explanations for the novel findings in studies 2 and 3 through investigation of pacing strategies employed by these athletes. Six athletes with CP and 13 AB athletes performed two trials of eight sets of ten shuttles (totalling 1600 m). One trial was distance deceived and the other was non distance deceived. The CP group ran slower than the AB group in both trials, and differences in pacing were observed in the deceived trial in the CP group. This novel study provided evidence for a possible pacing strategy underlying the exercise performance and fatigue profiles observed in the athletes with CP documented in the previous studies. The work described in this thesis lends novel insights and understanding to the physiology and physiological adaptations of highly functioning ambulant athletes with CP. The findings might have important implications with respect to the understanding of rehabilitation, coaching and clinical management of individuals with CP.
24
O’Connell, Kevin Sean. "Investigation of selected collagen genes in exercise-related musculoskeletal soft tissue phenotypes". Doctoral thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/12960.
Testo completoAbstract (sommario):
Includes bibliographical references.Previous findings have suggested that functional variants within collagen encoding genes are associated with several musculoskeletal soft tissue injuries and other exercise-related phenotypes. Specifically variants within the functional COL5A1 3’- untranslated region (UTR) have previously been associated with (1) chronic Achilles tendinopathy, (2) Anterior Cruciate Ligament (ACL) ruptures in females, (3) endurance running performance and (4) range of motion (ROM). Since this gene encodes for an important structural component of the collagen fibril it has been hypothesised that variants within other collagen fibril encoding genes, such as COL3A1, COL6A1 and COL12A1, will also be associated with these and/or other musculoskeletal soft tissue injuries and exercise-related phenotypes. The COL5A1 rs12722 and COL12A1 rs970547 gene variants have been previously associated with risk of ACL ruptures in females [153;154] and/or chronic Achilles tendinopathy [131;181]. The first aim of this thesis was therefore to investigate the COL3A1 rs1800255 and COL6A1 rs35796750 gene variants as risk factors for these musculoskeletal soft tissue injuries.
25
Dove, Mary Ann. "Socio-ecological factors in talent development in cricketers in a diverse society". Doctoral thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29800.
Testo completoAbstract (sommario):
Introduction: In recent years, there has been a move to understand the environment and context in which athletes develop. South Africa’s unique context provides an opportunity to understand how environmental factors could influence talent development in cricket. Since democracy, there has been limited representation of Black African cricketers at the elite levels in South Africa. Therefore, the aim of this thesis was to determine the role that socio-ecological factors may play in the development of cricket talent in a diverse society. Methods: Qualitative research methods were used to explore the experiences and perceptions of South Africa’s male cricketers as they progressed through the talent pathway from exposure to the game to the elite level. The perceived effectiveness of the introduction of an ethnic target policy was also explored. Seventy-one semi-structured interviews were conducted with a purposive sample of players from all ethnic groups (n=43), and with knowledgeable and experienced key informants (n=16). A thematic analysis of the data resulted in the identification of themes which are presented using a multi-level socio-ecological framework. Results: All players progressed to the elite level; however, their access points to and routes through the pathway varied. This progress was influenced by the inter-relationship of distal and proximal socio-ecological factors that they experienced during their cricketing careers. These influences can be summarised into five talent development components that acted either as barriers or enablers to progress: (1) access to opportunities and competition, (2) holistic player development, (3) effective support networks, (4) inclusive team environments, and (5) adaptive mind-sets. In addition, various intrapersonal characteristics were identified that further affect a player’s ability to achieve elite cricketing success. Finally, it was determined that an ethnic target policy alone is not an effective intervention for developing cricket talent in a diverse society undergoing transition. Conclusion: A socio-ecological framework to talent development lends additional support to the idiosyncratic, multifactorial, dynamic and complex way in which cricket expertise is achieved, particularly in diverse societies. It provides stakeholders involved in the talent development process with evidence to inform policy and practice, as well as design effective interventions.
26
Tam, Nicholas. "Towards an improved understanding of the biomechanical implications and risk of injury of barefoot running". Doctoral thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/12998.
Testo completoAbstract (sommario):
Includes bibliographical references.Barefoot running is a subject of significant interest, both in scientific publications and in the lay media as a result of its alleged benefits for runners. These benefits include the potential to reduce injury risk, more economical running and broadly speaking, a better understanding of running biomechanics. Although there are numerous scientific publications describing differences between barefoot and shod running, there is a dearth in understanding whether all runners are able to adapt to the proposed benefits and how this may affect long-term injury risk. Thus, we sought to investigate the biomechanical, neuromuscular and metabolic changes associated with habitually shod runners during the transition to pure barefoot running over an 8- week progressive training programme. This thesis begins with a critical review of the literature, which evaluates the theories and evidence for barefoot running, as well as describing the necessary future research to confirm or refute the barefoot running hypotheses. Our first study aimed to describe acute changes occurring in habitually shod runners when first exposed to barefoot running. We were particularly interested in the variability in response, and whether we could identify factors that predicted potentially favourable changes in kinematic and kinetic outcomes. Fifty-one runners were recruited and assessed using a 3-D motion capture system and integrated force platforms using conventional methods. We found that loading rate was significantly greater in the barefoot condition, but that high individual variability existed, particularly in the barefoot trials. We found that an increase in ankle dorsiflexion is associated with an increase in initial loading rate when in the barefoot condition, supporting previous findings in this regard. We then performed a supervised, pure barefoot running training programme, over 8 weeks, to determine whether the biomechanics of barefoot running would adapt gradually to habituation. Twenty-three runners were recruited for participation, and performed comprehensive biomechanical and neuromuscular assessments before and after the 8-week programme. The first finding was runners do not adapt similarly to barefoot training, and that biomechanics do not change significantly over the 8-week period. High variability in ankle kinematics and loading rate were found, with three sub-groups identified, namely positive responders (reduced loading rate after training), non-responders (no change in loading rate) and negative responders (increase in loading rate after training). We found significant associations between initial loading rate the changes in ankle flexion angle at initial ground contact, presumably as a result of its influence on footstrike. This finding suggests that conscious instruction might be necessary in order to achieve reductions in collision forces during barefoot running. With respect to neuromuscular variables, a persistently higher gastrocnemii muscle preactivation was found in the barefoot condition before and after the training intervention. Increased gastrocnemius pre-activation was associated with lower initial loading rate. An increase in gluteus medius and peroeus longus and a decrease in tibialis anterior pre-activation were also associated with a reduction in initial loading rate after barefoot training. This finding suggests a refined neuromuscular activation strategy prior to ground contact in the barefoot condition to stabilize the hip and centre of mass. Lastly, oxygen cost of transport was found to improve as a result of the barefoot training programme in the male runners and this improvement was found to be associated with a decrease in ground contact time and increase in stride frequency, but no a change in ankle flexion angle at initial ground contact. The outcomes from this thesis elucidate the highly variable response of individuals to barefoot running. This advises individuals choosing to transition to barefoot running to do so with caution. With this in mind, we suggest certain characteristics that may be used as screening mechanisms to indicate individual suitability to barefoot running based on the “collision force theory”. Further, benefits associated with barefoot running other than varied responses in initial loading rate such as improvements in oxygen cost of running are pre-dominantly hypothesised to be a result of musculo-tendinous adaptations, neuromuscular strength and motor control.
27
Noakes, Timothy. "Collected studies". Doctoral thesis, University of Cape Town, 2002. http://hdl.handle.net/11427/13969.
Testo completo
28
Huchu, Linet. "The association between cardiorespiratory fitness and performance in a submaximal stepping test standardised for external workload". Doctoral thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/22962.
Testo completoAbstract (sommario):
Submaximal step tests are used to predict maximal oxygen consumption and work capacity. However, if the external workload is not controlled the interpretation of the test results may be inaccurate. The purpose of the research was to develop a submaximal test of cardiorespiratory fitness using a novel step test designed specifically to overcome the weaknesses of the previously published step tests. A series of studies contributed to the theoretical development of the submaximal step protocol, piloting the protocol, reliability studies, validation of the protocol and finally a cross-validation of the protocol. The first study tested the hypothesis that stepping tests configured for the same external workload, but varying in stepping frequency, elicit the same physiological stress. Participants (n = 31) performed three step tests at 16, 20 and 24 steps per minutes in random order. External workload was standardised at 45 kJ. Energy expenditure, heart rate recovery, rating of perceived exertion, maximum heart rate and total heart beats were significantly different between tests (p < 0.05) with the biggest differences occurring between 16 and 24 steps per minute. Maximum heart rate as a percentage of age predicted heart rate increased from 70% at 16 steps per minute to 81% at 24 steps per minute. The study concluded that standardisation of external workload with different exercise intensities does not result in the same physiological responses. The second study tested the reliability of the step test. Participants (n = 34) performed a step test three times in a week at a cadence of their choice (16, 20 or 24 steps per minute). The study showed that the step test is repeatable for most variables measured and therefore is a reliable test of fitness. The third study used the outcome variables measured during the step test to develop equations which predicted VO₂max measured directly in a maximal test on a treadmill. A diverse sample of participants (n = 273), differing in sex, level of habitual physical activity and age were recruited for the study. Several models for predicting VO₂max were determined. The most parsimonious equation was: VO₂max (ml.kg⁻¹.min⁻¹) = -0.10911 (age) - 0.06178 (body mass) - 0.75481 (body fat %) +0.00208 (METS) + 0.11636 (HRR) - 0.019551 (MHR) + 0.07955 (Av HR) + 83.34846 (R² = 0.75, standard error of estimate = 5.51 ml.kg.min⁻¹) where METS is metabolic equivalent, HRR is heart rate recovery, MHR is maximum heart rate and Av HR is average heart rate. Cross validation was done (n = 50) to test the accuracy of the prediction equation. The relationship between the predicted VO₂max and the measured VO₂max was r = 0.87. In conclusion the standardised step test can predict VO₂max in a heterogeneous population of males and females, varied ages (20 to 60 years), physical activity levels and fitness levels.
29
Noorbhai, Mohammed Habib. "The batting backlift technique in cricket". Doctoral thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/24908.
Testo completoAbstract (sommario):
The batting technique in cricket consists of various elements such as the grip, stance, backlift, downswing, impact with the ball and follow through. Whilst there has been an extensive amount of research into these batting elements, there is little research specifically on the backlift technique. Therefore, we aimed to investigate and provide a scientific understanding of the batting backlift technique (BBT) in cricket. We aimed to investigate the BBT of the most successful batsmen (n = 65) in the last 120 years as well as players in the Indian Premier League (IPL) (n = 30). It was found that these batsmen did not conform to the current cricket coaching method that advocates a straight batting backlift technique (SBBT). Instead, 77% of successful batsmen and 90% of IPL batsmen employed a lateral batting backlift technique (LBBT) in which they lifted their bats in the direction of second slip or beyond with the bat face towards the off-side. Using this technique, both the toe of the bat and face of the bat points directly towards the off-side (usually between slips and point). The number of players using the LBBT was significantly greater than those using the SBBT (χ2 = 19.2, df = 1, p < 0.001). Given these findings, we were curious to determine whether this finding was similar at other levels of cricket. The second study therefore employed biomechanical and video analyses to evaluate the BBT of current semi-professional, professional and international cricketers (n = 155) from South Africa and the United Kingdom. The backlift of these batsmen was then compared to their career statistics. It was found that a LBBT is more prevalent at the highest levels of the professional game and a likely contributor factor for successful batting at the highest level (p≤0.05). The LBBT was also found to positively affect other components of the batting technique such as the stance and scoring areas. We then proceeded to investigate the BBT amongst the lower levels of cricket (junior and adolescent cricketers). The third study consists of an intervention study that employed a biomechanical analysis of coached and uncoached cricketers (n = 80). It was found that more than 70% of uncoached cricketers adopted a LBBT, whereas more than 70% of coached cricketers adopted the SBBT. Having found that the LBBT is a likely contributing factor for past and current successful batsmen, it was then important to understand what BBT the current cricket coaches are teaching at various proficiency levels. The fourth study explored the teachings of the BBT among international cricket coaches (n = 161) using a mixed methods approach through an online evaluation survey. This study was able to show that a majority of cricket coaches teach what is advocated in coaching manuals and mostly coach the SBBT as opposed to the LBBT at various levels of the game. In the fifth and sixth studies, this thesis further describes two innovative coaching tools that can improve and assist with the coaching of the LBBT. Firstly, a novel coaching cricket bat was investigated through a pilot and intervention study. In the pilot group, cricketers using the coaching bat scored approximately 1 more run per ball or an average of approximately three more runs in total when using the coaching bat than the normal bat (F = 6.70, df = 1, p = 0.012). In the intervention study, the experimental group scored double the total number of runs (an additional 16 runs) and an average of approximately 3 more runs per player in the post-match than in the pre-match, which showed a large effect (ES = 5.41) (t = 3.32, df = 5, p = 0.021). The coaching cricket bat might be used to coach young cricket players to hit the ball more effectively as well as how to adopt a more LBBT. Secondly, a mobile application was developed, which can be used by players, coaches and scientists to analyse and improve the BBT among cricketers at all levels. In summary, this thesis has shown that the LBBT is a likely contributing factor to successful batsmanship at all levels of cricket ability (junior cricketers, adolescent cricketers, semi-professional cricketers, professional cricketers, international cricketers and former elite/successful cricketers). Coaching a LBBT to young batsman may be challenging and therefore a coaching cricket bat has been developed and has shown to be a promising training aid for coaching the LBBT to young cricketers. A mobile application has also been designed and tested to assist in the coaching of the BBT in cricket. A way forward for further research in this area of cricket batting is documented at the end of the thesis.
30
Smith, James Antony Harris. "Exercise-induced protection against insulin resistance and type 11 diabetes : the role of calcium". Doctoral thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/2767.
Testo completoAbstract (sommario):
Includes abstract.Includes bibliographical references (p. 89-106).
Regular exercise protects individuals against developing insulin resistance and type II diabetes. This effect of exercise does not appear to be due to an improvement in the insulin signalling pathway but instead due to an increase in the content of the insulin-regulatable glucose transporter (GLUT4) in skeletal muscle (84). Understanding the mechanisms by which exercise increases GLUT4 levels in skeletal muscle may reveal targets for pharmaceuticals to treat insulin resistance and type II diabetes. Although in vitro binding assays have shown that GLUT4 expression during exercise is mediated by the binding of myocyte enhancer factor-2A (MEF2A) to its cis-element on the Glut4 promoter (122), this has not been demonstrated in vivo. Moreover, the mechanisms by which exercise increases MEF2A binding to the Glut4 promoter have not been fully characterised.
31
Burgess, Theresa Lee. "Cardiorespiratory, kinematic, neuromuscular and metabolic characteristics during the recovery period after an ultramarathon race". Doctoral thesis, University of Cape Town, 2009. http://hdl.handle.net/11427/2746.
Testo completoAbstract (sommario):
Includes abstract.Includes bibliographical references (p. 325-399).
The aim of this study was to investigate the effects of exercise-induced muscle damage caused by a 90 km ultramarathon on submaximal oxygen consumption and stride length. The experimental group consisted of 11 male runners (39.7 ± 9.3 years) competing in a 90 km ultramarathon. Ten male runners (41.0 ± 10.8 years) who did not run the 90 km ultramarathon formed the control group. Maximum oxygen consumption and peak treadmill running speed were measured two weeks before the ultramarathon. Daily measurements of muscle pain and plasma creatine kinase (CK) activity were recorded for seven days after the ultramarathon. Muscle pain, plasma CK activity, and blood lactate concentrations were recorded before, and oxygen consumption, respiratory exchange ratio (RER), heart rate, rate of perceived exertion (RPE), and stride length were all measured during a 15-minute submaximal treadmill test seven days before the ultramarathon, and on days 4, 7, 14, 21, and 28 after the ultramarathon. Peak blood lactate concentrations were determined 3 minutes after the completion of each treadmill test. Plasma CK activity and muscle pain remained significantly elevated in the experimental group for two days (p < 0.00002) and four days (p < 0.02) respectively after the ultramarathon. There was a significant increase in the post-submaximal treadmill test blood lactate concentrations, compared to pre-test values for each day (p < 0.00001). Submaximal oxygen consumption was significantly reduced in the experimental group for up to 28 days (p < 0.0004), and stride length was significantly reduced for 14 days (p < 0.05) after the ultramarathon. Furthermore, in the experimental group RER was significantly increased for up to seven days (p < 0.05), and RPE was significantly increased for up to four days (p < 0.04) after the ultramarathon. In conclusion, the decreased submaximal oxygen consumption following the ultramarathon may be interpreted as a positive training adaptation. However, other responses to the ultramarathon were not compatible with improved running performance. Furthermore, symptoms other than pain should be used to define the recovery period after an ultramarathon race.
32
Feldmann, Daneil. "Inactivity and overfeeding related changes in skeletal muscle composition and metabolism in captive felids - are they at risk of developing metabolic syndrome?" Master's thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/24478.
Testo completoAbstract (sommario):
Obesity and physical inactivity are established key risk factors in the development of skeletal muscle insulin-resistance and type II diabetes in human and domestic animal populations. Wild animals are similarly exposed to these risk factors as a result of captivity. This study aimed at describing the skeletal muscle properties of captive lions (Panthera leo) who present with obesity and are physically inactive, with a group of free roaming wild lions. Skeletal muscle biopsies were collected from the Triceps brachii and analysed for fibre type composition, fibre size, and maximum oxidative (citrate synthase (CS), 3-hydroxyacyl CoA dehydrogenase (3HAD) and glycolytic (phosphofructokinase (PFK) and lactate dehydrogenase (LDH) enzyme capacities. The type IIA fibres were the predominant fibre type in both the wild (48%) and captive (44%) lions. No significant differences were evident in the overall fibre type composition between groups, although a trend towards less type I (28% vs 36%) and more type IIX (28% vs 16%) fibres in the captive group were observed. The captive lions displayed significantly larger cross-sectional areas (CSA) of the type I (5847μm² vs 3318 μm²) and IIA fibres (8344μm² vs 4360μm²) with no difference evident in the CSA of the IIX fibres. Relationships were observed between body mass and the CSAs of type I (r = 0.68, P = 0.0002) and IIA (r = 0.44; P = 0.03) fibres. Metabolically, the captive lions displayed higher flux through the glycolytic pathway as represented by their higher PFK activities (551 ± 287 vs. 338 ± 123 μmol/min/g protein, P < 0.05). In contrast, their CS activities (11 ± 3 vs. 14 ± 2 μmol/min/g protein) were lower than free roaming lions, suggesting lower oxidative capacity. No differences in LDH and 3HAD activities were observed between the two groups. Relationships were observed between 3HAD activity and MHC IIx fibre content (r = -0.43, P = 0.001), 3HAD activity and MHC I content (r = 0.55, P = 0.001). A positive correlation was observed between CS activity and MHC I content (r = 0.35, P = 0.009). In light of previous research, the data collected from this project follows that observed in exercise training models, where a sedentary lifestyle decreases oxidative capacity of muscle and increases type II fibre content. However, due to the low sample size in the free roaming wild lion group, interpretation of the data is difficult. Therefore, future research must strive to increase the sample number of the free roaming group.
33
Schabort, Elske Jeanne. "The reliability of laboratory performance testing". Master's thesis, University of Cape Town, 1997. http://hdl.handle.net/11427/26671.
Testo completoAbstract (sommario):
The reproducibility of a measurement in a laboratory test impacts on the power of that test to detect the small, but significant changes in an athlete's performance when determining the influence of a new training or nutritional intervention. Until recently, however, sport scientists have not been concerned with establishing the reliability of many of their testing protocols. Therefore, the purpose of this thesis was to examine the reliability of several laboratory tests of performance and to determine those factors which may impact on the reproducibility of those tests. Possible factors that could contribute to the reliability of a performance test include the type of exercise protocol employed (continuous, intermittent), the equipment on which the subject performs the test, the intensity and duration of the testing protocol, the subject's state of fitness and whether he is familiar with the testing conditions.
34
Pienaar, Paula Roxana. "Microvascular endothelial function in a multi-ethnic group of apparently healthy South African men and women: Implications for testing and the relationship between insulin resistance and microvascular reactivity". Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/13967.
Testo completoAbstract (sommario):
Endothelial dysfunction is associated with cardiovascular disease risk factors and precedes structural changes in the blood vessels that occur prior to clinical manifestations. Measuring ethnic differences in microvascular endothelial function will provide insight into the disparate cardio-metabolic disease profiles that exist within a multi-ethnic South African population. Moreover, it has been shown that insulin resistance is associated with microvascular endothelial dysfunction in obese persons4, but it is unclear whether this relationship is mediated by body fat in apparently healthy individuals with and without insulin resistance. To our knowledge this has not been done in a South African population. Aims: The overall aim of this thesis was to measure microvascular endothelial function using Laser Doppler Imagery (LDI) and iontophoresis of acetylcholine (ACh) and sodium nitroprusside (SNP) in a multi-ethnic, apparently healthy group to determine whether: 1) there are ethnic differences in microvascular endothelial function and 2) whether the association between microvascular endothelial function and insulin resistance (IR) is independent of body fat in women with and without IR.
35
Bohlmann, Isabelle Marie Therese. "Measurement of physical activity for public health purposes : validity and reliability of the International Physical Activity Questionaire(IPAQ)". Master's thesis, University of Cape Town, 2002. http://hdl.handle.net/11427/26547.
Testo completoAbstract (sommario):
Physical inactivity is a well-recognized risk factor for chronic diseases of lifestyle and has been associated with an increased incidence of morbidity and mortality. Current recommendations for the "dose" of physical activity that may be regarded as "protective" for these chronic diseases are 30 minutes or more of moderate-intensity physical activity on most, or preferably all, days of the week. However, when quantifying physical activity, it is not clear which factors influence the reporting of moderate and vigorous activity levels. Even in the literature, there is lack of agreement on the energy expenditure corresponding to so-called 'moderate' and 'vigorous' physical activity. Background (study 1): Self- reported physical activity levels are inversely related to chronic disease risk factors. The strength of this association depends, in part, on quantifying the intensity of activity that may be regarded as 'moderate or vigorous', which may be confounded by individual and cultural perceptions of relative exercise intensity, age, fitness, height, and habitual levels of activity. Aim (study 1): The purpose of this study was to i) examine the individual and group differences in self-selected walking pace corresponding to symptoms used to describe moderate and vigorous intensity and ii) to determine factors that may be associated with these differences. Methods (study 1): A convenience sample of 63 women and 39 men were recruited (N=102). Subjects were asked to walk for six minutes on an indoor track at a pace they regard as 'moderate', rest until heart rate returns to pre-exercise levels, then walk at a pace they consider 'vigorous'. Habitual levels of energy expenditure (EE), maximal oxygen consumption (VO₂max) and% fat were also determined. Results (study 1): Mean self-selected walking pace for moderate activity levels was 5.54 km-h⁻¹ (95% Confidence Interval (C.I.): 5.40; 5.69), and corresponded to 58% of age-predicted maximum heart rate (%HR.max) (95% C.I.: 56; 60). Mean self-selected vigorous pace was 7.03 km·h⁻¹ (95% C.I.: 6.85; 7.20), at 72 % HR.max (95% C.I.: 69; 74). The %HR.max for both moderate and vigorous intensity physical activity fell within the ACSM recommendations (55- 69%HR.max for moderate intensity activities, and 70 - 89 % HR.max for vigorous intensity activities). Multivariate analysis revealed that the factors predicting self-selected walking speed were gender, age, VO₂max, % fat and habitual vigorous EE. The only significant predictor of moderate pace was VO₂max. Education, occupation and habitual moderate EE were not associated with walking speed or intensity. Conclusion (study 1): These results show that subjects could accurately differentiate absolute and relative walking intensities and understood what was meant by the terms 'moderate' and 'vigorous'. However, absolute pace and relative intensity may vary according to differences in gender, fitness, age, height, body fat% and habitual levels of vigorous activity. These factors are important to consider when prescribing exercise using descriptors such as "moderate" and "vigorous". Background (study 2): None of the various methods used to measure habitual physical activity in the general population have proven entirely satisfactory in terms of reliability and accuracy. A major problem is that no "gold standard" exists for the validation of various questionnaires that can be used in large sample population studies. Ongoing efforts to improve the validity and reliability of the measurement of physical activity by self-report will enable cross-cultural and international comparisons to examine secular trends. Aim (study 2): The second part of this study assessed the validity and reliability of a recently developed International Physical Activity Questionnaire (IPAQ) which was interviewer-administered in both a short and long version, and queried activity performed in a "usual" week. Methods (study 2): Urbanized subjects (N = 82) were selected from a wide range of educational, activity level and socio-economic backgrounds. The long version IPAQ was designed to quantify the average weekly time and energy expenditure spent in occupation, transport-related activities, household chores, and leisure time activities. The short version IPAQ was designed to measure total weekly moderate, vigorous, walking and sitting related activity. Test-retest reliability was reported as the intra-class correlation between calculated time and energy expenditure (METmin·w ⁻¹) in different questionnaire items determined from three IPAQ administrations. Validity was assessed using biometrical and physiological parameters as criterion measures (Computer Science and Applications. Inc. activity monitor counts, body mass index, estimated VO₂max, % fat). Results (study 2): Test-rest reliability coefficients for the long IPAQ ranged from r = 0.38 tor= 0.75, with the highest correlation coefficients obtained in work related activities, and the lowest in household chores. Test-retest reliability in the short IPAQ ranged from r= 0.32 tor= 0.71, with the highest correlations obtained for sitting and the lowest for total moderate activity. Criterion validity for CSA counts and total physical activity in the long IPAQ was r = 0.50 (P < 0.001), for CSA counts and total vigorous activity r = 0.35 (P < 0.01), and for CSA counts and total job activity r = 0.51 (P < 0.001). Measurement of reliability and validity in this South African population compared favourably to physical activity questionnaires used in other population studies. Conclusion (study 2): The IPAQ provides a relatively valid and reliable estimate of physical activity in this population. In evaluating the relationship between physical activity and morbidity, it is important to consider the accuracy and reliability of the tool used to measure self-reported activity. Failure to show an association may represent a real phenomenon, or may simply reflect the inability of the physical activity questionnaire used to detect true physical activity levels.
36
Henst, Rob. "The role of chronotype in the participation and performance of South African and Dutch marathon runners". Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/13131.
Testo completoAbstract (sommario):
Includes bibliographical references.Introduction: Our circadian rhythms are internal biological rhythms of approximately (circa) 24 - hours (dies) allowing us to synchronize our internal biological “clock” with external time cues. Many innate biological functions are dependent on time-of-day, such as secreting adrenaline and cortisol in the mornings and melatonin in the evenings. The time-of-day at which these and other physiological functions are active, change or reach a certain level may influence a person’s diurnal preference, i.e. preference for mornings (morning-types) or evenings (evening-types), and is referred to as ‘chronotype’. Many different factors may affect a person’s chronotype, including age, sex, physical activity, ethnicity and geographical location. Certain clock-related genotypes have also been shown to be associated with chronotype. For example, some studies have found that the 5-repeat allele of the PER3 variable number tandem repeat (VNTR) polymorphism (PER35) is associated with a preference for mornings. Recent research has shown a high prevalence of morning-types and PER35VNTR allele carriers in trained South African runners, cyclists and triathletes. It was proposed that the early morning start-times of these endurance events might select people with a preference for mornings, since morning-types may cope better with rising early and being physically active in the early morning. Alternatively, the habitual early waking for training or endurance events may have conditioned the athletes to adapt to become morning-types. However, the geographical location of South Africa (i.e. climate and day length) and the fact that each group was physically active may also have contributed to this finding. Comparison of South African and Dutch runners would allow us to explore the effects of race start time and geography on this observation, since marathons in The Netherlands on average start at 11:41, and since the two countries differ significantly in latitude and as such have noticeable differences in daylight exposure. Aims: The aims of this study were 1) to compare the PER3VNTR genotype and chronotype distribution of South African and Dutch recreational marathon runners and active but non-competitive controls; 2) to investigate the relationship between the PER3VNTR genotype and chronotype in both the Dutch and South African samples; and 3) to determine whether marathon race time is associated with chronotype and PER3VNTR genotype in Dutch and South African marathon Methods: Ninety-five trained South African male marathon runners, 97 South African male active but non-competitive controls, 90 trained Dutch male marathon runners and 98 Dutch male active but non-competitive controls completed a questionnaire capturing demographics, training and race history, including personal best and most recent full and half-marathon race time (if applicable) and the Horne-Östberg morningness-eveningness personality questionnaire (HÖ-MEQ, a tool to assess a person’s chronotype). Each participant provided a buccal cell swab from with total genomic DNA was extracted to determine his PER3VNTR polymorphism genotype. The official race time from each runner who completed the designated marathons in South Africa or the Netherlands was collected from the event websites. Results: The South African and Dutch runners were more morning-orientated than their respective control groups and the South African runners were more morning-orientated than the Dutch runners. The PER3 VNTR polymorphism distribution was similar between the four groups and was not associated with chronotype. The marathon performance of the morning-type South African runners was better than the evening-types, and a higher HÖ-MEQ score (morningness) correlated with better personal best and most recent half-marathon race time. Similar observations were not found in the Dutch runners. Discussion: Since a higher prevalence of morning-types in South African marathon runners compared to Dutch marathon runners was found, it is proposed that the early marathon start-times in South Africa may favour morning-types, who are able to cope with those early morning start times. Alternatively, one could argue that through repetitive early-morning racing (i.e. participating in competitive running events), the chronotype of South African runners may be conditioned to that of a morning-type over time. It is proposed that this ability to cope with early morning marathon start times may lead to better marathon performances for morning-types than neither-types and evening-types in the South African running group. This effect does not occur in the Netherlands, where marathons start later in the morning and do thus not favour a certain chronotype. The difference in daylight exposure between the two countries as a function of latitude does not seem to affect chronotype, since the active but non-competitive control groups did not differ significantly between South Africa and the Netherlands. Unlike the findings from a previous study, the PER35allele was not more prevalent among the South African runners, but rather the distribution wasi n line with what has been described in most, but not all, other populations. No association between the PER35VNTR xpolymorphism and chronotype was found in any of the four groups. Since the four groups investigated in this study comprised physically active individuals, it is proposed that this lack of association may be due to the habituation effects of physical activity and early morning start times of marathon events(for only the South African runners). Conceivably,this habituation may even shift the diurnal preference of those with the PER34/5 and PER34/4VNTR genotypes towards morningness, disassociating any relationship between chronotype and the PER3VNTR genotype. Conclusion: The early morning start time of South African marathon events may favour morning-types, due to their ability to cope with being physically active in the early morning. We propose that the PER3VNTR genotype cannot solely explain the higher prevalence of morning-types in the South African runners in this study, however, it is very likely that the PER3VNTR genotype does play an important role in the chronotype distributions found in the study of Kunorozva et al.(2012). Since the PER3VNTR genotype was not associated with chronotype in any of the four groups, it is proposed that habituation to early-morning marathon racing may be the causal effect of the high number of morning-types in the South African runners group, and the apparent disassociation between chronotype and the PER3VNTR genotype. We also propose that the habituation effect of physical activity and training time-of-day on chronotype in the other groups may dissociate the PER3VNTR genotype with chronotype in a similar manner to which the early-morning start times of South African endurance events dissociates the two. No effect of geographical location on chronotype was found when comparing the Dutch and the South African groups. The morning-orientated South African runners seem to perform better in marathon running than the more evening-orientated runners do, which may be caused by their ability to cope with these early-morning marathon events. Further studies may explore whether marathon performance in later chronotypes can be improved by training-based habituation.
37
Burden, Stephen Barry. "The seasonal and lifetime incidence of low back pain in South African male first league squash players". Master's thesis, University of Cape Town, 1996. http://hdl.handle.net/11427/26593.
Testo completoAbstract (sommario):
Previous studies have been conducted to determine the incidence of low back pain (LBP) in both the general population as well as in participants of different sporting activities. The purpose of this study was to determine the seasonal and lifetime incidence of LBP in male first league squash players.
38
Miller, Caron-Jayne. "Intrinsic and extrinsic factors associated with change in range of motion (ROM) after a single stretch session and repeated loading following an endurance run". Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/10688.
Testo completoAbstract (sommario):
Static stretching is commonly performed by athletes and clinicians on the assumption that it increases joint range of motion (ROM). However, observations from our laboratory indicate that there is an apparent inter-individual variance in the change in ROM in response to static stretching. Furthermore, prolonged repetitive loading has also been shown to affect ROM of a joint or series of joints. In particular, runners have a significantly decreased hamstring ROM. The aim of this study was to investigate the factors which are associated with a change in ROM in response to 1) a static stretch session and 2) prolonged repetitive loading. The findings showed that there is a variable response in the change in ROM following both a SSS intervention and in response to participation in a 42.2 or 56 km road race. More specifically, about 10% of the participants had a reduction in ROM after the SSS while the majority of participants had a reduced ROM after completing the marathon or ultra marathon.
39
Schoeler, Lieselotte Maria. "Personality traits and cognitive performance in elite athletes". Master's thesis, University of Cape Town, 2009. http://hdl.handle.net/11427/6056.
Testo completoAbstract (sommario):
Includes abstract.Includes bibliographical references (leaves 42-58).
Mental performance consists of cognitive components, such as memory capacity, motor function, or decision making, and psychological components, such as personality traits, psychological well-being, or coping strategies. While certain personality traits have been shown to be associated with specific strengths and weaknesses in an individual’s cognitive abilities only few studies have been done to investigate this relationship in athletes. Our study therefore aims to investigate the correlations between certain personality traits and cognitive performance in a sample of elite hockey players. 25 male athletes completed the ‘WebNeuro Sport’ assessment by the Brain Resource Company.
40
Coleman, Kirsty Lee. "Exercise tolerance and skeletal muscle structure and function in patients with chronic obstructive pulminary disease". Master's thesis, University of Cape Town, 1998. http://hdl.handle.net/11427/17935.
Testo completoAbstract (sommario):
Bibliography: pages 143-154.Exercise intolerance is well documented in patients with chronic obstructive pulmonary disease (COPD). Historically, this exercise intolerance has been attributed to the central factors of lung damage and subsequent heart failure. However, recent evidence suggests that (i) patients with cardiac and renal failure suffer from skeletal muscle (SM) abnormalities that impair exercise tolerance and (ii) patients with chronic obstructive pulmonary disease (COPD) may have metabolic and functional abnormalities of SM. However, no studies have conducted a detailed investigation of SM structure and function and their relation to exercise tolerance in patients with COPD.
41
Sewry, Nicola. "Key performance indicators and predictors in Varsity Cup rugby". Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/13267.
Testo completoAbstract (sommario):
Rugby union is a popular sport worldwide, and due to the professional nature of the sport the demands on players continues to increase, resulting in acute and chronic fatigue. The aims of the study were to investigate the tools used to monitor and predict changes in training status and determine the effectiveness of these to: (i) measure the subjective nature of coaches and their selection relating to the players’ performance, and (ii) to use performance indicators to correlate to team performance. The University of Cape Town Rugby Varsity Cup Team (First XV squad) were monitored from their pre-pre-season until the end of their competitive season. Players completed a testing battery (anthropometry, strength, muscular endurance, speed and aerobic fitness) during the season, along with Rating of Perceived Exertion and body mass was recorded every practice. Players also completed the HIMs test (measure of heart rate recovery) weekly. Coaches rated players every practice on three variables and the matches were recorded and video analysis performed to determine key performance variables. Most of the players improved in their testing battery between pre-pre-season and pre-season. Average session load varied across the phases of the season and was highest in the pre-preseason. Change in load however, was not reflected by changes in heart rate recovery which remained relatively stable across the season. The players’ body mass varied throughout the tournament, with certain players having a larger coefficient of variation compared to others. There was no relationship between performance in the testing battery and selection for matches. The coaches all had different ratings for the players, with no correlation between players selected and those not selected. There was a correlation between the subjective rating of players in the week leading up to the match and the match ratings of Coach 3 (head coach). The Varsity Cup rugby union players followed similar trends described in previous literature in physiological testing batteries, training loads and player management. The novel aspect of this study was the collection of data from the coaches involved. This qualitative data provides insight into the coaches’ selection process or lack thereof within a team environment. The data also illustrates the differences between the coaches’ interpretation of the players’ “performance”. The Varsity Cup is a relatively young tournament and should be further investigated to properly understand the differences between it and professional and amateur rugby union.
42
Du, Toit Jacques. "Playing time of professional senior rugby players across all levels of South African rugby, 2007 -2012: implications for transformation". Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/5927.
Testo completoAbstract (sommario):
Includes abstract.Includes bibliographical references.
A single governing body to govern South African rugby was formed in 1992. This allowed for changes to governmental policies to South African sport, resulting in South African sport being fully representative of the population. The South African Rugby Union (SARU) therefore has a continual challenge to make rugby fully representative at both provincial and national levels. Previously rugby has been dominated by white players at all levels. The SARU has implemented various programmes in order to accelerate the development of players of colour. Previously the success of these programmes has not been evaluated because the players representing different ethnic groups have not been quantified in a systematic way. The aim was to quantify playing time and playing numbers of South African professional rugby players of different ethnic groups from 2007 to 2012 at all professional levels (Springboks, Super Rugby, Currie Cup and Vodacom Cup). Quantifying playing time and playing numbers was done to establish changes in profile of South African rugby players across the given time period. Thus the efficacy of the SARU programmes to accelerate transformation was indirectly evaluated. A further aim was to determine if there had been a change in ethnic profiles between the various rugby unions from 2007 to 2012.
43
Marsh, Jarred. "Injury incidence and severity at the South African Rugby Union (SARU) Youth Weeks Tournaments: a four year study". Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29198.
Testo completoAbstract (sommario):
Introduction
Rugby Union (hereinafter referred to as ‘rugby’) is a contact sport with players being exposed to repetitive collisions throughout a match. As the risk of injury is relatively high, incidence surveillance studies within rugby has become popular. However most of the studies have focussed on senior players. The data on injuries among youth rugby players are limited. This makes it difficult to develop the game to make it safer for youth of all ages.
Objectives
The first objective of this study was to establish if any injury trends exist across different ages of youth rugby players (13 to 18 years). The second objective was to determine the patterns of injuries changed over four years (2011 to 2014).
Methods
The South African Rugby Union (SA Rugby) hosts four local youth tournaments annually to for local rugby talent: Craven Week under-13, Grant Khomo under-16, Academy Week under-18 and Craven Week under-18. Injury data were collected from the four SARU Youth Week Tournaments between 2011 and 2014. These data were compiled into one central SARU injury surveillance database. Injury categories were used to group data: ‘Type’, ‘Location’, ‘Event’ and ‘Severity’ of injury were assessed. Injuries were defined as either ‘Time-loss’ (those injuries that prevented a player from match participation for one or more days), or ‘Medical attention’ (injuries that required the player to seek medical attention at the time of or after injury but were not required to miss a match). Injury rates were represented by injury incidence densities (IIDs) (corresponding 95% confidence intervals (95% CIs) for IID were calculated for the number of injuries regardless of whether one person was injured more than once) per 1000 hours of match play. Incidence densities were considered to be significantly different from each other if their 95% CIs did not overlap and using Poisson regression analysis.
Results
The ‘overall’ combined IID across all four years was 54.6 injuries per 1000 hours of match play (95%CI: 51.0-58.2). The combined ‘time-loss’ IID was 18.9 injuries per 1000 hours of match play (95%CI: 16.8-21.0). ‘Time-loss’ injuries were greatest in 2011 (23.2 per 1000 match hours (95% CI: 18.5-28.0)). However, ‘time-loss’ injuries rates were significantly reduced in 2013, when compared to these injury rates in 2011 (13.3 (9.7-17.0). Craven Week under-13 presented significantly greater ‘overall’ injury incidence densities when compared to the older age groups (71.9 per 1000 match hours (95% CI: 62.4-81.4)). Overall, joint/ligament/tendon injuries were most common ‘overall’ and ‘time-loss’ injury sustained by players between 2011 and 2014 (30% and 33% respectively). This was followed closely by concussion injuries, which accounted for 29% of ‘time-loss’ and 12% of ‘overall’ injuries. A large proportion of both ‘overall’ (57%) and ‘time-loss’ (55%) injuries occurred during the tackle event, with the tackler being injured more often than the ball-carrier (37% and 18% respectively). However, there were no statistically significant differences when comparing ‘overall’ and ‘time-loss’ IID between the different tournaments from 2011 until 2014.
Discussion
Significant differences were found when comparing ‘overall’ and ‘time-loss’ IID between the different tournaments from 2011 until 2014. Craven Week under-13 presented significantly greater ‘overall’ injury incidence densities. This finding contradicts previous literature within youth rugby research. The tackle (combination of tackler and ball-carrier) still accounts for the highest proportion both ‘time-loss’ and ‘overall’ injury events (57% and 55% respectively). This is in accordance with previous studies. However, a point of concern was that concussion accounted for 29% of all ‘time-loss’ injuries and 12% of all ‘overall’ injuries. This finding suggests a gradual increase in the number of concussions suffered during the SARU Youth Week Tournaments between 2011 and 2014. Further research is required to determine the reason for this pattern.
Conclusion
Further research within youth rugby cohorts is required to determine the risk associated with involvement at various level of participation. Injury prevention programs should place focus on reducing the prevalence of concussion at youth level by educating players and coaches about safe tackle techniques. Future studies should focus on local youth cohorts for seasonal
44
Schutte, Lynne. "The effect of repeated bouts of downhill training on running performance and recovery after a 30-km time trial". Master's thesis, University of Cape Town, 2001. http://hdl.handle.net/11427/26545.
Testo completoAbstract (sommario):
Purpose: The present study was designed to examine the effect of repeated bouts of either downhill or level running on running performance in, and recovery from, a 30-km time trial. Methods: Sixteen male subjects with a mean (± SD) age of 33.8 ± 5.8 years, body mass of 72.0 ± 7.3 kg and a stature of 176.6 ± 4.5 cm were randomly allocated to either a downhill (n=9) or a level group (n=7). The protocol consisted of a training phase, followed by a 30-km time trial and a recovery phase. During the training phase subjects ran either at a -10% grade (downhill group) or a 0% grade (level group) on a treadmill for nine 40-minute training runs [70% of peak treadmill running speed (PTRS)]. Thereafter all the subjects participated in a 30-km time trial (70% of PTRS), where heart rate (HR), rate of perceived exertion (RPE) and stride length (SL) were recorded, followed by five 15-minute submaximal recovery runs. The first recovery run was performed before the start of the training phase and again on four occasions after the 30-km time trial. HR, RPE, SL, minute ventilation (Vi), oxygen consumption (VO₂), carbon dioxide production (VCO₂) and respiratory exchange ratio (RER) were recorded during these 15-minute runs. Plasma creatine kinase (CK) activity and muscular soreness were assessed for the duration of the study. Results: HR decreased in the downhill group during the training phase, suggesting a HR training effect. Muscle pain and plasma CK activity in the downhill group increased after the first 40-minute downhill training run. These indicators of muscle damage did not show any further increases during the training phase, suggesting a "repeated bout effect". Towards the end of the 30-km time trial the level group, showed a greater heart rate drift (HRD) and an increased RPE, suggesting that they were not able to resist fatigue to the same extent as the downhill group. HR and RPE recorded during the recovery phase suggested that the downhill group showed a better recovery after the 30-km time trial. During the recovery phase the downhill group experienced no increase in muscle pain after performing the 30-km time trial, in contrast to the level group who experienced muscle pain for five days after the 30-km time trial. Plasma CK activity, was blunted after the 30-km time trial in the downhill group in contrast to the level group. Conclusion: The results of the investigation support the hypothesis that the inclusion of downhill training into a training program cause changes, which can be interpreted as enhancing performance during an endurance event and recovery after the event.
45
Bellinger, Brett. "The effect of oral creatine supplementation on one hour cycling performance and metabolism". Master's thesis, University of Cape Town, 1995. http://hdl.handle.net/11427/26524.
Testo completoAbstract (sommario):
The effect of oral creatine (Cr) supplementation with 20 g/day for 7 days on one-hour cycling performance and metabolism was investigated in a double-blind placebo controlled study. Twenty endurance-trained male cyclists volunteered for the study that was approved by the University of Cape Town ethics committee. The subjects' peak sustained power output was measured and they underwent a familiarization one-hour cycle on a cycle ergometer. Five days later subjects had a muscle biopsy and an indwelling cannula was inserted into a forearm vein before performing a maximal one-hour cycle (T1) during which blood samples were taken at regular intervals. Following the cycle, the subjects each received either Cr or placebo tablets to be ingested four times per day for the following week. After the loading week the subjects again reported to the laboratory, had a muscle biopsy and underwent and the same test routine (T2) with blood sampling as the previous week. Resting muscle total Cr measured by HPLC increased significantly (p<0.001) in the Cr group from 123.0 ± 3.8 mmol/kg dry wt to 159.8 ± 7.9 mmol/ kg dry wt, but was unchanged in the placebo group. The extent of Cr loading was not related to baseline Cr levels (r=0.46, NS). No differences were noted in the resting levels of adenine nucleotides in either group. Analyses of the plasma samples indicated no change in plasma lactate concentration, but a significant lowering of indicators of adenine nucleotide degradation including concentrations of plasma ammonia (p<0.05) and hypoxanthine (p<0.01) in the Cr group from T1 to T2. Plasma urate concentration was significantly lowered (p<0.01) from T1 to T2 but there were no differences between groups. Cr supplementation did not significantly improve performance in the one-hour trial (Cr group: 39.1 ± 0.9 km vs 39.8 ± 0.8 km and placebo group: 39.3 ± 0.8 km vs 39.2 ± 1.1 km). We hypothesised that Cr supplementation affects the purine nucleotide cycle through improved maintenance of low intracellular ADP during exercise as a result of enhanced efficiency of the Cr-PCr shuttle. Cr supplementation had no effect on lactate and carbohydrate metabolism and did not improve performance significantly during a one-hour cycle trial.
46
Schoeler, Gunnar. "The validation of muscle power output measures in lower and upper body resistance exercises". Master's thesis, University of Cape Town, 2009. http://hdl.handle.net/11427/2763.
Testo completoAbstract (sommario):
Includes abstract.Includes bibliographical references (p. 104-115).
The reliability and comparability of results obtained from different methods of assessment has been the source of debate for the last decade. Aim: To investigate the reliability and comparability of measurements of force, velocity and power measured simultaneously during upper and lower body resistance exercises for the following three methods: a) power derived from ground reaction force, i.e. using a force plate (FP), b) power derived from the displacement of the bar, i.e. displacement tracking laser (L) and c) power as a combination of force derived from ground reaction force (FP) and velocity derived from the displacement of the bar (L) (FPL). Methods: 15 Males with a history of resistance training of at least one year participated in the study.
47
Durandt, Justin. "A description of the profiles of U18 rugby players who attended the Craven Week tournament between 2002-2012". Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29657.
Testo completoAbstract (sommario):
Rugby union has rich tradition in South Africa with the national team having won the Rugby World Cup in 1995 and 2007. The major rugby nations South Africa competes against have clearly defined rugby talent identification (TID) and development (TDE) pathways. These pathways are not as well described in South Africa where the South African Rugby Union (SARU) has adopted a model of identifying talent at an early age through competition. For example, national competitions occur at U13 (Craven Week), U16 (Grant Khomo Week) and U18 (Craven Week and Academy Week) levels. Previous research on talent identification has highlighted the pitfalls of early talent identification. In particular different rates of maturation can influence the manifestation of talent. In a collision sport such as rugby the early maturers have a distinct advantage. An added complexity in the South African context is the need to provide an appropriate development environment within which transformation can take place. At all levels in South African professional rugby, white players dominate team selection. One of the reasons suggested for this dominance is the physical size of white players compared to their black and mixed race (coloured) counterparts. Rugby is a contact sport and physical size is associated with success, so the need to quantify physical difference between racial groups at a junior level over time is important. The first objective of the thesis was to examine the profiles of U18 Craven Week rugby players to gain insight into the development pathway from U13 to U18. A second aim was to understand factors influencing transformation by measuring the physical profiles of the various racial groups over time. The thesis consists of two studies. The specific objective of the first study was quantify how many players in the 2005 U13 Craven Week (n=349) participated in the subsequent U16 Grant Khomo and U18 Craven Week. The study showed that 31.5% of the players who played in the U13 Craven Week, were selected to play at U16 Grant Khomo Week and 24.1% were selected for the U18 Craven Week tournaments. Another interpretation is that 76% of the players selected for the U13 tournament did not play at the U18 Craven Week tournament. The objective of the second study was to determine whether there are differences in body mass, stature and body mass index (BMI) between racial groups in U18 Craven Week players. Another objective was to determine whether these measurements changed between 2002-2012. Self-reported body mass and stature were obtained from U18 players (n=4007) who attended the national tournament during this period. BMI was calculated for each player. The body mass, stature and BMI of these players in South Africa were significantly different between racial groups. For example, white players were 9.8 kg heavier than black players, who were 2.3 kg heavier than coloured players (p<0.0001). The body mass of all groups increased from 2002-2012 (p < 0.0001). White players were 7.0 cm taller than black players, who were 0.5 cm taller than coloured players (p < 0.0001). The stature of players did not change significantly during the study period. The average BMI of white players was 0.9 kg.m⁻² greater than black players who were on average 0.7 kg.m⁻² greater than coloured players (p<0.0001). The BMI of all groups changed similarly over the study period. To conclude, these results question the effectiveness of the u13 tournament in identifying talent and providing an effective development pathway to U18 Craven Week. The SARU also needs to be aware of the ongoing disparities in size between the racial groups playing rugby at an U18 level in South Africa. These size differences may have implications for transforming the game and making it representative of the South African population.
48
Goyaram, Veeraj. "Regulation of skeletal muscle glucose transporter 4 expression in fructose-fed exercised rats". Master's thesis, University of Cape Town, 2013. http://hdl.handle.net/11427/2751.
Testo completoAbstract (sommario):
Includes abstract.Includes bibliographical references.
Several studies have found that the expression of skeletal muscle glucose transporter 4 (GLUT4) is decreased by high fructose consumption but increased by exercise. However, the amounts of fructose used in these studies were extremely high and the effects of moderate feeding protocols are not known. While it is known that exercise enhances GLUT4 expression via increased histone H3 acetylation and binding of the myocyte enhancer factor- 2A (MEF2A) transcription factor to its binding domain on the Glut4 gene promoter, the impact of fructose consumption on this interaction has not been studied. Moreover, there is no direct evidence that an increase in MEF2 binding is due to increased accessibility of the MEF2 binding domain to transcription factors. This study tested the hypothesis that both exercise and high fructose consumption affect GLUT4 expression by altering the accessibility of the MEF2 binding domain on the Glut4 gene promoter via remodelling of chromatin in that region. Male Wistar rats (n=30) were randomly assigned to three dietary groups: a) standard Chow, b) Chow + 10% fructose drink and c) Chow + 10% maltodextrin drink. All rats had access to drinking water and chow ad libitum for a period of 13 days. In the last 6 days of the experiment 5 animals in each group performed 3 x 17 min daily bouts of intermittent swimming, with a load equivalent to 5% bodyweight attached to their tails. The remaining 5 rats from each group were untrained. Animals were fasted overnight on the last day of the experiment, anaesthetized and sacrificed on the morning of day 14. Triceps muscle were harvested and used: (a) for measurement of total GLUT4 content by western blot, (b) to obtain nuclei for assessment of accessibility of a 350bp region encompassing the MEF2 element on the Glut4 gene using nuclease digestion assay, and (c) to measure the acetylation of histones H3 and bound MEF2A in the region above using chromatin immunoprecipitation (ChIP) assay. Blood was also collected and assayed for fasting serum glucose, insulin and free fatty acids.
49
Leith, David. "Metabolic and lifestyle profiling of overweight female runners compared to lean counterparts: exploring the implications and causes of their elevated body weight". Master's thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/22715.
Testo completoAbstract (sommario):
There appears to be an emerging phenotype of recreational runners who are overweight despite being regularly active. This conflicts with the common perception that exercise protects against weight-gain, and it may be caused by underlying insulin-resistance. Alternatively, recent research has brought attention to metabolically healthy obese (MHO) individuals, who have increased adiposity but no commonly associated metabolic abnormalities, such as insulin-resistance, hypertension, dyslipidaemia and systemic inflammation. This study aimed to determine whether overweight (OW, BMI ≥ 25 kg.m⁻²) female runners were at risk of developing metabolic pathology and compare the findings to lean (LN, BMI < 23 kg.m⁻²) counterparts. A secondary aim was to explore potential inherent or lifestyle factors that may have predisposed or contributed to weight-gain in OW runners. METHODS. Twenty (10 OW, 10 LN) female recreational runners (years of running experience 7.1 ± 4.4 OW; 8.0 ± 3.7 LN) matched for mean age (38.7 ± 4.6 OW; 37.7 ± 4.3 LN), current mileage in km.week⁻¹ (42.0 ± 10.9 OW; 44.5 ± 12.1 LN) and running calibre expressed as energy expenditure (kcal.min⁻¹) in their most recent half-marathon (9.0 ± 1.1 OW; 9.2 ± 1.1 LN) were recruited for this study. Body fat percentage (BF%) was determined using DXA. Participants completed questionnaires about health history, lifestyle and eating habits and validated questionnaires concerning recent sleep and stress. Their diet was recorded using 3-day diet records and analysed using the South African Food Data System (Medical Research Council of South Africa). Habitual sleep and physical activity were quantified using 7-day actigraphy (Actiwatch 2) and accelerometry (Actigraph GTX3+) respectively. Blood pressure and resting metabolic rate were measured after an overnight fast. Blood samples were analysed for cardio-metabolic parameters and an Oral Glucose Tolerance Test was performed for insulin-sensitivity. RESULTS. OW exhibited a greater body weight (74.4 ± 6.4 kg OW; 59.4 ± 7.8 kg LN, p < 0.001) but similar fat-free-mass (49.4 ± 5.6 kg OW; 45.4 ± 5.9 kg LN) to the LN group. OW had a higher BF% (32.1 ± 3.9 OW; 21.8 ± 3.9 LN, p < 0.0001), and systolic (118 ± 10 mmHg OW; 107 ± 5 mmHg LN, p < 0.05), but not diastolic (72 ± 6 mmHg OW; 68 ± 4 mmHg LN) blood pressure. There was no difference between groups in serum uric acid, alanine aminotransferase, % HbA1c, total cholesterol, HDL-cholesterol, triglycerides or free-fatty-acids. OW had higher levels of C-reactive protein (1.30 ± 0.97 mg.L⁻¹ OW; 0.59 ± 0.35 mg.L⁻¹ LN, p < 0.05), total cholesterol / HDL-cholesterol (2.70 ± 0.40 OW; 2.30 ± 0.42 LN, p < 0.05) and LDL-cholesterol (2.99 ± 0.65 mM OW; 2.43 ± 0.72 mM LN, p < 0.05), but these were within normal ranges. IDL-cholesterol constituted a significantly greater proportion of total cholesterol in OW compared to LN, but HDL- and LDL- cholesterol sub-fraction distributions were similar. Indices of hepatic (HOMA-IR, 1.06 ± 0.51 OW; 0.86 ± 0.24 LN), and whole-body (Matsuda, 7.84 ± 2.46 OW; 9.16 ± 2.28 LN) insulin-sensitivity were variable and similar between groups. Total area-under-the-curve of the OGTT insulin response tended to be higher in OW (p = 0.08). Two OW runners had insulin-resistance (Matsuda < 5); but no participants had the metabolic syndrome. RMR (kcal.kg FFM⁻¹.day⁻¹) was lower in OW (29.5 ± 2.1 OW; 31.6 ± 2.3 LN, p < 0.05), but there were no significant differences in lifestyle factors (diet, physical activity, sleep and stress). Total energy intake in kcal.day⁻¹ (1928 ± 354 OW; 2166 ± 489 LN) and % macronutrient composition as Protein/Fat/Carbohydrate/Alcohol (20/44/33/3 OW; 16/43/36/5 LN) were both similar between groups. OW and LN also exhibited similar activity in steps.day⁻¹ (10 742 ± 3552 OW; 12 073 ± 3273 LN) and percentage accelerometer wear-time spent in Sedentary/Light/Moderate-Vigorous physical activity (75/14/11 OW; 72/15/13 LN). Both groups attained circa 7 hours.night⁻¹ of sleep, with good sleep onset latency (7.3 ± 5.8 minutes OW; 5.8 ± 3.5 minutes LN) and sleep efficiency (91.6 ± 4.4% OW; 90.7 ± 2.8% LN), and they reported reduced to average levels of recent stress. DISCUSSION. OW runners presented with greater mean adiposity than LN counterparts, but the two groups were not as distinct as anticipated. OW runners did present with greater metabolic risk according to some traditional risk factors, including inflammation, systolic blood pressure, LDL-C and total cholesterol. However, the first three were within normal ranges and the clinical relevance of the latter is questionable. It was, therefore, concluded that on average the OW group was not at metabolic risk. Only two OW runners and no LN runners were insulin-resistant according to indices derived from the OGTT. These findings may primarily reflect the insulin-sensitising effects of regular exercise and the consequent fitness of the OW runners. Appetite-dysregulation is speculated to have played an integral role in their prior weight-gain. We did not identify any lifestyle discrepancies that could have explained this weight-gain. The cross-sectional nature of this study made it difficult to assess past behaviour during weight-gain, and inter-individual variation was considerable. In combination with the small sample size, these factors limited the generalisability of the results. Future exploration of the 'overweight-runner' phenotype is warranted to clarify the mechanisms of weight-gain in habitual runners and consequent lifestyle changes that may promote meaningful weight-loss.
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Bakkum, Amanda. "A randomised control trial for the restoration of functional ability in patients post total knee arthroplasty: a comparison of eccentric versus concentric cycling ergometry". Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/16477.
Testo completoAbstract (sommario):
Includes bibliographical referencesPurpose: The predominant impairment to function following a total knee arthroplasty (TKA) is a distinctive reduction in quadriceps muscle strength. It has been suggested that eccentric rehabilitation may be more beneficial than traditional concentric only rehabilitation at improving muscle strength, physical functioning and quality of life in this population. The aim of this study was therefore to determine if an eccentric cycling ergometry rehabilitation intervention (a) was feasible in participant's early after TKA surgery (Study 1), (b) resulted in greater improvements in muscle strength and endurance, as well as muscle activity and muscle volume (Study 2) and, (c)resulted in greater knee functional ability, health related quality of life and physical activity levels (Study 3), when compared to an concentric cycling ergometry rehabilitation intervention. Finally, knee and hip kinematics, ground reaction force and muscle activity was described during the sit-to-stand transfer within this population (Study 4). Methods: Eighteen age- and sex-matched participants', three to nine month's post-TKA were recruited and randomly divided into either an eccentric or concentric cycling rehabilitation intervention. The participants were required to perform three exercise sessions a week, over a period of eight weeks. Isokinetic strength and muscle activity of the quadriceps and hamstring muscles, sit-to-stand motion capture analysis and knee functional ability and health related quality of life questionnaires (Knee Injury and Osteoarthritis Outcome Score, SF-36Health Survey and Tegner Activity Scale) were assessed pre and post- rehabilitation intervention. Data Analysis: Two-way repeated-measures analysis of variance were used to analyse the effects of time and the ECC and CON intervention groups and the group/time interaction for each of the dependent variables. Results: The eccentric rehabilitation intervention was well tolerated with regards to pain levels in participants' as early as three months post-TKA, the peak level of pain perceived per session, never exceeding a "mild" classification. The eccentric intervention resulted in greater power (P= 0.029) and work output (P ≤ 0.001) with a reduced overall heart rate (P= 0.014) ; moderate decreases in biceps femoris (BF) muscle activity (-3.2%) and increases in the lean thigh volume (+807.32) of the uninvolved limb; as well as improvements in the physical fun ctioning (+12.2%) and physical role functioning SF-36 scores (+22.2%) and the level of physical activity (+0.9) (Tegner activity scale). The concentric intervention resulted in decreases in vastus lateralis (VL) muscle activity (-8.17%) and work fatigue (-7.34%) and increases in the lean thigh volume (+677.49) and the hip abduction angle (+ 2.67°) (sit-to-stand) of the involved limb. Conclusion: The eccentric rehabilitation intervention is well tolerated with regards to pain and is characterised by significantly greater power output produced and work performed at significantly lower heart rates. Eccentric cycling ergometry matched in perceived exertion and duration, is associated with greater improvements in physical functioning outcome scores, physical activity level and knee flexion muscle efficiency during concentric contractions, when compared with concentric cycling ergometry. However, knee extensor muscle endurance and efficiency during concentric contractions, as well as muscle volume of the involved limb increased more significantly after concentric training in comparison to eccentric training, Further research is required to establish which training modality is the most feasible and effective in restoring knee function in participant's three months post-TKA.