Rozprawy doktorskie na temat „Swimming – Physiological aspects”

The purpose of this study was to examine the effect of swimming distance and rest interval on the intensity of swimming (relative to VO2 max) and the contributions of the three energy systems (aerobic, anaerobic, and alactic) during these interval sets. Nine male college swimmers performed fourteen different interval training sets. Distances were 25, 50, 100, or 200 yards with rest intervals of 10 seconds, 1, and 3 minutes. During these sets only the distance to be swum and the rest interval for the set was given. No qualitative information from the coach was provided. These interval sets were performed by the swimmers with the influence from timers being kept minimal. Oxygen cost during the swim was determined from the velocity of the swim based on a linear regression for swimming velocity and oxygen uptake for each swimmer. The same interval sets were completed with pace controled where venous blood samples were obtained 1, 3, 5, and 7 minutes after the completion of each training set. 81ood samples were analyzed for lactate accumulation, blood pH, p0.,, pCO2, and hemoglobin. From these values bicarbonate, base excess, and blood oxygen saturation were calculated using equations developed by Siggard-Anderson. The results of this study do indicate that there is a predictable relationship between swimming distance and rest interval on swimming intensity (relative to VO., max). There was a curvilinear L relationship between swimming intensity (relative to VO max) and rest interval for 50, 100, and 200 yard interval sets. The correlation at these distances were r-0.96, 0.93, and 0.94 respectively. There was a linear relationship between intensity and the distance swum for the 10 second, 1, and 3 minute rest intervals. The correlation for these rest intervals were r= 0.99, 0.99, and 1.00 respectively. There was an increase in the relative contribution of aerobic energy as the distance of the swim increased for all three rest intervals. At a given swiming distance there was a greater contribution of non-aerobic energy as the rest interval increased. Contrary to continuous swimming, greater swimming velocity does not directly correspond to greater contributions of anaerobic energy during intermittent swimming. The distance and rest interval during intermittent training greatly effect the relative contributions of the three energy systems. The intensity of the swim and the relative contributions of each energy system should be considered when planning specific training regimens.

The purpose of this study was to determine if mild heat stress induced by wearing a wet suit while swimming in relatively warm water (25.4 ± 0.1°C) increases the risk of heat injury during the subsequent cycling and running stages. Specificlly, during an Olympic distance triathlon in a hot and humid environment (32°C & 65% RH). Five male triathletes randomly completed two simulated triathlons (Swim=30 min; Bike=40 km; Run=10 km) in the laboratory using a swimming flume, cycle ergometer, and running treadmill. In both trials, all conditions were identical, except for the swimming portion in which a full length, sleeveless neoprene wet suit was worn during one trial (WS) and a competitive brief swimming suit during the other (SS). The swim portion consisted of a 30 min standardized swim in which oxygen consumption (V02) was replicated, regardless of WS or SS. During the cycling and running stages, however, the subjects were asked to complete the distances as fast as possible. Core Temperature (T) was not significantly different between the SS and WS trials at any time point during the triathlon. However, mean skin temperature (TSk) and mean body temperature (Tb) were higher (p<0.05) in the WS at 15 (TSk=+4.1°C, Tb=+1.5°C) and 30 min (TSk=+4°C, Tb=+1.6°C) of the swim. These TSk and Tb differences were eliminated by 15 min of the cycling stage and remained similar (p>0.05) through the end of the triathlon. Moreover, there were no differences (p>0.05) in V02, heart rate (HR), rating of perceived exertion (RPE), or thermal sensation (TS) between the WS and SS. Additionally, no significant differences were found in cycling (SS=1:14:46 ± 2:48 vs. WS=1:14:37 ± 2:54 min), running (SS=55:40 ± 1:49 vs. WS=57:20 ± 4:00 min) or total triathlon times (SS=2:40:26 ± 1:58 vs. WS=2:41:57 ± 1:37 min). Therefore, the primary finding was that wearing a wet suit during the swimming stage of an Olympic distance triathlon in 25.4°C water does not adversely affect the thermal responses or the triathlete's ability to perform on the subsequent cycling and running stages.
School of Physical Education

Despite similar rates of energy expenditure during training, competitive swimmers have been shown to store significantly greater amounts of body fat than competitive runners. In an attempt to explain these discrepancies, male collegiate swimmers (n=8) and runners (n=8) were monitored during 45 min of swimming and running, respectively (75% V02 max), and during two hours of recovery. In addition, a group of male competitive triathletes (n=6) were similarly monitored during and after both swimming and running exercise.Blood samples were obtained after 15 min rest prior to exercise and at 0, 15, 30, 60 and 120 min of recovery and were analyzed for glucose, lactate, glycerol, free fatty acids, insulin, glucagons, norepinephrine (NE) and epinephrine (E). Respiratory gases were collected at 15 min intervals during exercise and at 15, 30, 45, 60, 90 and 120 min of recovery. Heart rate and mean body temperature were recorded at 10 min intervals throughout recovery. There were no differences in post-exercise oxygen consumption or heart rate while the RER suggested increased fat oxidation after exercise for the swimmers and the swimming triathletes. The mean body temperature and mean skin temperatures were significantly lower throughout 120 min of recovery for the swimmers compared to the runners. The triathletes demonstrated a similar tendency but these differences were not significant. The serum glucose levels were significantly greater (P<0.05) immediately post-exercise for the runners compared to the swimmers (6.71 +0.29 and 4.97 +0.19 mmol•1-1, respectively). Blood glucose values were also significantly greater immediately post-run for the triathletes (6.40 +0.26 and 4.87 ±0.18 mmol-l-1 for running and swimming, respectively). Blood glucose values remained elevated for runners and the running triathletes up to 30 min of recovery. Free fatty acids were similar after the run and the swim, but glycerols were increased immediately after running in the runners (P<0.05) and the triathletes (P<0.05). Differences in blood glucose levels or fat release were not explained by differences in NE, E or cortisol. The glucagon-to-insulin (G:I) ratio was significantly increased after exercise in the swimmers and the swimming triathletes. This, combined with a reduced RER after the swimming trials, suggests that the reduced glucose levels were due to reduced hepatic glycogen stores. The results of this study suggest that there were differences in substrate utilization during running and swimming exercise of the same intensity. These differences were not explained by NE, E or cortisol; however, the increased G:T ratio suggests increased carbohydrate use during exercise in the swimmers. Finally, body fat differences between runners and swimmers were not explained by differences in post-exercise energy expenditure or fat oxidation.

A "velocity-video" system was developed with the intent of measuring forward body velocity changes and technical skill during swimming. The system consists of a "swim-meter", video camera, A-D converter, Apple IIE computer, Microkey system, VCR and monitor. A correlation of 1.0 was found between the velocity computed by the "velocity-video" system and a known speed. Furthermore, comparison of the velocity pattern of breaststroke from video with digitized film revealed a correlation of 0.95. These results suggest that the "velocity-video" system is a valid method of describing swimming velocity and corresponding changes in body position. The second part of this investigation examined the relationship between physiological economy (ml 02-U_1-LBW-7L), technical skill, swim power, and performance between "superior" and "good" male and female breaststrokers. Swimmers were categorized based on best 100 yd performance time. To study physiological economy oxygen uptake was determined after a 400 yd submaximal breaststroke swim. No significant difference in economy (ml 02•m-1 -LBW-1) was noted between the superior and good swimmers for both males and females. The superior male swimmers, however, were found to have lower blood lactate values compared to the good male breaststrokers', 1.85 + 0.39 vs. 4.49 ± 0.86 mM•1-1. The superior males and females were found cover a greater distance per stroke compared to the good males and females, respectively. The ability to generate power and/or peak power was found to be an important factor in sprint performance (r = 0.91 and 0.92, respectively). During a submaximal effort the superior swimmers spent a greater amount of time during the glide and leg recovery phases of the breaststroke cycle than the good swimmers. The results of the present study suggest that the superior breaststrokers were characterized by there ability to minimize drag during the glide and leg recovery phases of the stroke cycle. This suggests greater technical skill as evidenced by the superior swimmers' ability to cover a greater distance per stroke cycle at a given speed.

The purpose of this study was to investigate the influence of oral NaHCOa administration on the alteration of acid-base balance and performance of high-intensity interval swimming. Ten male college swimmers were studied on five test days within a two-week period. Each test day consisted of five 100-yd freestyle swims with a two-minute rest interval between each bout. Subjects received two NaHCO3, two placebo and one no-drink treatments for the five test days. One hour before the onset of swimming the subjects were given 300 ml of citric acid flavored solution containing either NaCl (placebo) or NaHC03 (experimental), or received no drink. The dose of NaHCO3 solution was 0.25 9/kg-1 body weight. Before the sprint trial test a 300-yd warmup swimming was performed followed by a nine-minute rest. Performance times for each 100-yd swim were recorded. Blood samples were obtained before and one hour after treatment, two minutes after warmup and the last bout of swim. Blood, pH, lactate, standard bicarbonate (SBC) and base excess (BE) were measured. After the statistical analysis had shown there were no differences between the corresponding values of two trials for the same treatment, the data for identical treatments were combined and reanalyzed statistically as one group. All the corresponding variables between placebo and no-drink revealed no differences. Performance times of the fourth and fifth swimming bouts were faster (P < 0.05) and blood lactate after exercise was higher (P < 0.05) in NaHCO3 condition. Blood pH, SBC, BE were higher (P < 0.05) at post-treatment, post-warmup and post-last bout of swim in NaHCO3 condition. The difference between NaHCO3 and the other two conditions on the increment of lactate (2.0 mM) was proportional to that on the decrement of SBC (2.2 meq/1) after exercise. The data from the placebo and NaHCO3 treatments shown a positive correlation between hydrogen ion and lactate concentrations (r = 0.923) and a negative correlation between SBC and lactate concentrations (r = -0.941) after warmup and exercise. These data are in agreement with previous findings that during repeated bouts of exercise pre-exercise administration of NaHCO3 improves performance, possibly by facilitating the efflux of lactate and hydrogen ions from working muscles and thereby delaying the onset of fatigue.

Twelve competitive male swimmers were studied for a comparison of lactate/velocity profiles to heart rate/velocity profiles during a season of swim training. Lactate concentration (mM) and post-exercise heart rate (sum of three) after a 200-yard submaximal swim (approximately 90% of maximal attainable velocity) and a maximal swim were determined three times during the season: at the beginning (T1), after two months of training (T2) and after four months of training (T3). Both profiles demonstrated a significant rightward shift at T2 and a smaller, further shift at T3. Both lactate and heart rate significantly decreased at an absolute and relative exercise intensity in response to training. It is concluded that either parameter can be useful in monitoring training progress and for determining optimal training intensities. Because of the expense and difficulty of blood lactate measurements, heart rate/ velocity profiles can provide a practical and non-invasive alternative to blood lactate testing.

This thesis contains three cross-sectional studies and an equipment development study, presented in the form of journal submissions, regarding the hydrodynamics experienced by swimmers during the various phases of the freestyle tumble turn.

Thirty-eight female Wistar rats were studied to determine the response of citrate synthase (CS) and glycogen (GLY) to two similar programs of endurance training. Animals were randomly assigned to one of three groups: run-trained (RUN), swim-trained (SWIM) or sedentary control (CON). The treadmill trained animals ran at a speed of 27 m/min. up an eight degree incline. The swim-trained animals swam with 2% of body weight attached to their tails. The duration of the exercise protocols was 2 hours/day, the frequency 5 days/week and the length of the training regimen was 10 weeks. Liver GLY content (mmoles/g) for the exercise trained groups was significantly higher (p < 0.01) than CON. There were no significant differences between RUN and SWIM animals in the GLY levels of the hindlimb muscles. The GLY levels of the forelimb muscles were significantly greater (p0.01) in the SWIM animals compared to the RIJN animals, apart from the pectoralis (EEC). The CS activity in the soleus (SOL) and red -vastus (RV) of the RUN animals was significantly larger (p <; 0.01) than SWIM. The plantaris (PLANT) of the SWIM animals had significantly greater CS activity than the RUN animals. In the forelimb muscles, only -the deltoid (DEL) of the SWIM group was higher in CS activity than the RUN groups. The results of this study indicate that the mechanisms responsible for increased GLY storage in skeletal muscle are under independent control to those factors governing the changes in the oxidative enzyme CS. Differences in muscle GLY levels and CS activity between RUN and SWIM rats can be explained by contrasting mechanics in these two (nodes of exercise and the resulting fiber recruitment patterns.

The purpose of this study was to describe women collegiate swimmers' armstroke sequence at selected velocities. In addition, this study was designed to determine the timing angle during the course of a stroke cycle. Seven members of the Ball State University Women's Swim Team were asked to participate in this study. The test consisted of the subject swimming approximately fifteen meters freestyle (front crawl) at stroke rates of 24, 30, 40, 48, 60 strokes per minute. The subjects attempted three trials at each stroke rate, on a continuum from slow to fast. The following parameters were determined from video analysis: stroke length (SL), velocity (m/s), time of one complete stroke cycle (SCT), timing between the arm cycles (RAE), recovery arm entry as a percentage of SCT (RAE%) and the timing angle. A correlation between the timing angle and V of r = 0.48 was found to be significant at the 0.05 level. A correlation between the SCT and the timing angle of r = -0.62 was found to be significant at the 0.05 level. A correlation of r = -0.43 between SL and the timing angle of less than 90 degrees is believed to benefit theangle was found to be significant at the 0.05 level. This indicates that as the swimmers' SCT decreased, the timing angle increased. And, as the swimmers' SL decreased the timing angle increased. It appears that timing angles increase with increasing V. The mean timing angle for ninety trials was 66.03 degrees with a SD of 17.68. This study indicates that women collegiate swimmers use a timing angle of less than 90 degrees. A timing swimmers' body position, balance and SL.
School of Physical Education

Swimming performance is primarily judged on the overall time taken for a swimmer to complete a specified distance performing a stroke that complies with current regulations defined by the Fédération Internationale de Natation (FINA), the International governing body of swimming. There are three contributing factors to this overall time; the start, free swimming and turns. The contribution of each of these factors is event dependent; for example, in a 50m event there are no turns, however, the start can be a significant contributor. To improve overall performance each of these components should be optimised in terms of skill and execution. This thesis details the research undertaken towards improving performance-related feedback in swimming. The research included collaboration with British Swimming, the national governing body for swimming in the U.K., to drive the requirements and direction of research. An evaluation of current methods of swimming analysis identified a capability gap in real-time, quantitative feedback. A number of components were developed to produce an integrated system for comprehensive swim performance analysis in all phases of the swim, i.e. starts, free swimming and turns. These components were developed to satisfy two types of stakeholder requirements. Firstly, the measurement requirements, i.e. what does the end user want to measure? Secondly, the process requirements, i.e. how would these measurements be achieved? The components developed in this research worked towards new technologies to facilitate a wider range of measurement parameters using automated methods as well as the application of technologies to facilitate the automation of current techniques. The development of the system is presented in detail and the application of these technologies is presented in case studies for starts, free swimming and turns. It was found that developed components were able to provide useful data indicating levels of performance in all aspects of swimming, i.e. starts, free swimming and turns. For the starts, an integrated solution of vision, force plate technology and a wireless iii node enabled greater insight into overall performance and quantitative measurements of performance to be captured. Force profiles could easily identify differences in swimmer ability or changes in technique. The analysis of free swimming was predominantly supported by the wireless sensor technology, whereby signal analysis was capable of automatically determining factors such as lap times variations within strokes. The turning phase was also characterised in acceleration space, allowing the phases of the turn to be individually assessed and their contribution to total turn time established. Each of the component technologies were not used in isolation but were supported by other synchronous data capture. In all cases a vision component was used to increase understanding of data outputs and provide a medium that coaches and athletes were comfortable with interpreting. The integrated, component based system has been developed and tested to prove its ability to produce useful, quantitative feedback information for swimmers. The individual components were found to be capable of providing greater insight into swimming performance, that has not been previously possible using the current state of the art techniques. Future work should look towards the fine-tuning of the prototype system into a useable solution for end users. This relies on the refinement of components and the development of an appropriate user interface to enable ease of data collection, analysis, presentation and interpretation.

The purpose of this study was to separate acute and chronic effects of moderate exercise on the immune system by analyzing three sets of experimental and control groups; (1) 72 hours, (2) 1 week, (3) 2 weeks post exercise. Mice swam 5 days per week for 3 weeks accumulating a total of 125, 225, and 225 minutes of exercise in weeks 1, 2, and 3, respectively. Moderate swimming exercise did not result in a significant increase in SDH levels (p > 0.05). There was no change in tissue cell responses as measured by mitogen responsiveness, nor in splenic and thymic cell counts in response to the training regimen at any time point (p ≥ 0.05). Total, CD4, CD8, and T cell counts in the lymph nodes were significantly suppressed at 72 hours and 2 weeks post exercise (p ≤ 0.05). It appears that chronic exercise resulted in an increased trafficking of lymphatic cells, which could be interpreted as a sign of heightened immune reactivity.

Blood flow distribution during forced and voluntary diving in ducks, and the energetic cost of diving was investigated. It has been suggested that in order for the leg muscles to generate enough power for ducks to dive, blood flow to those tissues must be maintained. A technique to determine blood flow distribution which could be used during voluntary diving was first developed and tested during forced laboratory dives of ducks. This technique was then used to determine the blood flow distribution during voluntary diving. Regional blood flow distribution was visualized by utilizing a radioactive tracer technique (macro aggregated albumin labelled with ⁹⁹ⅿ technetium). The tracer when injected into an animal is trapped and held by capillaries. During forced dives in dabbling (Anas platyrhynchos) and diving (Aythya affinis) ducks the blood flow distribution was found to be restricted to the thoracic and head areas. Whereas during a voluntary dive in A. affinis blood flow distribution was shown to be preferentially directed towards three tissue areas, the heart, brain, and active leg muscles. The work required to dive was determined from the measurement of subsurface drag forces and buoyancy in A. affinis. Subsurface drag increased as a nonlinear function of swimming velocity. At a velocity of 1 m•s⁻¹, the drag force was approximately 1.067 N. The average measured buoyant force of 11 ducks was 0.953 N. The calculated mechanical work done by ducks during a 14.4 s unrestrained dive was 9.34 J. The power output during voluntary was estimated to be 0.751 W (0.0374 ml 0₂•s⁻¹). During diving buoyancy is clearly the dominant force (8.8 J) against which ducks have to work while drag (0.54 J) adds little (~6%) to the energetic cost of diving.
Science, Faculty of
Zoology, Department of
Graduate

The purpose of this study was to analyze specific biomechanical and physiological variables in disabled swimmers performing a functional backcrawl. The effect of selectively placed flotation devices on the body position, exercise heart rate, and perceived exertion of the swimmer was compared to swimming with no flotation. The participants in the study included eight able-bodied males 21.5 (+2.51) yrs. and four disabled males 29.25 (+2.22) yrs. Each subject performed the backcrawl for 3 consecutive lengths of a 25 meter pool under four separate trial conditions: free swimming, swimming with the hip flotation device, the knee flotation device, and the ankle flotation device. Immediately following each trial a post-exercise heart rate was taken and the subject was asked to rate perceived exertion. Full recovery was allowed after each trial. Trials were video taped and digitized to determine the mean angles at the neck, trunk, hip, and knee during one complete stroke cycle. The investigator recognizes that this generalization presents the possibility for a bias in the data and that further study would warrant the utilization of the different phases of the stroke for determination of body angles. The results of the study demonstrated that a significant difference did exist between the disabled and able-bodied hip angle during free swimming. Within the disabled group, no significant differences were evident when comparing the body angles during free swimming to the same angles while swimming with each of the flotation devices. Correlations between heart rate and ratings of perceived exertion for all subjects (n=12) were significant in each of the four trial conditions.
School of Physical Education

The swimming track start is a complex motor skill that utilizes asymmetric lower limb action. The purpose of this study was to explore whether it could be optimized by applying the commonly accepted view that there are asymmetries in the function and behaviors of the lower limbs. Initially, the study aimed to examine the relationship between various measures of lower limb asymmetry and the swimmers' preferences for forward foot placement in the swimming track start. Participants underwent a 7 week training period whereby both the left foot forward (LFF) and the right foot forward (RFF) track starts were practiced. The philosophy behind this training protocol was to ensure that participants received equal practice with the preferred and non-preferred stance so that a dominant stance, if it existed, could emerge. Consequently, the relationships between the dominant track start stance and the lower limb asymmetry measures could be determined more accurately. Participants were male (N=11) and female (N=11) swimmers, aged 12-16 years, from the UWA-Uniswim National Age Squad. Kinetic and kinematic data were collected for the track start prior to and following the 7 week training intervention. The intervention was finished when a participant had completed approximately 14 dive sessions where both the LFF and RFF track starts were practiced. The performance criterion measure was time to 5 m. Despite significant differences in vertical force and velocity contributions following the intervention, time to 5 m did not improve for either the LFF or the RFF track start. Four different measures of lower limb asymmetry were collected, including footedness, the preferred track start stance, and the dominant take-off limb for the unilateral and bilateral counter-movement jump (CMJ). Sixteen of 22 participants displayed changes in their dominant track start stance. Eleven participants showed biases for one stance (6 for the LFF & 5 for the RFF), and 11 participants remained or became more symmetrical. Results indicated that the preferred track start stance was the only measure of asymmetry that was significantly related to track start performance (x2[2]= 6.71, p=.04 for pre-intervention & x2[2]=7.77, p=.02 for post-intervention). All other measures of lower limb asymmetry were shown to be unrelated to track start preference and performance. It was suggested that the 7 week training intervention did not provide a sufficient amount of time to see conclusive effects on 5 m time or to make conclusive comparisons between the dominant track start stance and measures of asymmetry. Since the preferred track start corresponded with better performance less than 50% of the time, it was suggested that swimmers and coaches experiment with different dive techniques to find the start which is most effective for them and spend more time on them during training.

Forty Sprague Dawley rats were randomly separated into one of three experimental groups: Run-Trained (RT), Swim-Trained (SW), or Control (CON). The runners were further separated into 2 groups: Good-runners (RT1), or Poor-runners (RT2) according to their performance on the treadmill. All of the trained groups were endurance trained at approximately 80% V02 max for two hours per day, five days per week in the appropriate mode of exercise. After nine weeks of equi-intensity training, the perimetrial fat pads were removed and the calls isolated. The adipocytes from the trained animals were significantly smaller in volume and diameter than the adipocytes from the controls. Adipocytes from all of the trained groups were significantly more sensitive to insulin than the CON group according to the definition by Kahn (60). The cells from the RT1 and SW groups were significantly more responsive to insulin than both the RT2 and CON groups. The adipocytes from the RT1 group were also significantly more responsive to insulin than the SW group. The differences in cell responsiveness to insulin were highly correlated to the average size of the cells studied. From the data presented in this study threeconclusions were drawn: 1) Both running and swimming at the reported intensity, duration, and frequency have a significant effect on the morphology and metabolism of the isolated adipocyte, 2) Adipocyte morphology, insulin sensitivity, and insulin responsiveness are dependent on the frequency, intensity, and duration of a given exercise training protocol, and 3) Each type of exercise training has its own drawbacks: with swimming, the rats may experience some hypoxia which may alter their metabolic fuel utilization, and during running not all of the animals may be capable or willing to complete the run.Ball State UniversityMuncie, IN 47306

Orientador: Miguel Arcanjo Areas
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: Esteróides androgênicos anabolizantes (EAA) são indicados clinicamente para promover aumento da síntese protéica após queimaduras, cirurgias, radioterapia, no tratamento contraceptivo, no hipogonadismo, na osteoporose, na sarcopenia relacionada à idade e à pacientes portadores de HIV. Por outro lado, o uso indiscriminado dos EAA, com intuito de aumentar o desenvolvimento muscular, o desempenho físico, a capacidade aeróbia, a tolerância ao treinamento de alta intensidade e até mesmo para fins estéticos, é crescente entre atletas e esportistas recreacionais. O uso abusivo de EAA está relacionado à toxicidade cardíaca e hepática em consequência do aumento do estresse oxidativo. Por outro lado, estudos apontam a melatonina como substância com significativa ação antioxidante, apresentando efeitos benéficos no tratamento de doenças cardíacas. Este trabalho teve por objetivo avaliar os efeitos da melatonina sobre biomarcadores do estresse oxidativo e parâmetros cardiovasculares e hepáticos em ratos adultos sedentários ou treinados com natação e tratados com estanozolol. Os ratos foram distribuídos nos seguintes grupos: sedentário (S), sedentário+estanozolol (SE), sedentário+estanozolol+melatonina (SEM), treinado (T), treinado+estanozolol (TE) e treinado+estanozolol+melatonina (TEM). Realizou-se avaliação eletrocardiográfica no início e ao final do período experimental (6 semanas), sendo, então, determinada a pressão arterial, atividade de enzimas antioxidantes e da fosfatase alcalina e histologia do coração e do fígado. Os resultados mostraram que o estanozolol provocou bradicardia, queda do peso relativo do fígado e aumento da atividade das enzimas superóxido dismutase cardíaca e hepática, catalase cardíaca e fostatase alcalina hepática. Quando associado ao treinamento, estanozolol aumentou a pressão arterial sistólica e diastólica, o peso relativo do coração, desviou o eixo elétrico cardíaco para esquerda e provocou alterações hepatotóxicas. A administração da melatonina nos ratos tratados com EST, por sua vez, impediu o aumento da pressão arterial sistólica e diastólica e da atividade das enzimas catalase cardíaca, fostatase alcalina hepática além de impedir o desvio do eixo elétrico cardíaco causado pela hipertrofia ventricular esquerda induzida pelo estanozolol. Além disso, melatonina reduziu as alterações nos hepatócitos induzidas pelo estanozolol. Concluímos que, em nossas condições experimentais, a melatonina atenuou os efeitos adversos ao sistema cardiovascular e ao fígado causados pelo uso de doses suprafisiológicas de estanozolol
Abstract: Anabolic androgenic steroids (AAS) are nominated for clinical use to promote protein synthesis after burns, surgery, radiotherapy, on contraceptive treatment, osteoporosis, hypogonadism, age-related sarcopenia and HIV patients. However, the indiscriminate use of ASS aiming to stimulate muscular development, physical performance, aerobic capacity, tolerance to high-intensity training and with aesthetic purpose is increasing among athletes and recreational sportsmen. The abusive use of ASS is related to oxidative stress-induced cardiac and hepatic toxicity. Nonetheless, many studies point to melatonin as a substance with antioxidant properties, with beneficial effects on cardiovascular diseases treatment. The purpose of this study was to assess melatonin's effects on oxidative stress biomarkers, cardiovascular and liver parameters in stanozolol-treated trained rats. Rats were divided into the following groups: sedentary (S), sedentary+stanozolol (SS), sedentary+stanozolol+melatonin (SSM), trained (T), trained+stanozolol (TS) and trained+stanozolol+melatonin (TSM). Electrocardiography assessment were performed at the beginning and at the end of experimental period, and then, blood pressure, antioxidant enzymes and phosphatase alkaline activities, heart and liver histology were determined. Stanozolol induced bradycardia, relative liver weight decreased and increased cardiac and liver superoxide dismutase, cardiac catalase and liver phosphatase alkaline activities. Stanazolol plus training induced increased systolic and diastolic blood pressure, relative heart weight, left cardiac axis deviation and toxic liver damage. Melatonin induced decreased systolic and diastolic blood pressure, cardiac catalase and liver phosphatase alkaline activities, and prevented stanazolol-induced left cardiac axis deviation. Furthermore, melatonin decreased stanozolol-induced liver damage. In conclusion, under our experimental conditions, the side effects of supraphysiology doses of stanozolol on liver and cardiovascular system are mitigated by melatonin
Mestrado
Fisiologia
Mestre em Biologia Funcional e Molecular

Exercise intensity and its distribution is probably the most important and most heavily debated variable of endurance training. Training induces adaptation but also induces stress responses. Controlling the training-intensity distribution may provide a mechanism for balancing these two effects. It has been reported that elite endurance athletes train with a high volume and load, relative to the sport. These athletes spend the vast majority (>80%) of training time at relatively low intensities (lower than the lactate threshold, zone one), and therefore <20% of training time above the lactate threshold (zones two and three). Experimental studies support the beneficial effects of a high training volume in zone one, and show detrimental effects of replacing zone one training with training in zone two. This is likely due to enhanced recovery from training in zone one compared with training in zone two. The acute recovery following training sessions in zones two and three has been reported to not be different, but the recovery following training in zone one has been reported to be faster. Improvements in physiological adaptation and endurance performance have been reported to be greater following training programmes with higher exercise intensities. Therefore, it has been suggested that a polarised training model, which includes ~80% of training in zone one with ~20% of training in zone three is more beneficial than a threshold training model, with the majority of training in zone two. However, research into an optimal training-intensity distribution is limited. Therefore, the aims of this thesis were to assess the effectiveness of training-intensity distribution on the improvements in physiological adaptation, endurance performance and assess if manipulating training-intensity distribution had an effect on immune function. Study one revealed that the lactate threshold, the lactate turnpoint and maximal performance measures in swimming, cycling and running, assessed using the methods outlined in the study, are reproducible in trained endurance athletes. These tests can therefore be used by trained endurance athletes as part of a physiological testing programme to assess not only endurance performance, but also to demarcate training intensity zones for exercise intensity prescription and monitor moderate to large adaptations to training. Practitioners should take care when deciding on the duration between tests to test for adaptations from training, as adaptations need to be greater than these detected test-retest variations to be considered physiologically meaningful. To the best of the author’s knowledge, study two was the first study to have assessed training-intensity distribution in a group of multisport athletes. Training was monitored over a 6-month period, and testing took place every two months to assess the effect of the training on physiological adaptation. Although speculative due to the number of variables involved, the results suggest that a greater proportion of training time spent in zone one and a lower proportion of training time spent in zone two is beneficial to physiological adaptation. However, given the number of variables associated with assessing the training-intensity distribution in multisport athletes, it is not easy to draw conclusions as to the effectiveness of the training in the different disciplines on the key measures of adaptation in the different disciplines. Study two highlighted the need for future research to focus on experimental manipulation of training-intensity distribution and thus improve our understanding of its impact on the training-induced adaptations in endurance athletes. Study three manipulated the training-intensity distribution in trained endurance athletes in just one discipline, to reduce the number of variables involved. A polarised training model was compared to a threshold training model on the effectiveness to improve physiological adaptation and endurance performance. Results revealed that a polarised training model is recommended for trained cyclists wishing to maximally improve performance and physiological adaptation over a short-term (six week) training period. The first part of study four assessed the effect of a polarised and a threshold training model on immune function markers in trained cyclists. Both endurance training programmes had similar volume, and were sufficient to induce improvements in performance and physiological adaptation. However, despite likely differences in recovery, both training programmes had no effect on the proportion of low or high differentiated or senescent CD8+ or CD4+ T-cells in blood. Therefore, training adaptation was achieved at no cost to this particular aspect of immune function. From these results and evidence from previous studies, it seems likely that athletes need to be overreached to induce any change in immune function following a period of intensified training. The second part of study four assessed the impact of an ironman triathlon race on Epstein-Barr virus (EBV) and Varicella-Zoster virus (VZV) antibody titres and the frequency of low and high differentiated and senescent blood T-cells in trained endurance athletes. Previous work has revealed that an ironman triathlon race increases the proportion of senescent CD4+ T cells and decreases the proportion of naive CD4+ T cells, and thus induces changes the immune space which could leave an individual at a greater risk of infection. This study however, did not find any changes in the proportions of these T cell subsets following an ironman triathlon race. The mean results of this study suggest that there is no relationship between EBV and VZV-specific antibody concentrations and the proportion of senescent, low and highly differientiated T cells. However, on analysis of individual subject data, it seems possible that subjects with a high antibody titre for EBV or VZV 3 wks before a competition might be more at risk of infection post race. A greater subject number would be needed in order to make a more conclusive statement about this relationship. The results of this thesis suggest that future research is required in the area of training-intensity distribution. Firstly, our understanding of the physiological mechanisms responsible for the effectiveness of a polarised training model in trained endurance athletes is limited, and thus studies should attempt to address this issue. Our current knowledge on the mechanisms underlying a blunted T cell response following strenous exercise is also limited. A change in the immune space to a greater proportion of senescent T cells and a lower proportion of naive T cells might contribute to this blunted response. In the current thesis however, the proportions of these T cell markers were unchanged following the training/racing interventions. It is possible that with a higher training load, there could be changes in these markers, and thus this is an exciting area that could have potential implications on athlete health. Finally, testing for antibody titres in endurance athletes is possibly an avenue to detect individuals at the greatest risk of infection if subjected to a large physical and/or mental stress. This could have implications on maintaining athlete health and therefore, allowing athletes to train consistently.

The purpose of the present study was to determine the effects of using intermittent hand cooling during high intensity, intermittent training on measures of thermoregulatory, performance and psychophysical variables in elite level swimmers in warm pools (30.50.5°C). Following a standard warm-up, ten male swimmers (20.3±3.2 yrs) were instructed to maintain the fastest average 100m time for an 8x 100m freestyle swimming set separated in a cool pool (CP), warm pool with cooling (WPC), and warm pool with no-cooling (WPNC). Time at 50m and 100m, core temperature (Tc), and heart rate (HR), as well as the rate of perceived exertion (RPE), thermal comfort (ThC) and thermal sensation (ThS) were recorded following each repetition. Participants were cooled during the 90 second rest interval between repetitions using the Rapid Thermal Exchange (RTX) [AVAcore Technologies Inc., Ann Arbor, MI]. There was a significant increase in performance when comparing the second 50m split time (1.16 ± 1.58s ) and 100m time (1.50 ± 1.98s) for the final repetition in the WPC condition compared to the final repetition in the WPNC condition (p<0.05). FIR, ThC and ThS were lower in the CP condition than the WPC and WPNC conditions (p<0.05). There was no significant difference in Tc and RPE between conditions. It was concluded that the results may be due to a placebo effect and at this time there appears no physiological or psychophysical advantage in using the RTX during high intensity, intermittent training of elite swimmers.