Caffeine is the most widely consumed socially acceptable drug in the world and is commonly used for its ergogenic properties with demonstrated performance enhancing effects in endurance, power and strength based activities. Despite a wealth of evidence concluding a caffeine induced performance benefit, the direct effects of the drug on peripheral physiological processes have not been fully examined. Early works showed high dose caffeine has direct force potentiating effect on skeletal muscle, a notion that has only recently been confirmed by James et al. (2005) to also occur at a maximal human physiological concentration (70µM). The present research, using mouse muscle as a model for mammalian muscle in general, provides an in-depth assessment of the direct effect of physiological concentrations of caffeine on isolated skeletal muscle performance. This research uniquely: quantifies the dose response relationship; assesses the effects of caffeine on maximal and sub maximal muscle power output and fatigue; looks at the relationship between muscles with different fiber type compositions. As high concentrations of caffeine and taurine are a constituent of many energy drinks, the suggested interaction of these ingredients to further potentiate muscle mechanical performance was also assessed. The study further examines how mammalian muscle mechanical properties change over an age range of development to aged, and how this differs between muscles with predominantly different anatomical locations and functions. In light of this the age related direct effect of physiological concentrations of caffeine was assessed in order to examine whether the ergogenic benefit changed with age. The present results demonstrate a direct muscle performance enhancing effect of physiological concentrations of caffeine that is likely to promote greater benefit on long duration endurance based activities. Furthermore, the present study demonstrates that there is no direct effect of physiological concentrations of taurine and no further performance enhancing benefit when combined with caffeine. Finally this research uniquely highlights the muscle specific age related changes in mechanical performance and further indicates that the direct effect of caffeine changes with age.

Graduation date: 2004

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.

This thesis examined the impact of oxygen (O2) availability on prefrontal cortex and muscle tissue oxygenation during repeated-sprint exercise (RSE) in men and women. Men and women matched for initial-sprint mechanical work performed during ten, 10-s sprints (30s of rest) in normoxia (21% FIO2) and acute hypoxia (13% FIO2). Mechanical work and arterial O2-saturation (SPO2) were obtained for every sprint. Oxy- and deoxygenated haemoglobin concentrations (O2Hb, HHb) were obtained via near-infrared spectroscopy. Hypoxia elicited lower SPO2 and work (14.8% & 7.4%, P < 0.05), larger (45.1%, P < 0.05) and earlier reductions in cortical oxygenation, and no differences between sexes. Cortical de-oxygenation and work decrement were strongly correlated (R2=0.85, P < 0.05). Muscle de-oxygenation was greater in men than women (67.3%, P < 0.05). These results show that O2 availability influences cortical oxygenation and performance equally in men and women, and suggest a more efficient muscle O2 uptake in women. / ix, 108 leaves : ill. ; 29 cm

Adolescent athletes of this era are more pressurized than adolescents of previous generations to perform at an optimum level (Micheli & Jenkins 2001, p49). The importance of winning can result in adolescent athletes developing inappropriate nutritional practices such as neglecting hydration and consuming insufficient carbohydrate (Micheli & Jenkins 2001, p57). Consuming insufficient fluid leads to dehydration which reduces a soccer player’s ability to continue training. Consuming inadequate carbohydrate reduces performance and blood glucose levels during training. This study aimed to determine the hydration status, fluid and carbohydrate intake of male, adolescent soccer players during training. A cross-sectional study was conducted among 122 amateur male, adolescent soccer players (mean age = 15.8 ± 0.8 years; mean BMI = 20.4 ± 2.0 kg/m2). The players’ hydration status before and after training, was measured using urine specific gravity and percent loss of body weight. Their carbohydrate intake, as well as the type and amount of fluid consumed, were assessed before, during and after training. A questionnaire was administered to determine the players’ knowledge regarding the importance of fluid and carbohydrate for soccer training. The study had an 87.1% response rate. The mean environmental conditions did not predispose players to heat illness. However, the players were at risk of developing heat illness during six of the 14 training sessions. Although the mean urine specific gravity indicated that players were slightly dehydrated before and after training, 43.8% of players were very or extremely dehydrated before training and 53.6% after training. A few (3.3%) were extremely hyperhydrated before training and after training (7.0%). On average players lost less than 1% of body weight during training and less than 3% of players dehydrated more than 2%. Players consumed mainly water before (289.17 ± 206.37 ml), during (183.20 ± 158.35 ml) and after (259.09 ± 192.29 ml) training. More than 90% stated that water was the most important fluid to consume before, during and after training. Very few (4.7%) correctly stated that carbohydrate should be consumed before, during and after training. Players were found to be slightly dehydrated before and after training and therefore were not consuming enough fluids during training. Players consumed inadequate amounts and types of fluid and carbohydrate. This not only compromises their performance but also health. Players were not aware of the importance of fluid and carbohydrate for soccer training. This study is unique in that it focused on the carbohydrate and hydration practices of socioeconomically disadvantaged adolescent soccer players during training. The study sample therefore represents a high risk group about which there is limited published data both locally and internationally. This study generated important baseline information which was lacking before on the hydration status, fluid and carbohydrate intake of adolescent soccer players in South Africa. / Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.

Introdução: A capacidade física humana é influenciada por fatores ambientais e genéticos. Ao associar à genética e o esporte existe a possibilidade de se identificar os indivíduos com a maior capacidade de responder ou adaptar-se ao treinamento com menores chances de sofrerem lesões. Objetivo: Avaliar a frequência dos genes, ACTN3 e da ACE I/D, em lutadores de domínio. Metodologia: Fizeram parte da presente pesquisa 23 atletas, sendo 11 lutadores de Judô, 4 lutadores de Wrestling e 8 lutadores de Jiu Jitsu, todos do sexo masculino com idade média de 27,3±6,9 anos, com experiência nacional e internacional em suas respectivas modalidades e categorias de peso. A genotipagem dos polimorfismos do ACTN3 e ACE I/D foi realizada por reação em cadeia da polimerase (PCR) a partir do DNA genômico. As frequências genotípicas e alélicas foram comparadas com populações controle e de atletas pelos testes do Qui-Quadrado e exato de Fisher, para todas as análises foi adotado p˂0,05. Resultados: As frequências genotípicas e alélicas do ACTN3 (RR=52,2%,RX=26,1% e XX=21,7%; R=65,2% e X=34,8%) e do ACE I/D (DD=50%, ID=25% e II=25%; D=65,2% e I=34,8%) não diferiram significativamente da população controle, porém quando comparado aos atletas de luta foi encontrada um diferença significativa. Conclusão: Em conclusão os dados da presente pesquisa indicam uma associação do gene da ACTN3 e da ACE I/D com lutadores de domínio. / Introduction: The human physical capacity is in influenced by environmental and genetic factors. The associate to genetics and the sport has the possibility to identify individuals with the greater capacity to respond or adapt to for training with lower chances of suffering from lesions. Objective: evaluate the frequency of the genes, ACTN and the ACE I/D, in fighters of dominion. Methodology: Were part of the present research 23 athletes, with 11 fighters of judo, 4 fighters of wrestling and 8 fighters of jiu jitsu, all male with a mean age 27.3±6,9 years. With national and international experience into their respective weight categories and modalities. Genotyping of the polymorphism in the ACTN3 and ACE I/D was performed by reaction polymerase chain (PCR) from DNA genomic. The frequencies genotypic and allelic were compared with control populations and athletes by the tests of chi-square and fishers exact, for all analyzes was adopted p˂0.05. Results: the frequencies genotypic and allelic of ACTN3 (RR=52.2%,RX=26.1% e XX=21.7%; R=65.2% e X=34.8%) and the ACE I/D (DD=50%, ID=25% of II=25%; D=65,2% e I=34,8% did not differ significantly on the population control. However when compared the athletes of struggle was found a meaningful difference. Conclusion: In conclusion the data of the data of the present survey indicate an associate of the gene of ACTN3 and the ACE I/D with fighter‟s domain.

Os fatores genéticos e o meio ambiente são pontos relevantes no que tange a capacidade física do ser humano. O objetivo deste estudo foi avaliar o genótipo dos genes, ACTN3 e da ACE I/D, em lutadores de alto rendimento na modalidade de percussão. Neste estudo fizeram parte do conjunto amostral 15 atletas de alto rendimento da esportes de combate e arte marcial, sendo sendo 6 lutadores de Karatê, 4 lutadores de Taekwondo, 4 lutadores de Muay Thai e 1 lutador de Boxe, todos do sexo masculino com idade média de 25,06 anos, com experiência nacional e internacional em suas respectivas modalidades e categorias de peso. A genotipagem dos polimorfismos do ACTN3 e ACE I/D foi realizada por reação em cadeia da polimerase (PCR) a partir do DNA genômico. As frequências genotípicas e alélicas foram comparadas com populações controle e de atletas pelos testes do Qui-Quadrado, e exato de Fisher, para todas as análises foi adotado p˂0,05. Os resultados obtidos para as frequências genotípicas e alélicas do ACTN3 (RR=35,71%,RX=57,14% e XX=7,14%; R=64,28% e X=33,71%) e do ACE I/D (DD=30,76%, ID=50,84% e II=15,36%; D=65,2% e I=34,8%) não diferiram significativamente da população controle e com estudos relacionados a força. Em conclusão os dados da presente pesquisa seguem os padrões esperados para população no que tange a frequência genotípicas e em sua distribuição alélica nos genes da ACTN3 e da ACE I/D com lutadores de percussão. / Genetic factors and the environment are relevant points regarding the physical capacity of the human being. The objective of this study was to evaluate the genotype of genes, ACTN3 and ACE I / D with fighters in high yield in the form of percussion. In this study were part of the sample set of 15 high-level athletes in combat sports and martial arts, 6 fighters from Karate, 4 fighters Taekwondo, 4 fighters Muay Thai and 1 boxing. All fighters being present, all males with average age of 25.06 years with national and international experience in their respective weight classes and methods. Genotyping of polymorphisms of ACTN3 and ACE I / D was performed by polymerase chain reaction (PCR) chain from the genomic DNA. The genotypic and allelic frequencies were compared with control populations and athletes by Qui-Quadrado and Fisher exact tests for all analyzes was adopted P=0.05. The results obtained for genotypic and allelic frequencies of ACTN3 (RR = 35.71%, 57.14% and RX = XX = 7.14%; R = X = 64.28% and 33.71%) and ACE I / D (DD = 30.76%, 50.84% and ID = II = 15.36%; D = I = 65.2% and 34.8%) did not differ significantly from the control population e power sports In conclusion the data of this study follow the expected population in relation to genotypic and allelic frequency distribution in the ACTN3 gene and ACE I / D fighters of percussion.