Dysregulation of intramuscular triglyceride (IMTG) turnover in human skeletal muscle in sedentary and obese states leads to accumulation of lipid metabolites that contribute to skeletal muscle insulin resistance and ultimately progression to type 2 diabetes (T2D). People with T2D display low levels of IMTG turnover in comparison to insulin sensitive and trained individuals. IMTG stores are used as an energy substrate during 1 h of moderate-intensity exercise in trained individuals only and can be increased by consumption of a high fat, high calorie (HFHC) diet in sedentary and trained states. This thesis explores the metabolic and molecular regulation of proteins that regulate IMTG turnover, specifically focusing on the effects of 1) a HFHC diet and 2) a moderate-intensity exercise bout and 3) IMTG stores in different diseases states (lean, obese and T2D). Chapter 2 determined there were no sex-specific differences or main effects in functional outcomes of cardiovascular (arterial stiffness) and metabolic health (glucose tolerance and metabolic flexibility) in response to 7 days HFHC diet. Chapter 3 provides novel evidence that 7 days HFHC diet induces fibre type specific increases in IMTG stores primarily underpinned by an increase in perilipin-3 (PLIN3) protein expression and a redistribution of perilipin-2 (PLIN2) to lipid droplets (LD) storing IMTG. This occurred with no impairments in skeletal muscle insulin signalling and it is therefore proposed that increases in IMTG content assisted by PLIN2 and PLIN3 minimise the accumulation of lipid metabolites known to disrupt the insulin signalling cascade. Chapter 4 revealed that hormone sensitive lipase (HSL) preferentially redistributes to LD associated with perilipin-5 (PLIN5) following 1 h of moderate-intensity exercise. Chapter 5 developed a PLIN5 immunoprecipitation mass spectrometry protocol which identified phospholipase A2- group II, subgroup A (PA2GA) as a novel protein associated to PLIN5 in muscle from lean sedentary humans. In conclusion, this thesis presents novel data on key proteins that regulate IMTG turnover in human skeletal muscle.

Introduction: Sympathetic nerve activity (SNA) undergoes physiological modulation by respiration but it remains unclear whether this process is altered by age and hypertension. Aims: To establish relationship between respiration and neural regulation of the cardiovascular system in aging and hypertension. Methods: Multiunit muscle SNA, BP, respiratory parameters and heart rate were recorded at rest in young and older healthy men and hypertensive patients, then repeated in hypertensive group after acute and long-term device-guided slow deep-breathing (SDB) training. Results: Muscle SNA was higher in older subjects but showed similar modulation by respiration in both age groups. In young acute SDB reduced SNA, with no effect on sympathetic and cardiac baroreflex sensitivity. The sympathoinhibition was not related to changes in baroreflex sensitivity, but it reflected increases in lung inflation afferent input and/or reduction in central respiratory-sympathetic coupling. Long-term SDB training inhibited muscle SNA in hypertensive patients and led to acute increase in heart rate variability and longer-term BP reduction. There were no changes in baroreflex sensitivity, cardiac structure/function or arterial stiffness in response to SDB training. Conclusions: The study provides new mechanistic insights into sympathetic regulatory pathways in hypertension and aging, which may help to establish anti-hypertensive strategy based on respiratory modulation.

This thesis investigated three commonly used nutritional interventions that are often claimed to alter substrate metabolism and improve exercise performance: green tea extract (GTE), coffee and vitamin D. GTE and caffeine have been hypothesized to increase fat oxidation at rest and during exercise, thereby lowering the reliance on skeletal muscle glycogen and improving endurance exercise capacity. We observed that 7 days GTE supplementation resulted in an increase in metabolites related to fat and energy metabolism at rest but not during moderate intensity exercise. The current thesis also found that endurance exercise performance can be improved to the same extent by either using coffee or caffeine. However, these improvements in endurance exercise performance were independent of changes to fat oxidation during exercise. We also demonstrate that athletes living in Birmingham, United Kingdom, display a high prevalence of vitamin D deficiency during the winter and thus require nutritional support. However, despite the high prevalence of vitamin D deficiency, there was no association between vitamin D status and skeletal muscle function or exercise performance. Short term vitamin D supplementation at doses above the current recommended daily allowance was highly effective in correcting vitamin D deficiency to sufficiency. But supplementation did not alter any measure of performance.

Youth sport has been advocated as a vehicle through which more physically active lifestyles can be encouraged among children and adolescents. Employing objective assessments of physical activity (PA), the purpose of this thesis was to investigate the value of youth sport as a context for PA promotion and obesity prevention. Results from Study 1 indicated 37% of youth sport football participants did not meet recommended levels of moderate-to-vigorous PA (MVPA) during their youth sport engagement. Study 2 demonstrated negative associations between daily PA levels of grassroots footballers and obesity linked health outcomes, with the reverse true for sedentary time (ST). Guided by self-determination theory (Deci & Ryan, 1987), findings from Studies 3 and 4 revealed perceptions of coach provided autonomy support were positively associated with sport related autonomous motivation, and in turn, higher MVPA participation (daily MVPA as well as PA accrued during youth sport) and lower ST. This thesis underlines the value of youth sport as a setting through which levels of PA can be increased, and ST reduced among youth. Research described within also points to the important role of the coach-created environment and player motivation in predicting variability in PA engagement and ST among young grassroots footballers.

Triathlon comprises of three disciplines: swimming, cycling and running. Of these, running performance has been found to be most strongly related to race success. Studies investigating the effect of long term multidisciplinary training on running technique are limited. This thesis set out to further explore these chronic adaptations and apply this theoretical understanding to investigate training modification in triathlon. Results of the first two experiments showed that long term kinematic adaptations to running, present in both male and female triathletes. This is most likely due to the volume of cycling undertaken and the subsequent effect it has on the hip musculature. Consequently, a hip flexibility programme was designed and implemented. However, despite improvements in static flexibility, this programme did not affect running technique. In a subsequent study, flexibility training combined with running technique drills also failed to bring about any modifications in running kinematics. Findings of a longitudinal case study demonstrated that, in addition to chronic and acute running technique adaptations, intermediate changes linked to varying training demands also exist showing the level of variability of the running technique. It is concluded that adaptations to cycling are the cause of differences in running technique between triathletes and runners and that these modifications are difficult to reverse. However, the additional intermediate variations observed demonstrate technique can be changed as a result of training requirements.

The overall aim of this project was to investigate the acute cardiovascular post-exercise response in healthy individuals. The aim of the first study was to establish the within day and between day reproducibility of supine and tilt baroreflex sensitivity (BRS) utilising time (sequence) and spectral indices in 46 healthy adult males employing three repeat measures; baseline, + 60 min and + 24 h. Reproducibility was assessed by the 95% limits of agreement (LOA) to assess the extent of agreement and an alternative approach of estimating the technical error of the measurement (TEM) to assess reproducibility was also undertaken. The LOA indicated same day reproducibility was marginally better than between day reproducibility for spectral parameters while between day reproducibility was marginally better than same day reproducibility for sequence parameters with reproducibility markedly improved across all BRS outcome measures during tilt. Precision expressed by TEM for all spectral outcomes was good in both supine and tilt BRS (< 6 %) although precision was lower, but acceptable, for sequence BRS outcomes in both positions (< 11%). Thus, all BRS outcome measures and the tilt procedure were incorporated into the exercise study. The aim of the second study was to compare the response of supine and tilt BRS following a single bout of moderate intensity exercise and high intensity exercise. Further details are given in the full abstract above.

A series of field based investigations were undertaken to establish the mood state and salivary immunoglobulin-A (S-IgA) response to different training loads in amateur boxing. Mood states were initially monitored via the Profile of Mood States (McNair, Lorr & Droppleman, 1971) and thereafter through the development of a boxing specific, shortened version. S-IgA was analysed through enzyme-linked irnmunosorbent assays. Results ofthe early investigations showed mood disturbances in fatigue, vigor, tension and anger with intensified training. Immunological data showed S-IgA to significantly decrease following interval training, with the principal factor in the suppression being a reduction in saliva flow rates. Boxers were seen to have unusually low saliva flow rates compared to sedentary individuals and this was linked to the weight-classified nature of the sport. There was no relationship found between psychological and immunological measures. Subsequent investigations focused on the recovery process from amateur boxing. Massage was compared with control conditions as a post training recovery intervention. Results showed massage to induce psychological regeneration in the form of decreased perceptions of fatigue and increased recovery. Massage did not affect saliva flow rates post training. A final laboratory based investigation documented the effects of massage on psychological regeneration, physiological recovery and repeated amateur boxing performance on a boxing ergometer. Massage was seen to promote psychological regeneration, but did not affect blood lactate clearance or subsequent performance when compared with a no-massage condition. It was concluded that amateur boxing training can result in detrimental psychological and immunological effects. It was argued that the role of passive recovery strategies in sport are still poorly understood and researched, but that preliminary support could be given to the vast amount of anecdotal evidence suggesting positive psychological effects of massage as a regeneration strategy. The use of massage for physiological recovery and as a performance enhancement modality was questioned.

This thesis aimed to investigate and model the vo2, response to exhaustive constant intensity running of a short duration. Study I was a Douglas bag based study that compared the vo2, response of physically active subjects to 2, 5 and 8 minute bouts of constant intensity exhaustive exercise performed in both cycling and running. Nine male subjects took part and each completed a ramp test in addition to the three constant intensity tests in both modes of exercise. In the 5 and 8minute tests the subjects achieved 97.0 ± 4.2 and 97.5 ± 2.0 % for cycling, and 98.5 ± 1.8 and 99.2 ± 2.3% for running, of the ramp test Vo,peak. In the 2 minute test, a significantly lower percentage was attained (89.9 ± 5.5% and 91.8 ± 2.5% for cycling and running respectively). In cycling VO, was still increasing over the final minute of the test, whereas in running there was no difference between the last two 30 second samples (P~0.98). It was concluded that in severe intensity exercise of a short duration VO2 may not achieve its maximum and· that in running it may plateau at this sub-maximal rate. Study 2 validated the QP9000 for the measurement of vo2, during running on a breath-by-breath basis. Six male subjects performed a ramp test and tests at rest and at moderate and severe intensities. Each test was performed twice, once using the QP9000 and once using a Douglas bag system. No difference was found for VO, between the two systems (P~0.358). The SD of the differences between the systems across exercise intensities was 97 ± 57 ml.min·1 It was concluded that the QP9000 provides a valid measure of VO, at all exercises intensities. Study 3 investigated the vo2, response of trained runners to 800 m pace running, following a track based time trial. Eight male subjects (Vo,max 68.8 ± 5.6 m1.kg·'min-') took part in the study. That vo2, reached a plateau below Vo, was confirmed by a gradient of -29 ± 275 ml.min-' during the final 30 seconds of exercise. The asymptotic vo2, was only 85.3 ± 6.6 % of the Vo,peak from a ramp test and the response was shown to be extremely fast (time constant (T) of 10.7 ± 3.4 seconds). These breath-by-breath data confirmed the response indicated in Study I. Study 4 explored the single exponential model used to describe the vo2, response and the nature and level of breath-by-breath noise in severe intensity running. Five male subjects performed a ramp test to determine the speed at anaerobic threshold (AT). Each subject then performed five 8-minute runs at a speed corresponding to 90% of the AT and five exhaustive runs at a speed that would elicit exhaustion in about 2-minutes. Analysis of the noise to signal ratio of the severe intensity data showed that the noise was Gaussian and that averaging data over repeated transitions reduced this ratio. Computer simulations of noise equivalent to the noisiest subject's data demonstrated that the use of two repeated severe intensity transitions would give 95% confidence limits of < ± 1.2 seconds for T. Study 5 examined the effect of prior supra AT exercise on the VO, response to exhaustive severe intensity running. Ten middle and long distance runners each completed a ramp test to determine AT and Vo,peak. Subjects then ran exhaustive transitions, lasting approximately 2-minutes, that were preceded by moderate (90% AT) or heavy (50% of the difference between AT and Vo,peak) intensity running. Each transition was repeated. Increased metabolic acidosis (from prior heavy intensity exercise) did not increase the asymptotic vo2, (P ~ 0.226), and this figure represented only about 90% of Vo,peak from the ramp test. The mean response time (MRT) (time to reach 63% of the overall response) was faster following heavy exercise (20.9 ± 1.9 s vs. 18.9 ± 1.0 s, P<0.05). This was however due to a reduction in the duration of the initial (cardiodynamic) phase of the response rather than a speeding of the primary (phase 2) kinetics. Study 6 analysed the differences in this response between sprint and endurance runners. Six male athletes were recruited for each group based on best times for 100 m and 10 000 m. Subjects performed repeated transitions at a speed that would elicit exhaustion in approximately 2-minutes. No difference was found in the model of the VO, response between groups. When all subjects were analysed however a strong negative relationship was demonstrated between Vo,peak (from a ramp test) and the percentage of this Vo,peak that was reached in the constant speed test (r ~ -0.811, P ~ 0.001). It was concluded that the VO, response was dependent on the aerobic capabilities of the individual. In conclusion the thesis demonstrated a vo2, response in trained subjects during exhaustive severe intensity running that was different to that which is suggested by the majority of the literature. The vo2, response tends neither to VO, required nor to Vo,max, but rather tends to a plateau that is sub-maximal. This thesis was unable to identity the mechanisms that might result in such a shortfall in the response. However there appears to be a close link with the aerobic capabilities of the individual.

Leary (1992) suggests a self-presentation perspective could fruitfully be applied to sport. In support of this, early research has revealed that self-presentation concerns underpin a large percentage of competitive anxiety and stress in sport (James & Collins, 1997; Wilson & Eklund, 1998). However, little progress has been made towards the identification of athletes who are most at risk of experiencing self-presentation concerns. The main aim of this thesis was to examine self-presentation concerns in athlete populations. More specifically, the aims were firstly to develop a valid measure of self-presentation concerns in sport. Secondly, the impact of gender, age, skill level and type of sport on self-presentation concerns was examined. To achieve these aims five studies, including three validation, one quantitative and one qualitative study, were conducted. The validation studies provided evidence to suggest that the Self-Presentation in Sport Questionnaire (SPSQ) is a valid and reliable measure of self-presentation concerns in sport, suitable for administration to athletes over the age of eighteen. However, shortened versions ofthe SPSQ, suitable for children and adults, demonstrated a weakened internal structure and consequently these instruments ought not to be administered in their present state. The quantitative study investigated the impact of gender, skill level and type of sport on self-presentation concerns in swimmers, water polo players and divers utilising the SPSQ. The findings indicated that females exhibit consistently higher self-presentation concerns compared to males, as do non-elite athletes when compared to the elite. Furthermore, self-presentation concerns were affected by the situation in different ways dependent on the athletes' gender. Finally, differences in the self-presentation concerns experienced in adolescence and adulthood were qualitatively assessed. Differences were identified across the type of self-presentation concerns experienced, the strategies used to make an impression, and the targets of self-presentation. Overall the research conducted provides a valid measure of self-presentation concerns in sport, which can be utilised in future self-presentation studies. Furthermore, the impact of a number of individual and situational variables on self-presentation concerns has been revealed.

This thesis aimed to establish why the incidence of a V02-plateau is typically high (>80%) for a discontinuous test but not for a continuous test, how treadmill grade influences V02peak and the incidence of a V02-plateau for a speed incremented test, and whether it is possible to develop a continuous protocol for which the incidence of a plateau in the V02-running speed relationship is >80%. Study 1 was a large study that addressed several issues. Each subject (n = 10) completed a discontinuous test (DCT) in which running speed was increased every 3 min, a continuous test in which the speed was increased every 3 min (CT), a ramp test in which the speed was increased every 5 s (5%RT60), and a run to exhaustion at a.speed calculated to elicit 105% V02 peak (105%T). For each test, the treadmill grade was set at 5%, and the sampling period was set at 60 s. Each subject also completed 2 further tests: a ramp test (5% grade) for which the sampling period was 30 s (5%RT30); and a ramp test (60 s samples) for which the treadmill grade was set at 0% (O%RT). The peak V02 (mean ± SD) was higher for the 5%RT60 than for the DCT (59.9 ± 7.9 vs. 57.8 ± 8.1 ml.1 kg·.1 min; p < 0.05), but the incidence of a V02-plateau was higher for the DCT (80% vs. 50%). The incidence of a plateau was also higher for the 5%RT60 than for the O%RT (50% vs. 30%), as was the peak V02 (59.9 ± 7.9 vs. 57.8 ± 7.9 rnl.kg·1.min·1; p = 0.003). The peak V02 was lower for the 105% T than for the 5%RT60, and the difference between the two values was negatively correlated with the duration of the 105%T (r = -0.89, p = 0.001). The incidence of a plateau was lower for the 5%RT30 than for the 5%RT60 (20% vs. 50%); the reason for this appeared to be that the variability in V02 was higher for the 30 s samples. It was concluded that discontinuous tests should not be used for the assessment of V02m", and that factors which influence the variability in V02 might be important determinants of the incidence of a plateau. Study 2 evaluated the effect of sampling period and exercise intensity on the variability in V02. Eight subjects completed 4 runs at -70% V02P" during which 12 samples of expirate were taken over periods 000, 60, 90, or 120 s. In addition, V02 was determined over twelve 30 s periods during runs at -70 and -96% V02Peak (n = 6). The SD for V02 decreased as sampling period increased from 30 to 60 s (1.3 ± 0.7 vs. 0.6 ± 0.2 ml.kg·1.min·1; p < 0.05), but no further decrease was observed as the sampling period increased beyond 60 s. This SD also decreased as exercise intensity increased (1.1 ± 0.2 vs. 0.6 ± 0.3 ml.kg·1.min·1; p = 0.005), such that the SD for 30 s samples taken during the run at -96% was the same as that for the 60 s samples taken at -70% V02Peak (P = 0.96). It was concluded that the only valid approach to defining a V02-plateau is one in which the sampling period decreases as exercise intensity increases. Study 3 evaluated three ramp tests for the assessment of V02max in runners. Each subject (n = 12) completed 3 tests: a constant speed, increasing grade test (lOT); a constant grade, increasing speed test on a level treadmill (0% T); and a constant grade, increasing speed test conducted at a 5% grade (5% T). For each test, the sampling period decreased as the exercise intensity increased and the individual V02 data were fit to both a linear model and a (two-piece) plateau model. For each test, the SEE was lower for the plateau model than for the linear model (p < 0.0005) and a V02-piateau was observed in >90% of subjects. However, V02max, was higher for the 5%T (64.0 ± 4.7 ml.kg·1.min·1) than for the O%T (62.6 ± 4.6 rnl.kg·1.min·1), and higher still for the lOT (65.1 ± 4.3 ml.kg·1min·1) (p < 0.05). It was concluded that whilst an upper limit for V02 is typically reached when trained runners perform a treadmill ramp test, the V02 at which this limit is reached depends on the conditions under which the test is performed.