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Physical inactivity and obesity are associated with elevated systemic oxidative stress and the activation of JNK, p38 MAPK, NF-κB, and protein kinase C (PKC) signalling pathways in skeletal muscle. Sustained activation of these stress and mitogen activated protein kinase (SAPK) pathways are associated with impaired glycaemic control, and the development and progression of cardiometabolic disease. Paradoxically, acute exercise also increases oxidative stress and SAPK signalling, yet glycaemic control and skeletal muscle function are enhanced. Research now supports a role for the transient induction of oxidative stress and associated activation of SAPK signalling in the physiological response and adaptation to acute exercise and exercise training. High-intensity interval exercise (HIIE) is a potent exercise stimulus for the improvement of metabolic health and skeletal muscle adaption, however the effect of HIIE on oxidative stress and SAPK signalling is unclear. The aims of this thesis were to explore the effect of HIIE on glycaemic control, exercise-induced oxidative stress, and skeletal muscle SAPK signalling, in a series of independent but related studies.

Sleep times and patterns are related to sport performance. Previous research suggests that sleep patterns contribute to differences in laboratory maximal effort treadmill tests, but little research has been done on maximal effort testing in the field. Further, research is lacking on whether sprint and acceleration times are correlated to sleep patterns. PURPOSE: The purpose of this study is to determine if a relationship exists between field performance testing and sleep patterns in female high school field hockey players. METHODS: Within the first week of pre-season training female high school field hockey players (n=15, age=15.47±1.06) completed a demographic survey, Pittsburgh Sleep Quality Index (PSQI) scale, and a seven-day sleep-wake journal using an online survey platform (Qualtrics, Provo, UT). Sleep latency, overall sleep quality, and duration of sleep were three PSQI measures chosen for analysis. The onset of sleep time and concentration were two measures used from the sleep-wake journal for analysis. A beep test and six 40m sprints with 10m splits were conducted within the first week of pre-season training, with 48 hours between each test. Beep test was a 20m multistage test that involved running in accordance to a pre-recording of beeps. Field tests were conducted on a level grass field under research supervision. An average of six 40m sprints and 10m splits were taken for analysis. RESULTS: PSQI revealed no participants suffered from sleep disorders. A Pearson correlation was conducted between performance and sleep pattern variables. A positive strong correlation exists between 40m average sprint time and 10m average sprint time (r= 0.896, p≤0.05). A negative correlation exists between onset of sleep and total sleep time (r= -0.598, p≤0.01). There were no correlations between performance and sleep pattern variables. CONCLUSION: These results indicate maximal effort field-testing does not correlate with sleep patterns in female high school field hockey players.

The use of global positioning systems (GPS) in team sports is now widespread, providing coaches with a useful tool for accurately quantifying the physical demands of training and competition. A number of training load metrics have been identified using these systems, however it was previously unclear which variables were most appropriate for use in a teamsport setting. Furthermore, traditional match analysis techniques do not accurately detect within-match fluctuations in running intensity that may provide insight into developing specific training and recovery methodologies. This series of studies first established the peak running intensities achieved during professional rugby league competition, using a novel moving average technique. This method outlined a considerable oversight in traditional methods, where the peak periods of play may have been missed. Secondly, these studies investigated the contextual factors affecting running intensity within interchange rugby league players. Next, the importance, reliability and usefulness of acceleration-based measures using GPS technology within team sports were evaluated. A comprehensive assessment of the peak running intensities achieved during team-sport competition was then performed, with particular reference to the football codes. Lastly, a novel application of power law analysis was used to quantify the relationship between running intensity and the duration of the moving average applied. This series of studies provides coaches with a precise overview of the true peak intensities of competition, and furthermore presents a simple, practical tool for estimating match running intensity as a function of time. As a result, coaches may provide players with an environment where technical, competitive and physical traits can be developed concurrently, using specific methodologies such as small-sided games. If athletes are exposed to the rigors of competition during training they will become more resilient, and when faced with these situations during a match, these events will be less “catastrophic”.

Regulation of pH in skeletal muscle comprises intracellular buffering of hydrogen ions (H+) and acid/base (H+/HCO3−) transport across the sarcolemma. During high-intensity exercise H+ transport is primarily lactate-coupled through the monocarboxylate transporters (MCT)1/4, with non-lactate-coupled transport provided by the sodium/hydrogen exchanger (NHE) system. The chaperone protein basigin is essential for MCT functioning. Intracellular buffering comprises metabolic and physicochemical buffering (βm), the latter mainly from the histidine-based proteins and dipeptides, and inorganic phosphate. The sodium-coupled bicarbonate transport proteins (NCBT) enhance intracellular buffering and H+ efflux, while the cytosolic and sarcolemmal carbonic anhydrase (CA) isozymes may enhance activity of each transport system by physical or functional interactions.

The Na+,K+-ATPase (NKA) is a key protein involved in the maintenance of skeletal muscle excitability and comprises 2 subunits (α and β), each of which express multiple isoforms at a protein level in skeletal muscle (α1-3 and β1-3). The fibre-specific expression, adaptability and roles of each isoform in human skeletal muscle are explored in this thesis. Research utilising muscle biopsies typically uses samples obtained from the vastus lateralis muscle, which in healthy young people comprises similar proportions of type I and II fibres. Analyses using whole muscle pieces don’t allow the detection of fibre-type specific differences and changes occurring at a cellular level. Hence analysis of skeletal muscle samples at the single fibre level offers important advantages in understanding NKA regulation. This thesis therefore investigated the isoform abundance of the NKA in human skeletal muscle single fibres and their adaptability following intense repeated-sprint exercise (RSE) training in healthy young adults (Study 1); with ageing (Study 2) and after high-intensity interval training (HIT) in the elderly (Study 3) and after voluntary inactivity and resistance training in healthy young adults (Study 4).

Salbutamol is a β2 adrenergic agonist widely used for the treatment of asthma and known to reduce plasma potassium concentration [K+]. The International Olympic Committee had been concerned that salbutamol may give an inequitable advantage to athletes. However, little work has investigated whether salbutamol has beneficial effects on plasma [K+], K+ dynamics during exercise and how these potential changes may impact on exercise performance. This study investigated the effects of salbutamol on K+ regulation at rest, during repeat sprint exercise was also explored.

Participation in a physically demanding team sport, such as Australian football (AF), can result in post-exercise physical performance decrements as well as increases in psychometric measures, muscle damage and inflammation. The use of both cold water immersion (CWI) and contrast water therapy (CWT) as a means of post-exercise recovery is becoming more prevalent in the team sport environment. Both modalities are utilised in an attempt to enhance physical performance recovery while reducing perceived muscle soreness and fatigue. Although increasing in popularity, conflicting evidence exists regarding their effectiveness. Comparisons within the same team sport population are lacking, while little information on the efficacy of either intervention exists in AF. Therefore, the effects of a single 14 min exposure of both CWI and CWT on restoring repeat 20 m sprint time, jump performance and psychometric measures was investigated following AF training (Study 1) and an AF match (Study 2). The effects of both modalities post-match on moderating the appearance of markers of muscle damage and inflammation was also investigated (Study 3). Australian football training and match participation reduced repeat sprint, countermovement and squat jump performance and increased perceptions of fatigue and muscle soreness. Match participation also greatly increased inflammatory and muscle damage markers. Both CWI and CWT were more successful than a passive recovery at attenuating decrements in physical performance and reducing exercise induced increases muscle soreness, fatigue and markers of muscle damage, with CWI being the most effective. Neither CWI nor CWT altered the postexercise inflammatory response and therefore most likely had no effect on blunting the inflammatory pathways involved in muscle repair. Results demonstrate that AF participation leads to post-exercise declines in physical performance, an acute phase inflammatory response, muscle damage and heightened perceptions of soreness and fatigue. It was established that in well trained AF players, both modalities were more effective at attenuating these changes than a passive recovery with CWI being more effective. These findings add to the body of knowledge regarding the use and efficacy of CWI and CWT in team sport and would be of benefit to team sport athletes/coaches in decreasing any confusion regarding their use and in helping them to determine the best modality for their recovery needs.

This thesis investigated acceleration in soccer and the ability to improve acceleration capacity using supplementation and a training intervention both separately and in combination. Study one determined the validity and reliability of 5 and 10 Hz global positioning systems (GPS) for measuring instantaneous speed during the acceleration, deceleration and constant speed phase of straight-line running. The criterion measure used to assess GPS validity was instantaneous speed recorded using a tripod-mounted laser. Ten Hz GPS devices were 2-3 times more accurate than 5 Hz when compared to a criterion value for instantaneous speed during tasks completed at a range of speeds (coefficient of variation; 3.1 - 11.3%). Similarly, 10 Hz GPS were up to 6-fold more reliable for measuring instantaneous speed than 5 Hz units (coefficient of variation; 1.9 - 6%). Newer GPS may provide an acceptable tool for the measurement of constant speed, acceleration and deceleration during straight-line running and have sufficient sensitivity for detecting changes in performance in team sport. However, researchers must account for the inherent match-to-match variation reported using these devices.

The aim of this thesis was to investigate the acute and chronic effects of high-intensity intermittent exercise, in the form of repeated-sprint exercise (RSE) and indoor football (futsal), on performance responses and skeletal muscle molecular adaptations in young, healthy and middle-aged, sedentary individuals.

Elite athletes constantly search for the edge over their opponent (Applegate and Grivetti 1997). Indeed, athlete training and competition schedules have resulted in a need to fully recover rapidly from such sessions (Dawson, Gow et al. 2005; Cormack, Newton et al. 2008a; Cormack, Newton et al. 2008b; Elias, Varley et al. 2012; Elias, Wyckelsma et al. 2012; Mooney, Cormack et al. 2012). To overcome the stressors from training and competition, sports compression garments which offer low levels of compression, are commonly used to enhance recovery due to their ease of use, accessibility and affordability. Although a substantial body of research exists investigating compression garment use after a variety of exercise stimuli (Kraemer, Bush et al. 1998a; Kraemer, Bush et al. 1998b; Kraemer, Volek et al. 2000; Kraemer, Bush et al. 2001a; Kraemer, Bush et al. 2001b; Chatard, Atlaoui et al. 2004; Kraemer, French et al. 2004; Duffield and Portus 2007; Duffield, Edge et al. 2008; French, Thompson et al. 2008; Montgomery, Pyne et al. 2008a; Montgomery, Pyne et al. 2008b; Davies, Thompson et al. 2009; Duffield, Cannon et al. 2010; Jakeman, Byrne et al. 2010b; Jakeman, Byrne et al. 2010a; Kraemer, Flanagan et al. 2010; De Glanville and Hamlin 2012), their influence on perceptual, biochemical and performance recovery after actual team sport training and competition, where physical contact is a key component, is lacking. Further, the positive physiological actions of compression garments have mostly been established using a medical style garment, which typically exert a greater volume of compression, in clinical settings. Recent research has sought to determine performance, perceptual and physiological differences when wearing compression garments during exercise that offer varying levels of compression, where the level of compression (low, medium, or high) made no difference to performance or physiological measures (Ali, Creasy et al. 2011; Dascombe, Hoare et al. 2011). It remains unknown if differences in recovery, where the garment is worn exclusively post exercise, would occur between a sports (low level of compression) and medical (high level of compression) style garment in team sport scenarios. Thus this thesis investigated the influence of wearing compression garments on perceptual, biochemical and performance variables following repeat sprint exercise on consecutive days in recreationally trained individuals (Chapter 4); following elite Australian football (AF)training (Chapter 5) and competition (Chapter 6). It also included a comparison between a sports (Spo) and medical (Med) style compression garment. A magnitude based effects approach, using effect sizes and the smallest worthwhile change was used to analyse treatment effects.