Attempts to implement dedicated evidence-based sports science research in Gaelic Football are challenging. Current structures within Gaelic Football render the sport less conducive to research analysis. The tenet that all Gaelic Footballers “are born not made” still has its adherents in today’s management circles. Atavistic attitudes to sport scientific experimentation persist. This doctorate dissertation seeks to address important issues that have the potential to maximise performance in Gaelic Football. The underlying theme of this thesis is to understand the prevalence and aetiology of injury, and the provision of researched suggestions designed to enhance performance. The first study is a detailed prospective epidemiological study of injuries sustained by Gaelic Football players during a single competitive season (Newell et al., 2006). The design of the study was based on Van Mechelen’s (1992) model of ‘sequence of prevention of sports injuries’. To date there has been no prospective epidemiological study of injuries in Gaelic Football. Two of the main findings arising from the injury surveillance study were the high incidence of hamstrings injury and the frequency of injuring occurring in the final quarter of training and games (Newell et al., 2006). As a follow-up to the initial injury surveillance study (Newell et al., 2006), the next phase of study focussed on the aetiology of hamstrings injuries and in particular to investigate if hamstrings muscle strength or functional hamstrings/quadriceps ratio (H:Q ratio) is a predictor of hamstrings injury in Gaelic Football.The linear regression model fitted to the functional H:Q data identified two players as potential hamstrings injury candidates, one of whom sustained a hamstrings injury during the playing season. A subsequent intervention programme aimed at reducing the incidence of hamstrings injury was devised but team managers were generally unwilling to embrace an intervention as they did not wish, as they saw it, to interfere with components which were essential for player preparation. Dehydration is a recognised risk factor for injury, although the direct evidence linking dehydration and injury has not been established. The goal of the next phase of research was to investigate the fluid and electrolyte balance of individual elite (Newell et al., 2008) and club Gaelic Football players and devise personal hydration strategies, as a means of controlling the potential impact of dehydration while prospectively recording injuries. The two hydration studies (conducted in warm and cool conditions) have shown that changes to pre and post training body mass (using weigh scales), assessing pre-training hydration status (using a refractrometer, and reagent strips), and monitoring of the amount of fluids consumed during training (individualised drinks bottles) can help determine individual hydration requirements. The results of both studies indicated: a wide variation in sweat rates and fluid and electrolyte balance, evidence of pre and post dehydration, and that a single hydration strategy, based on published guidelines, is unlikely to be suitable for an entire team. Conducting regular testing during varying environmental conditions will help to establish a routine for fluid intake for all situations. Both studies provide support for an enlarged dedicated epidemiological research study to provide direct evidence linking dehydration to injury. However a study of this magnitude would require the full support of the Gaelic Football Association.

Falls and fall-related injuries are among the most common, serious, and medically-expensive problems facing the growing older population. Regular physical activity has been proposed to reduce falls, but no research has examined the efficacy of compliance with official recommended amounts of physical activity over the adult life-course and falls in community dwelling older adults. From the development and implementation of a new questionnaire to assess guideline related lifetime physical activity levels and falls history with a sample of 314 community-dwelling older adults, it was identified that lifetime adherence to the 2004 Department of Health physical activity guidelines offered no protective benefit for reduction in falls, fear of falling or fall outcome. A sub-sample of the 314 participants was then invited to participate in three laboratory investigations. Biomechanical measures of stability were utilised in studies investigating quiet standing, straight line walking and performing a 360º standing turn with groups of young adults (n = 15), older non-fallers (n = 15), older single fallers (max n = 13) and older multiple fallers (n = 14). During standing, young adults placed their centre of mass (COM) anterior to their centre of pressure (COP), whilst older adults primarily placed their COM posterior to their COP. There were no differences between faller groups and it was therefore concluded that quiet standing was not a challenging enough task to differentiate faller status. During walking, multiple fallers displayed greater COM-COP separation than the non-fallers and single fallers, and greater COM acceleration than the non-fallers at heel strike in the antero-posterior direction thus identifying both measures as capable of i differentiating between faller status groups in similar populations. At the initiation of the 360º standing turn, multiple fallers demonstrated a significantly shorter latency between reorientation onset of the thorax and the pelvis compared to all the other groups and thus exhibited a more en-bloc strategy of turning. Therefore, the onset of body segment reorientation was identified as capable of differentiating between fallers and non-fallers in otherwise healthy, community dwelling older adults. Discussion of and conclusions drawn from the findings of the four empirical studies identify the need for future research to identify more appropriate falls-related physical activity recommendations for public health messages for adults, and recommend the use of biomechanical variables such as COM-COP separation, COM acceleration and the assessment of segment reorientation in future falls-related research and as outcome measures for the efficacy of physical activity intervention programmes for fall prevention.

The metabolic syndrome is highly prevalent in western society, and the numbers affected by obesity and diabetes continue to rise. This thesis reviews the mechanisms at play and the gaps in the literature that, if filled, may increase knowledge of treatment regimes for affected individuals. Experimentally, it was demonstrated that the oral glucose tolerance test can be a reliable tool to measure insulin sensitivity following adequate dietary and exercise control. Acute and chronic cinnamon ingestion was shown to improve insulin sensitivity. Feeding frequency was found to alter insulin and ghrelin responses and relationships following mixed-meal ingestion. And finally, postprandial lipaemia was found to be attenuated for up to 24 hours following moderate-intensity exercise, illustrating the requirement of daily exercise. In summary, oral glucose tolerance tests are suitable for experimental interventions; and the clinical management of factors associated with the metabolic syndrome should perhaps consider dietary supplements, meal frequency, and exercise timing in addition to the traditional dietary and physical activity guidelines currently in practice.

The regulation of pulmonary blood flow and ventilation during exercise is mediated by numerous factors, yet the role of certain cardiovascular and pulmonary reflex control systems is unknown. Therefore this thesis investigated the pulmonary vascular response to the activation of the muscle metaboreflex alone, and combined with activation of the muscle mechanoreflex. The ventilatory responses to the activation of the muscle metaboreflex were also studied under a background of activated ventilatory chemoreceptors. Finally the effect of increased metabolism on the ventilatory sensitivity to carbon dioxide was investigated in healthy humans. We found that activation of the muscle metaboreflex induced pulmonary vasoconstriction that was alleviated by muscle mechanoreflex activation. Furthermore a respiratory response to the activation of the muscle metaboreflex was observed in hypercapnia but not when breathing room air. Finally we found that increases in metabolic rate induced elevations in the ventilatory sensitivity to carbon dioxide. Overall these data suggest that the interplay between cardiovascular and respiratory control systems contribute to the regulation of pulmonary haemodynamics and breathing during exercise. Our findings could be implicated in the reduced exercise tolerance seen in chronic heart failure patients.

Increase in body temperature is a major factor limiting endurance performance in the heat and it is shown in this thesis that the effects of raised body temperature on performance, perception and neuroendocrine response to exercise are mediated by an interaction of body temperatures. Prolactin has been used as an indicator of hypothalamic activity and the pathways regulating its release have been investigated using pindolol as a 5-HT\(_ \) antagonist. The prolactin response to a buspirone challenge has been shown to be approximately 50% serotonergic and 50% dopaminergic, but with a wide inter-subject variation. Passive heating is a potent stimulus for prolactin release and it was shown that 5-HT\(_ \) stimulation plays virtually no part in this process, raising the possibility that prolactin release during hyperthermic exercise may also be largely due to withdrawal of dopamine inhibition. A comparison of exercise tolerance in the heat and the sensitivity of central serotonergic and dopaminergic pathways further indicates the importance of dopamine in central fatigue. The action of caffeine in enhancing endurance performance has been shown not to involve the hypothalamus and this draws attention to other pathways that may be involved in central fatigue including the basal ganglia and limbic system.

It is commonly believed that with increased age, movement dexterity becomes slower and increasingly clumsy when performing simple every day tasks. In the General Introduction of this PhD thesis (Chapter 1), literature that supports evidence for this relationship was reviewed. In addition, literature that has attempted to understand co-variance factors that may influence the age and dexterity relationship were also presented. From this, the general thesis hypothesis raised was that other factors such as sense of touch, attention ability or strength might also correlate with age and so possibly could also explain the reduced dexterity variable. Five empirical chapters present the experiments conducted to address the hypothesis, and the data from these are discussed in the General Discussion (Chapter 7). The empirical chapters consisted of three main areas of experimentation. That is, Chapter 2 ran preliminary screening data, Chapters 3 and 4 tested the effects of selective attention ability on the age - dexterity relationship and Chapters 5 and 6 tested the effects of strength on the age - dexterity relationship. In more detail, Chapter 2 used standard clinical measurements to assess the effects of age on fine and gross movement dexterity, sense of touch, selective attention and strength. The data showed that all factors declined with increased age, but that strength and selective attention seemed particular relevant to general upper limb dexterity. In Chapter 3, the impact of selective attention ability was assessed using a modified and motion tracked dexterity task. This demonstrated that the age and dexterity relationship was not generalised across all movements, but instead was specific for phases of action that contained a selective attention component. Chapter 4 followed up these data by showing evidence of impaired selective attention and inhibition with increased age. Chapter 5 sought to clarify the impact that strength had on the age and dexterity relationship. The findings showed that while age and strength were related, age explained more of thedata’s variance for steadiness and movement tracking dexterity, whereas strength explained more of the data’s variance for aiming and tapping dexterity. In Chapter 6, the findings of Chapter 5 were tested by directly manipulating hand grip strength and measuring the resultant effects on tapping dexterity. The data supported Chapter 5 and confirmed that hand grip strength had a clear impact on the age and dexterity relationship. Together, the data presented in the PhD thesis suggest that other factors contribute to the effects of age on dexterity, and support the idea that better management of these confounding factors may allow for a better understanding of the age and dexterity relationship and furthermore, help older adults enjoy better movement dexterity.

Exercising muscle needs a constant supply of oxygen for the aerobic metabolism of carbohydrate and fat, and regulation of the blood supply to muscle during exercise is therefore critical. Heart rate, stroke volume and minute ventilation all increase during exercise, and sympathetic vasoconstriction diverts blood to exercising muscle. It is well recognised that receptors in skeletal muscle play a vital role in the regulation of blood flow, including receptors sensitive to products of anaerobic metabolism such as lactate and hydrogen ions: metaboreceptors. Activation of the muscle metaboreflex signals the need for an increase in blood flow, and leads to an increase in cardiac output, ventilation and sympathetic vasoconstriction to non-essential organs. Exercise intolerance is one of the most disabling symptoms in patients with a range of cardiorespiratory diseases. Abnormalities of skeletal muscle favouring anaerobic metabolism have been documented in both chronic heart failure and chronic obstructive pulmonary disease (COPD), and this is thought to be relevant to exercise limitation in these diseases. Studies looking at patients with chronic heart failure have demonstrated an increase in muscle metaboreflex activity. It is thought that abnormal skeletal muscle generates greater quantities of anaerobic metabolites, leading to increased metaboreceptor activation. This in turn causes an increased sympathetic nervous system and ventilatory response to exercise. Patients with COPD have been shown to demonstrate similar skeletal muscle abnormalities, so we hypothesised that we would also find an increase in muscle metaboreflex activity in this group. It is possible to quantify muscle metaboreflex activity by exercising a small muscle group to fatigue then isolating it from the rest of the circulation with a sphygmomanometer cuff. This traps the metabolic products of exercise in the muscle and leads to prolonged stimulation of metaboreceptors. This can be measured as a sustained increase in blood pressure and ventilation when compared with control recovery without cuff inflation. The aims of this thesis were as follows: (i) to assess if it is possible to quantify the muscle metaboreflex in a group of patients with COPD and to determine whether muscle metaboreflex activity is increased in patients with more severe disease, (ii) to determine whether supplementation with oral creatine monohydrate alters muscle metaboreflex activity, upper limb strength or endurance and respiratory muscle strength in patients with COPD, (iii) to assess the effects of diabetic autonomic neuropathy on muscle metaboreflex function, and (iv) to evaluate whether pulse transit time is of use in the measurement of muscle metaboreflex activity. In our first study, we looked at a group of patients with stable COPD and found that rhythmic forearm exercise followed by post-exercise forearm ischaemia led to a sustained increase in blood pressure and minute ventilation when compared with control recovery. These findings are in keeping with previously published observations in normal subjects and in patients with chronic heart failure. We found that there was no difference in muscle metaboreflex activity between the groups of patients with moderate or severe disease. We then performed a randomised, double-blind, placebo-controlled, crossover trial looking at the effects of loading a group of patients with stable COPD with creatine monohydrate. We demonstrated a small increase in body weight and an increase in peak inspiratory and expiratory mouth pressures, but there were no effects on muscle metaboreflex activity or forearm muscle strength, endurance or recovery. A group of patients with type I diabetes mellitus was then used to study the effects of autonomic neuropathy on muscle metaboreflex function. We found that there was no difference in metaboreflex activity between subjects with diabetic autonomic neuropathy and subjects with diabetes but no evidence of autonomic neuropathy, suggesting that the afferent and efferent limbs of the muscle metaboreflex were intact. Our final study evaluated whether pulse transit time could be used to assess muscle metaboreflex activity. Pulse transit time is defined as the time taken for a pulse wave to travel between two arterial sites, and can be easily and non-invasively measured. It is thought to reflect blood pressure and arterial tone. In a group of healthy subjects, we found that pulse transit time fell with rhythmic handgrip exercise, and post-exercise muscle ischaemia led to a sustained fall in pulse transit time when compared with control recovery. Pulse transit time therefore shows promise in the measurement of muscle metaboreflex activity, but further studies are required. Studies comparing pulse transit time with more invasive measurements such as muscle sympathetic nerve activity would be of particular interest.