Schoolboy rugby injuries are a cause for concern in medical and non-medical circles, but few scientific investigations into their nature and frequency have been undertaken. The majority of reported rugby injury surveys are retrospective, have considered only specific injuries, or have reported only those seen at one location. Also, most studies have not distinguished minor injuries from major injuries. A pilot study conducted at one school in Cape Town during the 1982 rugby season, showed clear patterns of injury related to the age of players, their level of competition, playing position, the stage of the rugby season and the phase of play at the time of injury (Nathan et al. 198 3) . The studies as reported in this thesis were designed as a comprehensive follow-up study. The research methods and definition were similar but a much larger sample was studied and new areas not covered by the pilot study were introduced. During two 18-week seasons, in which approximately 4 700 players from 26 high schools played 6766 rugby matches, 905 players were prevented from participating in rugby for at least one week due to injury. The incidence and nature of injuries occurring to these players were followed in a prospective study and results were analysed for: (i) overall number and incidence of injured players; (ii) age-group and playing level; (iii) time of the season; (iv) phase of play; (v) playing position; (vi) type of injury; (vii) anatomical site; (viii) specific diagnoses; (ix) match vs practice injuries; (x) number of days off rugby; and (xi) medical treatment. The use of correspondence as a survey method resulted in 40 to 50% of injuries not being reported over the two-year period of the study. It appeared that the most accurate method of data collection was direct personal contact between the researcher and the injured player.

The studies included in this dissertation address the role of blood flow and cellular oxygenation in skeletal muscle fatigue, with an underlying interest in age-related differences in muscle fatigue. In the first study, I found that blood flow immediately post-contraction was tightly coupled to contraction intensity throughout an incremental isometric dorsiflexor contraction protocol in healthy young men. This relationship was independent of fatigue, and the onset of fatigue occurred before any reduction or plateau in blood flow. These data suggest that fatigue during intermittent incremental contractions does not result from a blood flow limitation. The second study used magnetic resonance spectroscopy of deoxymyoglobin to examine the role of intracellular oxygenation in muscle fatigue during slow and rapid incremental contractions in healthy young men and women. Data from this study showed that the rate of deoxygenation relative to force during contractions was predictive of fatigue, and this was true for slow and rapid contractions. Further, intracellular oxygenation was lower, and fatigue greater, during more metabolically demanding rapid contractions. These data support a role for intracellular oxygenation in the development of fatigue. The final study investigated whether differences in intracellular oxygenation could explain age-related differences in muscle fatigue. During slow contractions, intracellular oxygenation was higher, but fatigue lower, in older compared to young subjects. After matching a subset of subjects by muscle strength, age-group differences in oxygenation were eliminated, but fatigue was still less in older subjects, suggesting that while differences in oxygenation exist between young and older subjects, they cannot explain the age-group differences in fatigue. This conclusion was supported by a similar oxygenation, but greater fatigue, in young compared to older subjects during rapid contractions. Based on these findings, intracellular oxygenation does not appear to play a role in the age-related differences in fatigue observed in this and other studies. Together, data from this dissertation suggest that intracellular oxygenation plays a role in the development of muscle fatigue, despite the ability of blood flow to match contraction intensity. Differences in oxygenation, however, cannot explain age-related differences in muscle fatigue.

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This project is the first to investigate blood perfusion in the human hamstrings during isometric exercise with a near infrared spectroscopy (NIRS). A Kin Com dynamometer has been used to fix the knee positions and to measure torques during contractions. Both the NIRS optodes and the electromyography (EMG) electrodes were attached to the skin over the hamstrings. Previous studies used a NIRS to measure muscle blood flow in the forearm, quadriceps and calf muscles. The changes in haemoglobin concentrations were calculated using Spike 2 software. A total of 46 male volunteers participated in the four series of experiments described in this thesis. The following overall conclusions can be drawn: perfusion decreases in the hamstrings during contractions and then returns to normal levels after a period of time, changing the limb position at which the contractions are made does not affect the perfusion, warm-up exercises increase in blood perfusion for 8 minutes at 30 and 40% of MVC. The perfusion did not significantly change during an episode of DOMS or in the injured and non-injured limbs. These conclusions show the importance of warm-up before sports activities but not necessarily avoid injury. It can be concluded that there is no association between such conditions with hamstring injuries. The maintained perfusion at different conditions is a positive finding as the perfusion is not restricted indicating good delivery of oxygen despite muscle injury.

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.

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The aim of this thesis was to explore the effects of state anxiety, trait anxiety, and defensiveness on a psychomotor task that required working memory resources. Results from study 1 confirmed that a random response generation task was sensitive to changes in response rate and used limited working memory resources. ARM MANOV A showed that participant behaviour became less random as response rate increased (A. =.239, F9,1 = 14.491)

Injury surveillance research has established that over 20 % of cricket injuries are related to the upper limb (Leary & White, 2000; Ranson & Gregory, 2008; Stretch, 2003), with bowlers associated altered rotational joint range of motion (Aginsky et al., 2004, BellJenje & Gray, 2005 and Stuelcken et al., 2008). As the applicability of such observations is limited, the aim of this thesis was to provide researchers with a greater understanding of the pathomechanics of shoulder injuries afflicting cricket bowlers though quantifying associated musculoskeletal adaptations and subsequently through the development and validation of a bowling specific kinematic model, establish the influence these may impart on bowling technique. The use of diagnostic ultrasound within the first experimental study in a cohort of bowlers without a history of shoulder injury, established a high prevalence of supraspinatus (45 %) and subscapularis (50 %) tendon pathology, providing insight into common musculotendinous pathology and adaptations that are indicative of the future potential of injury. Data presented within the second study aimed to first quantify the kinematics of the shoulder during the bowling delivery in relation to humerothoracic motion and, second, the influence of rotation sequence to described humerothoracic motion was investigated. Findings established that whilst the bowling delivery was associated with large variability, future research must acknowledge the contribution of the scapula to shoulder motion. As such, due to the complexity of quantifying shoulder motion during cricket bowling, the following three experimental studies evaluated and developed the CSBT shoulder model through modifying current methods. The mCAST method in conjunction with an acromion cluster, was established to not only reduce resultant RMSE associated with scapula landmarks by up to 0.016 m, but also increase the repeatability and robustness of reconstructing GHJ location using the SCoRE method. The emphasis of the final experimental study was to apply the CSBT shoulder model to establish the contribution of individual rotator cuff muscles to shoulder joint stability and, to identify phases of the bowling delivery which increases the risk of injury. This case study established that during the bowling delivery the shoulder experiences large multi-planar forces placing demand on musculature, in particular supraspinatus and Subscapularis to stabilise the joint. These findings in conjunction with those of the first experimental study, not only identify structures at risk of injury but also establish that for the effective formulation of injury prevention strategies the bowling delivery must be investigated in its entirety.

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.