Thesis (M.Sc.(Emergency Medicine))--University of the Witwatersrand, Faculty of Health Sciences, 2014. / Aim. The aim of the study was to analyse the prevalence and type of injuries over two years of a Johannesburg High School rugby festival by assessing the injuries (number, anatomical sites, types and severity), to compare the injuries between the two years and to compare the injuries between the three days of the festival. Methods. The study design was a retrospective, descriptive and observational study. The study population was the participating rugby players at the two rugby festivals in 2010 and 2011. Medical records of rugby related injuries in schoolboy participants were used for capturing injury data. Results. A total of 626 players participated (322 and 304 in 2010 and 2011 respectively) of which there were a total of 100 injury data sets analysed. The injury rate per player in year one was 16.8%, and 15.2% in year two. There was no statistical difference (P = 0.6526) in the injury numbers between the two years. The injury profiles between the respective days between the two years were not statistically different. Most injuries were to the head/face, with the majority being concussion related. The next commonest injuries were to the neck area. Most injured players had not had previous similar injuries. Tackles were the commonest mechanism of injuries. Twenty four percent of injuries were deemed severe enough to stop the players from continuing play. Few required referral for investigations or specialist physician care and most were managed with simple first aid at the primary care level. Conclusion. The nature and mechanisms were in keeping with numerous local and international studies of schoolboy rugby players, but with a lower injury frequency. Providing medical services at rugby events such as these festivals is a requirement and adequate standardised record keeping is recommended to increase knowledge and monitor trends as the dynamic nature of the game of schoolboy rugby continues to develop and change.

Contemporary research into training load in team sports primarily focusses on the physiological load demands, whereas the biomechanical load still remains largely unexplored. While the former refers to the work-energy relationship when the players move around the pitch, the latter refers to the external forces the players are exposed to from their movements around the pitch. Monitoring of the biomechanical load helps practitioners estimate the stresses on an athlete’s musculoskeletal structures as a consequence of the external forces acting on their body. Monitoring of the biomechanical load is currently restricted to laboratory settings, but the recent introduction of GPS devices with integrated accelerometers in team sports may enable practitioners to monitor whole-body biomechanical load during training sessions and match-play. The aim of this thesis was therefore to explore if body-worn accelerometry can be used for whole-body biomechanical load monitoring in team sports. The first study of this thesis showed that although a linear relationship exists between body-worn accelerometry (e.g. from GPS integrated accelerometers) and whole-body accelerations, the linear relationship based on Newton’s second law of motion is weak regardless of accelerometer location (trunk, pelvis or tibia). Body-worn accelerometry only measures the acceleration of the segment it is attached to and is therefore inadequate to measure the complex multi-segment dynamics of the whole body during team sports movements. The second study of this thesis did however offer a potential solution to that problem, and it was demonstrated that the complex multi-segment dynamics of the body and the associated ground reaction forces (GRF), a surrogate for whole-body biomechanical load, can be estimated with a mass-spring-damper model (MSD-model). Nonetheless, the MSD-model’s accuracy to estimate GRF slightly decreases for sharp changes of direction at high intensities, because the absorption of energy and generation of energy are decoupled. Finally, a novel approach to estimate GRF from the combination of trunk-mounted accelerometry and a MSD-model was introduced in this thesis. This approach showed that trunk accelerometry data has the potential to generate the eight model parameters required to estimate GRF from a MSD-model, though further work is required in particular towards improving the model’s ability to estimate GRF across a wide range of activities. The novel approach introduced in this thesis has the potential to give practitioners in team sports the opportunity to monitor whole-body biomechanical load due to player-ground interaction in the field, a necessity if they wish to predict the consequent musculoskeletal structural adaptations of training sessions and match-play.

The importance of protein feeding for maximising the anabolic effect of resistance exercise is well established. Ingestion of amino acids or intact protein sources with and without carbohydrate during exercise recovery further stimulates muscle protein synthesis. Less clear is the impact of an acute bout of resistance exercise on the protein synthetic rate of muscle already stimulated by food intake. This thesis demonstrates that an acute bout of resistance exercise further augments the protein synthetic rate of muscle already stimulated by food intake. Simulating everyday practice, whereby resistance exercise is typically performed in the fed state, an exercise-induced elevation in muscle protein synthesis was accompanied by an increased phosphorylation status of signaling proteins downstream of mammalian target of rapamycin (mTOR). Recent studies advocate the potential role for protein feeding in improving subsequent performance following acute bouts of fatiguing endurance-type exercise. However, previous studies have focussed upon carbohydrate nutrition, rather than examining the role of protein feeding for exercise recovery in the context of an intense period of endurance training. Increasing dietary protein intake partially countered the blunted minimal mobilisation of antiviral lymphocytes during exercise following intensified training. In addition, the number of negative symptoms of psychological stress experienced following intensified training was attenuated with additional dietary protein intake. The mechanism(s) underpinning the suggestion that a high protein diet may potentiate a better maintainence of endurance performance following intensified training could not be definitively elucidated from our experimental design. The most likely explanation appears to be related to psychological status.

Older adults at a high-risk of falling (HROA) look away prematurely from targets they are stepping on in order to fixate future constraints in their walking path. This gaze behaviour is associated with decreased stepping accuracy. The first aim of this thesis was to investigate a possible causal link between premature redirection of gaze from a target and reduced stepping accuracy. Results showed that when older adults voluntarily delayed gaze transfer from a target, their foot placement showed greater accuracy and consistency. Secondly, we investigated a possible relationship between increased anxiety about upcoming obstacles and early gaze transfers away from an initial target. We found that progressively increasing task complexity resulted in associated increases in anxiety, extent of early gaze transfers and stepping inaccuracies in HROA. Finally, we investigated the extent to which young, low-risk older adults and HROA can perform visually guided online alterations to foot trajectory during the swing phase towards a target. We found that adjustments made by older adults (specifically HROA) were characterised by increased latencies and reduced magnitude. We suggest that age- and fall-risk related differences in strategies governing visual sampling and the allocation of attention during adaptive locomotion contribute to incidences of elderly falls.

Obstructive sleep apnoea (OSA) is a common chronic condition characterised by repetitive nocturnal upper airway collapse that evokes intermittent hypoxia (IH). Although animal research has demonstrated a causal relationship between IH and cardiovascular disease there is a relative paucity of human research. Using a variety of different models of OSA we investigated the effects of IH on respiratory control and oxidative stress. In addition, we attempted to use Doppler ultrasound to investigate the effects of hypoxic airway occlusions on the pulmonary circulation but concluded that it is not a feasible alternative to invasive catheterisation. In a number of studies we showed that the expression of respiratory plasticity following IH is only evident when arterial levels of CO\(_2\) are raised above normal levels. Furthermore, in stark contrast to previous findings in animals, exposure to acute continuous hypoxia also evokes respiratory plasticity in humans. In addition, we showed that combined postprandial hyperglycaemia and hyperlipidaemia augments the degree of oxidative stress during IH. Finally, we demonstrated that IH accentuates the magnitude of postprandial hyperglycaemia. These studies demonstrate the complexity of respiratory control in humans and they highlight significant species differences. Furthermore, they highlight a fascinating synergy between IH and the postprandial state.

Increasing fat oxidation rates during exercise may be beneficial for the athletic population. At rest, ingestion of Green Tea Extract (GTE) has been found to augment fat oxidation, but there are limited data on the effects during exercise. This thesis systematically investigated the effects of GTE ingestion on exercise metabolism in physically active males. We set out to determine if longer-term feeding of GTE could increase fat oxidation rates during a steady state exercise bout to a greater degree than an acute dose. However, irrespective of the length of ingestion no measureable change in substrate metabolism was found. Due to the large individual differences in fat oxidation at a given absolute and relative exercise intensity, we investigated the effects of acute GTE ingestion during a graded exercise test. Again, no change in fat metabolism was found over a wide range of exercise intensities. Finally, we collected fat oxidation data from a large cohort of athletes. From these data we set new criteria to define individuals as either a fat or carbohydrate metabolic type. Although it is still not known fully what determines metabolic type, the use of a nutritional intervention may be more effective in one type over the other.

The research in this thesis is concerned with the effect of chronic stress, caregiving and bereavement, and ageing on immune and endocrine parameters. First, there was no difference in serum anti-CMV antibody titre between younger caregivers and matched controls, but CMV seropositive caregivers with more negative health behaviours had higher CMV antibody titre. Second, there was no difference in neutrophil function between caregivers and controls in both younger and older group, while only younger caregivers showed a higher serum cortisol:cortisone ratio than controls. Further, those caregivers that reported higher anxiety and burden symptoms had lower neutrophil phagocytosis. Third, caregivers had more senescent KLRG1\(^+\) T cells than controls, but comparable number of “exhausted” PD-1\(^+\) T cells and thymic output. Finally, young bereaved adults showed similar neutrophil function and serum cortisol and DHEAS levels as non-bereaved controls, whereas older bereaved adults had impaired neutrophil function and a higher cortisol:DHEAS ratio. These findings suggest that chronic stress can have differential effects on immune and endocrine parameters, but in some cases, presence of immunosenescence is required for immune decrements to be observed. Further, they emphasise the importance of focusing on the individual's response to chronic stress rather than their chronic stress status, per se.

Q Factor represents the horizontal distance between pedals on a bicycle, measured from the outside edge of each crankarm. The action of pedalling is based upon human gait, which utilises a step width lower than standard Q Factors (150mm for road bicycles). The aims of this thesis were to understand the kinematic and physiological effects of manipulating Q Factor. Lower Q Factors than standard afforded increased gross mechanical efficiency and individually determined optimal Q Factor (OQ) provided increased power output during laboratory time trials. Self selected Q Factor (SSQ) was lower than standard in trained cyclists and could be predicted using a simple suspension task. The use of SSQ compared with Q Factors higher and lower than SSQ provided a combination of kinematic stability and increased efficiency, lowering the risk of injury and the oxygen cost of cycling. Lower Q Factors than the standard 150mm for road bicycles provide performance and kinematic benefits that have not been examined previously. As part of the overall package of bicycle fit, individual cyclists will be able to make measurable improvements by finding and utilising their self selected Q Factor.

The origin of physiological tremor has been studied for many years. Several central and spinal mechanisms which provide an oscillatory input to the muscles have been proposed. Nevertheless, any neural control signal inevitably has to work upon a resonant peripheral system involving the series-coupled elastic muscle-tendon complex and the inertia of the limb. In this thesis I look into the potential role for mechanical resonance to explain tremor. First, I show that the resonant component of hand tremor depends on the velocity of hand movement. Movement reduces muscle stiffness (a process called muscle thixotropy) and the tremor frequency falls. Second, I demonstrate that rhythmic tremor is abolished when eliminating resonance by recording tremor in isometric conditions. Third, I replaced EMG by an artificial drive. This generated tremor which behaved similarly to physiological postural and dynamic tremor. Finally, I studied the relationship between EMG and tremor in the transition from posture to movement. Muscle converts EMG into acceleration differently for static and moving limbs. These findings suggest that there is a key role for mechanical resonance in the generation of physiological tremor. A frequency-specific neural input is not necessary to produce any of the characteristic peaks in postural or dynamic tremor.

South Asian (SA) women in the United Kingdom (UK) are disproportionately affected by chronic diseases and inactivity. However, there is limited published research documenting PA/ST among SA women. The purpose of this PhD research is to employ a mixed methods design to quantify PA/ST among SA women in the UK, assess validity of common methods of PA/ST data collection and to provide a better understanding of the factors that may influence PA/ST in this group. Methods: 140 SA women wore an accelerometer and 36% (n=50) of the sample completed the International Physical Activity Questionnaire (IPAQ). 17% (n=24) of the sample participated in semi-structured interviews. Results: SA women are engaging in similar amounts of PA/ST as the general UK population. IPAQ data underestimated PA/ST when compared to objective data. There were no significant correlations between measurements of the two methods. SA women had difficulty understanding the terminology, content and context of the IPAQ, and difficulty recalling ST.