Includes abstract. / Includes bibliographical references. / Maximal oxygen consumption (VO2max) is typically defined by the presence of the "plateau phenomenon" during incremental exercise tests, in which O2 consumption levels-off in spite of increases in workload. This is thought to reflect a limitation in the capacity of the heart to pump O2 enriched blood to the exercising limbs. Some researchers however question not only the biological validity of the "plateau concept", based on mathematical and methodological issues, but whether O2 delivery to the exercising muscles indeed sets the upper limits for VO2max. This thesis aimed to address some of these controversies.

The central governor model (CGM) proposes that muscle recruitment is regulated by the brain through subconscious homeostatic control of afferent feedback. It has been suggested that the dopaminergic system plays a key role in the CGM, with dopaminergic activation leading to lower fatigue thresholds. Key neural circuits, including the central autonomic network (CAN), may also play a role in altering thresholds by reducing conscious bodily awareness, known as interoception. However, few studies have directly examined the dopaminergic neurotransmitter system and CAN connectivity, during exercise-induced fatigue. Although there is reason to suspect that subjects with high activity (HA) and low activity (LA) levels have different fatigue thresholds, potential differences in dopaminergic function and related circuity have not been compared across these groups. In this thesis, I was therefore interested in examining the impact of a dopaminergic agent, methylphenidate (MPH) on: a) brain connectivity at rest before exercise and during exercise, b) on heart rate (HR) at rest before exercise and during exercise. Furthermore, c) I was interested in whether the effect of MPH administration (MA) on HR and functional connectivity (FC), between CAN regions, pre-exercise impacted HR and FC during exercise and whether this differed between HA and LA subjects. In order to measure the effect of MA on brain connectivity at rest and during exercise I used a functional magnetic resonance imaging (fMRI) scanner. To measure the effect of MA on fatigue thresholds, I used a MRI compatible handgrip device which recorded grip force output during a fatiguing handgrip task. To measure HR before and during handgrip exercise I used a MRI compatible electrocardiogram (ECG) machine. My first study aimed to determine the effect of MA on resting state (R-fMRI) FC between CAN regions and its correlation with HR before exercise. My second study aimed to see the effect of MA on task HR, force output and, FC and EC between CAN regions, during a fatiguing handgrip task. My third study aimed to see the effect of MA on the relationship between HR and FC pre-exercise and HR and FC during exercise and whether this differed between LA and HA subjects. I found that: 1.) MA decreased R-fMRI FC between CAN regions, and that this was associated with an increase in HR during resting state 2.) MA decreased FC between CAN regions with an associated increase in task HR and force output during a fatiguing handgrip task 3.) After MA, R-fMRI FC determines task FC independent of HR 4.) MA significantly increased task HR in LA but not HA subjects 5.) After MA, R-fMRI FC determines task FC independent of HR in LA but not HA subjects. Taken together, the functional uncoupling of CAN regions and increased HR after MA suggests that MA increases the fatigue threshold by diverting attention away from interoceptive cues, such as HR. However, this finding may be more relevant in LA subjects, where MA is also associated with increased HR during exercise.

The purpose of this study was to examine the effects of live contingent music on exercise duration, frequency of negative verbalizations, and self-perception of pain, anxiety, and rehabilitation of physical therapy patients. Subjects (n=30) were patients in an extended care rehabilitation facility in Northwest Florida receiving physical therapy for various conditions. The independent variable was live contingent music played during a physical therapy session on the Restorator. Dependant variables included subjects' exercise duration, negative verbalization frequency, and self-perception of pain, anxiety, and rehabilitation levels. Analysis of Variance with Repeated Measures (ANOVA) statistical tests were conducted on all data. Subjects in the experimental group had significantly lower posttest pain and post-test anxiety levels and higher exercise duration percentages. Post-test rehabilitation levels and frequency of negative verbalizations produced no significant difference between groups. For all dependant variables, there were significant differences between sessions not differentiated by group, indicating general rehabilitative progress. This study confirmed that music decreased perceived pain and anxiety and increased exercise duration in physical therapy patients. This supports the need for further research regarding the use of music in physical therapy along with other types of therapies / A Thesis submitted to the School of Music in partial fulfillment of the requirements for the degree of Master of Music. / Spring Semester, 2003. / April 8, 2003. / Live Music And Exercise Duration / Includes bibliographical references. / Jayne M. Standley, Professor Directing Thesis; Clifford Madsen, Committee Member; Dianne Gregory, Committee Member.

Handgrip is a ubiquitous human movement that determines how we interact with our environment. It is involved in almost every aspect of daily life (e.g. opening a door, handling cutlery, using tools) and like all human movement, its application is limited by muscle fatigue. However, the supraspinal mechanisms of handgrip and handgrip fatigue are not fully understood despite the importance of this fundamental movement, numerous publications, and its presence as a longstanding research topic. This thesis investigates the brain mechanisms of handgrip and handgrip fatigue using fMRI. It begins with a review of the literature in Chapter one, which evaluates the theories and evidence for central control of handgrip and muscle fatigue as well as describing the rationale to perform the experiments in this thesis. The methodology and analyses are also reviewed to provide rationale for their use and to facilitate the interpretation of subsequent experimental results. In order to understand the supraspinal mechanisms of handgrip and handgrip fatigue it is logical to first understand the most fundamental grip type (power vs. precision) and pattern (static vs. dynamic) by which handgrip can be performed.

Includes bibliographical references. / Previous findings have suggested that functional variants within collagen encoding genes are associated with several musculoskeletal soft tissue injuries and other exercise-related phenotypes. Specifically variants within the functional COL5A1 3’- untranslated region (UTR) have previously been associated with (1) chronic Achilles tendinopathy, (2) Anterior Cruciate Ligament (ACL) ruptures in females, (3) endurance running performance and (4) range of motion (ROM). Since this gene encodes for an important structural component of the collagen fibril it has been hypothesised that variants within other collagen fibril encoding genes, such as COL3A1, COL6A1 and COL12A1, will also be associated with these and/or other musculoskeletal soft tissue injuries and exercise-related phenotypes. The COL5A1 rs12722 and COL12A1 rs970547 gene variants have been previously associated with risk of ACL ruptures in females [153;154] and/or chronic Achilles tendinopathy [131;181]. The first aim of this thesis was therefore to investigate the COL3A1 rs1800255 and COL6A1 rs35796750 gene variants as risk factors for these musculoskeletal soft tissue injuries.

Introduction: In recent years, there has been a move to understand the environment and context in which athletes develop. South Africa’s unique context provides an opportunity to understand how environmental factors could influence talent development in cricket. Since democracy, there has been limited representation of Black African cricketers at the elite levels in South Africa. Therefore, the aim of this thesis was to determine the role that socio-ecological factors may play in the development of cricket talent in a diverse society. Methods: Qualitative research methods were used to explore the experiences and perceptions of South Africa’s male cricketers as they progressed through the talent pathway from exposure to the game to the elite level. The perceived effectiveness of the introduction of an ethnic target policy was also explored. Seventy-one semi-structured interviews were conducted with a purposive sample of players from all ethnic groups (n=43), and with knowledgeable and experienced key informants (n=16). A thematic analysis of the data resulted in the identification of themes which are presented using a multi-level socio-ecological framework. Results: All players progressed to the elite level; however, their access points to and routes through the pathway varied. This progress was influenced by the inter-relationship of distal and proximal socio-ecological factors that they experienced during their cricketing careers. These influences can be summarised into five talent development components that acted either as barriers or enablers to progress: (1) access to opportunities and competition, (2) holistic player development, (3) effective support networks, (4) inclusive team environments, and (5) adaptive mind-sets. In addition, various intrapersonal characteristics were identified that further affect a player’s ability to achieve elite cricketing success. Finally, it was determined that an ethnic target policy alone is not an effective intervention for developing cricket talent in a diverse society undergoing transition. Conclusion: A socio-ecological framework to talent development lends additional support to the idiosyncratic, multifactorial, dynamic and complex way in which cricket expertise is achieved, particularly in diverse societies. It provides stakeholders involved in the talent development process with evidence to inform policy and practice, as well as design effective interventions.

Includes bibliographical references. / Barefoot running is a subject of significant interest, both in scientific publications and in the lay media as a result of its alleged benefits for runners. These benefits include the potential to reduce injury risk, more economical running and broadly speaking, a better understanding of running biomechanics. Although there are numerous scientific publications describing differences between barefoot and shod running, there is a dearth in understanding whether all runners are able to adapt to the proposed benefits and how this may affect long-term injury risk. Thus, we sought to investigate the biomechanical, neuromuscular and metabolic changes associated with habitually shod runners during the transition to pure barefoot running over an 8- week progressive training programme. This thesis begins with a critical review of the literature, which evaluates the theories and evidence for barefoot running, as well as describing the necessary future research to confirm or refute the barefoot running hypotheses. Our first study aimed to describe acute changes occurring in habitually shod runners when first exposed to barefoot running. We were particularly interested in the variability in response, and whether we could identify factors that predicted potentially favourable changes in kinematic and kinetic outcomes. Fifty-one runners were recruited and assessed using a 3-D motion capture system and integrated force platforms using conventional methods. We found that loading rate was significantly greater in the barefoot condition, but that high individual variability existed, particularly in the barefoot trials. We found that an increase in ankle dorsiflexion is associated with an increase in initial loading rate when in the barefoot condition, supporting previous findings in this regard. We then performed a supervised, pure barefoot running training programme, over 8 weeks, to determine whether the biomechanics of barefoot running would adapt gradually to habituation. Twenty-three runners were recruited for participation, and performed comprehensive biomechanical and neuromuscular assessments before and after the 8-week programme. The first finding was runners do not adapt similarly to barefoot training, and that biomechanics do not change significantly over the 8-week period. High variability in ankle kinematics and loading rate were found, with three sub-groups identified, namely positive responders (reduced loading rate after training), non-responders (no change in loading rate) and negative responders (increase in loading rate after training). We found significant associations between initial loading rate the changes in ankle flexion angle at initial ground contact, presumably as a result of its influence on footstrike. This finding suggests that conscious instruction might be necessary in order to achieve reductions in collision forces during barefoot running. With respect to neuromuscular variables, a persistently higher gastrocnemii muscle preactivation was found in the barefoot condition before and after the training intervention. Increased gastrocnemius pre-activation was associated with lower initial loading rate. An increase in gluteus medius and peroeus longus and a decrease in tibialis anterior pre-activation were also associated with a reduction in initial loading rate after barefoot training. This finding suggests a refined neuromuscular activation strategy prior to ground contact in the barefoot condition to stabilize the hip and centre of mass. Lastly, oxygen cost of transport was found to improve as a result of the barefoot training programme in the male runners and this improvement was found to be associated with a decrease in ground contact time and increase in stride frequency, but no a change in ankle flexion angle at initial ground contact. The outcomes from this thesis elucidate the highly variable response of individuals to barefoot running. This advises individuals choosing to transition to barefoot running to do so with caution. With this in mind, we suggest certain characteristics that may be used as screening mechanisms to indicate individual suitability to barefoot running based on the “collision force theory”. Further, benefits associated with barefoot running other than varied responses in initial loading rate such as improvements in oxygen cost of running are pre-dominantly hypothesised to be a result of musculo-tendinous adaptations, neuromuscular strength and motor control.

Includes bibliographical references. / A collection of published studies establishing the central governor model of exercise physiology, and the aetiology of the hyponatraemia of exercise.

Submaximal step tests are used to predict maximal oxygen consumption and work capacity. However, if the external workload is not controlled the interpretation of the test results may be inaccurate. The purpose of the research was to develop a submaximal test of cardiorespiratory fitness using a novel step test designed specifically to overcome the weaknesses of the previously published step tests. A series of studies contributed to the theoretical development of the submaximal step protocol, piloting the protocol, reliability studies, validation of the protocol and finally a cross-validation of the protocol. The first study tested the hypothesis that stepping tests configured for the same external workload, but varying in stepping frequency, elicit the same physiological stress. Participants (n = 31) performed three step tests at 16, 20 and 24 steps per minutes in random order. External workload was standardised at 45 kJ. Energy expenditure, heart rate recovery, rating of perceived exertion, maximum heart rate and total heart beats were significantly different between tests (p < 0.05) with the biggest differences occurring between 16 and 24 steps per minute. Maximum heart rate as a percentage of age predicted heart rate increased from 70% at 16 steps per minute to 81% at 24 steps per minute. The study concluded that standardisation of external workload with different exercise intensities does not result in the same physiological responses. The second study tested the reliability of the step test. Participants (n = 34) performed a step test three times in a week at a cadence of their choice (16, 20 or 24 steps per minute). The study showed that the step test is repeatable for most variables measured and therefore is a reliable test of fitness. The third study used the outcome variables measured during the step test to develop equations which predicted VO₂max measured directly in a maximal test on a treadmill. A diverse sample of participants (n = 273), differing in sex, level of habitual physical activity and age were recruited for the study. Several models for predicting VO₂max were determined. The most parsimonious equation was: VO₂max (ml.kg⁻¹.min⁻¹) = -0.10911 (age) - 0.06178 (body mass) - 0.75481 (body fat %) +0.00208 (METS) + 0.11636 (HRR) - 0.019551 (MHR) + 0.07955 (Av HR) + 83.34846 (R² = 0.75, standard error of estimate = 5.51 ml.kg.min⁻¹) where METS is metabolic equivalent, HRR is heart rate recovery, MHR is maximum heart rate and Av HR is average heart rate. Cross validation was done (n = 50) to test the accuracy of the prediction equation. The relationship between the predicted VO₂max and the measured VO₂max was r = 0.87. In conclusion the standardised step test can predict VO₂max in a heterogeneous population of males and females, varied ages (20 to 60 years), physical activity levels and fitness levels.

The batting technique in cricket consists of various elements such as the grip, stance, backlift, downswing, impact with the ball and follow through. Whilst there has been an extensive amount of research into these batting elements, there is little research specifically on the backlift technique. Therefore, we aimed to investigate and provide a scientific understanding of the batting backlift technique (BBT) in cricket. We aimed to investigate the BBT of the most successful batsmen (n = 65) in the last 120 years as well as players in the Indian Premier League (IPL) (n = 30). It was found that these batsmen did not conform to the current cricket coaching method that advocates a straight batting backlift technique (SBBT). Instead, 77% of successful batsmen and 90% of IPL batsmen employed a lateral batting backlift technique (LBBT) in which they lifted their bats in the direction of second slip or beyond with the bat face towards the off-side. Using this technique, both the toe of the bat and face of the bat points directly towards the off-side (usually between slips and point). The number of players using the LBBT was significantly greater than those using the SBBT (χ2 = 19.2, df = 1, p < 0.001). Given these findings, we were curious to determine whether this finding was similar at other levels of cricket. The second study therefore employed biomechanical and video analyses to evaluate the BBT of current semi-professional, professional and international cricketers (n = 155) from South Africa and the United Kingdom. The backlift of these batsmen was then compared to their career statistics. It was found that a LBBT is more prevalent at the highest levels of the professional game and a likely contributor factor for successful batting at the highest level (p≤0.05). The LBBT was also found to positively affect other components of the batting technique such as the stance and scoring areas. We then proceeded to investigate the BBT amongst the lower levels of cricket (junior and adolescent cricketers). The third study consists of an intervention study that employed a biomechanical analysis of coached and uncoached cricketers (n = 80). It was found that more than 70% of uncoached cricketers adopted a LBBT, whereas more than 70% of coached cricketers adopted the SBBT. Having found that the LBBT is a likely contributing factor for past and current successful batsmen, it was then important to understand what BBT the current cricket coaches are teaching at various proficiency levels. The fourth study explored the teachings of the BBT among international cricket coaches (n = 161) using a mixed methods approach through an online evaluation survey. This study was able to show that a majority of cricket coaches teach what is advocated in coaching manuals and mostly coach the SBBT as opposed to the LBBT at various levels of the game. In the fifth and sixth studies, this thesis further describes two innovative coaching tools that can improve and assist with the coaching of the LBBT. Firstly, a novel coaching cricket bat was investigated through a pilot and intervention study. In the pilot group, cricketers using the coaching bat scored approximately 1 more run per ball or an average of approximately three more runs in total when using the coaching bat than the normal bat (F = 6.70, df = 1, p = 0.012). In the intervention study, the experimental group scored double the total number of runs (an additional 16 runs) and an average of approximately 3 more runs per player in the post-match than in the pre-match, which showed a large effect (ES = 5.41) (t = 3.32, df = 5, p = 0.021). The coaching cricket bat might be used to coach young cricket players to hit the ball more effectively as well as how to adopt a more LBBT. Secondly, a mobile application was developed, which can be used by players, coaches and scientists to analyse and improve the BBT among cricketers at all levels. In summary, this thesis has shown that the LBBT is a likely contributing factor to successful batsmanship at all levels of cricket ability (junior cricketers, adolescent cricketers, semi-professional cricketers, professional cricketers, international cricketers and former elite/successful cricketers). Coaching a LBBT to young batsman may be challenging and therefore a coaching cricket bat has been developed and has shown to be a promising training aid for coaching the LBBT to young cricketers. A mobile application has also been designed and tested to assist in the coaching of the BBT in cricket. A way forward for further research in this area of cricket batting is documented at the end of the thesis.