The biochemical basis of muscle function during stress imposed by isokinetic exercise has mainly focused on measuring muscle proteins (CK and myoglobin) and lactate present in the blood plasma, whereas the range of low-molecular weight metabolites during muscular stress has received limited attention. This study investigated the effect of concentric isokinetic exercise of the knee extensor and flexor muscles (functional to standing, walking and running), at 80% and 40%MVC intensities of equal workloads, on saliva, urine and blood serum matrices. A hypothesis-free approach was employed to mathematically determine, by chemometrics, which untargeted metabolites measured by 1H NMR spectroscopy are altered in response to muscular exercise of this nature. The results demonstrate that the saliva matrix is highly susceptible to 1H NMR spectral interference from salivette exposure (a routine method of saliva collection in sports/exercise) with 1H resonances arising throughout the spectrum, exceeding the affected spectral region of δ 3-4 documented in the literature. Short-chain organic acids (lactate, acetate, n-butyrate and formate) and N-acetyl sugars were the strongest discriminators of saliva sampled pre- and post-exercise. However, the origin of these metabolites is equivocal since bacterial metabolism and salivary gland secretion via exercise stimulation of the autonomic nervous system both contribute towards salivary composition. Urinary citrate, glycine and hippurate exhibited a decrease following isokinetic exercise, whereas trimethylamine N-oxide increased. According to the literature, this pattern has previously been associated with kidney stress on the renal papilla and tubules from the filtration of myoglobin protein from the blood which accumulates as a result of leakage from the muscle membrane during stress or injury. Thus, these urinary biomolecular markers may reflect renal filtration of muscle proteins present in the blood following exercise and may be indirectly representative of isokinetic exercise-induced muscular stress. The serum matrix was less sensitive to exercise-induced change than urine in this isokinetic intervention study, since the homeostasis of blood is maintained by the renal system. Further work is needed to cross-validate conventional assays used to measure biomarkers of muscular stress with the metabolomics platform to confirm that urinary trimethylamine N-oxide, citrate, glycine and hippurate are indirect biomolecular markers of muscular exercise. In sports medicine, NMR-urinalysis may provide diagnostic and prognostic information on injured and recovering athletes to determine whether or not they are fit to play, and predict risk of injury based on their current state of health.

Childhood obesity is associated with multiple health co-morbidities and various musculoskeletal disorders, affecting the lower limb and feet. Limited research has been undertaken which quantifies the impact of obesity on the function of the paediatric foot and lower limb. Furthermore, it is yet undetermined whether overweight children display similar functional changes as their obese counterparts. The primary aim of this research was to advance understanding on foot function and lower limb biomechanical movement characteristics in children; analysing differences between obese, overweight and normal weight children. Having determined the reliability of the measurement protocols, 100 children were recruited for assessment of body mass status and plantar foot loading. Following this, a sub-group of 45 children were recruited and three-dimensional gait analysis was undertaken. Plantar foot loading and lower limb temporal-spatial, kinematic and kinetic gait characteristics were analysed during barefoot level walking. Multiple regression was undertaken to determine relationships between body mass status, foot loading and lower limb gait biomechanics. Findings demonstrated that overweight and obese children displayed marked differences in foot loading and lower limb gait biomechanics when compared to normal weight children. The research identified that increased loading at the midfoot and 2nd- 5th metatarsals significantly predicted change in the kinematic and kinetic walking parameters at the hip and ankle in overweight and obese children. These findings provide evidence of an atypical biomechanical function of the foot and lower limb. This work advances understanding on the implications of excessive body mass on the functional characteristics of the paediatric foot and lower limb. This research identifies for the first time, differences in foot loading and lower limb gait biomechanics in overweight and obese children relative to those of normal weight. This work also provides important information as to the use of plantar pressure assessment in predicting change to the lower limb biomechanical movement characteristics of these children. This work underpins the need for further longitudinal work that further enhances our understanding on the consequences of excessive body mass on the foot and lower limb musculoskeletal and locomotor systems in children.

The hyperbolic power duration relationship for high intensity exercise is defined by two parameters: a power asymptote (critical power; CP) and a curvature constant (W′) which have been associated with sustainable, and non-sustainable metabolism, respectively. Conventionally, the power duration relationship is derived from a series of constant work-rate (CWR) prediction trials. However, it may be advantageous to establish this relationship using the 3 min all out test, or a series of time trial (TT) tests. The validity, plasticity and applicability of the power duration relationship derived using these different protocols has not been experimentally verified. Moreover, although the CP has been shown to represent a threshold in muscle metabolic and neuromuscular responses during single legged knee extension exercise, it is unclear whether this is also the case during whole body exercise. The purpose of this thesis, therefore, was to: 1) evaluate the predictive validity of the laboratory based 3-min all out test; 2) investigate the plasticity and applicability of the power-duration relationship; 3) elucidate the mechanistic bases for fatigue during whole body exercise above and below CP. In study 1, the CP (r=-0.83, P < 0.001) derived from the 3 min all out test was more strongly associated with 16.1-km road cycling TT performance than; maximum oxygen uptake (V̇O2max) (r=-0.60, P > 0.05); gas exchange threshold (GET), (r= 0.60, P > 0.05); and, respiratory compensation point (RCP), (r=-0.68, P < 0.05). In study 2, the power duration relationship derived from CWR prediction trials overestimated ramp incremental exercise performance by 2.9 ± 2.4%, and the predictive error was associated with the magnitude of the W′ (r= 0.56; P < 0.05). Study 3 demonstrated that the CP derived from a series of self paced TTs (265 ± 44 W) was greater (P < 0.05) than the CP derived from CWR prediction trials (250 ± 47 W), while W′ was not different between the protocols (TT: 18.1 ± 5.7 kJ, CWR: 20.6 ± 7.4 kJ), and the increase in CP was associated (r=0.88, P < 0.05, n=20) with faster mean response time of pulmonary O2 uptake during the TTs (TT: 34 ± 16 s, CWR: 39 ± 19 s, P < 0.05). In study 4, muscle biopsies revealed a similar (P > 0.05) muscle metabolic milieu (i.e., low pH, low [PCr] and high [lactate]) at the limit of tolerance (Tlim) for all severe intensity ( > CP) work rates irrespective of duration (~2-14 min). The muscle metabolic perturbation was greater at Tlim following severe-intensity exercise compared to exercise heavy intensity exercise (< CP, > GET), and also following severe and heavy intensity exercise compared to moderate intensity exercise (< CP, < GET) (all P < 0.05). Moreover, the rates of change in M-wave amplitude and neural drive were significantly correlated with changes in muscle metabolic ([PCr], [lactate]) and blood ionic/acid base status ([lactate], [K+]) during severe and heavy intensity exercise (all P < 0.05), but not during moderate intensity exercise (P > 0.05). Finally, study 5 found no differences in muscle carnosine content or the power duration relationship following 4 weeks of beta-alanine (BA) supplementation (6.4 g.d-1). Therefore, the results of this thesis demonstrate that the CP model is a powerful predictor of exercise performance, but only when the work rate forcing function of the prediction trials is closely matched to the performance trial. Furthermore, this thesis provides novel insights into the underlying mechanisms that characterise the power-duration relationship during whole-body exercise which explains the plasticity and thus applicability of the power duration relationship.

Background: Total hip replacement (THR), is one of the most common elective surgical operations performed in the United Kingdom. There is however little evidence examining physical activity in this population or interventions to increase it. Study 1: A systematic review examined physical activity change in the THR population pre- compared to up to one year post-THR. Studies were eligible for inclusion if they presented a pre-operative and post-operative measure of physical activity. A total of 17 studies were included. The quality of the included studies was rated as low to moderate. There was no significant difference in pre- versus post-operative physical activity (p > 0.05). The lack of significant physical activity difference should be considered in the light of the poor to moderate methodological quality. Study 2: No previous studies have assessed change in physical activity pre- compared to more than one year post-THR. A secondary data set analysis was undertaken to assess this, and examine if having a THR significantly predicted physical activity. This showed a significant decrease in physical activity pre- compared to post-THR (p < 0.05) nor was having a THR a significant predictor of physical activity (p > 0.05). Study 3: A feasibility randomised control trial was undertaken to examine the feasibility of a pedometer-prescribed walking intervention post-THR. The primary outcome measure was the Oxford Hip Score. Secondary measures were physical activity and quality of life. There was no significant between group differences for any measure (p > 0.05). The intervention was poorly adhered to. There is a need to better understand the barriers to physical activity intervention adherence in this population. Conclusions: These studies have contributed new knowledge to the field. The lack of improvement in physical activity pre- compared to post-THR and the results of the feasibility RCT highlighted the need to better understand barriers to physical activity in this population.

The purpose of this thesis was to optimise preparation for endurance runners competing in a hot environment. A multidisciplinary approach was adopted, investigating acute and chronic interventions to identify the most effective preparation. The determinants of endurance performance model (Bassett & Howley 2000) facilitated simultaneous investigation of the efficacy of interventions as well as the physiological mechanisms through which interventions influence performance. Finally, a retrospective analysis was conducted to identify the relationship between physiological markers and endurance running in the heat, in order to inform training prioritisation. Study 1 investigated the validity and reliability of skin temperature (TSKIN) measurement tools at rest and during treadmill running, to identify an appropriate measurement tool for use in subsequent studies, without restrictive trailing wires. A thermal camera provided insufficient levels of validity and reliability for safe monitoring of TSKIN, while telemetry thermistors provided a viable and more convenient alternative to the criterion measure of hard-wired thermistors. Study 2 investigated the effect of evidenced and practical internal (eg. ice slurry ingestion) and external precooling (eg. ice packs, forearm immersion and cold garments) strategies during incremental running in the heat. No differences were observed across the determinants of endurance performance between cooling techniques, with both eliciting modest reductions in blood lactate accumulation, compared with no cooling, which may prevent a decrement in the lactate turnpoint speed under heat stress. However, external cooling elicited a greater reduction in TSKIN and thermal sensation, alleviating perceived thermal strain further than internal cooling. Study 3 investigated ischaemic preconditioning (IP), which may enhance endurance performance through haemodynamic and/or metabolic mechanisms, prior to incremental running in the heat. IP had no effect on the determinants of endurance performance. The thermoregulatory responses to exercise-induced hyperthermia may supersede previously reported effects of IP, which is not recommended as an ergogen prior to exercise in the heat. Study 4 investigated the effect of a chronic strategy, involving five days of controlled hyperthermia heat acclimation (HA), on the determinants of endurance performance and a 5 km time trial in the heat. Heat acclimation improved V̇O2max, the lactate thresholds and 5 km performance. Alleviated physiological, thermal and metabolic strain were observed, likely attributable to enhanced cardiovascular stability and heat dissipation. Five days of controlled hyperthermia HA appears to be a potent strategy to support endurance running in the heat. Study 5 directly compared acute (external precooling), chronic (HA) and combined (precooling & HA) strategies during 5 km running. Precooling did not improve performance following HA, despite modest alleviation of physiological strain, which may indicate an inappropriate pacing strategy. Heat acclimation improved performance further than precooling (HA +6.6%, precooling +3.7%), indicating HA should be prioritised, although precooling appears beneficial when acclimation is not possible. Multiple, linear regression indicated the physiological determinants of endurance performance do not accurately predict endurance performance in the heat (R2=0.72, standard error of the estimate =105.6 s). The unexplained variation during endurance performance in the heat may reflect a greater prominence of perceptual measures to influence running in the III heat. Preparation for competition in the heat should therefore prioritise improving perceived thermal and exertional strain under heat stress, alongside improving traditional physiological markers.

This thesis began with practitioner observations in a specialist personal training practice, where anecdotal themes were noted from middle-aged clients (45-65 years old). Sedentary, exercise-averse individuals reported poor experiences of physical education in secondary school, whereas active clients gave a different narrative. These themes suggested differing life course trajectories that could result in ‘corporeal dissociation’ (CD), a term, defined here to describe a state of physical detachment that might result in adult inactivity. ‘Lives lived’ were investigated through a lifecourse theoretical perspective, within a pragmatic paradigm. Methodological Bricolage employed both qualitative and quantitative multi-methods to look at the research questions from differing perspectives. In Study 1, 10 practitioners were interviewed qualitatively to see if the original observations were replicated in other practices within the same geographical area. Data was analysed using content and emergent thematic analysis and it was found to be so. In Study 2, 800 middle-aged men and women across England completed a quantitative online survey that covered 63 experiences, grouped thematically, between the ages of 11-16: ‘home’, ‘about me’, ‘school’, ‘friends and leisure activities’. Data was statistically analysed using Principal Component Analysis followed by ANOVA and 16 significant dispositions and experiences centred around PE emerged as signifiers of corporeal dissociation in middle age. Study 3 took a sample of 8 men and 8 women from Study 2. It used narrative inquiry and established lifecourse themes of activity and inactivity that link adolescence and middle-age, with the individual’s relationship with their PE teacher being the biggest signifier and influence on later physical activity. Results show that corporeal dissociation can be found in practice and its origins in PE experience identified. Tentative life path signifiers have been determined and have been mapped between school and middle age. The outcome of the study is an understanding and definition of corporeal dissociation and a scalable tool for the practitioner to identify corporeal dissociation in new clients to help aid initial exercise adherence by prescribing suitable exercise programming.

No description available.

It is well accepted that the increasing sedentary lifestyle are helping fuel the dramatic rise of health related problems whilst having a negative impact on the economy, requiring new ways by which to promote and educate with regards to the need and benefits of participating in both short and long term physical activities. The increasing ubiquity and sensor enhancement of mobile devices and phones in particular provide the necessary technology for these purposes. The work presented in this thesis discusses persuasion and the suitability of technology in particular mobile phones to influence behaviour focusing on the use of sensors for this purpose. Mobile exercise monitoring is discussed along with the benefits of including kinetic and physiological sensors in such activities, demonstrated via a mobile persuasive health application utilizing heart rate to assess, record, and monitor fitness levels through built-in cardio-respiratory tests together with location tracking for heart rate analysis over time and location. Video games and in particular 'exergaming' to promote heath is then discussed, presenting a mobile exergame implementing kinetic enabled control mechanisms requiring a degree of physical interaction and heart rate to trigger in-game predefined actions. To conclude the use of a low-cost EEG headset in the area of 'biometric gaming' is presented introducing a mobile biometric game utilizing EEG inputs to trigger in-game conditions discussing the reliability and efficiency of such technology at interpreting such values and the relative impact on gaming, and it possible use in cognitive monitoring. These projects demonstrate the potential of using physiological and kinetic sensors in conjunction with mobile phones to deliver and promote physical activity, structured and/or opportunistic, to change attitudes and participation on daily physical activities using the data obtained from such sensors along with techniques of persuasion to further validate as well as reinforce the reasons behind doing so.

A number of studies have shown exercise to stimulate human growth hormone (hGH) secretion, although most of these have considered prolonged submaximal or resistance exercise. Only a few have studied maximal sprint exercise, and these studies have demonstrated considerably elevated circulating hGH concentrations during recovery. However, there is little agreement in the literature regarding the regulation of hGH secretion during and after exercise. This thesis describes a series of experiments considering the hGH response to sprint exercise, with the intention of gaining a better understanding of some of the mechanisms involved in regulating the exercise-induced hGH release.

In some circumstances, dietary nitrate (NO3-) supplementation can favourably alter the physiological response to exercise. Recent research highlights a potential preferential effect of NO3- supplementation on type II muscle fibre function. The purpose of this thesis was to investigate the practical applications of NO3- supplementation in sport and exercise settings requiring a substantial contribution of type II muscle fibre recruitment such as team and sprint sports. Specific questions addressed in this thesis include whether NO3--rich beetroot juice (BR) supplementation can influence the performance of sprint and high-intensity intermittent exercise and if BR supplementation, when combined with sprint interval training (SIT), can enhance performance and muscle metabolic adaptations in competitive team sport players. In addition, since cognitive performance is a key aspect of team sport performance, the effect of BR supplementation on decision-making during high-intensity intermittent exercise was also assessed. Chapter 4: Total work done during a prolonged intermittent sprint test (IST) designed to mimic the metabolic demands of team sport play was 3.5% greater following short-term BR supplementation (123 ± 19 kJ) compared to short-term NO3--depleted beetroot juice (PL) supplementation (119 ± 17 kJ) (P < 0.05). Decision-making reaction time was shorter in the second half of the IST in BR (817 ± 86 ms) compared to PL (847 ± 118 ms) (P < 0.05). Chapter 5: Short-term BR supplementation improved the performance of sprint running compared to PL over distances of 20 m (1.2% improvement; BR: 3.98 ± 0.18 vs. PL: 4.03 ± 0.19 s; P < 0.05), 10 m (1.6% improvement; BR: 2.53 ± 0.12 vs. PL 2.57 ± 0.19 s; P < 0.05) and 5 m (2.3% improvement; BR: 1.73 ± 0.09 vs. PL: 1.77 ± 0.09 s; P < 0.05). Relative to PL, BR supplementation also increased the distance covered in the Yo-Yo intermittent recovery test level 1 by 3.9% (BR: 1422 ± 502 vs. PL: 1369 ± 505 m; P < 0.05). Decision-making reaction time was shorter in BR (615 ± 98 ms) compared to PL (645 ± 120 ms) (P < 0.05) at rest but not during the Yo-Yo IR1 test. Chapter 6: 4 weeks BR ingestion significantly reduced the O2 cost of moderate intensity exercise (by 5%; P < 0.05) and significantly increased the peak work rate (WR) attained during incremental exercise (P < 0.05). When 4 weeks SIT was combined with 4 weeks of BR ingestion, peak WR increased more than when SIT was combined with PL supplementation (SIT+BR: 24 ± 8 W increase vs. SIT+PL: 16 ± 15 W increase; P < 0.05). Although the change in time to task failure during severe-intensity exercise was not statistically different between SIT+BR (69% increase) and SIT+PL (55% increase), there was evidence of a more favourable muscle metabolic response to severe-intensity exercise in SIT+BR. Specifically, at the 3-min iso-time during severe-intensity exercise, muscle pH was higher and muscle (and blood) [lactate] was lower in SIT+BR only (P < 0.05). These findings demonstrate that BR supplementation may be ergogenic in sprint cycling, sprint running and high-intensity intermittent exercise and that when combined with SIT, BR supplementation may enhance the resultant exercise performance adaptations and some muscular adaptations to exercise. The results of this thesis also suggest that BR supplementation may improve cognitive performance, specifically decision-making reaction time, during team sport exercise.