There is evidence that physical activity (PA) levels are declining in English children. Sedentary screen based media activities, including computer use and video game play have been linked to low PA levels and unhealthy energy intake (EI). These behaviours appear to be particularly prevalent in boys during mid-to-late childhood. Recent laboratory-based studies have found active video games can increase children’s energy expenditure (EE) and PA levels to moderate to vigorous levels, in comparison to matched conditions such as resting and seated video game play and so could increase children’s PA. However, the previous active video gaming studies have utilised various protocols that probably do not accurately reflect the real life active video gaming practices of children. Recently it has been established that there is EI in adolescents during active video gaming. If this is so, the EI during active video gaming could potentially counteract the EE from active video game play. The purpose of this thesis therefore, was to establish the acute appetite, EI and PA responses to active video gaming, in 8-11 y boys. There is sparse information regarding the habitual active video gaming behaviours of children during mid-to-late childhood. Consequently, in study one a questionnaire was designed specifically, to understand the real-life active video gaming practices of 40 7-11 yr-olds. By utilising the survey findings, in study two an acute intervention was designed to investigate the subjective appetite sensations (hunger, prospective food consumption and fullness), EI and PA in response to active video gaming in 21 8-11 yr-old boys. Each boy completed four individual 90 min gaming bouts in a randomised order which were; 1) seated video gaming no food or drinks, 2) active video gaming no food or drinks, 3) seated video gaming, food and drinks offered ad libitum and 4) active video gaming, food and drinks offered ad libitum. The study determined that there were no differences in acute sensations of hunger, prospective food consumption and fullness, or EI (MJ) between the seated and active video gaming bouts during which foods and drinks were offered ad libitum (bouts 3 and 4). Physical activity levels due to active video gaming were light and from seated video gaming were sedentary. Energy intake during both bouts was greater than the estimated EE, thus producing a positive relative energy balance state in the boys. As subjective appetite findings did not explain the high EI during both seated and active video gaming, the objective study of appetite was necessary. A previous adult study had established good reproducibility in GLP-17-36, glucagon, leptin and insulin by using the less invasive fingertip capillary sampling. Since fingertip capillary sampling had not been utilised to measure plasma concentrations of the above mentioned hormones in children during gaming, in study three, preliminary testing established good reliability for fasting plasma GLP-17-36 and blood glucose in 8- 11 yr-old boys. Enabling study three to compare acute satiety related signalling, subjective appetite, EI and PA in 21 8-11 yr-old boys, in response to one bout of active video gaming and one bout of seated video gaming, during which food and drinks were offered ad libitum. The satiety-related signals, namely plasma GLP-17-36 and blood glucose were measured alongside subjective appetite sensations and EI during active and seated video game play and in a post-gaming test meal. A significant increase in glucose showed the boys had consumed a greater proportion of carbohydrate (CHO) during active video gaming. However, as more total energy was consumed during seated video gaming, and plasma GLP-17-36 was higher during active video gaming, according to the ‘glucostatic theory’, there may have been a satiety response. The satiety signals may not have been strong enough to override the hedonic response to food intake, especially as fullness sensations were higher during active video gaming. Physical activity levels were light due to active video gaming and sedentary from seated video gaming and so on cessation of both bouts, the relative energy balance of the boys was positive. The positive relative energy balance state was then not compensated for by a reduction in EI in a post-gaming test meal. Instead, the additional EI resulted in an increase in the positive relative energy balance state, of the 8-11 yr-old boys. The overall findings of this thesis established that EI appears to be commonplace in the majority of 8-11 yr-old children during active video gaming. Parents should encourage their children to play active, rather than seated video games to reduce sedentary time and also discourage EI during game play.

DNA methylation, an epigenetic modification which can regulate gene transcription independently from alterations to the nucleotide sequence, can be manipulated by lifestyle factors such as diet and exercise, hypothetically reversing aberrant DNA methylation associated with disease pathogenesis. The underlying mechanisms by which these changes occur are currently poorly characterised, however, in vitro data suggest that inflammatory mediators are involved. Furthermore, regular exercise appears to reduce inactivity-associated systemic inflammation, possibly by alterations to the methylome, thereby suggesting a cyclic relationship between exercise, inflammation, and epigenetic modification. The aims of this research programme, therefore, were to: characterise the acute changes that occur to the de novo DNA methyltransferases following exercise in peripheral blood mononuclear cells (PBMCs), and the role of exercise-induced systemic inflammation in this process; investigate how these changes then translate into functional modifications to the methylome; and to determine whether a training programme utilising sedentary individuals manipulates DNA methylation of genes involved in chronic systemic inflammation associated with physical inactivity. Pilot investigations corroborated previous in vitro data that recombinant IL-6 is able to regulate nuclear concentrations of DNMT3A and DNMT3B in PBMCs. In order to isolate the influence of circulating proteins independently from genetic polymorphisms that may influence susceptibility to epigenetic change, cells were stimulated with exercise-conditioned plasma following intense endurance exercise which elicited significant alterations in nuclear concentrations of DNMT3A and DNMT3B. Eccentric exercise, which is typically not associated with elevations in circulating cytokines, did not cause any significant changes in nuclear or cytoplasmic DNMT concentration, or global DNA methylation; this supports the hypothesis that transient systemic elevations in inflammatory cytokines are important regulators of epigenetic modifications associated with exercise. Lack of transcriptional changes in DNMT3A following both exercise training and an acute maximal bout suggests that, in line with in vitro data, that the observed elevations in nuclear DNMT concentration are largely due to cellular relocalisation and not gene expression of this enzyme. It remains to be elucidated whether the training regime, and the subsequent response to an acute maximal bout, is able to elicit differential methylation of IL6, NFκB2, and ASC, however, in vitro stimulation of PBMCs with the cytokines IL-6 and IL-1β did cause significant changes to IL6 promoter methylation, further supporting the role of these proteins in epigenetic regulation. The data presented in this thesis support the postulation that exercise-induced changes to DNA methylation in PBMCs likely occur due to systemic elevations of inflammatory proteins, in particular IL-6, which causes manipulation of de novo DNMT nuclear concentrations due to cellular translocation of the enzymes themselves. While it was not possible to determine whether exercise directly modified gene-specific methylation, in vitro experiments suggest that inflammatory cytokines are able to regulate IL6 promoter methylation in human PBMCs.

Athletes and practitioners are continually looking for new strategies that could minimise the negative effects of exercise-induced muscle damage (EIMD) and hasten the recovery process. One strategy that has shown promise in recent years is the use of functional foods rich in phytonutrients. A functional food that has attracted a lot of attention recently, although primarily for its performance enhancing effects, is beetroot (Beta Vulgaris L.). In addition to displaying a range of physiological effects that may benefit athletic performance, beetroot also exhibits antioxidant (AOX) and anti-inflammatory effects, both of which could be of benefit for reducing secondary damage and enhancing exercise recovery. Nonetheless, the effect of beetroot on exercise recovery is yet to be systematically investigated in the literature. Thus, the overarching aim of this thesis was to test the efficacy of beetroot supplementation, in the form of beetroot juice (BTJ), as a recovery intervention following strenuous exercise. The series of investigations that set out to address this aim have led to many novel and interesting findings. To start with, study 1 was the first to show that a commercially available BTJ is a rich source of phytonutrients and therefore possesses a high AOX capacity in comparison to several other fruit and vegetable juices. Secondly, and perhaps the most novel finding in this thesis, was that BTJ showed promise as an efficacious recovery intervention following some bouts of muscle-damaging exercise. Although not a consistent finding throughout this thesis, BTJ was able to improve the recovery of dynamic muscle function and reduce muscle pain after eccentric-heavy exercise. Another important finding was that BTJ, despite being rich in AOXs, did not adversely affect the acute adaptive response to exercise, as measured by the repeated bout effect (RBE). In contrast to the findings in the earlier studies, however, BTJ was not found to be beneficial for recovery after long distance running. Importantly, the final study in this thesis provided the first evidence that BTJ is more beneficial than sodium nitrate (SN) for enhancing some aspects of recovery. This study highlighted the importance of the phytonutrients in BTJ other than nitrate on recovery after exercise. In summary, the collective findings of this thesis provide new information on the potential application of a phytonutrient rich functional food, in BTJ, for recovery from strenuous athletic performance.

The aim of this thesis was to develop our understanding of the Functional Re-adaptive Exercise Device (FRED): a novel prototype exercise device proposed to facilitate the activation the deep paraspinal and anterolateral abdominal wall musculature in a manner consistent with the requirements of motor control training in people with low back pain. Firstly, the intra- and interday reliability and precision of measurement of ultrasound imaging of the lumbar multifidus (LM) and transversus abdominis (TrA) were established. LM and TrA demonstrated good (ICC ≥ 0.75) to excellent (ICC ≥ 0.9) intrarater reliability for both intra- and interday measurements of absolute linear muscle thickness across all conditions. Normalised thickness change, expressed relative to resting values, also demonstrated good reliability between days, with ICCs in excess of 0.75 across all conditions. Secondly, the typical nature of LM and TrA function during this mode of exercise was evaluated in relation to commonly used assessment techniques such as the abdominal drawing-in manoeuvre, active straight-leg raise, and contralateral arm-lift. All contraction conditions successfully resulted in active relative thickness change of LM and TrA. Relative thickness change of the LM when using the FRED was favourable in that it was lower than that observed in loaded contralateral arm raise and walking conditions, suggesting that one of the key features of specific motor control training (contraction intensity of 30-40 % MVC) has been met. Thirdly, activity of the LM and TrA during this mode of exercise and other commonly used corrective/rehabilitative techniques based on relatively static challenges to stability was compared (gym ball, balance board). All stability challenges successfully induced non-volitional concomitant activation of both the LM and TrA. Additionally, it was observed that the LM followed a pattern where all standing conditions elicited greater recruitment than seated conditions, with no additional effect of surface lability. Contrastingly, the TrA only demonstrated an effect of surface instability during FRED conditions. The preferential contraction ratio of the TrA in comparison to IO and EO was greatest during use of the exercise device in the standing position. Fourthly, the intrinsic kinematic stability of the lumbopelvic region whilst using the exercise device was examined, revealing further evidence of the underlying mechanisms facilitating LM and TrA contraction. Key differences between FRED exercise and overground walking included reduced axial rotation of the trunk with respect to the pelvis (i.e. increased lumbopelvic stability) and a more anteriorly tilted pelvis. FRED exercise potentially moved the pelvis into a more advantageous position for the recruitment of TrA and LM. However, the unstable base of support afforded by FRED exercise would seem to add a challenge to movement control that could result in greater TrA and LM activity than overground walking. Finally, the pattern of global muscle activation during this exercise was examined, and provided evidence as to the tonic nature of FRED mediated muscle activity of the lumbar paraspinal and anterolateral abdominal muscles. FRED exercise a) promoted more tonic activity of the lumbopelvic musculature compared to overground walking, b) resulted in greater spinal extensor activity than spinal flexor muscles compared with overground walking, and c) resulted in greater knee extensor activity compared with overground walking.

Pacing patterns vary between sports, between athletes and between competitions. There is much literature investigating pacing patterns in laboratory and staged competitive situations which have suggested that fast start, parabolic and even pacing patterns could be optimal for short, middle and long distance events, respectively, in elite athletes. However, there is little information about optimal pacing patterns to win medals in competitive situations in middle distance events and even less information specifically for female and developing athletes. This thesis describes and explains the variation in pacing needed to win a medal in swimming and running middle distance events for male and female elite athletes using data from international competitions. Pacing patterns seen in competitive middle distance events by developing swimmers were also investigated. Following a literature review, two methodological chapters developed a suitable video data capture method and then identified a suitable sample size for the collection of retrospective data. The first experimental chapter identified that a variable pacing pattern that included a conservation period of reduced relative pace and an end-spurt of increased relative pace was optimal in order to win a medal in elite men’s 400 m freestyle swimming and 1500 m running. The second experimental chapter identified the same need for conservation of relative pace earlier in the race and an increase in relative pace for an end-spurt at the end of a race in order to win a medal in female elite 400 m freestyle swimming. The third experimental chapter identified that the same pacing patterns were optimal for age group swimmers at regional competitions but that the youngest swimmers needed to develop a more optimal performance template. The fourth and final experimental chapter of this thesis used three case studies to show that a higher training load and lower positive affect led to improved pacing patterns in developing athletes. This thesis contributes to the literature on pacing by identifying the optimal changes in relative speed needed to win a medal in competitive middle distance events.

In my thesis I explain patterns and developments of current participation in sport and physical activity among a group of men and women in the transition to early mid-life (38-43 years of age). I examine their perceptions of the activity and sense of sporting identity over their lives. There is limited research on mid-life experiences of sport and physical activity and more often this takes a social survey approach. The interpretive research on mid-life is still an emerging field, previous research has often focused on a single sport sub-culture, those who are heavily involved in sport, or women only. In depth, topical life history interviews and written timelines were completed with a group of sixteen individuals in this life stage, with varied experiences of sport and physical activity. The data was analysed using Brown and Gilligan's (1992, 1993) `voice centred relational method' of analysis, followed by 'constant comparison' (Glaser and Strauss, 1967) and coding (Strauss and Corbin, 1998). The major theme identified in this study was the complex construction of sport and participation, understood as it relates to the participants lives as a whole and its impact on their participation decision making. Sub-themes included; the different meaning and value of sport and self definition in relation to this, and changes in these across the life course (particularly the transition to midlife) and in relation to the ageing process and relationships. The research demonstrates the relationship between sport and the needs at this life stage, highlighting identity management, and values placed on the ethic of care and sport and physical activity as leisure. Conflicting feelings are experienced in relation to sport and physical activity due to constraints on and into participation. Further to this the thesis provides a grounded theory model of the construction of these activities in the transition to early midlife. The findings were interpreted with theoretical perspectives from: structuration (Giddens, 1979, 1984), dramaturgical (Goffman, 1971, 1972a), relational (Gilligan, 1993), role (Kelly, 1983; Turner, 1956, 1978; Zurcher, 1970, 1979), life cycle (Levinson et al, 1978, 1996), family life cycle (Rapoport & Rapoport, 1975), and role transition (Kelly, 1983) theories.

The severe health implications associated with physical inactivity highlight the need for research aiming to elucidate mechanisms underlying individuals’ experience of exercise. Affective responses to exercise have been identified as a central factor shaping exercise behaviour (Ekkekakis, 2003; Kwan & Bryan, 2010; Williams, et al., 2008). Research identifies that external and internal factors influence affective evaluations of exercise. One external factor influencing the evaluation of affective responses is the environmental stimuli comprising the exercise setting (Antoniewicz & Brand, 2014; DaSilva, et al., 2011). Therefore, study one examined the influence of environmental cues on affective and cognitive responses to exercise in an ecologically valid setting. Results revealed significant interactions between environmental cues and affect, and motivation; this suggests that intra-individual processes may influence exercise behaviour. The thesis subsequently investigated internal processes that influence affective evaluations of exercise; in particular, processes underlying the recall of affective experience (Kahneman, et al., 1993). Study two examined individuals’ recall of exercise related affect over a period of two weeks using a randomised control crossover design. Results indicated that exercise related affect fluctuated over the two-week period with a significant drop at 24 hours post low-to-moderate and high intensity exercise trials. Additionally, recalled affect better predicted anticipatory feelings than affect recorded during exercise. The study also found partial support for the peak and end rule particularly for the high intensity exercise. Extending study two’s findings, study three explored the recall of exercise related affect and anticipatory feelings using an experimental design with a self-paced exercise protocol. The study revealed significant changes across postexercise recall with follow-up measures at 8 and 24 hours indicating a substantial decline in affect. Overall findings revealed that contextual factors promote positive affect when aligned with one’s goals; however discordant contextual cues and goals can thwart positive affective responses. Further, recall of affective experiences of exercise dynamically change over time and recalled affect can predict anticipatory feelings of exercise. Lastly, all studies’ findings emphasise on the imperative role of idiographic analysis in research on affective responses to exercise.

Mental toughness (MT) originated within elite sport and was identified as an attribute of success. MT has emerged as being important for enhancing health-related lifestyle factors (HRLF; e.g., physical activity). Investigating the healthiness of one’s lifestyle appears a timely area to research given the current health status of the population. Therefore, the aim of this thesis was to investigate MT in relation to HRLF and weight loss. Study One investigated MT and HRLF in university students (n = 167). Self-reported MT, physical activity, exercise barriers, dietary behaviour, and psychological wellbeing were recorded. MT was significantly different between regular exercisers (M = 3.43 ± .42) and non-regular exercisers (M = 3.24 ± .54, p < .05). Components of eating identity, exercise barriers, and psychological wellbeing, were significantly correlated with MT. Study Two longitudinally investigated weight loss progress, and adherence to a weight loss support group, in slimming club members who were pursuing a weight loss goal (n = 132). MT and eating identity were assessed at baseline, three-months, and six-months, and weight was recorded at weekly meetings. Overall MT was not significantly related to weight loss (r = -.15, p > 0.05) or adherence to the service (r = .03, p > 0.05). Study Three sampled individuals who held a weight loss goal, but were not attending a weight loss support club (n = 78). Overall MT was not significantly related to weight loss (r = -.21, p > 0.05). MT was not significantly different between weight loss goal achievers (M = 3.62 ± .49) and non-goal achievers (M =3.42 ± .38, p > 0.05). Thus, irrespective of whether structured support is received, overall MT was not related to weight loss progress. II Study Four investigated the experiences of high (n = 9) and low (n = 7) mentally tough individuals pursing a weight loss goal. High and low MT individuals, identified using the MTQ48, were interviewed. Thematic analysis revealed that amongst the high mentally tough individuals, those who prioritised leading a healthy lifestyle reported weight loss success compared to those who prioritised other goals. Strategies to overcome low levels of MT (e.g., control), as well as receive additional support, appeared crucial for successful weight loss in low MT individuals. Study Five further investigated the low MT individuals’ (n = 7) perceptions, experiences, and attitudes, towards weight loss. Low MT individuals were sampled based on their MT score assessed via the MTQ48. Vignette based interviews extended the findings in Study Four. Thematic analysis revealed key findings, including the potential to change low MT individuals’ perceptions to enhance behaviour change. Overall, this thesis expanded the understanding of MT; the processes that one experiences when trying to lose weight appears to differentiate between high and low MT individuals, which offers an explanation as to why MT did not appear to play a significant role in weight loss outcomes. These findings challenged the predominant contemporary understanding of MT and demonstrated that MT was not associated with behaviour change to achieve weight loss.

Imagery and self-talk are functionally similar and theoretically connected psychological strategies. In accordance with the multi-strategy approach to psychological skills training, there have been suggestions that athletes should use imagery and self-talk in conjunction (Hardy, Gammage, & Hall, 2001a). Although intuitively appealing, these recommendations are premature due to the evidence suggesting that situational demands, functional requirements and individual differences may influence athlete preferences for usage. This thesis aimed to address this ambiguity and identify the factors influencing the use and effectiveness of imagery and self-talk in golfers. The first three studies used a variety of methodologies including surveys, interviews and focus groups to profile existing practice and determine the predominant factors affecting usage. The final study examined the performance effects associated with the use of an imagery and self-talk intervention, that had been created based on the profiled information. Study one determined the impact that individual differences in golfers’ preferred cognitive styles had on their use of imagery and self-talk in practice and competition. Results revealed that golfers’ preferred cognitive styles did not influence the formation of preferences for the use of one strategy rather than the other. Instead, all golfers reported using both strategies equally, although their use was reported more widely in competition than practice. Whilst study one ruled out preferred cognitive style as a determinant of golfers’ preferences for the use of imagery and self-talk, it did not clarify how and why the two intervention strategies were used independently and in combination. The purpose of study two was therefore to identify how golfers used imagery and self-talk in combination and separately, considering the influence of contextual factors and functional requirements. Findings indicated that rather than employing the use of the strategies continuously throughout competition, golfers emphasised their use prior to the execution of particular golf strokes in specific conditions. Study three identified the common characteristics of the competitive situations where golfers employed the use of imagery and self-talk. Findings revealed that golfers emphasised, and actively used, imagery and self-talk most when playing golf strokes under stressful competitive conditions. As a result of this finding, the next phase of study three examined how golfers used imagery and self-talk as problem and emotion focussed coping strategies when playing golf strokes under stressful competitive conditions. Results indicated that golfers predominantly used imagery and self-talk as problem focussed coping strategies, making more use of imagery than self talk. The purpose of the fourth study was to examine the effectiveness of using imagery in isolation, and in combination with self-talk, as a problem focussed coping strategy when dealing with golf strokes under stressful conditions in competitive situations. Findings revealed that golfers perceived their execution of golf strokes under stressful conditions to be most effective when imagery and self-talk were used in combination. However, this perceived advantage did not translate into identifiable performance gains during the monitored competitive rounds. Although the inherent variability of golf performance might have made it difficult to determine noticeable changes in performance, it was suggested that the lack of effects observed may have been due to the fact that imagery and self-talk as problem focussed coping strategies were simply ineffective. Findings taken together revealed that contextual factors are the most influential determinant of golfers’ use of imagery and self talk. Furthermore, golfers emphasise the use of imagery and self-talk most when they need to perform golf strokes under stressful conditions, applying their use as problem focussed coping strategies. However, results from the final study appeared to suggest that this approach to the use of imagery and self-talk might be ineffective.

Due to geometrical features, it is claimed that larger femoral heads in total hip replacement (THR) are superior in achieving normal biomechanics than smaller ones; and that hip resurfacing (RSF) is superior to THR. This has not been conclusively proven. Most studies have investigated level walking, which may not be demanding enough to highlight what could be small biomechanical differences between implants. Few biomechanical studies have compared more demanding tasks and not with patients with different femoral head sizes or RSF. This thesis aimed to address these omissions by investigating level walking, stair descent and sit-to-stand (STS) biomechanics between three groups (32mm THR, 36mm THR and RSF). Twenty-six osteoarthritis patients were recruited and tested pre-operatively, then three and twelve months post-operatively. Demographic differences between groups were expected due to patient considerations for different implants, so a study was performed to determine whether level walking biomechanics alter progressively during the aging process with a group of 63 healthy participants. Three matched sub-groups were extracted from this group as controls. There was no suggestion that gait deteriorates progressively with age. Hip reconstruction, irrespective of head size, can allow patients to return to the biomechanical levels of controls during level walking. Stair descent differences remained 12 months post-operatively in cadence (p=0.042) and peak hip power generated (p<0.001) compared to controls. The 32mm group exhibited vertical ground reaction force (vGRF) asymmetry pre-operatively (p<0.001) and 3 months post-operatively (p=0.013); and impulse asymmetry (p<0.001) pre-operatively during STS. The 36mm group exhibited impulse asymmetry (p=0.05)three months post-operatively. This thesis is the first biomechanical analysis of stair descent and STS of two THR groups and a RSF group. It has demonstrated stair descent differences at 12 months post-operatively and overloading of the healthy limb in some THR patients. The latter could be problematic for the healthy limb.