Introduction: At present there is a pandemic of low serum vitamin D (25[OH]D) concentration, partly due to a lack of sun exposure (the primary route for synthesis) and modern lifestyle choices. The bioactive form of vitamin D, 1,25-dihydroxyvitamin D (1,25[OH]2D3) exerts its biological activity by binding to the vitamin D receptor (VDR). These receptors play a central role in the biological actions of vitamin D and are expressed in nearly every tissue and cell type in the body (M. Holick, 2007). Vitamin D deficiency is widespread within many general and athletic populations and associated with a number of detrimental health conditions, including a long-term impact on cardiovascular health (M. Holick, 2007; Larson-Meyer & Willis, 2010; Pittas, Lau, Hu, & Dawson-Hughes, 2007), and the aetiology of osteomalacia and osteoporosis (M. F. Holick, 2009). Given the prevalence and potential negative morbidity associated with deficiency (Larson-Meyer & Willis, 2010), regular vitamin D testing has been recommended as part of routine athlete screening. Current literature shows inconsistent associations between vitamin D status and bone mineral density and cardiac health; (Bischoff-Ferrari, Kiel, et al., 2009; Marwaha et al., 2011) particularly in racial minorities and athletic populations. Whilst it is considered that athletes should have ‘sufficient’ vitamin D concentrations, the exact value to ‘optimise’ health is equivocal. Finally, there appears to be a ‘paradoxical relationship’ between ethnicity and vitamin D concentration, that has largely been ignored, i.e. blacks generally present with the lowest vitamin D concentrations but the greatest bone mineral density (BMD) and reduced risk of fracture (Cauley et al., 2005). Vitamin D–binding protein (DBP) may account for observed racial differences in manifestations of vitamin D (Powe et al., 2013). To date, research on vitamin D status in athletes has overlooked DBP. Whilst there are data that support the associations between vitamin D and markers of bone and cardiac health in the general population, definitive relationships in the athletic population are yet to be established. Therefore, the aim of this thesis was to examine the relationship between vitamin D and measures of bone mass and cardiac structure and function within a large, ethnically diverse cohort of healthy athletes, with a focus to the role of DBP in determining racial differences in bioavailable levels. Studies 1. Oral vs. Intramuscular Vitamin D Supplementation for Treating Insufficient Athletes 2. No Association between Vitamin D Deficiency and Markers of Bone Mass in Athletes 3. No Association between Vitamin D Status and Markers of Bone Mass in Non-Weight Bearing Athletes 4. Why don’t serum Vitamin D concentrations associate with BMD by DXA? A case of being ‘bound’ to the wrong assay? Implications for Vitamin D screening 5. Severely Vitamin D-Deficient Athletes Present Smaller Hearts than Sufficient Athletes Methodical overview Male athletes registered with the Qatar Olympic Committee (QOC) presented for pre-competition medical assessment at Aspetar Sports Medicine Hospital, Qatar. All athletes completed a vitamin D questionnaire that included questions specifically related to country of origin, sporting discipline, skin type, self-reported exposure to daily sunlight, use of sunscreen, dietary supplements and/or medication, and an assessment of skin colour. All individuals undertook bone densitometry and body composition analysis by dual-energy x-ray absorptiometry (DXA; Osteocore III, Perols, France, version 5.22b). Venous blood samples were collected from athletes following an overnight fast and was analysed for PTH, calcium, albumin and serum 25[OH]D. Athletes were split into four 25[OH]D categories; severely deficient (< 10 ng/mL), deficient (10–20 ng/mL), insufficient (20–30 ng/mL), or sufficient (>30 ng/mL). Serum vitamin D binding protein (DBP) concentrations (μg/mL) were determined using a commercially available kit (R&D Systems, UK). Free, bioavailable, and DBP-bound 25[OH]D were calculated using equations from supplementary material of (Powe et al., 2013). Lastly, all individuals assessed for family history of cardiovascular disease and personal symptoms, with a physical examination, 12-lead electrocardiogram and an echocardiogram. Results The key findings from the thesis are 1) serum 25[OH]D concentrations are not associated with markers of bone mass 2) bioavailable vitamin D is a better preceptor of BMD that serum 25[OH]D concentration and 3) severely 25[OH]D deficient athletes present with smaller cardiac structure that sufficient athletes. Conclusion In a healthy, ethnically diverse athletic population, there is no relationship between serum 25[OH]D concentration and makers of bone mass, regardless of sporting type and that bioavailable vitamin D is a better predictor of bone mineral density. Suggesting that our chosen method of assessment may not be appropriate to identify true deficiencies. Systematic screening to determine 25[OH]D concentrations is expensive, and demonstrates a poor relationship to bone mass in an ethnically diverse athletic population. It can be argued that vitamin D testing should be reserved for the symptomatic athlete (i.e. musculoskeletal injury, REDs). In turn, prophylactic vitamin D supplementation (2000IU/d D3) to ‘correct’ insufficient athletes with normal bone health can be questioned, since supplementation recommendations are based on a measure that is not associated with bone health. Severely 25[OH]D deficient athletes present with smaller (< 10 ng/ml) presented significantly smaller cardiac structures than insufficient (20–30 ng/ml) and sufficient (>30 ng/ml) athletes. The precise mechanism(s) causing this cardiac hypertrophy (or in our case, lack of hypertrophy) in the 25[OH]D-deficient state remains unclear. Clinically low vitamin D concentrations are detrimental to aspects of health that influence athletic performance. Therefore, the widespread prevalence of low serum 25[OH]D concentrations should not be ignored. However, vitamin D metabolism is a rapidly evolving field, with the prospect of a more complete picture of this complex endocrine system becoming ever so closer. The challenge for future research is to determine ethnically specific concentration ranges and evidenced based guidelines for the diagnosis and treatment of ‘true’ vitamin D deficiency and its impact on athlete health and performance.

No description available.

The common aim of the long and triple jumps is to attain maximum horizontal distance from the front of the take-off board. This is achieved by converting some of the horizontal velocity developed in the approach run into vertical velocity at take-off. The aim of this thesis was to examine a theoretical model and to identify kinematic and kinetic factors that facilitate the generation of vertical velocity in the long and triple jump take-offs. A pivot mechanism was defined to act between touch-down and the instant the centre of mass was directly above the toe of the support foot. This mechanism was found to be the largest contributor to the gain in vertical velocity in all take-offs, accounting for 83.0% in the long jump and 63.7%, 69.8% and 70.7% in the hop, step and jump take-offs. The contribution of the pivot to the gain in vertical velocity at take-off in the long jump was significantly greater than in each of the triple jump take-offs, (all P<0.002). A relative momentum approach was used to determine the contribution of the free limbs to the generation of vertical velocity. In the long jump, the free limbs made a 10.8% contribution to the gain in vertical velocity, compared to 12.2%, 19.0% and 19.0% in the triple jump take-offs. Multiple regressiona nalysesw ere used to identify factors relating to the generationo f vertical velocity in the long jump (n=14). The greatestg ains in vertical velocity were associatedw ith techniquest hat emphasiseda low centre of mass and extended knee joint at touch-down and the ability to resist knee flexion in the compression phase, R2=72.7%. The greatest losses in horizontal velocity were associated with excessiveh ip adduction, less hip extensiona nd greater increasesin height from touchdown to take-ofll R2=84.5%. Ground reaction forces and net joint moments were measured during short approach running jump tests. Peak vertical impact forces were greater in simulated 'drop' take-offs, 5080 N, compared to those experienced in 'flat' approach take-offs, 3250 N, (P=O. 002). Peak horizontal braking forces were 1800 N in both types of take-off. However, the peak net joint moments about the ankle, (403 N. m and 387 N. m), knee (233 N. m and 296 N. m) and hip (292 N. m and 249 N. m) were similar between the 'flat' and 'drop' take-offs. This suggests that athletes adapt their technique in the 'drop' take-off to distribute the larger forces effectively and to keep the net joint moments within controllable limits. Results indicated that strength about the ankle joint was particularly important in both types of take-off, but depending on the athlete's technique strength about the knee and hip are also vital. Greater flexion of the knee joint at touch-down and maximum knee flexion were found to be associated with greater average knee moments, R2=30.8% and 75.5% respectively, and greater angles of leg placement were moderately associated with greater average hip moments, R2=23.5%. In conclusion, this thesis has provided a greater insight into the kinetics and kinematics of jumping for distance. It has quantified the contribution made by the pivot mechanism and the free limbs to the generation of vertical velocity, and has assessetdh e demandso n the musculoskeletal system in terms of ground reaction forces and net joint moments. The results indicate that elite performers cannot rely on speed alone, and that strength and technique are major factors of successful performance.

The purpose of the thesis was to provide a detailed analysis of the physical demands of competitive international female soccer match-play and the physical characteristics of elite players. To date, the majority of research has focussed on sub-elite players with a lack of information available on international level competitors. The aim of the first study (Chapter 4) was to analyse match physical performance using a computerised tracking system (Prozone Sports Ltd., Leeds, England). A total of 167 individual match observations from 122 players competing in competitive international matches during the 2011-2012 and 2012-2013 seasons were completed. Total distance and total high-speed running distances (>14.4 km.h-1) were influenced by outfield playing position, with central midfielders completing the highest (10985 ± 706 m and 2882 ± 500 m) and central defenders (9489 ± 562 m and 1901 ± 268 m) the lowest distances, respectively. Greater total very high-speed running distances (>19.8 km.h-1) were completed when a team was without (399 ± 143 m) compared to with (313 ± 210 m) possession of the ball. The majority of sprints (>25.1 km.h-1) were over short distances with 95 % being less than 10 m. This study provides novel findings regarding the physical demands of different playing positions in competitive international female match-play and important insights for physical coaches preparing elite female players for competition. The aim of the second study (Chapter 5) was to determine the incidence and nature of repeated sprint and high-speed activity in match-play. Repeated sprint activity (a minimum of two efforts (>25.1 km.h-1) with 20 s or less recovery between efforts) was found to be rare during international female match-play with 1.1 ± 1.1 bouts per match. Repeated high-speed activity (a minimum of two efforts (>19.8 km.h-1) was influenced by playing position; with attacking-based players completing more bouts (37-40 bouts per match) than defensive players (22-33 bouts per match). Repeated sprint and high-speed bouts frequently comprised two efforts per bout, with a maximum of three and six efforts respectively. Collectively, this study provides physical coaches with useful data for replicating the demands of repeated high-speed activity and an understanding of the positional demands in order to aid the specificity of training. The aim of the third study (Chapter 6) was to attempt to apply a suitable approach for determining speed zones and to evaluate the application of specific zones to influence data outcome. Maximum match-play running speed in elite females was measured using Global Positioning System technology (STATSports, Viper, Ireland) in 230 individual match observations of 67 outfield players, during 19 international matches from 2011-2015. Female-specific speed zones and activity classifications were scaled appropriately to maximum match-play running speed. The resultant female-specific speed zones were on average 12.5 % lower than the standardised male zones, which if applied to the data in Chapter 4 would result in a small increases in total high-speed running (25 % to 28 %) and total very high-speed running (8 % to 9 %) relative to total distance. The calculated female-specific sprinting threshold (>22.0 km.h-1) corresponds to 82 % of the average maximum female match-play running speed presently observed and consequently might be more representative than the standardised male sprinting threshold (>25.1 km.h-1). However, as it was not possible to validate activity classifications in the current study it is suggested that the standardised thresholds should continue to be used to permit between playing position and gender comparisons, however, the activity classifications (e.g. walking, jogging, sprinting etc.) should be removed and replaced with the actual velocities. The aim of the fourth study (Chapter 7) was to examine the reliability of both anthropometric and performance measures in elite female soccer players. The data suggest that both junior and senior elite female players are able to adequately reproduce a variety of anthropometric (coefficient of variation = 0.1-1.3 %) and performance (coefficient of variation = 0.6-7.7 %) related tests and that reliable measures can be obtained using the present protocols and one familiarisation session. The sample size estimations (n<20) provided important insights for the participant recruitment in Chapter 8 and also suggest that the anthropometric and performance assessments are suitable for the longitudinal tracking of the fitness status of elite female players. The aim of the fifth study (Chapter 8) was to examine the physical characteristics of elite players, which were assessed in 471 national team players from 2011-2015. Anthropometric and performance variables improved with age; with large differences observed between U15s and seniors for body mass (53.9 ± 7.8 v 62.5 ± 5.8 kg), 30 m linear speed (4.78 ± 0.22 v 4.52 ± 0.17 s), countermovement jump (28.3 ± 4.0 cm v 33.4 ± 4.0 cm) and Yo Yo Intermittent Recovery Test Level 1 (1101 ± 369 m v 1583 ± 416 m). Similarities were observed for anthropometric and performance variables between the younger (U15 and U17) and older (U19 and senior) age groups. Goalkeepers generally exhibited inferior anthropometric and performance capabilities to outfield players. Faster linear speed times over short distances observed were in attackers (1.047 s v 1.061-1.077 s), greater repeated speed performance in wide midfielders and attackers (4.89-4.91 s v 4.92-4.99 s) and improved intermittent endurance performance in wide defenders (1483 m v 1260-1336 m) compared to other outfield playing positions. The normative physical characteristics presented, provide unique data for professionals involved in player recruitment and talent identification, whilst the positional differences in performance characteristics, coupled with an in-depth understanding of the demands of match-play can be applied to ensure training specificity. Collectively, the present data provides the most in-depth description of the physical demands and physical characteristics of elite female soccer players to date. The data describing the demands of match-play provides valuable insights for physical coaches preparing elite female players for competition, whilst the normative physical characteristic data provides important information to professionals involved in player recruitment and talent identification and those responsible for physical development.

No description available.

In recent years it has become clear that Western societies face a rapidly increasing ageing population. With ageing comes a significant reduction in functional capacity, cardiovascular function, increased cardiovascular disease risk and thus increasing health care costs. Exercise interventions in the elderly may prove to be a valuable tool in coping with an ageing population. It was, therefore, the purpose of this thesis to investigate; a) the effects of healthy ageing upon cardiac structure and function in adult males and females, b) the effects of a progressive aerobic exercise training programme upon cardiac structure and function in post-menopausal females as well as c) the effects of competitive exercise training on cardiac structure and function in post-menopausal female athletes and controls. The exact nature of left ventricular (LV) remodelling with age is the source of some controversy. Within a cross-sectional design cardiac structure and function was assessed in 124 women and 74 men (18-76 years). Left ventricular mass was maintained across the adult age-span in females (r= 0.02, P > 0.05) but was significantly and negatively associated with age in males (r= - 0.36, P < 0.05). The maintenance of LV mass in females despite an age-related decrease in LV volume suggested that remodelling of the LV with age was concentric in nature in females, with a relative wall thickening. In males, however, the large decrease in LV mass along with a smaller decrease in LV volume suggested a form of "eccentric atrophy" of the LV. Other data suggested an increase in male RV volume with age (c. 25%), no depression in LV and RV systolic function with age in either males or females and an expected age-related decrease in LV and RV diastolic filling (E:A ratio). Twenty post-menopausal females completed a progressive 12-month aerobic exercise training programme. Despite a significant and progressive increase in maximal aerobic capacity (pre, 23.7 ± 3.1 ml.kg'l.min"; post, 32.2 ± 4.1 ml.kg'I.min-I) there were few alterations in cardiac structure and function. It seems, therefore, that healthy sedentary females do indeed lose the ability to induce LV hypertrophy (LV mass pre, 155 ± 41 g; post, 136 ± 30 g) with training. There was some evidence of an increase in LV volume with training (and a much smaller trend toward an increase in SV). Other data showed no change with progressive exercise including LV systolic and diastolic function as well as volume data, systolic and diastolic function in the RV. Finally, nine post-menopausal female athletes were compared to an age- and lean body mass-matched control group. In agreement with the intervention study LV mass was not different in the athletes and controls (sedentary, 146 ± 31; active, 143 ± 25 g). To support and extend the training study LV volume (18%) and SV (25%), as well as RV volume (15%), were significantly greater in the athletes than the controls. The athletes also demonstrated an enhanced LV E:A ratio (sedentary 1.12; active, 1.53) although the increase in RV E:A was non significant. Both LV and RV systolic function were not different between groups. In conclusion, there is some evidence that healthy ageing of cardiac structure and function is different in males and females. Further, whilst functional capacity increases with exercise training in post-menopausal women there seems to be a lack of a LV hypertrophic response.

The purpose of an Exercise Referral Scheme (ERS) is to offer supervised, safe and appropriate group exercise and activities for individuals who can benefit physiologically and psychologically from increasing their level of physical activity. Referral from a health professional for activities is usually to a local leisure centre or alternative location. Assessments are carried out by professional, qualified staff who prescribe activity type and frequency. The activities are usually subsidised over a 10-14 week period, after which the cost is incurred by the individual. In recent years there has been a proliferation of ERS's as a means of increasing physical activity in the UK. Primary Care Trusts have invested in ERS, yet the evidence base for their ability to increase physical activity is debatable. Consequently, the overall aim of this research was to gain a greater understanding of the process of ERS through a case study example. By improving the services an ERS can offer to its participants, attendance and completion are likely to increase, ultimately resulting in increases in physical activity levels and therefore health. The present research has used mutli-methodological design to evaluate a community ERS in the North West of England. Four separate studies have allowed evaluation of characteristics of those who do not attend against those who do attend (study 1); those who complete an ERS against those who do not (study 2) and those who subsequently sustain physical activity 12 months post intervention (study 3). Furthermore, a qualitative tracking study followed participants' experiences whilst on an ERS specific to overweight individuals, over a 12 week period (study 4). Results indicate variances in individuals referred to the scheme; females being more likely to be referred and attend an ERS than males (p < 0.05) and those in the 46-60 year bracket being significantly more likely to attend (p < 0.05). Reason for referral was significant for attendance (p < 0.05), as well as month of referral (p < 0.05). Completion rates on the scheme were 42% at 12 weeks and were greatest for 31-45 year old males. However, overall there was a significant difference between age and likelihood of completing an ERS; individuals aged between 41-75 years were more likely to complete (p < 0.05). Family and friend participation support was significant to completion of the ERS. Gender (p > 0.05), pre-intervention physical activity levels (p > 0.05), family reward support (p > 0.05) and referral category (p > 0.05) were not significant to completion of an ERS. Post-intervention, physical activity levels were significantly increased by 15 METS (equivalent to 3, 15 minute bouts of moderate intensity exercise) (p < 0.05), although this was not significant at any other time over a 12 month period. Participants who perceived themselves to be participating in the nationally recommended levels of physical activity, increased from 41% at baseline, to 84% at 12 weeks (post-intervention), and 72% at 12 months. Qualitative analysis with overweight participants on an ERS showed problematic issues such as others perceptions relating to their inactive lifestyle. Participants gained most support from other overweight participants on the scheme, compared to significant others (e.g. spouse, friends) due to their clinical similarities. 58% of participants monitored completed the scheme, which is greater than completion of the general ERS. Outcomes of success on such interventions are discussed, along with experiences of participation in an ERS. The research has shown that the use of ERSs in primary care can increase the short term physical activity levels of previously sedentary individuals. Characteristics of individuals, who are more likely to attend, complete and sustain physical activity long term, have been determined. Future success of such schemes should involve psychological outcomes, and physiological factors other than increases in physical activity.

The control of blood pressure plays a vital part in homeostasis in humans. Poor regulation of blood pressure has been associated with an increased risk of events such as myocardial infarction, sudden cardiac death, and stroke. The studies in this thesis are designed to explore sources of variation in human BP control, and in particular to examine the interactions between BP status, activity and circadian variation. In study 1 the association between BP status and the acute exercise-mediated change in BP was investigated. A total of 32 participants, with pre-exercise MAP of 65-110mm Hg, cycled for 30 min at 70% peak oxygen uptake. Systolic and diastolic BP were measured (Portapres) before exercise and for 20 min after exercise. Changes in BP were regressed against pre-exercise values, and against the mean of pre- and post-exercise BP, an index known not to be prone to the influence of mathematical coupling and regression-to-the-mean artefacts. Correlations between pre-exercise BP and the exercise-mediated reductions were typical of those previously reported (r = 0.37-0.62, P < 0.05). Artefact-free indices of BP status (pre- and post-exercise mean) did not correlate with reductions in BP (P > 0.05), which were moderated more by maximal oxygen uptake and time of day (P < 0.05). These data indicate that, if statistical artefacts are not controlled for, the influence of BP status on the degree of PEH can be spuriously exaggerated to the extent that other more important moderators of BP change are masked. In study 2 meta-analytical methods were used to enhance the statistical power and precision with which to explore the association between BP status and exercise-mediated changes in ambulatory BP. Studies entered into the meta-analysis were required to meet inclusion criteria of ambulatory monitoring following exercise and comparisons to a control condition to minimize regression-to-the-mean artefacts. Blood pressure status was a significant moderator of PEH indicating that hypertensive patients will benefit from greater reductions in BP. Age, BMI and V02max were also identified as significant moderators PEH, indicating that older individuals with larger BMIs and lower fitness levels will benefit most from exercise. Pooled mean changes (95%CI) in daytime and nocturnal SBP were -3.8 (-5.4 to -2.3) and -3.0 (-4.7 to -1.3), respectively, and may be deemed as clinically significant reductions. Future meta-analyses should investigate the effects of chronic exercise on ambulatory BP and its cardioprotective effects. In study 3 the acute effects of PA on BP and symptoms of OSA were examined using blood pressure reactivity profiles during sleep and following waking. Ambulatory BP and actigraphy data were collected between 20:00-10:00h in 11 OSA patients and 18 healthy controls. Blood pressure reactivity indices were calculated (Jones et al., 2009) and compared between groups and over time using general linear models. The greatest mean (SD) systolic BP reactivity in the healthy controls was 15.4 (42.7) mmHg/activity count, occurring 0-2 hours after waking, whereas the peak systolic BP reactivity of 12.7(14.4) mmHg/activity count occurred during sleep in OSA patients (P < 0.05). This evidence of diminished nocturnal blood pressure control in response to activity may be associated with the peak incidence of MI in OSA, which occurs between 00:00 and 06:00 h (Kuniyoshi et al., 2008). In study 4 the focus moved from acute activity to chronic, with an investigation of leisure-time physical activity in OSA patients, in which the relationships with BP, OSA severity and daytime sleepiness were examined. Levels of leisure-time physical activity, estimated with self-reported activity questionnaires, were not significantly different between OSA patients (n=96) and a healthy control group (n=118). Compared with healthy controls, OSA patients displayed higher SBP, DBP and MAP (P < 0.05), but physical activity had no effect on BP in either group when adjusted for age and gender (P > 0.05). However, leisure-time physical activity was associated with reduced ODI and daytime sleepiness (Epworth Sleepiness Scale) in OSA patients (P < 0.05). The differences in daytime sleepiness between the lowest and highest activity groups were comparable to the reductions found with CPAP treatment. Physical activity would provide a useful treatment for OSA patients, potentially as an adjunct to traditional CPAP therapy. In study 5 the contribution of the mechanical and neural components of the cardiac baroreflex to diurnal variation in BP control were investigated. In 12 healthy participants, the modified Oxford method was used to quantify baroreflex gain for rising (Gup) and falling (Gdown) pressures in the morning (0700h) and afternoon (1600h). A novel analysis method based on linear mixed models (Atkinson et al., 2010) was employed to compare the integrated, mechanical and neural gains between the two times of day. There was significant diurnal variation in integrated gain, with an attenuated response in the morning (Gup= 13.0 ± 0.6; Gdown= 6.3 ± OA ms/mm Hg) when compared with the afternoon (Gup= 15.1 ± 0.6; Gdown= 12.6 ± OA ms/mm Hg). For rising pressures the diminished integrated gain in the morning was caused by a reduction in mechanical gain, whereas for falling pressures it was caused by a reduction in neural gain. It is proposed that the high prevalence of cardiovascular events in the morning is due to diminished mechanical transduction of pressure into arterial distension at this time. In study 6 postural influences on diurnal variation in cardiac baroreflex sensitivity were investigated, and the contribution of mechanical and neural baroreflex components were determined. Integrated baroreflex sensitivity was reduced in the morning and afternoon when an upright posture was assumed, and was primarily attributed to decreases in neural gain. Although observed at both times of day, reductions in baroreflex sensitivity due to the change in posture occurred to a greater extent in the afternoon. This caused the diurnal variation that was reported in the supine position to be attenuated for rising BP, and eliminated entirely for falling BP when participants changed to a standing position. The studies in this thesis have provided further knowledge and understanding of sources of variation in human BP control, including the effects of BP status, health status, fitness, physical activity, diurnal variation and postural changes. Methodological issues in BP research, clinical applications, and mechanisms responsible for BP regulation have also been addressed.

The accumulated stresses of training and competition may temporarily cause impairments in an athlete’s physiological and muscular function, leading to suboptimal performance levels. Cold-water immersion (CWI) has become a widely used post-exercise recovery method to accelerate the recovery process by purportedly reducing the symptoms associated with exercise-induced muscle damage (EIMD). However, the underlying physiological mechanisms, which mediate the effects of CWI, are not well understood. Therefore, the aim of this thesis was to investigate the influence of cold-water immersion (CWI) on limb blood flow and thermoregulatory responses following different modes of exercise. In study 1 (Chapter 4), the reliability of Doppler ultrasound in the assessment of superficial femoral artery blood flow (FABF) was examined under resting conditions. A Doppler ultrasound scan of the superficial femoral artery was measured on eight recreationally active male participants; twice on the same day separated by 5-min (within-day), and on a separate day (between-days). The coefficient of variation (CV) for mean blood flow (MBF) was ~16 % and ~20 % for within and between-days, respectively. A relatively small standard error of measurement (SEM) was found both within day, 13.30 mL·min-1 (95% CI, -14.79 to 38.40 mL·min-1) and between-day, 17.75 mL·min-1 (95% CI, -40.12 to 30.88 mL·min-1) for MBF differences. These findings suggest duplex Doppler ultrasound is a reliable method to collect measurements of FABF under resting conditions. The purpose of study 2 and 3 was to determine the influence of different degrees of water immersion cooling on FABF and cutaneous blood flow (CBF) and thermoregulatory responses after endurance (Chapter 5) and resistance (Chapter 6) exercise, respectively. Participants completed a prescribed endurance of resistance exercise protocol prior to immersion into 8 ºC (cold) or 22 ºC (cool) water to the iliac crest or rested non-immersion (CON) in a randomized order. Limb blood flow and thermoregulatory responses were measured before and up to 30-min after immersion. In both studies, thigh skin temperature (Tskthigh) (P < 0.001) and muscle temperature (Tmuscle) (P < 0.01) were lowest in the 8 ºC trial compared with 22 ºC and control trials. However, femoral artery conductance (FVC) was similar after immersion in both cooling conditions and was reduced (~50-55 %) compared with the CON condition 30-min after immersion (P < 0.01). Similarly, there was a greater thigh (P < 0.01) and calf (P < 0.05) cutaneous vasoconstriction during and after immersion in both cooling conditions relative to CON with no differences noted between 8 and 22 ºC immersion. Together, these findings suggest that colder water temperatures may be more effective in the treatment of EIMD and injury after both endurance and resistance exercise, respectively, due to greater reductions in Tmuscle and not limb blood flow per se. The aim of study 4 (Chapter 7) was to compare the influence of CWI and whole body cryotherapy (WBC) on FABF and CBF and thermoregulatory responses after endurance exercise. On separate days, participants completed a continuous cycle ergometer protocol before being immersed semi-reclined into 8 ºC water to the iliac crest for 10 min (CWI), or exposed to 2.5 min (30 s -60 ºC, 2 min -110 ºC) WBC in a specialized cryotherapy chamber, in a randomized order. Limb blood flow and thermoregulatory responses were measured before and up to 40-min after immersion Reductions in Tskthigh (P < 0.001) and Tmuscle (P < 0.001) were larger in CWI during recovery. Similarly, decreases in FVC were greater (~45-50 %) in the CWI condition throughout the recovery period (P < 0.05). There was also a greater skin vasoconstriction observed in CWI at the thigh (P < 0.001) and calf (P < 0.001) throughout the post-cooling recovery period. These results demonstrate that CWI may be a better recovery strategy compared with WBC due greater reductions in both Tmuscle and limb blood flow. This thesis provides a novel insight into the influence of different degrees of water immersion cooling, as well as WBC, on limb blood flow and thermoregulatory responses after different modes of exercise. These findings provide practical application for athletes and an important insight into the possible mechanisms responsible for CWI in alleviating inflammation in sport and athletic contexts.

Until recently there has been no generally accepted non-invasive method for determining energy expenditure during high intensity exercise. However, Medbø et al. (1988) have suggested that an individual's total energy (ATP) production from anaerobic metabolism may be determined by measuring the Accumulated Oxygen Deficit (AOD; ml O2 equivalents.kg-1 ). In recent studies it has been reported that there are strong correlations between AOD and anaerobic energy supply determined from changes in muscle metabolites during small muscle group (Bangsbo et al., 1990) and whole body cycle ergometer exercise (Medbø and Tabata, 1993; Withers et al., 1991). The purpose of the present thesis was: (i) to extend the limited information on AOD during running exercise for subjects with differing training backgrounds and particularly for women for whom no data are available; (ii) to investigate the relationship between AOD and human performance; and (iii) as determination of AOD is a time-consuming and costly laboratory procedure to develop a simple field test which accurately reflects AOD and thus anaerobic energy supply.