African runners dominate distance running both in South Africa and internationally. Therefore, the aim of this thesis was to compare selected exercise and skeletal muscle characteristics in well-trained African and Caucasian 10 km runners to determine if evidence exists of differences between these groups with respect to these physiological and biochemical characteristics. Furthermore, the relationship between exercise and skeletal muscle characteristics was investigated. Sedentary individuals from each population group were also studied to determine if differences existed in untrained skeletal muscle between groups. Maximal oxygen consumption and peak treadmill speed were measured using an incremental treadmill protocol whilst submaximal exercise characteristics were measured during a specifically designed protocol consisting of four sequential submaximal workloads relative to the peak treadmill speed of the individual. The final workload was maintained until fatigue with resistance to fatigue defined as total test time. Running economy was measured at a treadmill speed of 16.1 km/hr. Race pace characteristics were measured directly at race pace. Characteristics measured during exercise tests were oxygen uptake, minute ventilation, respiratory exchange ratio and heart rate whilst plasma lactate concentration was determined immediately after exercise. Skeletal muscle characteristics were determined by needle biopsy of the vastus lateralis muscle. Skeletal muscle enzymes citrate synthase, phosphofructokinase, 3-hydroxyacyl CoA dehydrogenase, hexokinase and carnitine palmityl transferase were assayed spectrophotometrically. Skeletal muscle buffering capacity was measured using by titration and fibre type proportions were analysed histochemically. Comparisons between groups were made with the Student's t-test for unpaired data whilst the relationships between variables were analysed using the Pearson's correlation coefficient. The first major finding was that when exercising at the same relative percentage of individual maximal treadmill velocity, African distance runners were able to exercise for longer than the Caucasians (1376±227 vs 1137±126 sec, p<0.01) with lower plasma lactate accumulation (4.8±3.2 vs 7.7±2.8 mmol/l,p<0.05). Time to fatigue was significantly related to a lower plasma lactate concentration (r=-0.63) and a lower respiratory exchange ratio (r=-0.53). The second major finding indicated that African runners were able to race 10 km at a higher percentage of their maximal oxygen uptake (93.5 vs 86.0%, p<0.005), whilst eliciting only a comparable plasma lactate concentration and respiratory exchange ratio. The third main finding was that the African runners were more economical than the Caucasian runners (p<0.05). The fourth main finding is that the African runners had a 50% greater activity of citrate synthase (p<0.005) and 3-hydroxyacyl CoA dehydrogenase (p<0.01) in the vastus lateralis than the Caucasians and this could not be explained by fibre type proportions, because the proportion of type I fibres was lower in the African runners (p<0.05). Citrate synthase activity, was related to the runners' ability to resist fatigue at high intensity relative to their individual peak treadmill velocity (r=0.70, p<0.05). A higher CS activity was related to a lower plasma lactate concentration and a lower RER. The sixth main finding of this thesis was that skeletal muscle buffering capacity of the Caucasian runners was higher than that of the African runners (p<0.05). A methodological study of buffering capacity in rats showed the buffering capacity was largely dependent upon fibre type and protein concentration, however these parameters could not explain the difference observed between the African and Caucasian runners. Furthermore, despite the differences in skeletal muscle characteristics observed between African and Caucasian runners in the current thesis, there was no evidence of these differences being inherently present in sedentary African and Caucasian individuals. In conclusion, the current series of studies do provide evidence of differences in selected exercise and skeletal muscle characteristics between African and Caucasian distance runners, with the African runners possessing exercise and skeletal muscle profiles that are considered to be more advantageous for endurance performance.

The monitoring of athlete workload is common practice within field-based team sports. Athlete monitoring is performed using both objective and subjective monitoring tools. Results from previous research investigating the relationships between measures of well-being and external workload in the form of match running performance, have been described as uncertain. A lack of research exists in quantifying the workload and well-being of student-athletes during congested periods of competition. Thus, the purpose of this study was to investigate and quantify the match running performance and well-being demands experienced, and understand the relationships between subjective and objective workload measures, in female student field hockey players during a congested period of competition. The cohort investigated comprised 16 female student field hockey players (age: 20 ± 2 y) in a South African university team. The reporting of player well-being (fatigue, soreness, stress, energy levels, motivation, sleep quality, total well-being), and session rating of perceived exertion (sRPE) was performed using a smartphone application before and after match-play on each of the five days of the tournament, and on Day 6. External workload variables during match play were recorded using global positioning system (GPS) wearable technology (Polar Electro Oy, Kempele City, Finland). Descriptive statistics, expressed as median and interquartile range (IQR), were calculated for all outcome variables for each day, and overall. To determine the strength and significance of the relationships between the three categories of variables (well-being, internal workload and external workload), Pearson correlation coefficients and Spearman rank order correlation coefficients were calculated. Overall match running performance scores for the competition included total distance (TD): 4,545 (3,834 - 5,305) m; average work rate: 116.8 (104.0 - 123.1) m·min-1; high intensity (>16 km·h-1) running distance (HID): 383 (257 - 538) m; and average high-intensity work rate: 11.1 (5.8 - 14.9) m·min-1. Overall player total well-being, internal workload (sRPE x player match time) and match time for the competition were 15.0 (13.0 - 18.0) AU, 287 (214 – 355) AU and 39.1 (32.9 - 47.6) min, respectively. External workload demands were lower than those reported in previous literature on elite female field hockey players. Even though scores in well-being in the current study demonstrated trends of increasing (worsening) over the duration of the competition, changes observed were trivial to small and non-significant. Analysis showed inconsistent and non-significant relationships between pre-game well-being and same-day match external workload. Furthermore, several significant (p < 0.05) relationships were demonstrated between external workload on the preceding day to well-being subscales on the subsequent day. Findings suggest that subscales (stress, fatigue, soreness) rather than total well-being score may be a more sensitive reflection of the workload experienced during congested tournaments. Furthermore, the current study supports the use of the sRPE-method of internal workload monitoring during field hockey match-play as a non-invasive and cost-effective means of reflecting player external workload. Prior to returning to sports training or academic commitments, due to the physical and psychosocial demands of such competitions, recovery should be prioritised within a student-athlete population. Key words: Congested competition, external workload, field hockey, GPS, internal workload, team sport, well-being. / Dissertation (MSc (Sports Science))--University of Pretoria, 2020. / Physiology / MSc (Sports Science) / Unrestricted

Title: The Association Of Risk Markers And The Prevalence Of Exercise Associated Muscle Cramps In Distance Runners Candidate: Izaan de Jager Promoter: Prof. MP Schwellnus Co-promoter: Dr. E Korkie Degree: MSc Sports Science Background: The epidemiology, clinical characteristics, severity and the risk markers associated with exercise associated muscle cramps (EAMC) in runners participating in different race distances have not been studied. Aim of the study: To determine the lifetime prevalence, clinical characteristics, severity, preferred treatment and potential risk markers associated with EAMC in distance runners. Design: Cross-sectional study. Setting: 2012-2015 Two Oceans marathon races (21.1km and 56km), South Africa. Participants: 76654 consenting race entrants. Methods: 106743 runners completed an online pre-race medical screening questionnaire as part of the entry for the 2012-2015 races. 76654 (71.8%) consenting entrants were included in this study (21.1km=47069; 56km=29585). The lifetime prevalence (%), retrospective annual incidence (%) and clinical characteristics (main muscle groups affected, timing of occurrence during a race, severity of EAMC, frequency of complex forms of EAMC, and preferred treatment of EAMC) were compared between 21.1km vs. 56km race entrants. Data are reported as frequency (%; adjusted for sex and age groups) and Risk Ratio (RR) with 95%CIs. Secondly, we apply a multivariate model to report independent risk markers associated with a history of EAMC (hEAMC) (sex, age, training variables, history of chronic disease, allergies, prescription medication use and running injuries) in all entrants and 21.1km and 56km entrants (prevalence risk ratios of hEAMC with 95%CI). Results: The lifetime prevalence (%) of EAMC was significantly higher in the 56km (16.0; 15.5-16.5) compared to 21km race entrants (8.8; 8.5-9.1). The onset of EAMC (%) was significantly more frequent in the first quarter (4.9; 4.3-5.7), second quarter (3.7; 3.2-4.4) and after the race (29.5; 28.1-31.1) among 21.1km race entrants, while the onset in 56km race entrants was more frequent in the third (13.7; 12.7-14.8) and fourth quarter (47.2; 45.6-48.9). Serious EAMC (6.9; 6.2-7.8), EAMC associated with dark urine (2.9; 2.4-3.5) and whole body EAMC (4.1; 3.5-4.7) was reported more frequently in 56km race entrants. Specific independent risk markers associated with hEAMC in 21.1km and 56km runners were: history of GIT disease (PR; 21.1km=1.47, 56km=1.58), history of running injury in last 12 months (PR; 21.1km=1.44, 56km=1.45), history of CVD (PR; 21.1km=1.42, 56km=2.10), history of risk factor for CVD (PR; 21.1km=1.34, 56km=1.45), history of allergies (PR; 21.1km=1.21, 56km=1.40), average slower training speed in last 12 months (PR; 21.1km=1.06, 56km=1.03) and increase years of recreational running (PR; 21.1km=1.05, 56km=1.11). Conclusion: More 56km race entrants report ever suffering from EAMC compared to 21.1km race entrants. The muscle groups affected, time of onset, severity (cramp duration), severity of serious EAMC and effective treatment modalities used to relieve acute muscle cramping differed between 21.1km vs. 56km race entrants. Independent risk markers associated with hEAMC identified in this study are male sex, older age, longer race distances runners, training variables, several chronic diseases, a history of allergies and the use of prescription medications for both 21.1km and 56km race entrants. / Dissertation (MSc)--University of Pretoria, 2020. / Physiology / MSc / Restricted

Includes bibliographical references / Elite kayakers are required to perform repetitive movements that create strength and flexibility asymmetries in their bodies, making them susceptible to injury. The first portion of this thesis is dedicated to investigating whether a supervised, corrective pre-habilitation programme of the kinetic chain, conducted twice a week for 10 weeks, would reduce these predisposing factors. A group of 19 marathon paddlers were assessed before and after the intervention, with nine of them receiving the intervention. The 10-week intervention programme was found to significantly improve scapular position and kinesis, thoracic spine extension and single arm pulling ability, thus suggesting improved shoulder function and reduced risk of injury. The second portion of the thesis involved novel biomechanical analysis of kayaking on the water and on a kayaking-ergometer. It is the first objective description of the three dimensional movements of the kayak in the literature. Sprint and marathon paddlers performed a 180 metre time trial using an instrumented paddle with an accelerometer and gyroscope attached to the boat for analysis of boat movement characteristics and paddler-generated forces. Similar patterns for paddle torque, boat acceleration and pitch were observed between male sprint paddlers and male marathon paddlers. However, the direction and timing of the roll and the yaw of the boat during the water phase of the kayak stroke differed between these groups of paddlers. In addition, substantial individual variation existed within the group of male marathon paddlers. On the kayaking ergometer, activation patterns of the trunk and pelvic muscles were measured using electromyography during a maximal 200 metre time trial. Gluteus medius, lower trapezius and erector spinae were measured for the first time in maximal kayaking. The latissimus dorsi, pectoralis major and external oblique muscles were more active during the contralateral phase than has previously been reported. When these paddlers performed a single arm pull test on the same day, the muscle activation patterns changed, and muscle groups were active according to their anatomical function and what has previously been described. First, variation of movement, flexibility and segmental training of the kinetic chain may be advantageous when incorporated with kayaking training to prevent shoulder injury risk factors in paddlers. Second, individual evaluation of three-dimensional boat kinematics and muscle recruitment timing provides objective insight into an individual's kayak technique, with potential benefits for improving technical performance and mechanical efficiency.

This thesis comprises a series of independent investigations examining rugby injuries occurring to players from under 14 to senior provincial level in the Cape Province (now the Western Cape). The first two studies report data aimed at gaining a more detailed understanding of rugby injuries in specific populations or under specific conditions, whilst the remainder of the thesis reports injury data from both a retrospective and a prospective epidemiological survey involving the same 3990 boys from 25 high schools. Following publication of data showing a progressive rise in the number of spinal cord injuries in the Western Cape, coupled with a sustained media attack on the attitudes of the (then) South African Rugby Board, certain experimental law changes were introduced to South African schoolboy rugby in 1990 and 1991. The purpose of the law changes was either to make the game safer or to make it more open and flowing, or both. Accordingly, the studies described in chapters 4 -8 set out to analyse the effects of these law changes on the incidence and nature of rugby injuries. This was accomplished by comparing data with a similar study conducted in 1983 and 1984 in the same 25 schools (Roux, 1992). The study reported in chapter 2 determined whether the use of neoprene (thermal) pants might reduce the risk of hamstring injury amongst 60 senior club rugby players, all of whom had previously sustained a hamstring muscle tear. The rationale was that the few seasons prior to this 1992 study had been characterised by an increasing use by rugby players of thermal or neoprene pants; a practice which seemed to have evolved spontaneously and without any scientific assessment of its value. We concluded that the wearing of thermal pants can reduce the risk of hamstring injury during rugby. However, other risk factors for injury are probably more important. These include levels of preseason physical fitness, correct warm up and stretching procedures before activity and adequate rehabilitation before returning to activity following injury. The objective of the study reported in chapter 3 was to determine the influence of preseason strength and endurance training on risk of injury in rugby players from two South African provincial teams during the 1992 rugby season. Players from one province followed a supervised scientifically-designed physical training programme, while those from the other did not follow a structured programme. The findings of the study, the first study to prove the relationship between pre-season preparation and early season injury, showed that inadequate pre-season endurance training is a major contributor to the high injury rate at the beginning of the season amongst provincial rugby players. Further, strength and endurance training are interrelated as risk factors. Thus, compared to players with adequate strength and endurance training, those with adequate strength training and insufficient endurance training are at greatest risk of injury, followed by players with insufficient strength and endurance training. It was also shown that contact practices 2 days after inter-provincial match contributed more to an increased number of injuries than to success; that "niggling" injuries may develop into more serious injury if players attempt to "play through" them; and that the lack of structured treatment and rehabilitation of an injury places players at risk of being re-injured.

The aim of this series of studies was to investigate the effects of oral caffeine ingestion (5 mg . kg-1) on whole-body, short-term, high-intensity exercise (ST; representing an exercise intensity of between 100% -150% V02 max), an area that has received scant attention in the past. It was found that, in common with other 'open-ended' tests, one ST assessment, the maximal accumulated oxygen deficit (MAOD), appeared to lack both validity and reliability. Although traditional reliability markers of MAOD were favourable, the 95% limits of agreement were unacceptably large. In addition, the validity of MAOD was also found to be questionable because a study of elite runners revealed that a large proportion were unable to accomplish a plateau in the V02 -exercise intensity relationship. A follow-up study developed an original bespoke 'preloaded' ST cycling protocol that combined constant-rate exercise with an 'all-out' effort. This protocol appears to have several features that make it a more appropriate assessment to use in ergogenic studies than the MAOD. The work also considered the original, and as yet, undeveloped potential, for the assessment of rating of perceived exertion (RPE) during ST. It was shown for the first time that RPE (Borg scale; 6-20) could be used reliably during constant-rate ST. Three of the ten studies demonstrated that caffeine can be ergogenic during ST, with improvements averaging 11 % (95% GI, 7.4% -14.5%) above placebo treatment. In addition, the caffeine studies contributed to a meta-analysis of the effects of caffeine on test outcome that resulted in an effect size greater than zero, with 95% confidence intervals not crossing zero. The studies have examined potential physiological and metabolic mechanisms of action that may help explain caffeine's impact on ST. These suggest that there is some evidence that caffeine both stimulates anaerobic glycolysis and reduces electrolyte disturbance during ST. Finally this work has demonstrated for the first time that the perceptual response during constant-rate ST, as measured by RPE, is blunted following caffeine ingestion. It is concluded that caffeine is ergogenic during ST, and that while the exact mechanism(s) of action remains unknown, one consistent test outcome is a reduction in RPE during constant-rate ST.

This thesis summarises a series of academic publications that make a contribution to the field of sports nutrition over a period of 30 years. It begins with research in the field of carbohydrate and endurance sport reflecting the early era of research into carbohydrate and endurance performance, and evolves into studies investigating the impact of sports nutrition and hydration on team sports. It presents papers and other peer reviewed outputs that focus on the application of scientific knowledge to enhance human performance, whilst demonstrating the increasing awareness of the relative importance of carbohydrate and hydration in a range of both female and male team and individual sports. The thesis also highlights the challenge faced by the manufacturers of sports nutrition products in making use of advances in science to develop new and innovative products. The thematic nature of this thesis shows how sports nutrition continues to evolve. As science identifies new and legal means of enhancing human performance, so sport, athletes and coaches will demand more advanced and specialised approaches to refuelling and hydration. This thesis draws together findings from a series of publications which demonstrate how scientists, coaches, athletes and sports nutrition manufacturers need to work closely together to research, identify and interpret the next stages in an exciting and demanding area of research. It also reflects the scientific advancement in the field of sports nutrition over a thirty year period, identifies possible areas for future research, and the continued application of hydration and nutrition strategies to enhance male and female endurance and team sports.

No description available.

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.