Browsing by Author "Noakes, Timothy"
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- ItemOpen AccessThe batting backlift technique in cricket(2017) Noorbhai, Mohammed Habib; Noakes, TimothyThe batting technique in cricket consists of various elements such as the grip, stance, backlift, downswing, impact with the ball and follow through. Whilst there has been an extensive amount of research into these batting elements, there is little research specifically on the backlift technique. Therefore, we aimed to investigate and provide a scientific understanding of the batting backlift technique (BBT) in cricket. We aimed to investigate the BBT of the most successful batsmen (n = 65) in the last 120 years as well as players in the Indian Premier League (IPL) (n = 30). It was found that these batsmen did not conform to the current cricket coaching method that advocates a straight batting backlift technique (SBBT). Instead, 77% of successful batsmen and 90% of IPL batsmen employed a lateral batting backlift technique (LBBT) in which they lifted their bats in the direction of second slip or beyond with the bat face towards the off-side. Using this technique, both the toe of the bat and face of the bat points directly towards the off-side (usually between slips and point). The number of players using the LBBT was significantly greater than those using the SBBT (χ2 = 19.2, df = 1, p < 0.001). Given these findings, we were curious to determine whether this finding was similar at other levels of cricket. The second study therefore employed biomechanical and video analyses to evaluate the BBT of current semi-professional, professional and international cricketers (n = 155) from South Africa and the United Kingdom. The backlift of these batsmen was then compared to their career statistics. It was found that a LBBT is more prevalent at the highest levels of the professional game and a likely contributor factor for successful batting at the highest level (p≤0.05). The LBBT was also found to positively affect other components of the batting technique such as the stance and scoring areas. We then proceeded to investigate the BBT amongst the lower levels of cricket (junior and adolescent cricketers). The third study consists of an intervention study that employed a biomechanical analysis of coached and uncoached cricketers (n = 80). It was found that more than 70% of uncoached cricketers adopted a LBBT, whereas more than 70% of coached cricketers adopted the SBBT. Having found that the LBBT is a likely contributing factor for past and current successful batsmen, it was then important to understand what BBT the current cricket coaches are teaching at various proficiency levels. The fourth study explored the teachings of the BBT among international cricket coaches (n = 161) using a mixed methods approach through an online evaluation survey. This study was able to show that a majority of cricket coaches teach what is advocated in coaching manuals and mostly coach the SBBT as opposed to the LBBT at various levels of the game. In the fifth and sixth studies, this thesis further describes two innovative coaching tools that can improve and assist with the coaching of the LBBT. Firstly, a novel coaching cricket bat was investigated through a pilot and intervention study. In the pilot group, cricketers using the coaching bat scored approximately 1 more run per ball or an average of approximately three more runs in total when using the coaching bat than the normal bat (F = 6.70, df = 1, p = 0.012). In the intervention study, the experimental group scored double the total number of runs (an additional 16 runs) and an average of approximately 3 more runs per player in the post-match than in the pre-match, which showed a large effect (ES = 5.41) (t = 3.32, df = 5, p = 0.021). The coaching cricket bat might be used to coach young cricket players to hit the ball more effectively as well as how to adopt a more LBBT. Secondly, a mobile application was developed, which can be used by players, coaches and scientists to analyse and improve the BBT among cricketers at all levels. In summary, this thesis has shown that the LBBT is a likely contributing factor to successful batsmanship at all levels of cricket ability (junior cricketers, adolescent cricketers, semi-professional cricketers, professional cricketers, international cricketers and former elite/successful cricketers). Coaching a LBBT to young batsman may be challenging and therefore a coaching cricket bat has been developed and has shown to be a promising training aid for coaching the LBBT to young cricketers. A mobile application has also been designed and tested to assist in the coaching of the BBT in cricket. A way forward for further research in this area of cricket batting is documented at the end of the thesis.
- ItemOpen AccessBiochemical changes in athletes during marathon and ultra-marathon races, with special reference to the incidence and prevention of hypoglycaemia(1984) McArthur, Penelope S; Noakes, TimothyFats and carbohydrates are the major fuels utilized during exercise and it has been suggested that carbohydrate depletion is the cause of exhaustion during prolonged exercise lasting more than two hours. However, there is some disagreement in the literature as to whether this exhaustion is due either to muscle glycogen depletion or to hypoglycaemia secondary to liver glycogen depletion. I therefore undertook three studies to determine the roles of hypoglycaemia in explaining fatigue in marathon and ultra-marathon runners.
- ItemOpen AccessCollected studies(2002) Noakes, TimothyA collection of published studies establishing the central governor model of exercise physiology, and the aetiology of the hyponatraemia of exercise.
- ItemOpen AccessDiet composition and perceptions around food in individuals with Type 2 Diabetes Mellitus following a long-term low carbohydrate high fat diet(2019) Murphy, Tamzyn; Smith, James; Noakes, TimothyBackground: Type II diabetes mellitus (T2D) is described as a progressive metabolic disease, characterised by disrupted glycaemic regulation, and is associated with high rates of morbidity and mortality. Low carbohydrate high fat (LCHF) diets may be particularly effective and sustainable for the treatment of T2D and have become a popular ‘self-therapy’. This study investigates the real-world dietary composition and potential effects of a long-term LCHF diet on T2D. Materials and Methods: A multi-method descriptive study investigating the diet and related aspects in 28 adult T2D patients perceiving to follow an LCHF diet for ≥ 6 months. Data collection included a quantitative phase (general detailed health and a food frequency (FFQ) questionnaires, 24-hour diet recall (24HR), 3-day food record, anthropometry, blood pressure, blood sampling, past medical records) and a qualitative phase (semi-structured interviews). Results: LCHF (duration 2.1 ± 1.5 y) consisted of 67% fat (143.2 ± 67.9 g, mainly saturated fat from added fat, eggs, meat, poultry, seafood and full cream dairy), 10% carbohydrate (64.0 ± 27.9 g, primarily from full cream dairy, nuts and seeds), 20 % protein (96.0 ± 37.4 g, primarily animal origin) and 3% alcohol (primarily wine). Cholesterol intake (616.3 (402.8–804.2) mg) was higher, and fibre (14.7 ± 7.5 g), calcium and folate lower than recommendations. Added sugar (0.5% of energy intake) and processed foods were seldom consumed. Daily energy intake was 1946.3 ± 807.2 kcal (436.7 ± 728.3 kcal. d-1 calculated energy deficit). Intermittent fasting (≥ 16 h. d-1) was followed by 61% of the group. From pre-LCHF to the time of the study, reductions were seen in obesity prevalence (- 50 %), body weight (- 16.9 ± 11.7 %), HbA1c concentration (- 2.45 ± 2.59 %) and T2D prevalence (36 % were no longer classified as T2D based on HbA1c and T2D pharmacotherapy). Non-pharmacologically-induced changes in HbA1c concentrations showed HbA1c reductions in 75 % of the group during the time on LCHF. LCHF was generally reported as sustainable, linked to reduced hunger and cravings and improvements in overall health and health-related quality of life (HRQoL). Challenges included constipation, initial adaptation and social difficulties related to LCHF. Discussion and conclusion: These findings are the first to describe the nature and composition of a self-selected ad libitum real-world LCHF diet and coexisting health parameters. LCHF can be sustainable in T2D patients and may be linked to improvements in glycaemic control, medication reduction, hunger, health and HRQoL.
- ItemOpen AccessEndogenous glucose production and gluconeogenesis during exercise in athletes on either a low-carbohydrate or mixed diet(2015) Webster, Christopher Charles; Noakes, Timothy; Smith, JamesINTRODUCTION. The LCHF diet produces major changes in whole-body substrate metabolism and energy stores such as reduced muscle and liver glycogen content, increased rates of fat oxidation and decreased rates of carbohydrate (CHO) oxidation. Despite reduced CHO availability, the rate of CHO oxidation that can be sustained during exercise in LCHF athletes is surprisingly high. The most probable source of this glucose is via the process of gluconeogenesis (GNG). However, endogenous glucose production (EGP) and GNG has not been studied during exercise in athletes on a LCHF diet. Therefore, the aim of this study was to determine if there are differences in EGP, GNG and glycogenolysis (GLY) during exercise in endurance-trained athletes who habitually eat either a mixed or LCHF diet. METHODS. Fourteen (7 LCHF, 7 Mix) endurance-trained male cyclists (VO₂max 61 ± 5 ml/kg/min LCHF; 6 3 ± 8 ml/kg/min Mix), matched for age (36 ± 6 y LCHF; 32 ± 5 y Mix), body composition (BMI 23.6 ± 1.8 LCHF; 23.4 ± 2.0 Mix) and relative peak power output (4.8 ± 0.4 W/kg LCHF; 5.0 ± 0.4 W/kg Mix), were recruited. Diets were analysed using the Automated Self-Administered 24-hour Recall (ASA24) analysis software. Participants cycled for 2 h at 55% of peak power output during which EGP was measured by infusion of [6,6- ²H₂ ]glucose, and fractional gluconeogenesis was measured by ingestion of ²H₂O. Blood samples were collected at regular intervals for isotope enrichment analysis. R ESULTS. Rates of GNG were similar during exercise in both the LCHF and mixed diet groups (2.8 ± 0.4 mg/kg/min LCHF; 2.5 ± 0.3 mg/kg/min Mix). The rates of GLY during exercise were significantly higher in the mixed diet group than the LCHF group (3.2 ± 0.7 mg/kg/min LCHF; 5.3 ± 0.9 mg/kg/min Mix) which resulted in significantly higher rates of EGP in the mixed diet group (6.0 ± 0.9 mg/kg/min LCHF; 7.8 ± 1.1 mg/kg/min Mix). There were significant differences in the mean fat oxidation rates (1.2 ± 0.2 g/min LCHF; 0.5 ± 0.2 g/min Mix) and CHO oxidation rates (1.3 ± 0.5 g/min LCHF; 3.1 ± 0.5 g/min Mix). Blood beta-hydroxbutyrate (βHB) concentrations were significantly higher in the LCHF group than in the mixed diet group throughout exercise but there were no differences in plasma glucose, plasma lactate, serum insulin or serum FFA concentrations. The diets of the two groups differed only in fat and CHO intake (%Protein / %Fat / %CHO: 21/72/7 LCHF; 16/33/51 Mix). DISCUSSION. Rates of fat oxidation and CHO oxidation were not associated with the rates of GNG. Apart from βHB, the precursor, substrate and insulin concentrations were remarkably similar in both groups and may have influenced GNG similarly in both groups. We conclude that rates of GNG are relatively stable across a broad range of habitual diets that can significantly alter substrate utilisation, and that dietary CHO modulates the rates of EGP via alterations in rates of GLY, both at rest and during exercise.
- ItemOpen AccessLeft ventricular function after ultra-distance triathlon : response is dependent on the cardiac loading conditions(2003) Hassan, Muhammad Yusuf; Noakes, TimothyThe purpose of this thesis is to establish if there is any evidence to support the hypothesis that altered ventricular loading conditions after the cessation of exercise may cause "cardiac fatigue". The studies that have shown post-exercise "cardiac fatigue" have not controlled for either preload or afterload or both, before and after exercise. These studies may rather have identified the effects of alterations in peripheral vascular function on left ventricular function after prolonged exercise. The research study in this thesis is to evaluate if the loading conditions of the heart affect the echocardiographic measurements after exercise that may be misinterpreted as "cardiac fatigue". Echocardiography as a tool of cardiac evaluation cannot be done during exercise because of the technical difficulty of doing a cardiac ultrasound on a human being in motion. The studies that have investigated post exercise "cardiac fatigue" have therefore measured cardiac function after exercise and retrospectively assumed that the cardiac dysfunction was present during exercise since the cardiac demands are at their peak during exercise. However, the post exercise period may be associated with altered loading conditions that may cause changes in the echocardiographic measurements that are similar to cardiac abnormalities.
- ItemOpen AccessRevealing complexities within flat-water kayaking: injury prevention and biomechanical analysis(2015) Fisher, Julia Marguerite; Tucker, Ross; Karpul, David; Noakes, TimothyElite 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.
- ItemOpen AccessSpinal cord injuries in South African Rugby Union (1980-2007)(2010) Hermanus, Fiona; Draper, Catherine; Noakes, TimothyObjectives and design. To address an apparent increase in the number of rugby-related spinal cord injuries (SCIs) in South Africa, a retrospective case-series study was conducted on injuries that occurred between 1980 and 2007. We aimed to identify preventable causes to reduce the overall rate of SCIs in South African rugby. Methods. We identified 264 rugby-related SCIs. A structured questionnaire was used, and it was possible to obtain information on a total of 183 players, including 30 who had died. Results. SCIs increased in number in the 1980s and in 2006. Forwards sustained 76% of all SCIs, and club players 60%. Players aged 17 had the highest number of SCIs. In only 50% of cases were medical personnel present at the time of injury, and 49% of injured players waited longer than 6 hours for acute management. Of players with an SCI, 61% had a catastrophic outcome after 12 months, including 8% who died during that time; 65% received no financial compensation; and only 29% of players had medical aid or health insurance. Conclusion. A register of all rugby-related SCIs in South Africa is essential to monitor the magnitude of the problem, identify potential risk factors, and formulate appropriate preventive interventions. The lack of reliable denominator data limits calculation of incident rates. Players from previously disadvantaged communities in particular suffered the consequences of limited public health care resources and no financial compensation.