Browsing by Subject "Sports Science"

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    A 12 week pre-season fitnes training programme for senior male high school rugby players : the effect of supervision on anthropometric, physiological and physical performance variables
    (1998) Clark, David Rodney; Lambert, Michael I
    The study comprises of two sections; i) a survey to determine the attitude towards fitness training for rugby and the current fitness training habits of elite high school rugby players in their penultimate year at school, ii) a training study on a sample of the same population group, to measure the effect of a 12 week fitness training programme, based on scientific principles, on anthropometric, physiological and performance variables. The training study also measured the efficacy of training supervision compared no supervision on these variables.
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    Biochemical changes in athletes during marathon and ultra-marathon races, with special reference to the incidence and prevention of hypoglycaemia
    (1984) McArthur, Penelope S; Noakes, Timothy
    Fats 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.
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    Carbohydrate metabolism during active and passive post-exercise recovery
    (1984) Peters, Edith M; Noakes, Timothy D
    It is known that light muscular activity performed during the immediate post-exercise recovery period, increases the rate at which lactate and protons are removed from the circulation. This study examined the effect which this light activity had on muscle glycogen and lactate levels, as well as the restoration of blood fuel and hormonal homeostasis. A further dimension of the study was to monitor the metabolic adaptations which took place in the inactive leg during light one-legged post-exercise activity. Eight subjects participated in this study. The testing procedure involved three phases: the assessment of each subject's maximal exercise capacity on the cycle ergometer; the imposition of an intense intermittent exercise protocol which was followed by a passive recovery of 90 minutes; and lastly, the repetition of the exhaustive intermittent protocol followed by a partially-active recovery phase during which the subject cycled with one leg at approximately 30 percent of two-legged VO2. max. for the first 45 minutes of the 90-minute recovery period. During the latter two phases, blood samples and muscle biopsies were taken at rest and during the post-exercise recovery. The light one-legged activity expedited the return of blood lactate and pH levels to basal values (p < 0,01), during the initial 30 minutes of recovery but slowed down the removal of lactate and protons during the latter 15 minutes of the active recovery. There were no significant differences in the blood glucose, pyruvate, alanine, and insulin levels during the different recovery protocols, but plasma glucagon levels were significantly lower 0,05) delayed as a result of activity during the immediate post-exercise period, but that muscle lactate levels were significantly lower in the passive leg than in the active leg after the first 45 minutes of the recovery period. As resynthesis of glycogen took place during the active recovery, this study appeared to indicate (i) that lactate oxidation was an important source of substrate during the initial 30 minutes of the active recovery (ii) that oxidation was possibly the primary fate of lactate during the active post-exercise recovery period and (iii) that intramuscular glyconeogenesis in the fast-twitch muscle fibres of the previously active legs was a distinct possibility. Apparent suprabasal production of lactate in the active fibres of the active leg during the latter stages of the active recovery, however, appeared to indicate partial reliance on exogenous glucose as substrate in these fibres during this stage of the recovery.
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    Development of a functional neuromuscular stimulation (FNS) muscle training program to prepare paraplegics for standing
    (1989) Schafer, Carol Linda
    Wheelchair-bound paraplegics are in an unnatural, almost all-day sitting position. This is physiologically disadvantageous as it may cause increased abdominal pressure, renal dysfunction, pressure sores, muscle atrophy and osteoporosis. Thus it would be beneficial, physiologically and psychologically, for a paraplegic to be able to stand for temporary periods of time. As a result of the muscle atrophy and functional degeneration that follows a spinal cord injury, it is essential for paraplegics to undergo a muscle restrengthening program, using Functional Neuromuscular Stimulation (FNS), before standing up under FNS control can be attempted. Six healthy spinal cord injured subjects with spinal lesions between CS and T9 (two tetraplegics and four paraplegics) exercised their quadriceps muscles at home using a portable two-channel FNS muscle stimulator. The muscles were exercised against an increasing load to maximise the training effect. Inclined standing exercise, under FNS control, was performed in the Inclistand. The subjects' general state of health and fitness were assessed, namely their responses during a maximal arm ergometry exercise test, arm muscle function, lung function, blood biochemistry and their dietary habits. Subjects have shown improvement in quadriceps muscle strength, fatigue resistance and muscle bulk to varying degrees - according to their individual circumstances. The tetraplegics responded in a different manner to that of the paraplegics. The muscle strength increased significantly by a mean (+SD) of 97,8 + 59,6% and 171,2 + 118,1% for the four paraplegics, left and right leg respectively. There was a mean improvement of 16% in fatigue resistance in the left leg (p=0,08), while the mean response of the right leg varied. Quadriceps muscle bulk increased by 4,43 + 3,4% (left) and 2,7 + 2,1% (right) (0,05<p<0,l). The amount of subcutaneous fat around the mid-thigh decreased significantly by 4,73 + 1,4% (left) and 3,43 + 1,1% (right leg). The group was in a state of general well-being, with the exception of one subject whose serum cholesterol concentration fell within the high risk category. This study therefore showed that the FNS was sucessful in improving the quadriceps muscle strength, bulk and fatigue response of the SCI people in our research group. The valuable experience gained from this FNS study will be used to improve the present program.
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    The effects of amlodipine on exercise performance in mild to moderate essential hypertensives
    (1997) Gillies, Hunter Campbell; Derman, Wayne
    The effect of the long acting dihydropyridine calcium channel antagonist, amlodipine, on the exercise performance of hypertensive patients is not known. The aim of this study was to determine the effects of amlodipine on maximal (MAX), prolonged submaximal (PSX) and on skeletal muscle function (SMF) in patients with mild hypertension. In a double-blind randomised crossover trial, ten physically active hypertensive patients performed i) graded exercise to exhaustion for determination of maximal oxygen consumption (VO₂ₘₐₓ), peak heart rate (HR) and systolic blood pressure (SBP); ii) PSX at 75% VO₂ₘₐₓ to determine, cardiorespiratory responses, cardiac output (Q), blood lactate [La], free fatty acid [FFA], glucose [G] concentrations and ratings of perceived exertion (RPE), and iii) tests of isometric SMF including maximal voluntary contraction (MVC) and time to fatigue (TTF) during repetitve isometric MVC's. Tests were performed following two week ingestion of amlodipine (5 mg daily) or placebo seperated by a two week washout period. Resting SBP was decreased following ingestion of amlodipine (142 ± 13 vs l33 ± 12 mmHg; vs placebo: [mean± SD]; P<0.05). However, VO₂ₘₐₓ ( 31 ± 5 vs 33 ± 5 mlO₂.kg.min⁻¹ ; amlodipine vs placebo), peak heart rate ( 167 ± 12 vs 165 ± l6b.min⁻¹;amlodipine vs placebo)and peak SBP(l8l ±21 vs 170± 16mmHg; amlodipine vs placebo) were not reduced following ingestion of amlodipine. Submaximal cycling time. VO₂, Q, BP, HR, ventilation, RPE, [FFA], [La] and [G] during PSX were unaltered following ingestion of amlodipine. Similarly ingestion of amlodipine did not alter tests of isometric SMF. These data suggest that: i) ingestion of amlodipine lowers resting SBP but does not alter the normal haemodynamic response during exercise; ii) MAX, PSX exercise performance and SMF are unaltered following ingestion of amlodipine in athletic hypertensive patients. These findings suggest that the regulatory mechanisms which maintain haemodynamic homeostasis during maximal and submaximal exercise are not influenced by ingestion of amlodipine in athletic hypertensive patients.
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    The effects of sodium chloride ingestion on fluid balance and body fluid distribution during exercise
    (1993) Sanders, Barry; Noakes, Timothy D
    The aim of the first experiment of this thesis was to determine whether the ingestion of a concentrated sodium chloride solution (100mEq/1) during exercise would expand the plasma volume when fluid was ingested at approximately half the rate at which it was being lost as sweat. Six male cyclists exercised for 90 minutes in the heat (32 ± 1 °C, 55 ± 5% RH) at 66 ± 1 % of VO₂ₘₐₓ while ingesting either no fluid CNF), water (W), or a saline CS) solution (100mEq/1). In the Wand S trials, subjects drank 400ml of the fluid immediately prior to commencing exercise, and 100ml of fluid every 10 minutes during exercise until 80 minutes. In the S trial sodium chloride was ingested in capsules. One capsule containing 0.585g of sodium chloride was ingested with every 100ml of water. At the end of the 90 minute exercise bout they rested in a sitting position for one hour in cool conditions (22 ± 1 °C and 70 ± 5% RH). After the initial drop in plasma volume due to the onset of exercise. plasma volume decreased progressively during the NF trial and was significantly less than the 10 minute value at 80 and 90 minutes (p<0.0033). At 40, 60, 80 and 90 minutes of exercise, the plasma volume in the NF trial was significantly less than in the W and the S trials (p<0.05). There was no significant difference between the W and the S trials at any time. Further, after the initial drop in plasma volume due to the onset of exercise. plasma volume did not decrease any further in either the W or the S trial. Plasma sodium concentrations in the NF and the S trial were significantly elevated at 40, 60, 80 and 90 minutes (p<0.0033). Plasma sodium concentration in the NF and the S trials were also significantly higher than in the W trial at 80 and 90 minutes of exercise (p<0.05). Since the ingestion of a sodium chloride solution containing 100mEq/1 did not have a beneficial effect on plasma volume and plasma sodium concentration, when fluid ingestion rates were approximately half of the rate of sweat loss, it is concluded the under these conditions, the ingestion of a concentrated sodium chloride beverage has no advantage over the ingestion of water. The aim of the second experiment of this thesis was to determine the effect of varying concentrations of sodium chloride ingestion on fluid balance, when the rate of fluid ingestion matched the sweat rate. Six male cyclists cycled for 4 hours at 55% of VO₂ₘₐₓ in mild conditions (20 ± 1°c and 70 ± 5% RH), while ingesting either a low salt (LS) (4.6 mEq/1), a medium salt (MS) (50 mEq/1) or a high salt (HS) (100 mEq/1) beverage. Each beverage also contained a glucose polymer in an 8% concentration (8g/100ml). The subjects ingested 400ml of beverage immediately prior to commencement of exercise, and 150ml of fluid every 10 minutes during exercise until 220 minutes. Sodium chloride in the MS and HS trials was given to the subjects as supplemental gel capsules so that the drink was palatable. At the end of exercise, subjects recovered in a sitting position for 30 minutes. At the end of the 4 hours of exercise, fluid loss via the urine was significantly greater in the LS and the MS trials than in the HS trial (p<0.05). As a result, the fluid deficits in the LS and the MS trials were significantly greater than the fluid deficit in the HS trial. There was no significant difference between the MS and the LS trials for urinary fluid loss. During the 4 hour exercise bout, plasma sodium concentrations in the LS, the MS and the HS trials were not significantly different from one another, nor were they significantly different from resting values. There was no significant difference in the rectal temperature response to exercise in the three trials. It can therefore be concluded that in conditions where fluid ingestion matches sweat rate, attenuation of urinary fluid loss to optimise fluid replacement, relies on the ingestion of sodium chloride in quantities greater than that lost in the sweat. Therefore, for the ingestion of sodium chloride in excess of that which is currently available in sports drinks to beneficial, fluid must be ingested in volumes matching sweat loss.
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    Epidemiology and prevention of rugby injuries amongst schoolboy, senior club and provincial rugby players in the Western Cape
    (2000) Upton, Patrick Anthony Howard; Noakes, Timothy D
    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.
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    Injury risk assessment and the incidence of musculo-skeletal injuries in recreational long-distance runners over a 3-month training period
    (2017) Smith, Tanya; Kroff, Jacolene; Lambert, Estelle V
    Background: Long distance road running is continually growing as competitive and recreational sport, globally. Despite its popularity, a high burden of incidence of injury exists among runners. Previous research has focussed on specific injuries, whereas others have investigated isolated risk factors that may contribute to running related injuries. The purpose of the study is to determine possible internal and external screening variables that may predict the incidence of running-related injuries in general. Methods: Forty one recreational runners participated in an observational study over the course of 12 weeks. Screening assessments consisted of injury history, training history, and anthropometric measurements. Functional and performance assessments included the Foot Posture Index (FPI), the Functional Movement Screen (FMS), vertical jump, single leg hop and sit-and-reach tests. Participants were monitored over a period of 12 weeks by completing a weekly online logbook regarding their training and possible incidence of injury. Monitoring was terminated after 12 weeks of observation. Differences between injured and non-injured runners were determined using Independent -T-tests for mean differences, or Mann-Whitney U Test for distributional differences (non-parametric data). Binomial Logistic regression models were used to determine the influence of internal, external functional and external behavioural factors on the risk for running injury, respectively. Results: The total group revealed a cumulative incidence of injury of 63% over the 12 weeks of observation. There was no gender difference between incidences of injuries over the 12 week observation training period (OTP). Injured runners achieved a higher total FMS score (median = 16, Interquartile Range = 3) compared to uninjured runners (median = 15, Interquartile range = 3; p = 0.006). Binomial logistic regression models of external functional (FMS, Vertical Jump, Sit-and-Reach scores) factors [X² (3) = 9.764, p = 0.021] were statistically significant. Only the FMS score contributed significantly to the incidence of injury (p = 0.013) of the three external functional factors in the Regression Model. Discussion and Conclusion: The study adds to current evidence that the assessment of the Functional Movement Screen is important in predicting injury, however, the present study shows that a higher score obtained during the FMS increase your odds to sustain an injury. The study is in contrast with the body of evidence that the incidence of previous injury is the strongest predictor of the incidence of a current injury. The study concluded that the Functional Movement Screen is a useful screening tool to determine a long distance runner's risk for running-related injuries and should be included in health-injury risk assessments of recreational runners.
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    Pulmonary function and acid-base balance high intensity constant-load exercise
    (1993) Odendal, Elsabe; Noakes, Timothy D
    The possibility that an inadequate response of the pulmonary system might limit high intensity exercise in man has received increasing attention over the past few years. However, very few scientific investigations have focused systematically on pulmonary function during high intensity constant-load exercise. Furthermore, many studies have examined only one part of the pulmonary system during exercise and some have not included blood gas measurements as a measure of the adequacy of pulmonary function. The studies reported in this thesis were designed to investigate the possible failure of the gas exchanging and pump functions of the pulmonary system during high intensity constant-load exercise. In particular, the aim was to determine the extent to which the pulmonary system might be a factor causing fatigue during this form of exercise.
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    Selected exercise and skeletal muscle characteristics of African distance runners
    (1996) Weston, Adele Robyn; Myburgh, Kathryn Helen
    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.