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Biomedical subjects

T Noakes

Publications and source records attributed to T Noakes.

15 recordsLinked to original sources
PubMed2006

Sodium supplementation is not required to maintain serum sodium concentrations during an Ironman triathlon.

CONTEXT: Critical assessment of recommendations that athletes consume additional sodium during athletic events. OBJECTIVE: To evaluate if sodium supplementation is necessary to maintain serum sodium concentrations during prolonged endurance activity and prevent the development of hyponatraemia. DESIGN: Prospective randomised trial of athletes receiving sodium (620 mg table salt), placebo (596 mg starch), or no supplementation during a triathlon. The sodium and placebo tablets were taken ad libitum, with the suggested range of 1-4 per hour. SETTING: The 2001 Cape Town Ironman triathlon (3.8 km swim, 180 km cycle, 42.2 km run). SUBJECTS: A total of 413 triathletes completing the Ironman race. MAIN OUTCOME MEASURES: Sodium supplementation was not necessary to maintain serum sodium concentrations in athletes completing an Ironman triathlon nor required to prevent hyponatraemia from occurring in athletes who did not ingest supplemental sodium during the race. RESULTS: Subjects in the sodium supplementation group ingested an additional 3.6 (2.0) g (156 (88) mmol) sodium during the race (all values are mean (SD)). There were no significant differences between the sodium, placebo, and no supplementation groups with regard to age, finishing time, serum sodium concentration before and after the race, weight before the race, weight change during the race, and rectal temperature, systolic and diastolic blood pressure after the race. The sodium supplementation group consumed 14.7 (8.3) tablets, and the placebo group took 15.8 (10.1) tablets (p = 0.55; NS). CONCLUSIONS: Ad libitum sodium supplementation was not necessary to preserve serum sodium concentrations in athletes competing for about 12 hours in an Ironman triathlon. The Institute of Medicine's recommended daily adequate intake of sodium (1.5 g/65 mmol) seems sufficient for a healthy person without further need to supplement during athletic activity.

Adult↗
PubMed1999

Decreased resting metabolic rate in ballet dancers with menstrual irregularity.

We studied 21 ballet dancers aged 19.4 +/- 1.4 years, hypothesizing that undernutrition was a major factor in menstrual irregularity in this population. Menstrual history was determined by questionnaire. Eight dancers had always been regular (R). Thirteen subjects had a history of menstrual irregularity (HI). Of these, 2 were currently regularly menstruating, 3 had short cycles, 6 were oligomenorrheic, and 2 were amenorrheic. Subjects completed a weighed dietary record and an Eating Attitudes Test (EAT). The following physiological parameters were measured: body composition by anthropometry, resting metabolic rate (RMR) by open-circuit indirect calorimetry, and serum thyroid hormone concentrations by radioimmunoassay. R subjects had significantly higher RMR than HI subjects. Also, HI subjects had lower RMR than predicted by fat-free mass, compared to the R subjects. Neither reported energy intake nor serum thyroid hormone concentrations were different between R and HI subjects. EAT scores varied and were not different between groups. We concluded that in ballet dancers, low RMR is more strongly associated with menstrual irregularity than is current reported energy intake or serum thyroid hormone concentrations.

Adolescent↗
PubMed1996

Development of public policy and physical activity initiatives internationally.

Epidemiological, pathological, clinical, and experimental studies over the past 40 years convincingly show that physical inactivity and low physical fitness contribute substantially to the major chronic diseases prevalent in industrialised societies. Several industrialised countries around the world report increases in physical activity participation among adults in recent years, but the prevalence of inactivity remains high. These increases in voluntary exercise are at least partially offset by decreasing daily energy demands due to increased mechanisation at home, at work and during leisure-time. In developing countries, physical inactivity is becoming a prevalent lifestyle due to rapid social and economic changes. Clinical interventions and mass appeals to be more physically active are limited in effectiveness against the background of increasingly sedentary lifestyles. Exercise scientists and public health officials need to turn attention to public policy and legislative initiatives to restructure physical and social environments to encourage more physical activity and discourage sedentary habits.

Adult↗
PubMed1992

Anabolic steroids.

Explore the source record for details and available documents.

Anabolic Agents↗
PubMed1989

Exercise training after experimental myocardial infarction increases the ventricular fibrillation threshold before and after the onset of reinfarction in the isolated rat heart.

Previous work has shown that exercise training increases the ventricular fibrillation threshold of the isolated perfused rat heart. The aim of our study was to determine whether exercise training that begins after myocardial infarction can similarly increase the ventricular fibrillation threshold. Rats that had suffered an experimental myocardial infarction were subject to a running training program. Thereafter, the ventricular fibrillation threshold was measured before and after the onset of acute reinfarction induced by a second coronary artery ligation. Ventricular fibrillation thresholds were significantly elevated in trained rats during normoxia (13.7 +/- 2.2 vs. 4.7 +/- 0.8 mA, p less than 0.01) and during acute ischemia (6.8 +/- 1.6 vs. 3.0 +/- 0.7 mA, p less than 0.02). The myocardial cyclic AMP level was lower in the nonischemic zone of the trained hearts (0.21 +/- 0.01 vs. 0.28 +/- 0.01 nmol/g, p less than 0.05), which also had lower cyclic AMP levels after epinephrine challenge (0.50 +/- 0.05 vs. 0.73 +/- 0.09 nmol/g, p less than 0.01; 1.41 +/- 0.11 vs. 1.85 +/- 0.09 nmol/g, p less than 0.02 after epinephrine 10(-7) M and 5 x 10(-6) M injection, trained vs. untrained). Both propranolol 10(-6) M and epinephrine 5 x 10(-7) M attenuated the difference in ventricular fibrillation thresholds before and after second coronary artery ligation and eliminated any difference in cyclic AMP content of both the nonischemic and ischemic myocardial tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Evidence for an inverse relationship between the ventilatory response to exercise and the maximum whole body oxygen consumption value.

Ventilatory responses to submaximal exercise loads indicate that in a population of 895 physically active and sedentary male and female subjects, exercise ventilation is inversely related to predicted VO2max. The correlation coefficients for males and females in this relationship are 0.61 (P less than 0.0001) and 0.26 (P less than 0.0001) respectively. The slopes of regression lines for VE/VO2 and VO2max in female and male subjects are -2.59 and -0.91 respectively. This is associated with changes in composition of the expired air in that PCO2 increases and PO2 decreases with greater VO2max. The difference between the mean oxygen and carbon dioxide partial pressures in expired air of individuals in the highest and lowest VO2max ranges are 1.2 kPa (9 mm Hg) and 0.8 kPa (6 mm Hg) respectively.

Age Factors↗
PubMed1977

Coronary heart disease in marathon runners.

Six highly trained marathon runners developed myocardial infarction. One of the two cases of clinically diagnosed myocardial infarction was fatal, and there were four cases of angiographically-proven infarction. Two athletes had significant arterial disease of two major coronary arteries, a third had stenosis of the anterior descending and the fourth of the right coronary artery. All these athletes had warning symptoms. Three of them completed marathon races despite symptoms, one athlete running more than 20 miles after the onset of exertional discomfort to complete the 56 mile Comrades Marathon. In spite of developing chest pain, another athlete who died had continued training for three weeks, including a 40 mile run. Two other athletes also continued to train with chest pain. We conclude that the marathon runners studied were not immune to coronary heart disease, nor to coronary atherosclerosis and that high levels of physical fitness did not guarantee the absence of significant cardiovascular disease. In addition, the relationship of exercise and myocardial infarction was complex because two athletes developed myocardial infarction during marathon running in the absence of complete coronary artery occlusion. We stress that marathon runners, like other sportsmen, should be warned of the serious significance of the development of exertional symptoms. Our conclusions do not reflect on the possible value of exercise in the prevention of coronary heart disease. Rather we refute exaggerated claims that marathon running provides complete immunity from coronary heart disease.

Adult↗
PubMedDate not supplied

A fivefold reduction in the incidence of recurrent ankle sprains in soccer players using the Sport-Stirrup orthosis.

A study was undertaken to evaluate the effect of a semi-rigid ankle orthosis (Sport-Stirrup) on the incidence of ankle sprains in soccer players during 1 playing season. Senior soccer players were divided into 2 groups: players with previous ankle sprains (N = 258) and players without such history (N = 246). The players in these groups were each randomly allocated to either a semi-rigid orthosis or a control group at the start of the playing season. All subsequent injuries during the season and the total number of playing hours were documented. There was a significant reduction in the incidence of ankle sprains (injuries/1000 playing hours) by ankles in the orthosis group with previous sprains (0.14) compared with the nonbraced group with previous sprains (0.86). The incidence of ankle sprains was significantly higher in the nonbraced group with previous sprains (0.86) compared with the nonbraced group without previous sprains (0.46). Thus, in this study, a semirigid orthosis significantly reduced the incidence of recurrent ankle sprains in soccer players with previous history of ankle sprains.

Ankle Injuries↗
PubMedDate not supplied

Adherence to cardiovascular risk factor modification in patients with hypertension.

AIM: The effectiveness of the support of a healthcare practitioner and a family member in producing changes in cardiovascular risk factor modification was tested in a randomised, controlled trial in patients with hypertension. METHODS: The primary outcome measured after the 24-week intervention was blood pressure change. Secondary outcomes included patients' adherence to the programme, their knowledge about hypertension, exercise capacity, body weight, self-reported ability to control stress, adherence to medication and salt restriction, as well as symptoms. RESULTS: There were no marked improvements in blood pressure regulation in either group. The differences between the experimental and control groups were 3 mmHg (CI -6.18-12.18) for systolic blood pressure and 4 mmHg (CI -1.48-9.48) for diastolic blood pressure. The estimated blood pressure effects were small increases in both diastolic and systolic blood pressure, due to larger changes in the control group. These small changes were of no clinical significance. This intervention was not successful in reducing blood pressure of hypertensive patients who participated in a lifestyle programme. Secondary outcomes did show positive changes as a result of the given intervention. The absolute difference in improvement between the two groups was significantly greater for the experimental group than for the control group for the following variables: 24% better adherence to the programme (p = 0.007); 10% higher mean percentage score of hypertension knowledge and its management (p = 0.04); 20% more patients could control their stress levels (p = 0.05); 26% more patients could control their salt ingestion (p = 0.02); and 20% had better adherence to their given medication regimen (p = 0.05). The experimental group had a statistically significant weight reduction of 1 (+/- 4) kg relative to the control group (p = 0.03). Both groups increased their exercise capacity during the trial (p = 0.03). On the completion of the intervention, significantly fewer patients in the experimental group than in the control complained of tiredness (p = 0.05). Patients who had a 75% adherence or more to the programme were found to have maintained their knowledge and their exercise capacity, but not their weight loss after a maintenance phase of 12 weeks, during which time there was no intervention. CONCLUSION: Patients in a supported environment such as the one in this study were able to modify their cardiovascular risk factors, even though there were non-significant changes in blood pressure reported in this study.

Antihypertensive Agents↗