Biomedical subjects

D Speedy

Publications and source records attributed to D Speedy.

3 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↗

PubMed2005

Three independent biological mechanisms cause exercise-associated hyponatremia: evidence from 2,135 weighed competitive athletic performances.

To evaluate the role of fluid and Na+ balance in the development of exercise-associated hyponatremia (EAH), changes in serum Na+ concentrations ([Na+]) and in body weight were analyzed in 2,135 athletes in endurance events. Eighty-nine percent of athletes completed these events either euhydrated (39%) or with weight loss (50%) and with normal (80%) or elevated (13%) serum [Na+]. Of 231 (11%) athletes who gained weight during exercise, 70% were normonatremic or hypernatremic, 19% had a serum [Na+] between 129-135 mmol/liter, and 11% a serum [Na+] of <129 mmol/liter. Serum [Na+] after racing was a linear function with a negative slope of the body weight change during exercise. The final serum [Na+] in a subset of 18 subjects was predicted from the amount of Na+ that remained osmotically inactive at the completion of the trial. Weight gain consequent to excessive fluid consumption was the principal cause of a reduced serum [Na+] after exercise, yet most (70%) subjects who gained weight maintained or increased serum [Na+], requiring the addition of significant amounts of Na+ (>500 mmol) into an expanded volume of total body water. This Na+ likely originated from osmotically inactive, exchangeable stores. Thus, EAH occurs in athletes who (i) drink to excess during exercise, (ii) retain excess fluid because of inadequate suppression of antidiuretic hormone secretion, and (iii) osmotically inactivate circulating Na+ or fail to mobilize osmotically inactive sodium from internal stores. EAH can be prevented by insuring that athletes do not drink to excess during exercise, which has been known since 1985.

Body Weight↗

PubMed2001

Changes in respiratory function during a wilderness multisport endurance competition.

OBJECTIVE: To document the changes in respiratory function seen in competitors during a typical wilderness multisport endurance event. METHODS: A prospective observational cohort study measuring forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) at baseline, midrace, and end of race in competitors in a 105-km ski/run/cycle/paddle race held midwinter in the mountains of Victoria, Australia. RESULTS: Twenty-five adult subjects (22 men) between 20 and 42 years of age were studied. The mean decline in FEV1 was 15.1% (95% CI 10.3-19.8) and for FVC was 13.0% (95% CI 8.1-17.9). Fourteen (56%) of the 25 subjects had a >10% decline in FEV1 and FVC, and 7 (28%) of the 25 subjects had a >20% decline. In 9 control subjects, aged between 21 and 55 years, there was no significant change in FEV1 or FVC from prerace to end of race. CONCLUSIONS: Significant declines in FEV1 and FVC are common during wilderness multisport endurance events. The focus of future research should be the etiology, which as yet remains speculative.

Adult↗