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. 2004 Dec;38(6):718–724. doi: 10.1136/bjsm.2003.007187

Weight changes, medical complications, and performance during an Ironman triathlon

K Sharwood 1, M Collins 1, J Goedecke 1, G Wilson 1, T Noakes 1
PMCID: PMC1724978  PMID: 15562165

Abstract

Background: Subjects exercising without fluid ingestion in desert heat terminated exercise when the total loss in body weight exceeded 7%. It is not known if athletes competing in cooler conditions with free access to fluid terminate exercise at similar levels of weight loss.

Objectives: To determine any associations between percentage weight losses during a 224 km Ironman triathlon, serum sodium concentrations and rectal temperatures after the race, and prevalence of medical diagnoses.

Methods: Athletes competing in the 2000 and 2001 South African Ironman triathlon were weighed on the day of registration and again immediately before and immediately after the race. Blood pressure and serum sodium concentrations were measured at registration and immediately after the race. Rectal temperatures were also measured after the race, at which time all athletes were medically examined. Athletes were assigned to one of three groups according to percentage weight loss during the race.

Results: Body weight was significantly (p<0.0001) reduced after the race in all three groups. Serum sodium concentrations were significantly (p<0.001) higher in athletes with the greatest percentage weight loss. Rectal temperatures were the same in all groups, with only a weak inverse association between temperature and percentage weight loss. There were no significant differences in diagnostic indices of high weight loss or incidence of medical diagnoses between groups.

Conclusions: Large changes in body weight during a triathlon were not associated with a greater prevalence of medical complications or higher rectal temperatures but were associated with higher serum sodium concentrations.

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Selected References

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  1. Armstrong L. E., Costill D. L., Fink W. J. Influence of diuretic-induced dehydration on competitive running performance. Med Sci Sports Exerc. 1985 Aug;17(4):456–461. doi: 10.1249/00005768-198508000-00009. [DOI] [PubMed] [Google Scholar]
  2. Caldwell J. E., Ahonen E., Nousiainen U. Differential effects of sauna-, diuretic-, and exercise-induced hypohydration. J Appl Physiol Respir Environ Exerc Physiol. 1984 Oct;57(4):1018–1023. doi: 10.1152/jappl.1984.57.4.1018. [DOI] [PubMed] [Google Scholar]
  3. Cheuvront S. N., Haymes E. M. Thermoregulation and marathon running: biological and environmental influences. Sports Med. 2001;31(10):743–762. doi: 10.2165/00007256-200131100-00004. [DOI] [PubMed] [Google Scholar]
  4. Craig E. N., Cummings E. G. Dehydration and muscular work. J Appl Physiol. 1966 Mar;21(2):670–674. doi: 10.1152/jappl.1966.21.2.670. [DOI] [PubMed] [Google Scholar]
  5. Gisolfi C. V. Fluid balance for optimal performance. Nutr Rev. 1996 Apr;54(4 Pt 2):S159–S168. doi: 10.1111/j.1753-4887.1996.tb03912.x. [DOI] [PubMed] [Google Scholar]
  6. González-Alonso J., Mora-Rodríguez R., Below P. R., Coyle E. F. Dehydration reduces cardiac output and increases systemic and cutaneous vascular resistance during exercise. J Appl Physiol (1985) 1995 Nov;79(5):1487–1496. doi: 10.1152/jappl.1995.79.5.1487. [DOI] [PubMed] [Google Scholar]
  7. González-Alonso J., Teller C., Andersen S. L., Jensen F. B., Hyldig T., Nielsen B. Influence of body temperature on the development of fatigue during prolonged exercise in the heat. J Appl Physiol (1985) 1999 Mar;86(3):1032–1039. doi: 10.1152/jappl.1999.86.3.1032. [DOI] [PubMed] [Google Scholar]
  8. Greenleaf J. E., Castle B. L. Exercise temperature regulation in man during hypohydration and hyperhydration. J Appl Physiol. 1971 Jun;30(6):847–853. doi: 10.1152/jappl.1971.30.6.847. [DOI] [PubMed] [Google Scholar]
  9. Latzka W. A., Montain S. J. Water and electrolyte requirements for exercise. Clin Sports Med. 1999 Jul;18(3):513–524. doi: 10.1016/s0278-5919(05)70165-4. [DOI] [PubMed] [Google Scholar]
  10. Marino F. E., Mbambo Z., Kortekaas E., Wilson G., Lambert M. I., Noakes T. D., Dennis S. C. Advantages of smaller body mass during distance running in warm, humid environments. Pflugers Arch. 2000 Dec;441(2-3):359–367. doi: 10.1007/s004240000432. [DOI] [PubMed] [Google Scholar]
  11. Nielsen B., Hansen G., Jorgensen S. O., Nielsen E. Thermoregulation in exercising man during dehydration and hyperhydration with water and saline. Int J Biometeorol. 1971 Dec;15(2):195–200. doi: 10.1007/BF01803897. [DOI] [PubMed] [Google Scholar]
  12. Noakes T. D., Adams B. A., Myburgh K. H., Greeff C., Lotz T., Nathan M. The danger of an inadequate water intake during prolonged exercise. A novel concept re-visited. Eur J Appl Physiol Occup Physiol. 1988;57(2):210–219. doi: 10.1007/BF00640665. [DOI] [PubMed] [Google Scholar]
  13. Noakes T. D., Myburgh K. H., du Plessis J., Lang L., Lambert M., van der Riet C., Schall R. Metabolic rate, not percent dehydration, predicts rectal temperature in marathon runners. Med Sci Sports Exerc. 1991 Apr;23(4):443–449. [PubMed] [Google Scholar]
  14. Nybo L., Nielsen B. Perceived exertion is associated with an altered brain activity during exercise with progressive hyperthermia. J Appl Physiol (1985) 2001 Nov;91(5):2017–2023. doi: 10.1152/jappl.2001.91.5.2017. [DOI] [PubMed] [Google Scholar]
  15. Pichan G., Gauttam R. K., Tomar O. S., Bajaj A. C. Effect of primary hypohydration on physical work capacity. Int J Biometeorol. 1988 Sep;32(3):176–180. doi: 10.1007/BF01045276. [DOI] [PubMed] [Google Scholar]
  16. Sawka M. N., Montain S. J., Latzka W. A. Hydration effects on thermoregulation and performance in the heat. Comp Biochem Physiol A Mol Integr Physiol. 2001 Apr;128(4):679–690. doi: 10.1016/s1095-6433(01)00274-4. [DOI] [PubMed] [Google Scholar]
  17. Sharwood Karen, Collins Malcolm, Goedecke Julia, Wilson Gary, Noakes Timothy. Weight changes, sodium levels, and performance in the South African Ironman Triathlon. Clin J Sport Med. 2002 Nov;12(6):391–399. doi: 10.1097/00042752-200211000-00012. [DOI] [PubMed] [Google Scholar]
  18. Speedy D. B., Faris J. G., Hamlin M., Gallagher P. G., Campbell R. G. Hyponatremia and weight changes in an ultradistance triathlon. Clin J Sport Med. 1997 Jul;7(3):180–184. doi: 10.1097/00042752-199707000-00005. [DOI] [PubMed] [Google Scholar]
  19. Speedy D. B., Noakes T. D., Rogers I. R., Hellemans I., Kimber N. E., Boswell D. R., Campbell R., Kuttner J. A. A prospective study of exercise-associated hyponatremia in two ultradistance triathletes. Clin J Sport Med. 2000 Apr;10(2):136–141. doi: 10.1097/00042752-200004000-00009. [DOI] [PubMed] [Google Scholar]
  20. Speedy D. B., Noakes T. D., Rogers I. R., Thompson J. M., Campbell R. G., Kuttner J. A., Boswell D. R., Wright S., Hamlin M. Hyponatremia in ultradistance triathletes. Med Sci Sports Exerc. 1999 Jun;31(6):809–815. doi: 10.1097/00005768-199906000-00008. [DOI] [PubMed] [Google Scholar]
  21. Walsh R. M., Noakes T. D., Hawley J. A., Dennis S. C. Impaired high-intensity cycling performance time at low levels of dehydration. Int J Sports Med. 1994 Oct;15(7):392–398. doi: 10.1055/s-2007-1021076. [DOI] [PubMed] [Google Scholar]
  22. Wyndham C. H., Strydom N. B. The danger of an inadequate water intake during marathon running. S Afr Med J. 1969 Jul 19;43(29):893–896. [PubMed] [Google Scholar]

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