The danger of an inadequate water intake during prolonged exercise

A novel concept re-visited
  • Timothy D. Noakes
  • Brett A. Adams
  • Kathryn H. Myburgh
  • Chris Greeff
  • Trevor Lotz
  • Mark Nathan


To prevent thermal injuries during distance running, the American College of Sports Medicine proposes that between 0.83 and 1.65 l of water should be ingested each hour during prolonged exercise. Yet such high rates of fluid intake have been reported to cause water intoxication. To establish the freely-chosen rates of fluid intake during prolonged competitive exercise, we measured fluid intake during, body weight before and after, and rectal temperature after competition in a total of 102 runners and 91 canoeists competing in events lasting from 170–340 min. Fluid intakes during competition ranged from 0.29–0.62 l · h−1; rates of water loss ranged from 0.69–1.27 l · h−1 in the runners; values were lower in the canoeists. Mean post-race rectal temperatures ranged from 38.0–39.0° C. There was no relationship between the degree of dehydration and post-race rectal temperature. We conclude that hyperthermia is uncommon in prolonged competitive events held in mild environmental conditions, and that exercise intensity, not the level of dehydration, is probably the most important factor determining the postexercise rectal temperature. During prolonged exercise in mild environmental conditions, a fluid intake of 0.5 l · h−1 will prevent significant dehydration in the majority of athletes.

Key words

Marathon running Dehydration Sweat rate fluid intake Rectal temperature 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Adams WC, Fox RH, Fry AJ, MacDonald IC (1975) Thermoregulation during marathon running in cool, moderate and hot environments. J Appl Physiol 38:1030–1037Google Scholar
  2. American College of Sports Medicine (1985) Position statement on the prevention of thermal injuries during distance running. Med Sci Sports Ex 16:ix-xivGoogle Scholar
  3. Armstrong LE, Costill DL, Fink WJ (1985) Influence of diurectic-induced dehydration on competitive running performance. Med Sci Sports Ex 17:456–461Google Scholar
  4. Blake JB, Larrabee RC (1903) Observations upon long distance runners. Boston Med Surg J 148:195–206Google Scholar
  5. Cohen I, Zimmerman AL (1978) Changes in serum electrolyte levels during marathon running. S Afr Med J 53:449–453Google Scholar
  6. Costill DL (1972) The physiology of marathon running. JAMA 221:1024–1029Google Scholar
  7. Costill DL (1972) Fluid replacement during and following exercise. In: Alexander JF, Serfass RC, Tipton CW (eds). Fitness and exercise. Chicago, Athletic InstituteGoogle Scholar
  8. Costill DL, Kammer WF, Fisher A (1970) Fluid ingestion during distance running. Arch Environ Health 21:520–525Google Scholar
  9. Dancaster CP, Whereat SJ (1971) Fluid and electrolyte balance during the Comrades Marathon. S Afr Med 45:147–150Google Scholar
  10. Gisolfi CV, Copping JR (1974) Thermal effects of prolonged treadmill exercise in the heat. Med Sci Sports Ex 6:108–113Google Scholar
  11. Godlonton JD (1985) Comrades Marathon — setting the facts straight. S Afr Med J 68:291Google Scholar
  12. Hiller WDB, O'Toole ML, Laird RH, Burch R, Travis M, Massimino AF, Medoff RJ (1986) Electrolyte and glucose changes in endurance and ultraendurance exercise: results and medical implications. Med Sci Sports Ex 18:S62-S63Google Scholar
  13. Hughson RL, Staudt LA, Mackie JM (1983) Monitoring road racing in the heat. Physc Sportsmed 11 (May):94–105Google Scholar
  14. Jardon OM (1982) Physiological stress, heat stroke, malignant hyperthermia — a perspective. Mil Med 147:8–14Google Scholar
  15. Leger L, Mercer D (1984) Gross oxygen cost of horizontal treadmill and track running. Sports Med 1:270–277Google Scholar
  16. Magazink A, Shapiro Y, Meytes D, Meytes I (1974) Enzyme blood levels and water balance during a marathon race. J Appl Physiol 36:214–217Google Scholar
  17. Maron MB, Horvath SM (1978) The marathon: a history and review of the literature. Med Sci Sports 10:137–150Google Scholar
  18. Maron MB, Horvath SM, Wilkerson JE (1975) Acute blood biochemical alterations in response to marathon running. Eur J Appl Physiol 34:173–181Google Scholar
  19. Maron MB, Wagner JA, Horvath SM (1977) Thermoregulatory responses during competitive marathon running. J Appl Physiol 42:909–914Google Scholar
  20. Maughan RJ (1985) Thermoregulation in marathon competition at low ambient temperature. Int J Sports Med 6:15–19Google Scholar
  21. Maughan RJ, Leiper JB, Thompson J (1985) Rectal temperature after marathon running. Br J Sports Med 19:192–196Google Scholar
  22. Mitchell JW, Nadel ER, Stolwijk JAJ (1972) Respiratory water losses during exercise. J Appl Physiol 32:474–476Google Scholar
  23. Myhre LG, Hartung GH, Tucker DM (1982) Plasma volume and blood metabolites in middle-aged runners during a warm weather marathon. Eur J Appl Physiol 48:227–240Google Scholar
  24. Myhre LG, Hartung GH, Nunneley SA, Tucker DM (1985) Plasma volume changes in middle-aged male and female subjects during marathon running. J Appl Physiol 59:559–563Google Scholar
  25. Noakes TD (1982) Heatstroke during the 1981 National Cross-Country running championships. S Afr Med J 61:145Google Scholar
  26. Noakes TD, Goodwin N, Rayner BL, Brankin T, Taylor RKN (1985a) Water intoxication: A possible complication during endurance exercise. Med Sci Sports Exerc 17:370–375Google Scholar
  27. Noakes TD, Lambert EV, Lambert MI, McArthur PS, Myburgh KH, Benade AJS (1988) Carbohydrate ingestion and muscle glycogen depletion during marathon and ultramarathon racing. Eur J Appl Physiol (in press)Google Scholar
  28. Noakes TD, Nathan M, Irving RA, van Zyl Smit R, Meissner P, Kotzenberg G, Victor T (1985b) Physiological and biochemical measurements during a 4-day surf-ski marathon. S Afr Med J 67:212–216Google Scholar
  29. Olsson K-E, Saltin B (1970) Variations in total body water with muscle glycogen changes in man. Acta Physiol Scand 80:11–18Google Scholar
  30. Owen MD, Kregel KC, Wall PT, Gisolfi CV (1986) Effects of ingesting carbohydrate beverages during exercise in the heat. Med Sci Sports Ex 18:568–575Google Scholar
  31. Pugh LGCE, Corbett JL, Johnson RH (1967) Rectal temperatures, weight losses, and sweat rates in marathon running. J Appl Physiol 23:347–352Google Scholar
  32. Robinson S (1963) Temperature regulation in exercise. Pediatrics 32:691–702Google Scholar
  33. Saltin B, Hermansen L (1966) Esophageal, rectal, and muscle temperature during exercise. J Appl Physiol 21:1757–1762Google Scholar
  34. Shephard RJ, Kavanagh T (1978) Fluid and mineral needs of middle-aged and post-coronary distance runners. Physc Sportsmed 6:90–102Google Scholar
  35. Sjodin B, Svedenhag J (1985) Applied physiology of marathon running. Sports Med 2:83–99Google Scholar
  36. Van Rensburg JP, Kielblock AJ, Van der Linde A, Van der Walt WH (1986) Physiological responses to a rugby match. S Afr J Res Sport Phys Ed Rec 7:47–57Google Scholar
  37. Wells CL, Schrader TA, Stern JR, Krahenbuhl GS (1985) Physiological responses to a 20-mile run under three fluid replacement treatments. Med Sci Sports Ex 17:364–369Google Scholar
  38. Wyndham CH (1977) Heatstroke and hyperthermia in marathon runners. Ann NY Acad Sci 301:128–138Google Scholar
  39. Wyndham CH, Strydom NB (1969) The danger of an inadequate water intake during marathon running. S Afr Med J 43:893–896Google Scholar

Copyright information

© Springer-Verlag 1988

Authors and Affiliations

  • Timothy D. Noakes
    • 1
  • Brett A. Adams
    • 1
  • Kathryn H. Myburgh
    • 1
  • Chris Greeff
    • 1
  • Trevor Lotz
    • 1
  • Mark Nathan
    • 1
  1. 1.Sport Science Centre, Department of PhysiologyUniversity of Cape Town Medical SchoolObservatorySouth Africa

Personalised recommendations