Sodium intake and post-exercise rehydration in man

  • R. J. Maughan
  • J. B. Leiper
Original Article

Abstract

This study examined the effect of the sodium content of drinks on the rehydration process after exercise. Six healthy male volunteers were dehydrated by a mean (SEM) of 1.9(0.0) % of body mass by intermittent cycle exercise in a warm (32°C), humid (54% RH) environment. Subjects exercised on four occasions at weekly intervals with each trial beginning in the morning, 3 h after a standard breakfast. Over a 30-min period beginning 30 min after the end of exercise, subjects ingested one of the four test drinks in a volume equivalent to 1.5 times their body mass loss. Drink composition was constant except for the sodium (and matching anion) content. Sodium content of drinks A, B, C and D was 2, 26, 52 and 100 mmol · l−1, respectively. Treatment order was randomised using a four-way crossover incomplete block design. Blood and urine samples were obtained before exercise, immediately before and after the rehydration period and at 0.5, 1.5, 3.5 and 5.5 h after the end of the rehydration period. Data were analysed by parametric or non-parametric statistical tests as appropriate. The volume of fluid consumed was the same on all trials [2045(45) ml]. From the 1.5-h sample onwards, a significant treatment effect on cumulative urine output was apparent, with the volume excreted being inversely related to the sodium content of the drink consumed. By the end of the trial, subjects were in net negative fluid balance on trials A [by 689(124) ml] and B [by 359(87) ml]; on trials C [−2(79) ml] and D [+98(67) ml], subjects were approximately euhydrated. Cumulative urinary sodium output was higher on treatment D than on the other trials after 5.5 h. Plasma volume was lower after exercise than before; on trials B, C and D, plasma volume was higher than the pre-exercise value from 0.5 h after the end of the rehydration period onwards. On trial A, plasma volume was higher than the pre-exercise value at 3.5 and 5.5 h after the end of the rehydration period. At 1.5 h after the end of the rehydration period, the increase in plasma volume was greater on trials C and D than on trial A. These results suggest that the fraction of the ingested fluid that was retained was directly related to the sodium concentration.

Key words

Dehydration Rehydration Fluid balance Exercise Electrolyte balance 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Costill DL (1977) Sweating: its composition and effects on body fluids. Ann NY Acad Sci 301:160–174Google Scholar
  2. Costill DL, Sparks KE (1973) Rapid fluid replacement following thermal dehydration. J Appl Physiol 34:299–303Google Scholar
  3. Dill DB, Costill DL (1974) Calculation of percentage changes in volumes in blood, plasma and red cells in dehydration. J Appl Physiol 37:247–248Google Scholar
  4. Edelman JS, Leibman J (1959) Anatomy of body water and electrolytes. Am J Med 27:256–277Google Scholar
  5. Gonzalez-Alonso J, Heaps CL, Coyle EF (1992) Rehydration after exercise with common beverages and water. Int J Sports Med 13:399–406Google Scholar
  6. Lambert CP, Costill DL, McConnell GK, Benedict MA, Lambert GP, Robergs RA, Fink WJ (1992) Fluid replacement after dehydration: influence of beverage carbonation and carbohydrate content. Int J Sports Med 13:285–292Google Scholar
  7. Lentner C (ed) (1981) Geigy Scientific Tables, 8th edn. Ciba-Geigy, BasleGoogle Scholar
  8. Maughan RJ (1991) Carbohydrate-electrolyte solutions during prolonged exercise. In: Lamb DR, Williams MH (eds) Perspectives in exercise science and sports medicine, vol. 4. Brown and Benchmark, Carmel, pp 35–85Google Scholar
  9. Maughan RJ, Owen JH, Shirreffs SM, Leiper JB (1994) Post-exercise rehydration in man: effects of electrolyte addition to ingested fluids. Eur J Appl Physiol 69:209–215Google Scholar
  10. Moore FD, Olesen KH, McMurrey JD, Parker HV, Ball MR, Boyden CM (1963) The body cell mass and its supporting environment. Saunders, PhiladelphiaGoogle Scholar
  11. Nadel ER, Mack GW, Nose H (1990) Influence of fluid replacement beverages on body fluid homeostasis during exercise and recovery. In: Gisolfi CV, Lamb DR, (eds) Perspectives in exercise science and sports medicine, vol 3.Fluid homeostasis during exercise. Benchmark, Carmel, pp 181–205Google Scholar
  12. Nose H, Mack GW, Shi X, Nadel ER (1988a) Role of osmolality and plasma volume during rehydration in humans. J Appl Physiol 65:325–331Google Scholar
  13. Nose H, Mack GW, Shi X, Nadel ER (1988b) Involvement of sodium retention hormones during rehydration in humans. J Appl Physiol 65:332–336Google Scholar
  14. Sawka MN (1992) Physiological consequences of hypohydration: exercise performance and thermoregulation. Med Sci Sports Exerc 24:657–670Google Scholar
  15. Verde T, Shephard RJ, Corey P, Moore R (1982) Sweat composition in exercise and in heat. J Appl Physiol 53:1540–1545Google Scholar
  16. Walker-Smith JA (1992) Recommendations for composition of oral rehydration solutions for children of Europe. J Pediatr Gastroenterol 14:113–115Google Scholar

Copyright information

© Springer-Verlag 1995

Authors and Affiliations

  • R. J. Maughan
    • 1
  • J. B. Leiper
    • 1
  1. 1.Department of Environmental and Occupational MedicineUniversity Medical SchoolAberdeenScotland

Personalised recommendations