The science of hydration in sports performance

In Referenceby Admin

  • Thirst does not stimulate until water loss reaches 1-2% body mass[1]
  • Mild dehydration (1-2.5% body mass loss)
    • reduces cognitive function [2-4]
    • reduces endurance & high-intensity exercise performance [4,5]
    • Increases physiological strain (ie. increase heart rate, core body temperature) [6]
      cellular effects: metabolism, hormone release, cell death [7]
  • Rare instances (1 in 1,000) athletes consume too much fluid, hyponatremia (low cellular sodium levels) can lead to life-threatening health problems [8]
  • National Athletic Trainers Association (NATA) & American College of Sports Medicine (ACSM) acknowledge the detrimental effects of dehydration on health and performance providing guidelines [9,10]
  • Studies of human hydration indices are in short supply [11] and in existing studies, it is difficult to assign a numerical value to euhydration due to its human complexity [12]
  • No significant correlations were found between Urine specific gravity and plasma osmolality (blood) [13]
  • Urine specific gravity lags behind during periods of rapid body fluid, not significantly different from baseline until 3% body mass loss [14]

References:

  1. Adolph, EF (1947) Physiology of man in the desert. New York, NY: Interscience.
  2. Edwards, A.M., Mann, M.E., Marfell-Jones, M.J., Rankin, D.M., Noakes, T.D., & Shillington, D.P. (2007). The influence of moderate dehydration on soccer performance: Physiological responses to 45-min of performance of sport specific and mental concentration tests. British Journal of Sports Medicine, 41, 385–391.
  3. Maughan, R.J., & Griffin, J. (2003). Caffeine ingestion and fluid balance: a review. Journal of Human Nutrition and Dietetics, 16, 411–420.
  4. Cheuvront, S.N., Carter, R., Montain, S.J., & Sawka, M.N. (2004). Daily body mass variability and stability in active men undergoing exercise-heat stress. International Journal of Sport Nutrition and Exercise Metabolism, 14, 532–540.
  5. Nielsen, B., Kubica, R., Bonnesen, A., Rasmussen, I.B., Stoklosa, J., & Wilk, B. (1981). Physical work capacity after dehydration and hyperthermia. Scandinavian Journal of Sport Sciences, 3, 2–10.
  6. Maughan, R.J. (2003). Impact of mild dehydration on wellness and on exercise performance. European Journal of Clinical Nutrition, 57, S19–S23.
  7. Lang, F., Busch, G.L., Ritter, M., Völkl, H., Waldegger, S., Gulbins, E., & Häussinger, D. (1998). Functional significance of cell volume regulatory mechanisms. Physiological Reviews, 78, 247–306
  8. Noakes, T.D. (2003). Overconsumption of fluids by athletes. British Medical Journal, 327, 113–114.
  9. National Collegiate Athletic Association. Wrestling Rules Committee. (2003). National Collegiate Athletic Association wrestling rules. Indianapolis, IN: Author.
  10. American College of Sports Medicine, Sawka, M.N., Burke, L.M., Eichner, E.R., Maughan, R.J., Montain, S.J., & Stachenfeld, N.S. (2007). Position stand: Exercise and fluid replacement. Medicine and Science in Sports and Exercise, 39, 377–390.
  11. Armstrong, L.E., Pumerantz A.C., Fiala, K.A., Roti, M.W., Kavouras, S.A., Casa D.J., Maresh C.M. (2010). Human hydration indices: acute and longitudinal reference values. International Journal of Sport Nutrition and Exercise Metabolism, 20, 145-153.
  12. Armstrong, L.E. (2007). Assessing hydration status: The elusive gold standard. Journal of the American College of Nutrition, 26, 575S–584S. 
  13. Sommerfield, L. M., McAnulty, S. R., McBride, J. M., Zwetsloot, J. J., Austin, M. D., Mehlhorn, J. D., … Utter, A. C. (2016). Validity of Urine Specific Gravity When Compared With Plasma Osmolality as a Measure of Hydration Status in Male and Female NCAA Collegiate Athletes. Journal of strength and conditioning research, 30(8), 2219–2225. 
  14. Popowski LA , Oppliger RA , Patrick Lambert G , Johnson RF , Kim Johnson A , Gisolf CV  (2001) Blood and urinary measures of hydration status during progressive acute dehydration. Medicine and Science in Sports and Exercise. 33(5): 747-753.