Advice

Javier Gomez Noya

  • Sip on fluids before, during and after exercise to replenish sweat losses, adjusting for your own hydration needs. Thirst isn’t a good guide for hydration.
  • Don’t forget that you lose sodium when you sweat, so you need to replace this with sports drinks or food containing adequate amounts of sodium during and after exercise, especially in hot weather, if you are a “salty” sweater or if you’re prone to cramps.
  • More than 50% of your body weight is fluid.1 If your body weight drops by just 2% from losing fluids, your performance will suffer.2-8 That’s 1.4kg for a 70kg individual. You can calculate and monitor this by weighing yourself immediately before and after exercise.
  • Rehydration should start soon after exercise so that you can quickly replace any fluid and sodium lost through sweat or urine.
  • Aim to drink about 1.5 litres of fluid for every 1kg of body weight lost during exercise.9
  • Check the colour of your urine. If it looks like apple juice, you need to drink more.10 If it looks like pale lemonade, you are getting enough fluids.
  • Start your exercise session in a hydrated state and match your fluid intake to your sweat loss.
  • Don't drink at rates that are greater than sweat losses as this can cause you to actually gain weight during running.
References
  • 1EFSA, 2008 Scientific of the Panel on Dietetic products, Nutrition and Allergies. Draft –Dietary reference values for water (Question No EFSA-Q-2005-015A)
  • 2Fallowfield, J.L., Williams, C., Booth, J., Choo, B.H. and Growns, S. (1996). Effect of water ingestion on endurance capacity during prolonged running. Journal of Sports Sciences, 14, 497–502.
  • 3McConell, G., Stephens, T. and Canny, B. (1999). Fluid ingestion does not influence intense 1-h exercise performance in a mild environment. Medicine and Science in Sports and Exercise, 31, 386–392.
  • 4Cheuvront SN, Carter R, Castellani JW, Sawka MN. 2005. Hypohydration impairs endurance exercise performance in temperate but not cold air. J. Appl. Physiol., 99: 1972-1976.
  • 5Grandjean A. & Grandjean N. 2007. Dehydration and Cognitive Performance . Journal of the American College of Nutrition, Vol. 26, No. 5, 549S–554S.
  • 6Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS. 2007. Exercise and fluid replacement. Med. Sci. Sports Exerc. 39: 377-390.
  • 7Lieberman H. 2007. Hydration and Cognition: A Critical Review and Recommendations for Future Research. Journal of the American College of Nutrition, Vol. 26, No. 5, 555S–561S.
  • 8Cian C, Koulmann N, Barraud P, Raphel C, Jimenez C, Melin B: Influence of variations in body hydration on cognitive function: effect of hyperhydration, heat stress, and exercise-induced dehydration. J Psychophysiology 14:29–36, 2000.
  • 9Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS. 2007. Exercise and fluid replacement. Med. Sci. Sports Exerc. 39: 377-390.
  • 10Armstrong, L.E., Maresh, C.M., Castellani, J.W., Bereron, M.F., Kenefick, R.W., LaGassee, K.E., and Riebe, D. (1994). "Urinary Indices of Hydration Status.", Int. J. Sport Nutr., 4, 265-279.

This information is not medical advice and should not replace consultation with your health care provider or nutritionist before starting a new exercise program or eating plan.