Blog: Hydration and fluid replacement

Losses as small as 2% body weight experienced as a result of sweating during exercise are likely to result in performance declines (Potgieter, 2013). In addition, dehydration increases the risk of experiencing a life threatening, usually heat related, illness or event during exercise (Rodriguez et al. 2009). This highlights the importance being well hydrated (euhydrated) before, during and after competition. An Ad libitum approach to hydration, dictated by thirst sensation, is a more beneficial drinking strategy than drinking as much as is tolerable during exercise (Noakes, 2010). Excess fluid intake should be avoided. This can increase the loss of important electrolytes such as sodium in the body; therefore, elevating the risk of a potentially lethal condition termed hyponatraemia (Montain, 2008). This condition is of more concern during long distance events (> 2 hrs), and is further exacerbated during exercise in the heat (Noakes, 2010). Nonetheless, thirst sensations should not be solely relied upon during exercise as they may underestimate actual fluid requirements (Potgieter, 2013). As a result, guidelines have been developed in relation to various sporting events to ensure adequate hydration status. Practical application

• Begin activity well hydrated by consuming 1 – 3 cups of fluid before exercise and allow enough time for normal urine output prior to the exercise bout.                                                                                                                                                               (Montain, 2008; Potgieter, 2013)

• Individual sweat rates vary greatly. Measuring body weight pre and post exercise is a simple method of estimating sweat rate. It is not advisable to consume fluid in excess of your hourly sweat rate, often athletes are advised not to drink in excess of 800mL/hr and certainly no more than 2L/hr.                                                                                                                                                                                                                 (Noakes, 2010; Potgieter, 2013)

• Sodium (and sometimes other electrolytes) should be included in fluid intake when exercising for long durations (> 2hrs). This is also important when an individual has high sweat rates and during exercise in the heat. This is also important to note for fluid replacement during recovery.                                                                                   (Potgieter, 2013)

References Montain, S. J. (2008). Hydration recommendations for sport 2008. Current Sports Medicine Reports. 7(4); 187 - 192. Noakes, T (2010). Is drinking to thirst optimum? Annuals of Nutrition and Metabolism. 57(2); 9 – 17. Potgieter, S. (2013). Sport nutrition: A review of the latest guidelines for exercise and sport nutrition from the American College of Sport Nutrition, the International Olympic Committee and the International Society for Sports Nutrition. South African Journal of Clinical Nutrition. 26(1); 6-16. Rodriquez NR, DiMarco NM, Langley S. (2009) Position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and athletic performance. Journal of the American Dietary Association. 109(3); 509-527.