ABSTRACT
From antiquity until the early 1970s, athletes were advised not to drink during exercise. But between 1975 and 1996, novel guidelines for fluid ingestion during exercise were promulgated by a number of influential organizations including the American College of Sports Medicine (ACSM) (1975, 1987, 1996a, 1996b), the National Association of Athletic Trainers (Casa et al. 2000; Binkley et al. 2002) and the United States (US) Army (Burr 1991; Montain et al. 1999; Gardner 2002), amongst others. These guidelines are based on five core doctrines: First, that all the weight lost during exercise must be replaced if health is to be protected and performance is to be optimized. Second, that fluid ingestion alone can prevent serious heat illness during exercise regardless of the circumstances in which the exercise is undertaken. Third, that uniquely in humans, although apparently not in any other mammal, the sensations of thirst underestimate the human’s real fluid requirements before, during and after exercise. As a result, unless properly informed, athletes will always drink too little, before, during and after exercise. Fourth, that the fluid requirements of all athletes, big and small, fast and slow, are sufficiently similar during all forms of exercise that a universal guideline is possible. And fifth, athletes can safely ingest any volume of fluid at any rate both at rest and during exercise without harmful consequences. Combined, these doctrines produce the guidelines that athletes should ‘replace all the water lost through sweating (i.e., body weight loss) (ACSM 1996a, p i), or consume the maximal amount that can be tolerated’ (ACSM 1996b, p i) or drink between 600-1200 ml per hour (ACSM 1996a, p i). Indeed the original US Army guidelines promoted even higher rates of fluid ingestion of up to 1800 ml per hour (Burr 1991).
