Since the mid-1990s, the public message has been overwhelmingly prevalent and clear hydration is important and critical to health and performance. Our own Toolbox Editor Dr. Stephen Cheung tested this assumption head-on in a unique way with a study that received a lot of media attention. What did he find?Hydration HistoryThe importance and need for hydration has been an ongoing scientific battle and debate over the past 40 years, when the first sports drinks started becoming popular. Since that time, the pendulum has firmly swung in favour of fluid replacement during exercise being important. In 1996, the American College of Sports Medicine (ACSM) developed a fluid replacement Position Stand that urged at least the full replacement of sweat loss during exercise.The core of this Position Stand was likely a classic study by Montain and Coyle (1992), where subjects cycled in the heat (33C, 50%RH) while receiving 0, 20, 48, and 81% of fluid replacement compared to sweat loss. The less the fluid replacement, the higher the heart rates and core temperatures.The importance of fluid replacement may become magnified in the heat, due to the increased demands for heat dissipation. In addition to great skin blood flow (and therefore less available to go to the muscles), there is also a greater rate of blood volume loss through sweating.In 2007, ACSM prepared a new position stand on fluid replacement (Sawka et al., 2007). Rather than full fluid replacement, it proposed 400-800 mL/h, varying depending on size, environment, exercise intensity, etc. It also...
View the full article
View the full article
