Fluid change promotes optimum physical performance
Proper fluid exchange helps to maintain hydration and promotes health, safety and optimal physical fitness of those involved in regular physical activity.
Med Sci 1996 Jan; 28(1):i-vii. American College of Sports Medicine stand. Exercise and fluid change.
– Convertino VA, Armstrong LE, Coyle EF, Mack GW, Sawka MN, Senay LC Jr, Sherman WM.
The American Academy of Sports Medicine believes that proper fluid exchange helps maintain hydration and thus promotes the health, safety and optimal physical performance of people involved in regular physical activity. This position is based on a comprehensive review and interpretation of the scientific literature on the effects of fluid change on exercise capacity and the risk of thermal injury related to dehydration and hyperthermia.
Based on the available evidence, the American College of Sports Medicine makes the following general recommendations regarding the amount and composition of fluid that should be consumed in preparation for, during, and after sporting events:
1) It is recommended to eat a balanced diet and drink appropriate liquids within 24 hours before the event, especially during the period that includes a meal before training, in order to ensure proper hydration before training or competition.
2) It is recommended that people consume about 500 ml (about 17 ounces) of liquid about 2 hours before exercise to ensure adequate hydration and time to expel excess ingested water.
(3) During exercise, athletes should start drinking early and at regular intervals, trying to drink at a rate sufficient to replace all the water lost through sweating (i.e. weight loss) or to consume the maximum amount that can be tolerated.
4) It is recommended that the swallowed liquids are cooler than the ambient temperature [between 15 and 22 degrees C (59 and 72 degrees F)] and tastier in order to increase the palatability and facilitate the fluid change. Liquids should be easily accessible and served in containers that allow for easy and minimal interruption of exercise and consumption of appropriate amount of fluids.
5) The addition of appropriate amounts of carbohydrates and/or electrolytes to the fluid replacement solution is recommended for physical exercise longer than 1 hour as it does not significantly affect the water supply to the body and can increase the efficiency of the body. During less than 1 hour of exercise, there is no evidence of any physiological or physical difference between the consumption of a carbohydrate electrolyte drink and clean water.
6) During intensive physical activity lasting more than 1 hour it is recommended to consume carbohydrates at a dose of 30-60 g/h(-1) to maintain carbohydrate oxidation and delay fatigue. This rate of carbohydrate uptake can be achieved without compromising the delivery of liquids by drinking 600-1200 ml.h(-1) solutions containing 4-8% carbohydrates (g.100 ml(-1)). Carbohydrates may be sugars (glucose or sucrose) or starch (e.g. maltodextrine).
7) It is recommended to include sodium (0.5-0.7 g.1(-1) water) in the irrigation solution consumed during physical activity lasting more than 1 hour, as it may be beneficial to increase the palatability, promote fluid retention and possibly prevent hyponatraemia in some people who drink excessive amounts of liquids. There is a small physiological basis for the presence of sodium in the n oral irrigation solution to increase water absorption in the intestines if sodium is sufficiently available from the previous meal.