CHENNAI: Water is essential for life. From the time that primeval species ventured from the oceans to live on land, a major key to survival has been prevention of dehydration. The critical adaptations cross an array of species, including man. Without water, humans can survive only for days. Water comprises from 75% body weight in infants to 55% in elderly and is essential for cellular homeostasis and life.
When we speak of water, we are essentially focusing first and foremost on all types of water — be it soft or hard, spring or well, carbonated or distilled water. Furthermore, we get water not only directly as a beverage but from food and to a very small extent also from oxidation of macronutrients (metabolic water). The proportion of water that comes from beverages and food varies with the proportion of fruits and vegetables in the diet.
Apart from urinary excretion, the other main fluid regulatory process is drinking, mediated through the sensation of thirst. The brain’s decision to start or stop drinking and to choose the appropriate drink is made before the ingested fluid can reach the intra- and extracellular compartments. The taste buds in the mouth send messages to the brain about the nature, and especially the salt of the ingested fluid, and neuronal responses are triggered as if the incoming water had already reached the bloodstream.
Hydration status is critical to the body’s process of temperature control. Body water loss through sweat is an important cooling mechanism in hot climates and in physical activity. Sweat production is dependent upon environmental temperature and humidity, activity levels, and type of clothing worn.
During challenging athletic events, it is not uncommon for athletes to lose 6-10% of body weight in sweat loss, thus leading to dehydration if fluids have not been replenished. However, decrements in physical performance in athletes have been observed under much lower levels of dehydration. Hypohydration appears to have a more significant impact on high-intensity and endurance activity such as tennis and long-distance running than on anaerobic activities such as weight lifting or on shorter-duration activities, such as rowing.
Strategies for hydration during exercise
Increased fluid intake is necessary with prolonged or intense exercise due to increased sweat production.
During vigorous exercise (>70% VO2max) understand that gastric emptying may limit fluid absorption. Athletes can train their gut to improve gastrointestinal comfort or adopt strategies to increase fluid intake before and after exercise.
Carefully monitor acute changes in body mass over an exercise bout to determine sweat rate, adequacy of fluid replacement and fluid needs for recovery for that session. Consider how well this can be used to evaluate general hydration strategies in similar situations.
Use changes in body mass, urine colour and thirst as awakening call to track daily changes in hydration status.
Exercising in the cold, or at high altitudes merits special considerations when determining the fluid needs of athletes. Athletes must also be mindful of their fluid needs during exercise in the cold.
Measure local environmental conditions to determine the risk of high sweat rates resulting in large fluid losses.
Increase fluid replacement during exercise in hot and humid environments to account for increased sweat losses.
Account for clothing or equipment requirements when evaluating fluid needs.
Modify fluid intake when exercising in cold or altitude according to an estimation of fluid losses noting that thirst may be less reliable as a guide to dehydration under these conditions.
During training, ensure that there is ample access to fluids that are palatable to athletes.
Understand the opportunities for fluid intake during that are specific to a sport or event, and any other practical issues that determine fluid intake.
Consider the risks of hyperhydration as well as hypohydration for any sporting event or individual athlete, and prepare appropriate practice and education strategies.
Practise intended competition drinking plans ahead of time to determine their suitability and allow time for readjustment.
Consider body size, acclimatisation status and thirst drive when developing hydration plans for individual athletes.
15 Promote healthy weight management strategies in weight division, acrobatic and appearance-based sports that minimise manipulation of body water.