During exercise, sweat losses will depend on a number of factors including body weight, genetics, clothing, the environment, and the intensity and duration of the exercise. Sweat rates can range between 0.2 to 2.0 litres per hour over a range of different sports in different environments. There is considerable variability of sweat losses between individuals, even within the same exercise on the same day, so individual hydration plans can help you to maintain your hydration status. The variability in sweat rate between and within individuals emphasizes that there is no single ‘one size fits all’ recommendation for fluid intake. In addition, the thirst drive has long been considered inefficient, as the stimulation to drink is not initiated until water loss reaches 1-2% reduction in body weight.
For most athletes some degree of dehydration will exist and is normal during exercise because sweat losses may exceed fluid intake. Some athletes find it difficult to drink enough fluids during exercise and in some sports access to fluids is limited. Maintaining hydration throughout exercise is one of the easiest and cheapest methods of enhancing performance and health. Simple measurements can be carried out minimal expense, to allow you to devise your own hydration strategy.
The amount of fluid lost as sweat is reflected in changes in pre- and post-exercise body weight. To calculate changes in hydration status the assumption is made that 1 g change in body weight represents a 1 mL change in hydration status. Click here to download our guide to calculating sweat rate.