Prevention of Dehydration Stress

In order to prevent the debilitating effects of dehydration there are a number of simple steps which should be taken.

1. Be fitter and leaner.

Fitter people acclimatize to hot conditions more rapidly because they sweat more readily than unfit people of the same weight and body fat levels. To be more precise, fitter people sweat at a lower core'temperature than their unfit counterparts, thus allowing for significant amounts of heat loss whilst minimizing the need for vasodilation. As a consequence of this reduced requirement for vasodilation a greater percentage of the cardiac output can be directed to the working muscles.

Endurance trained individuals generally have greater blood volumes than their untrained counterparts. This affords well conditioned individuals a reserve' of bodily fluids which also contributes to their greater resistance to fatigue when exercising in the heat.

Fat acts as an insulator and interferes with the loss of heat via vasodilation so leaner people are better able to dissipate heat. Fatter individuals, on the other hand, are less able to dissipate heat via vasodilation and must rely on sweating to a greater extent.

2. Drink before and during exercise.
Consumption of water prior to exercise minimizes the risk of dehydration during exercise. It is also prudent to replace fluids as they are lost from the body during exercise. In fact athletes engaged in prolonged and frequent exercise should aim to maintain their body weight during each training session.

Unfortunately, thirst is not a good indicator of water requirements during exercise as the thirst reflex responds slowly to the body's increasing demands for water.

The aim of drinking before exercise is to increase the body's fluid volume; however, any fluid which sits in the stomach, unabsorbed, will be of no benefit to the thermoregulatory process. Indeed the presence of a large volume of water in the gut may make vigorous exercise uncomfortable. If more water is taken, or if it is consumed too soon before exercise, some will remain in the stomach at the time when exercise commences.

During exercise smaller volumes should be consumed so that the water content of the gut is never too high. Brief drink stops should interfere minimally with the training benefits of the exercise session whilst minimizing the risk of heat stress. The amount of water which can be taken during exercise will vary between individuals and will also depend on the intensity and type of exercise undertaken.