It is important for people exercising to replace fluids that are lost through sweating to avoid dehydration. There is a multitude of sports drink choices out there, so how do you know what is right for you.

Importance of Water

While exercising, particularly in the heat, heavy sweating may occur, therefore resulting in the loss of both body fluids and electrolytes. The amount of fluid lost depends not only on the environmental temperature but on the humidity as well. Although there are some electrolytes lost in sweat, particularly sodium and chloride, there is a much greater proportion of water lost. Therefore replacing the water is far more important than the replacement of electrolytes.

The losses in body fluid potentially lead to health problems if they are not replaced. Some sports drinks come in powdered form, enabling you to make them up to any concentration as you wish. For these, if the recommended mixtures are followed these usually result in drinks too concentrated. The ideal replacement fluid consists mostly of water.

Fluid Temperature

The temperature of the fluid should be cool not warm, as this enables more rapid movement of the fluid out of the stomach. If a race or training activity in the heat is going to last for an extended period, try and find some way of replacing the fluid as you exercise (every 15-20 minutes). If that is not possible, you must aim to be well hydrated prior to exercise (a couple of glasses of water 15-20 minutes prior to exercise), and to replace the fluid as soon as possible after exercise.
 

Need a Tonic?

Reading the labels of many sports drinks you will come across the terms hypotonic, isotonic or hypertonic. Each of these have their benefits and you should understand the difference between these.
 

Hypotonic

Hypo means less. A hypotonic drink is more dilute than your body fluids (i.e. there are fewer particles such as sugars and electrolytes), which means that the drink can be absorbed faster than plain water itself.
 

Isotonic

Isotonic means that the fluid is at the same concentration (i.e. the same number of particles per volume) as your body fluids – it is therefore absorbed as fast as or faster than water. Such fluids provide an ideal compromise between rehydration and refueling.
 

Hypertonic

Hyper means greater than. Hypertonic drinks (for example cola, lemonade or fruit juice) are more concentrated than body fluids, and will be absorbed more slowly than plain water. Hypertonic drinks slow down the rate at which the stomach empties and therefore reduce the speed of fluid replacement. These are better post-exercise drinks that offer a higher dose of energy with the fluid.