Hydration is important in winter too

Exercising for less than an hour? Water is probably all you need.

Although you may not be sweating so much or starting to glow you will be losing moisture. How much is too much will depend on how hard you are running and how dry the air is.

It is important that runners maintain hydration and electrolyte balance so that our "homeostasis" is optimum. To do this we need to put back in what we take out. We need to match the fluids going in to those that are going out. Since this latest running boom began there have been cases of runners drinking incessantly as they have taken on board the message that hydration is important but failed to understand that we need electrolytes such as potassium, calcium and sodium in order to function. Too much water washes these out.

A good way to find out if you're drinking enough is to look at the colour of your urine. If it's dark, you're probably dehydrated. It should be the colour of straw. You could also weigh yourself before and after exercise. You shouldn't lose more than 2 per cent of body weight in fluid during any exercise session or your performance will decrease. This is more likely to occur in summer than in winter or when you're exercising indoors. During the winter months you will notice that when you're exercising at a high intensity for an hour or more you need to take more fluid and electrolyte on board, less than that and you should only need water.