Q+A: Why do I feel nauseous after racing?

Q I have a problem that seems to affect me after finishing half-marathons: I feel queasy and don’t want to eat or drink. The feeling seems to pass if I lie down for an hour or so. As advised, I always try to take on water at each drinks station. Do your have any idea why this happens?

A When you exercise hard there is increased bloodflow in the active tissues. For short exercises this affects your exercising muscle groups, but for longer bouts it travels to the large organs which are responsible for maintaining the body’s internal environment. The liver and the skin are two of the primary organs, but the stomach is also often affected, which can cause that knotted empty feeling that leaves you temporarily unable to eat or drink.

Some people also experience a mild hypoglycaemic reaction after prolonged exercise. The body’s energy-producing systems sometimes fail to keep pace with the demands placed on them, and blood-sugar levels fall low enough to make you feel faint, clammy and tight in the stomach. Palpitations and mild tremors are also not uncommon, but as blood-sugar levels return to normal the feeling usually passes.

Prevention is usually found in adequate pre-exercise nutrition and hydration, and the use of energy drinks while running instead of water. It may take bit of practice before you get an exact idea of how much to drink and eat. If this queasy feeling happens again, try taking on small amounts of sugary foods and regular small amounts of water until the feeling passes.

Nick Critchley, exercise physiologist with Medifit medical and fitness centres