Almost everyone gets muscle cramps – but what causes them?

What is a muscle cramp?

Almost everyone has had a muscle cramp, for example in the calf. Suddenly the calf muscle contracts sharply and causes intense pain. Muscle cramps can last a few seconds, sometimes even several minutes. Sometimes a muscle cramp also recurs. Cramps usually occur in healthy people during physical exertion or during pregnancy. People are also sometimes woken from sleep by cramps (often in the calf).

The cause of a muscle cramp

The mechanism behind muscle cramps is still largely unknown. It's thought that several causes can underlie a cramp. The main culprit is a fluid and electrolyte deficiency, which impairs cell metabolism. More complex theories look for the cause in the Golgi tendon organs, which could become "exhausted" and so lose their inhibiting effect on the muscle spindles (leading to uncontrolled contractions until exhaustion), or in a drop in muscular ATP concentration. In the latter case, it's thought that the myosin filaments briefly become unable to detach from the actin filaments.

Increased alcohol consumption also raises the likelihood of muscle cramps occurring. This is probably due to the dehydrating effect of alcohol.

Treating a muscle cramp

During a muscle cramp, the goal is to stretch the muscle and so release the contraction. As a second step, you should try to work out why the cramp happened.

Dehydration is often the cause. Even without physical exertion, fluid needs are 2-3 litres per day. Fluid needs increase with physical exertion, in warm, dry weather or at altitude. If your training sessions last longer than 45 minutes, isotonic drinks make sense (for endurance training and team sports).

Magnesium and calcium can slightly lower the cells' membrane potential, making the muscle generally less prone to cramps.

A low level of fitness increases the risk of muscle cramps. So if you regularly suffer from muscle cramps, you should do regular strength training and/or endurance training.