Muscle cramps

A cramp is a sudden, involuntary tightening of a muscle that causes sharp pain and makes the muscle hard to the touch. Cramps most often affect the calf, and less often the foot or thigh. They are common and usually harmless.

How long they last

According to the NHS, a cramp lasts from a few seconds to ten minutes, and the muscle may remain sore for up to 24 hours afterwards.

Causes

Often no cause is found. The NHS lists the following among the known ones:

• ageing;
• putting strain on the muscles during exercise, which is worse in hot or humid weather;
• the later stages of pregnancy;
• some medicines, including statins, which lower cholesterol, and diuretics, which increase the passing of urine;
• not drinking enough fluid;
• liver disease caused by heavy drinking.

Cramp during or after exercise appears to be mainly a matter of muscle fatigue: it occurs in muscles worked harder or longer than they are used to. Loss of fluid and salt in sweat may contribute in long, hot sessions, but the evidence that it is the main cause is weak.

What to do during a cramp

• Stretching the affected muscle usually stops the cramp. For the calf, the leg is straightened and the toes pulled up towards the shin.
• Massaging the muscle may help.
• Standing and putting weight on the leg can ease it.

Painkillers do not work quickly enough to help during a cramp, though paracetamol or ibuprofen can ease soreness afterwards.

Prevention

Regular calf stretches may reduce cramps, although they do not always prevent them. The NHS describes standing facing a wall with the feet flat on the floor and leaning forward until the calf is stretched, holding for two to three seconds, and repeating for about five minutes, three times a day, with the last session just before bed.

For cramp during exercise:

• training is increased gradually, so that muscles are not asked for more than they are prepared for;
• a warm-up comes first;
• fluid is taken regularly in long or hot sessions; see hydration and exercise;
• pace is eased at the first twinge.

Night cramps

Cramps in the calf at night are especially common in older people and in pregnancy. Stretching before bed, keeping the bedclothes loose over the feet, and sleeping with the feet supported so that the toes do not point downwards all help.

Treatment from a GP

A GP looks for an underlying cause and reviews any medicines. If stretching exercises do not help, quinine tablets are sometimes prescribed. Quinine is not suitable for everyone, and its risks and side effects are discussed first.

When to see a GP

The NHS advises an appointment where cramps disturb sleep, where there is also numbness or swelling in the legs, or where cramps last longer than ten minutes.

Pain, swelling, warmth and redness in one calf that does not pass is not a cramp and may be a blood clot, which needs urgent medical attention.