What is an exercise-induced cramp?

Exercise-induced cramps happen in muscles that are normally under your control, called skeletal muscles. But during a cramp, your muscle contracts strongly without you wanting it to, and it can be hard and tender.

Cramps are usually quite short-lived and they can stop as suddenly as they start. But sometimes, the pain and tenderness can last for several hours after the cramp has stopped.

Although any muscle can go into spasm, muscle cramps after exercise mostly affect:

• your calf muscle (gastrocnemius)
• the muscles in your foot
• the group of muscles in the front of your thigh (quadriceps)
• the group of muscles in the back of your thigh (hamstrings)

What causes exercise-induced cramps?

We don’t always know what causes muscle cramps during exercise, but there are two possible causes.

The most recent theory is that exercise-associated muscle cramps are due to muscle tiredness (fatigue).

Another, older idea is that cramps are due to dehydration and low levels of minerals called electrolytes in your body. But the evidence to support this idea isn’t conclusive.

It may be that exercise-induced cramp has different causes in different situations, or several things work together to cause cramps.

You’re more likely to get exercise-induced muscle cramps if you:

• do endurance sports, such as marathon running
• take part in team sports, such as rugby
• work physically hard or exercise in hot, humid conditions

How do I stop exercise-induced muscle cramps?

You should stop working out if you have a muscle cramp, and gently and slowly stretch the affected muscle. Hold it in a stretched position for up to 30 seconds – aim to feel the muscle relax. You may find it helpful to do this stretch a couple of times.

Try to rest and give your muscles time to recover, or the cramp might return. You might need to reduce the intensity and how long you exercise until you can exercise without cramping.

If you feel pain for more than eight hours after the cramps stop, see a physiotherapist to rule out an injury. If you have continuous cramps, a GP can help determine if you have an underlying issue.

How can I avoid exercise-induced cramps?

Because no one knows exactly what causes exercise-induced muscle cramps, it’s not certain what the best way to prevent cramps might be. But here are some things that may help.

Warm up and stretch

Although there’s no proof it will work, warming up and regularly stretching your muscles may reduce your chance of cramps.

It’s also helpful to keep your level of general fitness up and to set realistic goals. Slowly building up your fitness and strength allows muscles to adapt, without feeling too overloaded.

Try to get enough rest and build in some recovery sessions if you’re following a training plan. This can help to avoid fatigue, which is a possible cause of cramps.

Keep hydrated

It’s always important to stay properly hydrated when you exercise. You should drink enough water before, during, and after exercise – especially if the weather is hot or humid.

You can tell if you’re dehydrated by the color of your pee (urine).

If you sweat a lot during exercise, you lose fluid and electrolytes, such as salt (sodium). Although we don’t know for certain, large losses of fluid and electrolytes, through heavy sweating, could cause cramps.

If you’re doing moderate or hard exercise, homemade or commercially available sports drinks can help replace the fluid and electrolytes you lose through sweat.

If you’re doing low or moderate amounts of physical activity, water should be enough to keep you hydrated.

Balanced diet

It’s important to eat a balanced diet with enough carbohydrates because this can help prevent muscle tiredness (fatigue) which may cause cramps. Good nutrition also gives you the energy to be physically active and can help you recover from exercise.

You may find our tips on eating well for physical activity helpful: download the guide on nutrition for sport and exercise. If you’re an athlete in training, you may also find it helpful to get advice from a dietitian with experience in managing sports nutrition.