Exercise-induced cramp

Expert reviewer, Emmanuel Udomhiaye, Physiotherapist
Next review due July 2023

A muscle cramp is when your muscle suddenly contracts and becomes hard and tense. It can be very painful. Cramps that happen while you’re exercising, or immediately afterwards are known as ‘exercise-induced’, or ‘exercise-associated’ muscle cramps.

Cyclists stretching

About exercise-induced cramps

Cramps happen in muscles called voluntary (or skeletal) muscles which are usually under your control. But during a cramp, your muscle contracts strongly without you wanting it to and won’t relax.

Although any muscle can go into spasm, muscle cramps 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)

Cramps usually only last for a short time – typically less than a minute. But sometimes the pain can last for up to 10 minutes. And your muscle can feel tender for up to 24 hours afterwards. The cramp may happen again if you carry on your exercising and don’t allow the muscle time to recover.

What causes exercise-induced cramps?

No one knows for sure what causes exercise-induced muscle cramps but there are two main ideas.

The most recent theory is that these cramps are due to muscle fatigue, and to how this can affect the way your nerves control muscle contractions. It does seem that exercise-induced cramps are most likely to happen when your muscles are fatigued or tired.

Another, older idea is that cramps are due to dehydration, or low levels of various chemicals (electrolytes) in the body. It’s known that some athletes who lose lots of salt in their sweat when they exercise are more likely to get cramps.

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

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

  • do endurance sports, such as marathon running, especially towards the end of the event
  • are working physically hard, or exercising, in hot conditions
  • are in the first few weeks of a training programme
  • don’t always stretch before exercise, or don’t do it for long enough

It’s been found that a person’s risk of getting exercise-induced cramps goes up with increasing age and increasing body mass index (BMI). You may also be more likely to get cramps while exercising if you have a long-term medical condition such as heart disease.

How do I stop a muscle cramp?

If you have a muscle cramp during exercise, stop what you’re doing and gently and slowly stretch the affected muscle. You should keep holding it in a stretched position for at least 30 seconds – you’re aiming to feel the muscle relax. You may find it helpful to repeat this 30-second stretch so that you do it three or four times.

It might also help if you:

  • gently rub and massage your muscle
  • drink some water and have some salty food if you think you might be dehydrated

You’ll then need to rest, to give your muscle time to recover, or the cramp might return.

Here are some examples of muscle stretching exercises which should help.

Muscle: Calf (gastrocnemius)
Stretch: Stand in a lunge position with your affected leg stretched out behind you and push your heel towards the ground. Hold for 30 seconds. Or, instead, use your hand to pull your toes and foot upwards and hold for 30 seconds.

Muscle: Small muscles and fibrous tissue (plantar fascia) of your foot
Stretch: Hold your toes and pull them upwards to stretch your foot. Hold for 30 seconds.

Muscle: Front of your thigh (quadriceps)
Stretch: Stand upright and lift your ankle towards your buttocks while holding the top of your foot. Pull your heel gently in towards your buttocks to stretch. Hold for 30 seconds.

Muscle: Back of your thigh (hamstrings)
Stretch: Sit up straight on the ground with both legs extended straight in front of you. Put your palms on the ground and slide your hands towards your ankles. Hold for 30 seconds.

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How can I prevent muscle cramps?

Because no one knows for sure what causes exercise-induced muscle cramps, it’s not certain what the best way of preventing them might be. However, here are some things which may help.

Warm up and stretch

Have a gentle warm-up before you get into any intensive exercise. It’s thought that warming up and regularly stretching your muscles reduces your likelihood of developing cramp.

It’s also helpful to keep your level of general fitness up and to make sure you’re well prepared physically before an important sports event.

Keep hydrated

Drink enough water while you exercise and afterwards, particularly in hot conditions. It’s always important to stay properly hydrated when you’re exercising.

How much you need to drink varies hugely from person to person so it simply isn’t possible to give exact amounts. Don’t rely on your thirst to tell you whether you’re dehydrated. Instead, keep an eye on the colour of your urine because this is a really useful indicator of how hydrated you are. The infographic below illustrates how you can check your hydration levels by paying attention to the colour of your urine.

Image showing hydration level by urine colour

Download a larger version of the infographic (PDF, 0.7MB).

Replacing salt

If you’re sweating a lot when you’re exercising, you can lose electrolytes such as sodium (salt). It’s not known for certain but, if severe, this may cause cramp. If you’re going to be exercising in a hot environment for an hour or more, it may help to replace the sodium you lose. You may choose to do this with homemade or commercially available sports drinks. If you’re doing moderate amounts of exercise, you probably won’t need them.

Healthy diet

If you’re exercising, it’s also important to make sure you’re eating a healthy diet with enough carbohydrates. This may help prevent muscle fatigue, which can be a cause of cramps.

If you’re an athlete in training, you may find it helpful to get advice from a dietitian with experience of managing sports nutrition.

Bupa nurses have put together a simple guide with tips to help you eat well for sport and exercise: download the guide on nutrition for sport and exercise (PDF, 1.2MB).

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Related information

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    • Personal communication, Emmanuel Udomhiaye, Physiotherapist, July 2020
  • Reviewed by Dr Kristina Routh, Freelance Health Editor, July 2020
    Expert reviewer, Emmanuel Udomhiaye, Physiotherapist
    Next review due July 2023