What is a muscle cramp and what causes it?

 

 

 

 

A muscle cramp is defined as a sudden, involuntary (spontaneous or automatic) and painful contraction of all or part of a muscle. It goes away by itself within seconds and is often accompanied by a palpable knotting of the muscle.

Muscle cramps have certain specific features:

• They are very painful, and may cause persistent soreness even after the cramp has subsided;
• They come on suddenly and lessen on their own or with muscle stretching;
• They only involve one muscle or a part of that muscle;
• They are associated with forceful contractions of the muscle;
• They occur most commonly in the calf and foot muscles, followed by the hamstring and quadriceps muscles.

Who usually suffers from muscle cramps?

Cramps may occur in people with specific conditions, such as:

• Lower motor neuron disorders;
• Neuropathies;
• Metabolic disorders;
• Acute extracellular volume depletion.

However, muscle cramps also often occur in healthy people with no history of nerve or metabolic disorders. Cramps can occur during sleep, pregnancy or strenuous exercise. These muscle cramps are referred to as ‘benign cramps’.

The main risk factors for muscle cramps associated with exercise include a family history of cramping, previous occurrences of cramps during or after exercise, an increase in the intensity and duration of exercise, and inadequate training for the activity. In addition, it has been shown that muscle fatigue increases a person’s risk for developing muscle cramps.

What causes muscle cramps?

Although dehydration and/or electrolyte depletion are often thought to cause muscle cramps, scientific evidence does not support this. Recent experimental findings have suggested that spinal mechanisms are involved in the development of muscle cramps. It is believed that the nerves conducting messages between the muscle cells and the central nervous system are hyper-excitable and this results in cramping. This hypothesis seems to explain why certain medicines that act on the central nervous system, such as baclofen and diazepam, help to reduce the frequency and severity of muscle cramps.

There are still many unanswered questions when it comes to the exact cause of muscle cramps, but these recent findings are an important steps towards identifying the most effective and safe medicines for preventing and treating cramps.

Summary

• A muscle cramp is defined as a sudden, involuntary (spontaneous or automatic) and painful contraction of all or part of a muscle.
• A muscle cramp goes away by itself within seconds and is often accompanied by a palpable knotting of the muscle.
• Muscle cramps have certain specific features, such as pain, sudden onset and spontaneous recovery, the involvement of only one or part of a muscle, forceful contractions of the muscle, and the fact they occur more commonly in the calf and foot muscles.
• Cramps may occur in people with specific conditions, or in healthy people with no history of nerve or metabolic disorders.
• Cramps can occur during sleep, pregnancy or strenuous exercise.
• These muscle cramps are referred to as ‘benign cramps’.
• The main risk factors for muscle cramps include a family history of cramping, previous occurrences of cramps during or after exercise, an increase in the intensity and duration of exercise, and inadequate training for the activity.
• Muscle fatigue increases a person’s risk for developing muscle cramps.
• Recent experimental findings have suggested that spinal mechanisms are involved in the development of muscle cramps.
• These recent findings are an important step towards identifying the most effective and safe medicines for preventing and treating cramps.

References

1. Minetto E, Holobar A, Botter A, Farina D. Origin and Development of Muscle Cramps. Exercise and Sports Sciences Review2013; 41(1): 3-10.