What causes cramp?
Cramp involves the involuntary spasm of muscles, usually in the legs, that is transient in nature. It can occur in isolation or as a symptom of several other related health conditions. As a result, there are many possible causes of cramp and factors that are involved.
Idiopathic Cause
Idiopathic cramp refers to cramp that occurs without a known cause. It has been theorized that symptoms begin when a muscle is already in a shortened position and stimulated to contract further, causing a spasm. However, many people experience cramp occasionally without a clear, identifiable cause.
Muscle Overuse or Strain
Cramp can present as a result muscle strain or overuse, particularly over a long period of time. This is common during or following heavy exercise or after holding a particular position for a prolonged period.
Pregnant women are also more likely to suffer from cramps for the same reasoning. The additional weight while pregnant strains the muscles required to maintain coordination, and cramps can occur as a result.
Inadequate Blood Supply
The blood supply to the muscles is also important for healthy function, and inadequate supply may cause cramp. This is evident in individuals that suffer from arteriosclerosis, which involves narrowing of the arteries, who are prone to cramp.
Nerve Compression
Lumbar stenosis, which involves compression of nerves in the spine, may cause cramp, which typically worsens with continues movement. In some cases, leaning forward slightly in a flexed position can help to improve symptoms or delay onset. This also affects some individuals when they are sleeping.
Mineral Depletion
Abnormal concentration of the salts in the bloodstream can also cause cramp, including depletion of potassium, calcium or magnesium, known as hypokalemia, hypocalcaemia and hypomagnesia respectively.
Dehydration can result in the depletion of important minerals in the blood, leading to cramp. Additionally, some medications such as diuretics can alter the production of urine and change the concentration of salts in the bloodstream.
Underlying Health Conditions
There are also several health conditions that are associated with cramp and may be responsible for causing symptoms in some cases. Related health conditions include:
- Neurological conditions (e.g. motor neuron disease or peripheral neuropathy)
- Liver disease that leads to the accumulation of toxins in the blood
- Some bacterial infections (e.g. tetanus)
- High concentrations of toxins (e.g. lead, mercury) in the blood
- Dehydration can change the balance of electrolytes
- Abnormal thyroid activity
- Liver cirrhosis
- Diabetes
The symptoms of cramp can typically be resolved if the underlying cause is identified and adequately managed.
Medications
Some individuals may experience muscle cramps as an adverse effect when taking particular medications. These include:
- Diuretics for hypertension or oedema
- Statins used to manage high cholesterol
- Raloxifene used to prevent osteoporosis
- Nifedipine used to treat angina
- Nicotinic acid used to manage high cholesterol
Other Risk Factors
In addition to the causes outlined above, there are several risk factors for cramp that are associated with an increased probability of an individual to suffer from the condition.
For example, there is a correlation between age and susceptibility to cramp. It is hypothesized that this effect is due to the reduction in muscle mass over time, increasing the stress on the muscles that remain. The attachment of the tendons to the muscles may also be involved.
Additionally, pregnancy women are at an increased risk of suffering from cramp, as well as individuals that participate in high-intensity sport activities. These factors are likely to be related to the causes already discussed and the increased strain on the muscles.
References
- http://www.mayoclinic.org/diseases-conditions/muscle-cramp/basics/causes/con-20014594
- http://www.nhs.uk/CONDITIONS/LEGCRAMPSUNKNOWNCAUSE/Pages/Causes.aspx
- http://patient.info/health/Cramps-in-the-Leg
Further Reading
- All Cramp Content
- Preventing leg cramps
Last Updated: Aug 23, 2018
Written by
Yolanda Smith
Yolanda graduated with a Bachelor of Pharmacy at the University of South Australia and has experience working in both Australia and Italy. She is passionate about how medicine, diet and lifestyle affect our health and enjoys helping people understand this. In her spare time she loves to explore the world and learn about new cultures and languages.
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