What Is A Muscle Cramp?

Introduction

Muscle cramps are defined as the continuous, involuntary, painful and localised contraction of a whole muscle group, a single muscle or specific muscle fibres.¹ Cramps tend to last anywhere from a few seconds to minutes. Exercise-related muscle cramps most commonly need therapeutic interventions during sports. Heat-associated muscle cramps are frequently observed in sports, exercise and physical activity. This is thought to be a result of a loss of sweat and electrolytes. Exercise-associated muscle cramps are common and frustrating for athletes and those who are physically active. Exercise-associated muscle cramps normally occur in muscles that cross multiple joints. Their severity ranges from mild to serious. Yet, the exact cause is poorly understood and appears to vary. Whilst the experience of pain is usually limited to a certain area, the cause may not necessarily localised and can involve the whole body system.^1,2

It has been observed that exercise-associated muscle cramps are more common during the hottest months of the year and that incidence varies by sport, age and sex. It has also been shown that less experienced runners, older runners and those running faster were at a higher risk of experiencing muscle cramps.²

Currently, there are no studies looking only at muscle cramps, but rather ones investigating them alongside other variations. However, the following topics may shed some light on the epidemiology of muscle cramps.¹

• 80% of cramps occur in the calf
• Nocturnal cramps are thought to impact 6% of the adult American population and appear to be related to heart conditions and depression.
• In China, cramps are shown to affect the calf area of pregnant women. The incidence increases as pregnancy develops, with the highest incidence being in the third trimester.
• An American study has shown that 46% of patients with chronic obstructive pulmonary disease suffer from muscle cramps.
• An American study has shown that 74% of muscle cramps occur in athletes in hot conditions.

Nocturnal leg cramps

Nocturnal leg cramps impact 37% of the population over 60 years of age in America. Most commonly, the calf is the area affected. As a result of cramping, sleep is disrupted, and quality of life can be reduced. The exact cause of this type of cramp is unknown. Suggestions for a cause include standing at work and performing high levels of physical activity. Some predisposing factors could be electrolyte disturbances, neurological conditions, hormonal imbalances, metabolic disturbances or compressions of nerve roots. Drugs such as statins and diuretics could also be involved. Treatment is generally conservative, with techniques such as deep massage or stretching.¹

Muscle cramps in pregnant people

Leg cramps are commonly observed in pregnant individuals, with them being experienced by around 50% of pregnant people. They are particularly common during the third trimester and during the night. Again, the cause is unclear. Potential causes could involve neuromuscular function, weight gain, nerve compressions, blood flow, or increased work by muscles. It is known that pregnancy cramps have not to do with foetal growth problems. However, there may be a relationship between night cramps and snoring, which could be associated with problems with foetal growth and early births.¹

Calcium was suggested as a way to reduce muscle cramps. However, the evidence for its effectiveness is poor. There is stronger evidence for salt, but this may not be applicable due to dietary considerations. Currently, it is not possible to suggest a multivitamin with mineral supplements as it is not clear which ingredient is helping with cramps. If cramps are particularly bothering a woman during pregnancy, the most suggested prescription would be magnesium lactate or citrate.⁴

Exercise associated muscle cramps 

This type of muscle cramp is common shortly after or during exercise. There are two suggestions regarding exercise-associated muscle cramps. The first concerns dehydration and electrolyte balance. The second looks at a transient peripheral neurological disorder. Findings show that neural fatigue may contribute to muscle cramps. Stretching is used to lessen the muscle cramp.¹

While most patients can carry on to finish their exercise after muscle cramps, some athletes find they are unable to do so. In this case, rest is suggested to allow the neuromuscular activity to normalise. Pain relief can be provided by massage, electrical stimulation and cryotherapy.³

Neurogenic and myogenic muscle cramps

Neurogenic muscle cramps are localised to peripheral and central areas such as neuromuscular junctions. Myogenic muscle cramps typically result from disrupted energy production in muscle cells, most commonly occurring in metabolic myopathies linked to glycogen and lipid disorders. Investigations into muscle cramps should consider whether the cramp is neurogenic or myogenic. Needle EMG can be useful in doing this. For myogenic cramps, diagnosis and investigation should look at diagnosing underlying metabolic myopathies. If cramps are not due to an isolated finding, they can be determined to be of unknown cause.³

Treatment and management of muscle cramps

Cramps that occur infrequently and don’t impact a person’s life seldom need treatment. Also, there is no evidence to suggest that muscle cramps lead to any long-term damage to muscles, and serious damage in the form of tendon ruptures is extremely rare. There is some evidence to suggest that vitamin B supplementation can decrease the frequency of muscle cramps.³

Frequently used treatments and management techniques are:¹

• Static stretching
• Deep tissue massages
• Warming up thoroughly before exercise
• Hydrating with plain water or a carbohydrate-electrolyte drink
• Magnesium supplement (although evidence is weak)

If symptoms persist, it is recommended that you should seek advice from a medical professional.

Diagnosis of muscle cramps

Cramps are painful contractions lasting for a short duration and can be separated from other types of muscle contractions because of this.¹

Muscle cramps can also be assessed using a patient’s clinical history, as they are rarely seen during investigations. The frequency of cramps is used to assess severity, as those with cramps can count distinct episodes and separate these episodes from post-cramp soreness. Location is also considered when severity is being diagnosed.²

For diagnosis of exercise-associated muscle cramps, diagnosis is purely based on a thorough clinical examination and history. Reported symptoms include noticeable pain, cessation of activity, muscle twitching before cramps begin, rigid cramping muscles, locked joints, and reduced range of motion.²

Conclusion

Muscle cramps are painful muscle contractions which are short-lived, lasting from seconds to minutes. They rarely cause any long-term damage and often do not require treatment. There are many different forms of muscle cramps, including nocturnal cramps, cramps in pregnant women and exercise-associated muscle cramps. The causes of muscle cramps are largely undefined, with some suggestions pointing towards hydration and electrolyte imbalance. Treatment often includes stretching. Prevention can include proper hydration, muscle heating and stretching. Muscle cramps are typically diagnosed using the patient’s history, as they are rarely present during clinical examination.