Muscle cramps are involuntary muscle contractions that may last anywhere from a few seconds to a few minutes. They usually happen suddenly and can be very painful. The cramp can often be seen, and the affected muscle may be hard to the touch. While muscle cramps can be associated with certain serious conditions, this is rare.^[1]

There are several types of muscle cramps. In active individuals, cramps are termed exercise associated muscle cramps (EAMC). Muscle cramps in the legs or feet in bed are often termed rest cramps, or nocturnal leg cramps.^[1]

The main symptom of a muscle cramp is a sudden, involuntary, and painful contraction of a muscle. ^[1] Unfortunately, the cramp can still cause pain after it is over, even for days.^[2] Muscle cramps can be felt as hardness of the affected muscle, and may be seen depending on muscle location and individual variability.^[1]

While muscle cramps are commonly believed to be caused by dehydration or electrolyte imbalances, they are more likely due to muscle fatigue and nerve dysfunction.^[3][4][4][5]

A clinical diagnosis of muscle cramps is made based on the presence of common symptoms and triggers. Symptoms are sudden muscle contraction with pain. The muscle contraction can be felt as hardness to the touch, and may also be seen in certain patients. There are various triggers that can set things off, depending on the kind of muscle cramp. Exercise associated muscle cramps (EAMC) can occur after vigorous exercise (often endurance-based), usually in a muscle that was just worked out. Another characteristic of muscle cramps is that they can occur when attempting to contract a muscle already at its shortest length. Muscle cramps can also occur at rest, or after a trivial movement, especially when the muscle is relaxed and shortened.^[2][4]

Drugs are not recommended as first line treatment of routine muscle cramps. Muscle cramps can be often relieved by stretching of the affected muscle or massage.^[6] Stretching the muscle for 10 to 20 seconds, followed by 20 to 30 minutes of passive tension on the muscle (i.e., keeping the muscle lightly stretched but in a comfortable relaxed position), and then by rest, is often effective after the initial muscle contraction has subsided (in order to prevent further cramping).^[4]

There is limited evidence for supplementation for the treatment of muscle cramps.

Magnesium has been found to be ineffective for preventative use of muscle cramps in the elderly, and has mixed results in pregnancy.^[1][7][8][9]

One small trial of a B complex supplement containing 50 mg of fursultiamine (a derivative of Thiamine), 250 µg hydroxocobalamin (vitamin B12), 30 mg of pyridoxal phosphate (the active form of vitamin b6), and 5 mg of vitamin b2 showed 86% remission rate of muscle cramps in nocturnal leg cramps in elderly patients with hypertension. However, completion rate and compliance were not discussed in the study.^[10] Another small study found a B complex (100 mg thiamine, 40 mg pyridoxine) effective in reducing muscle cramp frequency and intensity in pregnant study participants.^[11]

Calcium and vitamin D supplementation (both together and alone) have been studied for leg cramps in pregnancy, but they were not found to be consistently effective at reducing cramping.^[12]

While dehydration and electrolyte abnormalities are one hypothesis for the cause of muscle cramps, the overall weight of the evidence suggests otherwise. For example, one trial of Ironman triathletes found no significant differences in post-race body mass losses (i.e., dehydration) and serum electrolytes in those with and without cramps.^[3] If cramps were based on system-wide hydration and electrolytes, there is no compelling explanation of how spasms happen in specific muscles. Instead, epidemiologic, animal, and electromyogram data indicate that cramps are more likely due to abnormal muscular control in the spine.^[13][4]

If an individual does find that their muscle cramps are improved by hydration and electrolytes, diet is a strong way to apply these therapies. For example, consumption of water-dense fruits for hydration, salt for sodium (caution to those with hypertension), dairy for calcium, and various vegetables, fruits and/or for potassium and magnesium.

Otherwise, focus on rest is important to relieve EAMC.^[4] Diet-wise this means focusing on consuming the appropriate daily amounts of meals of carbohydrates, proteins, and fats for a person’s activity level.

High-quality evidence shows that quinine derivatives, which are often used to treat parasitic infections like malaria, can benefit cramps. However, they are no longer recommended due to their potential for toxicity. There is also some potential for adverse reactions with quinine drinks such as tonic water , even though the dose of quinine in tonic water (40-80 mg/L) is much lower than the therapeutic dose for muscle cramps (200-300 mg daily).^[14]

Lower-quality evidence shows that nafronyl, calcium channel blockers such as diltiazem, and lidocaine may have some impact on muscle cramps.^[15]

IVs of magnesium, calcium, and even diazepam (also known as valium) have been used to treat severe forms of cramping, but this is cautioned against due to potential complications such as hypotension or respiratory depression.^[4]

Hydration and electrolyte drinks are frequently given as a treatment for muscle cramps, though the causative role of dehydration and electrolyte deficiency deficiency in muscle cramps remains controversial.^[4]

The underlying cause of muscle cramps is not well understood.^{[5] [5]} Much of the evidence is nonscientific or observational.^[16]

One hypothesis for the cause of muscle cramps is because of dehydration and/or electrolyte abnormalities. However, trials have shown no significant correlations between hydration, serum electrolyte levels, and muscle cramps.^[3][4]

A stronger hypothesis may be muscle fatigue and nerve dysfunction, and would help to explain why muscle cramps can occur after changes to exercise (e.g., unusually high volume or intensity, or unusual heat or humidity in the environment).^[4]PMID:33998664]

The cause may ultimately be multifactorial. People with muscle cramps should be examined by a licensed healthcare professional to explore the above potential causes, along with more rare causes of muscle cramps, such as:^[2]

• Drugs (e.g., nifedipine, cimetidine, terbutaline, salbutamol, clofibrate, penicillamine, diuretics, ethanol)^[2]
• Liver diseases, such as cirrhosis
• Neurological diseases, such as Charcot-Marie-Tooth disease^[5][1]