Painful Involuntary Skeletal Muscle Contractions

Painful involuntary skeletal muscle contractions/Charlie horse is a popular colloquial term used for painful involuntary spasms or cramps in the leg muscles, typically lasting anywhere from a few seconds to about a day. It is a sudden and involuntary contraction of one or more of your muscles. If you’ve ever been awakened in the night or stopped in your tracks by a sudden charley horse, you know that muscle cramps can cause severe pain.

Painful involuntary skeletal muscle contractions, or cramps, are common patient complaints and may be classified as examples of true cramp, tetany, contracture, or dystonia. The pathophysiologic and clinical features of each of these diagnoses are described. The approach to the patient with cramps should emphasize the history, physical examination, and, if the diagnosis is unclear, minimal routine laboratory data. Although many therapies have been proposed for ordinary cramps, the best evidence supports stretching exercises and quinine. Areas for future study of this common symptom are proposed.

Muscle cramps are a common problem characterized by a sudden, painful, involuntary contraction of the muscle. These true cramps, which originate from peripheral nerves, may be distinguished from other muscle pain or spasm. Medical history, physical examination, and a limited laboratory screen help to determine the various causes of muscle cramps. Despite the “benign” nature of cramps, many patients find the symptom very uncomfortable. Treatment options are guided both by experience and by a limited number of therapeutic trials. Quinine sulfate is an effective medication, but the side-effect profile is worrisome, and other membrane-stabilizing drugs are probably just as effective. Patients will benefit from further studies to better define the pathophysiology of muscle cramps and to find more effective medications with fewer side-effects.

A muscle  cramp is a sudden, involuntary muscle contraction or over-shortening; while generally temporary and non-damaging, they can cause mild-to-excruciating pain, and a paralysis-like immobility of the affected muscle(s). Onset is usually sudden, and it resolves on its own over a period of several seconds, minutes, or hours. Cramps may occur in a skeletal muscle or smooth muscle. Skeletal muscle cramps may be caused by muscle fatigue or a lack of electrolytes (e.g., low sodium, low potassium, or low magnesium, although the evidence has been mixed). Cramps of smooth muscle may be due to menstruation or gastroenteritis.

Types of Skeletal Muscle Contractions

 Praphysiologic muscle cramps

Paraphysiologic muscle cramps are commonly experienced, but they have no underlying medical condition. This includes cramps associated with:

  • Pregnancy – Up to 30% of pregnant women will experience leg cramps during their pregnancy, most frequently during the last trimester;
  • Exercise-The cause of exercise-associated muscle cramps (EAMC) is still largely unknown. It is believed to be highly related to physiological stress such as

Most people at some time of their life will experience an idiopathic muscle cramp. These cramps usually occur at night in the leg and foot muscles and can be triggered by even the slightest shortening of skeletal muscle.

Charley horse

Idiopathic muscle cramps can be classified into the following

  • Nocturnal cramps – Cramps that occur at night when in bed;
  • Autosomal dominant cramping disease – An inherited disease involving recurrent muscle cramping;
  • Continuous muscle fiber activity syndromes – Including Isaac’s syndrome, Stiff-man syndrome and cramp fasciculation syndrome (the uncontrollable twitching of muscles beneath the skin);
  • Sathoyoshi’s syndrome – Syndrome of progressive muscle spasm which includes diarrhea and alopecia;
  • Myokymia – Spontaneous muscle quivering;
  • Myokymia-hyperhidrosis syndrome – Myokymia paired with excessive perspiration;
  • Familial insulin resistance with acanthocytosis (spiky red blood cells) and acral hypertrophy – A rare syndrome characterized by enlarged hands and feet, velvety skin and muscle cramps;
  • Cancer-induced cramps 
  • Natural muscle atrophy – (muscle wasting): that occurs in people over 65 predisposes them to muscle cramps. 

The Symptom of Skeletal Muscle Contractions

Symptomatic muscle cramps constitute the majority of muscle cramps and are related to underlying disease in a number of different body systems.

Central and peripheral nervous system

  • Motor neuron disease including amyotrophic lateral scoliosis;
  • Parkinson’s disease;
  • Multiple sclerosis (MS);
  • Tetanus (lockjaw);
  • Radiculopathy; and
  • Peripheral neuropathies.

Muscular system

  • Some myopathies (diseases that affect skeletal muscles); and
  • Myotonia (temporary muscle stiffness or contraction).

Cardiovascular system

  • Venous disease (disease of the veins);
  • Peripheral arterial disease (arteriosclerosis); and
  • Hypertension (high blood pressure).

Diseases of the endocrine-metabolic system

  • Hypothyroidism (under-activity of the thyroid gland) and hyperthyroidism (over-activity of the thyroid gland);
  • Hyperparathyroidism (disease of the parathyroid gland); and
  • Deficiency of corticotropin (a hormone secreted by the pituitary gland).

Muscle cramps are also associated with

  • Liver cirrhosis and other liver dysfunction;
  • Bartter syndrome (disorder defect in the loop of Henle of the kidney);
  • Gitelman’s syndrome (an inherited defect in the distal convoluted tubule of the kidney);
  • Conn’s syndrome (disease of the adrenal gland);
  • Addison’s disease (disease of the adrenal gland);
  • Uraemia (an illness that accompanies kidney failure) and dialysis;
  • Heat cramps (cramps due to dehydration and electrolyte depletion);
  • Toxic.

Risk Factors for Skeletal Muscle Contractions

The exact cause of muscle cramp is not known, but risk factors may include:

  • Tight, inflexible muscles
  • Poor physical condition
  • Poor muscle tone
  • Inadequate diet
  • Physical overexertion
  • The physical exertion of cold muscles
  • Muscle injury
  • Muscle fatigue
  • Excessive perspiration
  • Dehydration – caused by, for example, about of gastroenteritis
  • Reduced blood supply (ischemia)
  • Wearing high-heeled shoes for lengthy periods.

Causes  of Skeletal Muscle Contractions

The cause of muscle cramps isn’t always known. Muscle cramps may be brought on by many conditions or activities, such as:

  • Exercising – injury, or overuse of muscles.
  • Pregnancy – Cramps may occur because of decreased amounts of minerals, such as calcium and magnesium, especially in the later months of pregnancy.
  • Exposure to cold temperatures – especially to cold water.
  • Other medical conditions – such as blood flow problems (peripheral arterial disease), kidney disease, thyroid disease, and multiple sclerosis.
  • Standing on a hard surface for a long time – sitting for a long time, or putting your legs in awkward positions while you sleep.
  • Not having enough potassium – calcium, and other minerals in your blood.
  • Being dehydrated – which means that your body has lost too much fluid.
  • Taking certain medicines – such as antipsychotics, birth control pills, diuretics, statins, and steroids.
  • Straining or overusing a muscle – This is the most common cause.
  • Compression of your nerves – from problems such as a spinal cord injury or a pinched nerve in the neck or back
  • Dehydration
  • Low levels of electrolytes such as magnesium, potassium, or calcium
  • Not enough blood getting to your muscles
  • Pregnancy
  • Certain medicines
  • Getting dialysis

Possible Causes of Skeletal Muscle Contractions

Muscle cramps can have many possible causes. They include

  • Poor blood circulation in the legs
  • Overexertion of the calf muscles while exercising
  • Insufficient stretching before exercise
  • Exercising in the heat
  • Muscle fatigue
  • Dehydration
  • Magnesium and/or potassium deficiency
  • Calcium deficiency in pregnant women
  • Malfunctioning nerves, which could be caused by a problem such as a spinal cord injury or pinched nerve in the neck or back
  • Calcium deficiency (in expectant mothers)
  • Dehydration
  • Inadequate/insufficient stretching before starting your workout
  • Malfunctioning nerves as a result of such problems as pinched nerves in the back or the neck, or spinal cord injury
  • Muscle fatigue

Drugs causing Skeletal Muscle Contractions

Always exclude a medicine-related cause. Implicated drugs include

  • Salbutamol and terbutaline
  • Raloxifene
  • Opiate withdrawal
  • Diuretics cause electrolyte loss
  • Nifedipine
  • Phenothiazines
  • Penicillamine
  • Nicotinic acid
  • Statin

Medications that can cause muscle cramps include

  • Lasix (furosemide), Microzide (hydrochlorothiazide), and other diuretics (“water pills”) used to remove fluid from the body
  • Aricept (donepezil), used to treat Alzheimer’s disease
  • Prostigmine (neostigmine), used for myasthenia gravis
  • Procardia (nifedipine), a treatment for angina and high blood pressure
  • Evista (raloxifene), an osteoporosis treatment
  • Brethine (terbutaline), Proventil and Ventolin (albuterol), asthma medications
  • Tasmar (tolcapone), a medication used to treat Parkinson’s disease
  • Statin medications for cholesterol such as Crestor (rosuvastatin), Lescol (fluvastatin), Lipitor (atorvastatin), Mevacor (lovastatin), Pravachol (pravastatin), or Zocor (simvastatin)

Cramps may also occur in association with metabolic disturbance, including:

  • Hyponatremia
  • Hypokalemia and hyperkalemia
  • Hypocalcemia
  • Hypomagnesaemia
  • Hypoglycemia

One or more of these may be the underlying etiology in many of the causes listed below. Blood tests measure the extracellular environment but do not reflect the intracellular fluid which is probably more important.

  • Arterial insufficiency.
  • Acute or chronic diarrhea.
  • Excessive heat and sweating causing Na+ depletion.
  • Hypothyroidism (associated with weakness, enlarged muscles, and painful muscle spasms).
  • Hyperthyroidism (associated with myopathy).
  • Lead poisoning.
  • Sarcoidosis.
  • Hyperparathyroidism (hypercalcemia).
  • Heavy alcohol ingestion and cirrhosis.
  • Hyperventilation-induced respiratory alkalosis.
  • Haemodialysis.
  • Parenteral nutrition.
  • Lower motor neuron disorders including amyotrophic lateral sclerosis, polyneuropathies, recovered poliomyelitis, peripheral nerve injury, and nerve root compression.

Many patients who complain of “cramps” actually have some other related phenomenon. What characteristics, then, can be helpful in making the correct diagnosis?

  • Quality – It is useful to find out about onset (abrupt or slow?), sensation (painful? stiff?), and appearance (if an abnormal posture is described, have the patient demonstrate it). With true cramps, the onset is sudden, the muscle feels taut and painful, and usually, it is visibly and palpably knotted (although this may not be readily apparent if only part of the muscle is involved).
  • Location – Determine if muscles are involved singly or in groups if certain muscles are consistently involved, and if the cramps remain limited or spread. While ordinary cramps often affect the leg (especially calf) muscles, other locations may point to a specific syndrome such as carpopedal spasms in tetany or unilateral facial involvement in hemifacial spasms.
  • Duration  Ordinary cramps last from seconds to several minutes if severe. Fleeting twitches or prolonged contractions suggest another type of disorder.
  • Precipitating or relieving maneuvers –  Attempt to uncover any relation to exercise; specifically, find out not only if the occurrence is at rest or during or after exercise but also the duration and intensity of exercise that may initiate cramps. Moreover, clarify if the cramps appear only sporadically or can be predictably expected at a certain level of exertion. One may also want to ask about other potential triggers such as movement, sensory or emotional stimuli, hyperventilation, cold, or fasting. Assess if anything alleviates the cramps.
  • The course of symptoms  A relatively recent onset suggests the possibility of acquired intercurrent illness, whereas affliction since youth may point to an inherited disorder.


  • Restless legs (Ekbom’s syndrome).
  • Intermittent claudication and ischaemic rest pain.
  • Muscle injury or strain.
  • Hypnagogic muscle jerking (when falling asleep).
  • Lumbar nerve root entrapment.
  • Ruptured Baker’s cyst.
  • Deep vein thrombosis or thrombophlebitis.
  • Peripheral neuropathy.
  • Occupational cramps – eg, writer’s cramp or musician’s cramp (focal dystonias, usually affecting the upper limb).
  • Causes of generalized muscle pain – eg, polymyositis, toxoplasmosis, alcohol-related myopathy, Guillain-Barré syndrome, polymyalgia rheumatic, Parkinsonism, fibromyalgia.

Potential investigations include:

  • U&Es
  • LFTs
  • TFTs
  • Serum calcium or magnesium
  • Creatine kinase
  • Lead levels

Limited evidence supports treating nocturnal leg cramps with exercise and stretching, or with medications such as magnesium, calcium-channel blockers, vitamin B or vitamin C. Quinine is no longer recommended to treat leg cramps.


  • In most cases the aetiology is benign and the patient needs to be reassured of this whilst steps are taken to help alleviate the problem. Exclude known causes of muscle cramps without excessive and unnecessary investigation.
  • Management depends upon the cause of the problem. Review drugs. Address any correctable problems – eg, use of diuretics and electrolyte imbalance.
  • The severity of symptoms and their impact on sleep, mood and quality of life will determine whether treatment is required. Asking patients to keep a sleep and cramp diary may be helpful to assess progress.
  • The evidence base for management of this common but usually benign condition is not strong.

Drug for Charley Horse

Types of prescription medications include

  • Analgesics – Prescription-strength drugs that relieve pain but not inflammation.
  • Anti-depressants – drugs that block pain messages from your brain and boost the effects of endorphins (your body’s natural painkillers).
  • Corticosteroids – Also known as oral steroids, these medications reduce inflammation.
  • Muscle Relaxants – These medications provide relief from spinal muscle spasms.
  • Neuropathic Agents – Drugs that address neuropathic—or nerve-related—pain. This includes burning, numbness, and tingling.
  • NSAIDs Prescription-strength drugs that reduce both pain and inflammation.
  • Opoid   Also known as narcotics, these medications are intense pain relievers that should only be used under a doctor’s careful supervision.
  • Topical Medications – These prescription-strength creams, gels, ointments, patches, and sprays help relieve pain and inflammation through the skin.


There is only limited evidence for the use of non-drug therapies for the treatment of lower-limb muscle cramps.

  • Passive stretching and massage of the affected muscle. This will help ease the pain of an acute attack – eg, for calf cramping, straighten the leg with dorsiflexion of the ankle or heel walk until the acute pain resolves.
  • Regular stretching of the calf muscles throughout the day. This may help to prevent acute attacks. Some people recommend stretching three times daily whilst others advocate stretching before going to bed.
  • Using a pillow to raise the feet through the night or raising the foot of the bed. This may help to prevent attacks in some people.
  • Note that whilst stretching exercises are unlikely to do harm, evidence for their efficacy is contradictory. In sport, stretching is widely advocated as likely to reduce injury and cramp but the quality of evidence tends to be poor, with failure to distinguish benefit from that due to improvement in physical fitness from training.
  • Avoiding over-training and risky conditions (eg, hot and humid environmental conditions) can be useful in preventing cramps


  • some preliminary studies have found that a number of people benefit from taking quinine. There is no information yet about quinine’s safety and long-term effectiveness. Some doctors may recommend quinine if the stretching has not helped, attacks are frequent, and/or the patient’s quality of life is being undermined by the leg cramps. A course of treatment usually lasts from four to six weeks – the patient takes the medication just before going to bed.
  • Pregnant women should not take quinine. Individuals who had a previous reaction to quinine, those with previous hemolytic anemia, optic neuritis, and/or glucose 6-phosphate dehydrogenase deficiency should not take quinine.
  • As the quinine dosage is very low, side effects are rare. In rare cases the patient may develop a blood disorder. Some patients may develop cinchonism after long-term quinine therapy, which may cause vomiting, nausea, vision and/or hearing problems and dizziness.

How do I Avoid Skeletal Muscle Contractions

In looking at the above risk factors, you can reduce your risk of cramping by trying the following tips:

  • Maintain your fitness.
  • Stretch regularly. 5 minutes of gentle stretching on the floor during a TV ad break each evening can be sufficient to drastically improve flexibility. Hold each stretch so that you are straining but not feeling pain, and release after 30 seconds.
  • Ensure you are getting the right minerals to maintain proper muscle function. Eating a varied diet is the best way to get a range of minerals. Cacao is a rich natural source of magnesium.
  • Try a supplement. Getting your RDI of some minerals is tough to do from food alone (adult women, for example, need 1300mg of calcium each day. That’s more than 4 glasses of milk). If you think you are struggling to get enough nutrients into your diet to stop cramping, you may benefit from taking a multivitamin that contains magnesium and nutrients to aid muscle relaxation or:
  •  Incorporate a Magnesium powder sourced from wholefoods (more readily absorbed by the body than tablets) OR Cacao Powder (cacao is rich in magnesium and potassium). It is possible to have too much magnesium, yet the side effects at the upper limit of recommended daily magneisum intake have not been shown to produce toxic effects when ingested as naturally occurring magnesium in food (according to as contrasted against magnesium tablets.
  • Try a Calcium Supplement or Chia Seeds (chia seeds are incredibly rich in calcium, critical for muscles).
  • Ensure you are drinking enough fluids throughout the day, especially before, during and after periods of physical exertion. Drink a glass of water first thing when you wake up in the morning to top up any fluids lost during sleep.
  • Know your exercise boundaries. In hot/humid conditions, take it easy to avoid excessive perspiration.
  • If muscle cramps persist despite trying the above, see your doctor. Genetic factors, diseases such as atherosclerosis or sciatica or some prescription medications may be contributing.

Natural remedies for muscle cramps

  • Mix 1 part oil of wintergreen – (available from pharmacies or essential oils suppliers) with 4 parts vegetable oil and massage it into the cramp. Wintergreen contains methyl salicylate (related to aspirin), which relieves pain and stimulates blood flow. You can use this mixture several times a day, but not with a heating pad–it could burn your skin. (Caution: Note that wintergreen is highly toxic when swallowed.)
  • Cramp bark has long been used as a muscle relaxant – A medical herbalist can makeup both a tonic to be taken internally and a rubbing lotion from this herb.
  • Take a long, warm shower or soak in the bath – For added relief, pour in half a cup of Epsom salts. The magnesium in Epsom salts promotes muscle relaxation.
  • Place an electric heating pad or a hot face washer – on the troublesome muscle to relax the cramp and increase blood flow to the affected tissue. Set the pad on low, apply for 20 minutes, then remove it for at least 20 minutes before reapplying.
  • Find the central point of the cramp – Press this spot with your thumb, the heel of your hand or a loosely clenched fist. Hold the pressure for 10 seconds, ease off for 10 seconds, then press again. You should feel some discomfort but not excruciating pain. After repeating this action several times, the pain should start to diminish.
  • Muscle cramps from dehydration – Cramps are often caused by dehydration, so if you get cramps frequently, drink more water.

If you tend to get cramps during exercise, drink at least 2 cups of water 2 hours before each work-out. Then stop and drink 100–250ml every 10 to 20 minutes during your exercise sessions. If you sweat a lot, consider a sports drink, such as Lucozade Sport, that replaces lost sodium and other electrolytes.

Minerals that prevent muscle cramps

  • Low levels of minerals known as electrolytes – which include potassium, sodium, calcium and magnesium, can contribute to cramps. You probably don’t need more sodium (salt) in your diet, but you may need other minerals. Good food sources of magnesium are wholegrain breads and cereals, nuts and beans. Potassium is in most fruits and vegetables, especially bananas, oranges and apricot. And dairy foods supply calcium. If you change your diet and you still get cramps, take 500mg of calcium and 500mg of magnesium twice a day, adding up to 1000mg of each supplement, or as professionally prescribed. Some people who get leg cramps due to a magnesium deficiency obtain rapid relief from supplements. Don’t take magnesium without calcium; the 2 minerals work as a pair.
  • If you take diuretics for high blood pressure – your increased need to urinate may be robbing you of potassium. The result is a condition called hypokalemia, which can cause fatigue, muscle weakness and muscle cramps. Ask your doctor if you can switch to a blood-pressure medication that isn’t a diuretic.

Muscle cramps at night

  • Drink a glass of tonic water – which contains quinine, before bedtime. Research supports the use of quinine for nocturnal leg cramps, but don’t take it as tablets; they can have serious side effects, such as ringing in the ears and disturbed vision.
  • To prevent night-time calf cramps – try not to sleep with your toes pointed. And don’t tuck in your sheets too tightly as this tends to bend your toes downwards, causing cramp.
  • Take 250mg of vitamin E a day –  to improve arterial blood flow, thus potentially preventing night-time leg cramps. Muscle cramps are usually temporary and don’t cause permanent damage, but contact your doctor if the cramp or spasm lasts for more than a day, or if it continues to bother you despite trying these home remedies. And call immediately if the spasm occurs in the lower back or neck, accompanied by pain that radiates down your leg or into your arm. Finally, if abdominal cramps occur in the lower right-hand part of your belly, it could signal appendicitis.


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Painful involuntary skeletal muscle contractions

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