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Muscle Spasms

What Are They, Causes, Diagnosis, and More

Author: Lily Guo

Editors: Alyssa Haag, Kelsey LaFayette, BAN, RN

Illustrator: Jillian Dunbar

Copyeditor: Joy Mapes


What is a muscle spasm?

A muscle spasm, also known as a charley horse or muscle cramp, refers to the involuntary and forceful contraction of a muscle, most commonly in the thighs, calves, feet, hands, and arms. They can also occur in the abdomen or along the rib cage. Muscle spasms are typically harmless, but they may result in an inability to use the affected muscle for a short period of time. 

What causes muscle spasms?

Muscle spasms can occur due to several causes, including a lack of nutrients, muscular tension, overuse of the muscle, increased demand of blood flow, or various underlying medical conditions.

Dehydration and imbalances of electrolytes (e.g., sodium, calcium, potassium, magnesium) can prevent muscle cells from receiving a necessary nutrient supply, causing them to become more prone to spastic and random contractions. Occupations that require working in hot environments (e.g., construction and factory workers, athletes) may predispose an individual to dehydration and subsequent muscle cramps.

Spasms due to muscular tension or overuse are typically experienced when holding a certain position for too long or when exercising without stretching the muscles. Similarly, strenuous exercise can cause muscular tension and lead to an increased demand for blood flow to the muscles. If the body cannot meet the demands of the muscle cells, muscle spasms can result. The risk of muscle cramps also increases with age, excess body weight, and pregnancy. However, in many cases, the exact cause of a muscle spasm may be unknown.

While muscle spasms are typically harmless, they may be tied to an underlying medical condition. Arteriosclerosis, a condition that causes narrowing of the arteries, is one example. In an individual with arteriosclerosis, blood flow to the extremities (e.g., the arms and legs) can be compromised, leading to oxygen and nutrient deprivation that may cause muscle cramps. Nerve compression in the lumbar spinal cord, the lowest major portion of the spinal cord, can be another trigger for muscle spasms, specifically cramping of the legs that worsens when walking long distances. Notably, neurodegenerative conditions, such as multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS), are associated with muscle spasms.

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What does a muscle spasm feel like?

The experience of a muscle spasm can range from minor discomfort with accompanying stiffness to a sudden, tight, and intense pain. This pain may prevent normal muscle function. During a spasm, there may also be visible muscle knots or twitching of the affected muscle when the muscle contracts, and the muscle may feel hard to the touch. Spasms are involuntary and may take time (i.e., seconds to minutes) to subside. Afterwards, the muscle may feel sore and tender. 

How are muscle spasms diagnosed?

A clinician typically determines the diagnosis of a muscle spasm after considering the individual’s full history of symptoms and physical examination. The clinician may want to know about the onset of the pain, how long the muscle spasms last, and how frequently they occur. Other helpful information may include which muscle or muscles are affected, whether the spasms occur consistently in the same muscles or affect various muscles, and the circumstances surrounding the spasms. Obtaining a full personal and medical history (e.g., occupation, hobbies, history of genetic disorders) can help the clinician rule out underlying factors predisposing the individual to muscle spasms.

If the individual’s medical history and physical examination are not sufficient to diagnose muscle spasms, the clinician may order blood tests to check the individual’s levels of sodium, potassium, calcium, and magnesium. A creatine phosphokinase (CPK) blood test can be used to detect muscle breakdown. CPK is released as a result of muscle damage, which can occur if muscle spasms are prolonged.

If there is concern for arteriosclerosis, imaging tests, such as ultrasound or magnetic resonance imaging (MRI), can be ordered to assess the blood vessels for narrowing. A computed tomography (CT) angiography, which involves injecting dye into an artery near the groin or wrist, can also be used to assess blood flow in the arteries.

Lastly, an electromyography (EMG), which tests the muscle’s response to electric stimulation, may be ordered to rule out any disorders of the nervous system, including MS and ALS, that could potentially cause muscle spasms

How are muscle spasms treated?

Often, muscle spasms do not require treatment since they typically disappear on their own. An individual may be able to ease a muscle spasm in the moment by stopping any activity that could have triggered the muscle twitches and attempting to gently stretch and massage the affected muscle. Applying gentle heat, such as with a heating pad, to tense or tight muscles can also relieve symptoms. If the pain persists, individuals may consider taking over-the-counter pain relievers, like ibuprofen, acetaminophen, or naproxen.

If the muscle cramps cause severe and recurring discomfort that does not improve with rest, a clinician may be consulted to rule out any underlying causes. Leg swelling, redness, and muscle weakness are additional indicators to seek medical consultation. In such cases, clinicians may prescribe muscle relaxants (e.g., baclofen, benzodiazepines) to inhibit painful contractions, and they may advise exercise therapy -- light, non-strenuous exercise techniques -- to stretch the muscles and prevent further muscle spasms.

In addition to stretching before and after exercising, drinking adequate amounts of fluid prior to exercise may help prevent muscle spasms

How long do muscle spasms last?

Muscle spasms can last anywhere from a few seconds to 15 minutes or longer. Within that time frame, multiple muscle spasms may occur before ultimately subsiding. 

What are the most important facts to know about muscle spasms?

A muscle spasm is the forceful and involuntary contraction of a muscle, usually in the upper or lower extremities. While painful, muscle spasms are generally harmless and can occur as a result of electrolyte imbalance, dehydration, or muscle overuse. Older age, excess body weight, pregnancy, and certain occupations can predispose an individual to muscle cramps. In certain cases, muscle spasms may be tied to an underlying health condition, such as arteriosclerosis or nerve compression. If muscle spasms recur and do not improve with rest, a clinician may be consulted for medical advice, diagnosis, or treatment. Diagnosis is typically made based on the individual’s medical history and the results of their physical exam. If the cause of muscle spasms can not be elucidated based on an exam, a clinician may order further testing (e.g., blood tests, imaging, EMG) to determine the diagnosis. Treatment is not usually required for most muscle cramps. However, drinking fluids and stretching prior to exercise may help reduce the frequency of muscle spasms, and applying gentle heat to a spasming muscle may relieve symptoms.

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Related links

Muscle Contraction
Skeletal Muscle Histology
Motor neurons and muscle spindles
Neuromuscular junction and motor unit
Sliding filament model of muscle contraction

Resources for research and reference

Cleveland Clinic. (2021, March 11). Muscle spasms. In Cleveland Clinic: Health library, Diseases & conditions. Retrieved March 8, 2021, from https://my.clevelandclinic.org/health/diseases/15466-muscle-spasms

Mayo Clinic Staff. (2021, March 3). Muscle cramp. In Mayo Clinic: Health information, Diseases and conditions A-Z. Retrieved March 8, 2021, from https://www.mayoclinic.org/diseases-conditions/muscle-cramp/symptoms-causes/syc-20350820

Wedro, B., & Shiel, W., Jr. (2021, February 26). Muscle spasms. In MedicineNet. Retrieved March 31, 2021, from https://www.medicinenet.com/muscle_spasms/article.htm