Effective treatment options and preventative strategies for cramps remain elusive
A MUSCLE CRAMP IS A HYPEREXCITABLE NEUROLOGIC PHENOMENON of excessive, involuntary muscle contractions.1 Skeletal muscle cramps are commonly referred to as charley horses, stitches, knots and muscle spasms. Numerous theories exist as to the causes of muscle cramps, but no explanation has been definitively accepted. A muscle cramp could come on quickly and end just as quickly. Most muscle cramps last seconds to minutes. Because muscle cramping occurs in a variety of situations and environments, presentations can vary, from the small muscles of the hand, like writer’s cramp, to the entire body locking up. Due to the variety of causes and multiple presentations, effective treatment options and preventative strategies remain elusive.
Exercise-associated muscle cramps (EAMC) are a type of cramp experienced among athletes during or immediately after participation in sports. Current belief is EAMC is the result of muscular fatigue resulting from repetitive and sustained muscle contraction.
Risk factors for developing muscle cramps
Trying to predict when a cramp will occur or who will suffer from one is arbitrary as the causes are not well recognized. However, there are common denominators found in those who experience cramps that might help estimate the risk of developing cramps and offer considerations for prevention and treatment. The following risk factors increase the chances of developing a muscle cramp:
Dehydration or depleting body fluids while exercising, particularly in excessively hot and humid environments. This mechanism suggests an electrolyte imbalance of sodium, calcium and potassium promotes cramping.
Nocturnal leg cramps (NLCs), also known as sleep-related leg cramps. The most affected muscle area is the calf. NLCs mostly affect people over age 60 and may indicate that cramps result from neurological causes. This disorder also appears to be related to the presence of other diseases, such as heart failure, nocturnal apnea and depressive syndrome.2
Tonic muscles, the nature of which is to shorten and tighten when placed under stress or injured. These muscles contain mostly slow twitch, endurance fibers. Tonic muscles prone to cramping include hamstrings, iliopsoas, gastrocnemius and soleus.
Pregnancy. Leg cramps during pregnancy are related to low electrolyte levels, including calcium and magnesium, circulation changes, pressure on the nerves caused by the growing fetus and stress on the leg muscles from carrying extra weight.
Medications. Commonly prescribed medication classes that have a potential link to cramping are diuretics, statins and long-acting β2-agonists.
It is important to state that these risk factors are associated with cramping and are not considered primary causes of cramping.
Current theories on the mechanism of muscle cramping
Dehydration-electrolyte theory is the classical explanation for muscle cramps. The theory states dehydration and a loss of electrolytes through sweating can cause muscle cramps.
Studies show cramping was associated with loss of electrolytes through sweat, though dehydration was not always implicated as the workers drank large amounts of plain water. Hyponatremia was specifically implicated. One interesting study gave factory workers plain water to drink throughout the day, while another factory with similar working conditions provided workers with water and sodium. The workers in the sodium group had a dramatic decrease in the incidence of cramping.3
A new study has demonstrated water intake after 2% dehydration induced by downhill running in the heat increased muscle cramp susceptibility, but ingestion of fluid containing electrolytes such as sodium, potassium, chloride and glucose after the dehydration made muscles more immune to cramping.4
The results suggest it is better to drink fluid containing electrolytes to prevent exercise-associated muscle cramps. It is necessary to note there were also athletes who were well-hydrated and had good electrolyte consumption who still experienced cramping. Although cramping often occurs in prolonged exercise in the heat, cramping can also occur without dehydration or electrolyte imbalance and in cool environments.5
Altered neuromuscular control
The altered neuromuscular control theory is the one that currently has the most scientific evidence in support of it. ‘Neuromuscular control’ is how the nervous system controls the muscles. This theory is based on the belief fatigue causes changes in the firing patterns of the nervous system which in turn leads to muscle cramps. The increased fatigue is thought to cause increased muscle activation and lead to uncontrolled contraction, leading to a muscle cramp.
Muscle tone is controlled via the spinal reflex. There are muscle spindle receptors in the muscle that increase the nerve’s activity and increase the muscle tone/contraction. The Golgi tendon organs decrease the nerve’s activity and decrease the muscle tone/contraction when stimulated. These receptors have the ability to influence each other’s output.6 Increased firing of the muscle spindle will lead to a decrease in Golgi tendon receptor activity and cause muscle tone to increase.
Infrequent cramps that do not interfere in someone’s life rarely need evaluation or treatment.
Most cramps typically go away without treatment and can be cared for at home.
Common home care for cramps includes:
- Gently massaging the cramped muscle
- Applying heat or ice to the affected muscle
- Drinking water containing electrolytes before, during and after exercise
- Stretching before and after exercise
Proactive steps to help lessen or prevent cramps include:
- Maintaining optimal skeletal alignment to reduce stress and help keep muscles in their optimal length for better function
- Regularly using custom flexible three-arch orthotics. Custom orthotics that align all three arches of the foot can help normalize skeletal alignment and reduce the impact of heel strike on the system. They may be particularly useful during pregnancy.
- Taking magnesium supplements. In pregnant women, there is ample evidence magnesium replacement is helpful in managing muscle cramps.6
- Engaging in low-impact aerobic exercise, which has been shown to be helpful in preventing nocturnal muscle cramps.7
MANUEL DUARTE, DABCO, DABCSP, DACBA, MSAc, MS, is an international lecturer, author and researcher. He is a graduate of Long Island University and the National University of Health Sciences (NUHS) and a professor emeritus at NUHS. Duarte is the previous owner of Body Fitness Physical Medicine and Sports Injury Clinic.
- Jansen PH, et. al. Diagnosis and differential diagnosis of muscle cramps: A clinical approach. J Clin Neuromuscul Dis. 2002;4(2):89-94.
- Garrison SR, et. al. Nocturnal leg cramps and prescription use that precedes them a sequence symmetry analysis. Arch Intern Med. 2012;172(2).
- Dill D, et. al. Industrial fatigue. J Ind Hyg Toxicol. 1936;8:417-31.
- Water intake after dehydration makes muscles more susceptible to cramp but electrolytes reverse that effect. BMJ Open Sport Exerc Med. 2019;5(1). Published online Mar. 5 2019.
- Wing Yin L WY, et. al. Cramping in sports: Beyond dehydration. Strength and Conditioning Journal. 2014;36(5):44-52.
- Dahle LO, et. al. The effect of oral magnesium substitution on pregnancy induced leg cramps. Am J Obstet Gynecol. 1995;173:175-180.
- Coppin RJ, et. al. Managing nocturnal leg cramps: calf-stretching exercises and cessation of quinine treatment: a factorial randomized controlled trial. Br J Gen Pract. 2005;55:186-19.