Some people deal with muscle cramps (Charley horses) on occasion, and others experience cramping multiple times each week.



While they aren't harmful, they can be pretty painful. And while the exact cause of cramping isn't known, you may be able to reduce the likelihood of getting them.



In this article, I'll address the following concerns:







What is a muscle cramp (Charley horse)?



A muscle cramp is a "painful, spasmodic, involuntary contractions of skeletal muscle during or immediately after physical exercise" (Schwellung MP et al.).



A cramp isn't the same as a muscle spasm. Spasms rarely cause pain and cause light, repeated contractions as opposed to a constant and significant contraction.



A Charley horse is a muscle cramp in the leg. The slang term stems from baseball as far back as the late 1800s.



Muscle cramps usually fall into two categories:




Exercise-associated muscle cramps (EAMC): Cramps that occur during or immediately after exercise in the muscles used during training or prolonged physical labor or activity.



Rest cramps or nocturnal cramps: Cramps that occur at night, most often in the thighs, calf muscles, or feet.




Pregnant women and older people are more likely to experience rest or nocturnal cramps. They are not the same as restless leg syndrome.



What causes muscle cramps?



We often assume scientists know everything about the human body. Yet, there’s a lot we don’t yet fully understand. The cause of muscle cramps is one such issue.



Exercise physiologists and scientists fall into two camps when it comes to the cause of muscle cramps. They believe cramps are caused by:




Dehydration or electrolyte imbalance



Nervous system excitation




Though most people have been sold the idea that cramping is about hydration and electrolytes, the evidence shows that’s probably not the primary cause.



Electrolyte imbalance and dehydration



High-quality research dating back to the 1920s and 1930s showed that physical labor performed under high heat caused cramping. Miners, ship’s stokers, and construction and steel mill workers were prone to muscle cramps.



Researchers observed that drinking plain water made the cramping worse.



Back then, they could measure blood levels of chloride, but not sodium, and noticed that low chloride levels were associated with higher rates of cramping. Today, we know that chloride and sodium levels go hand in hand, and sodium is the more significant concern.



In reality, sodium, potassium, magnesium, and calcium all play essential roles in muscle contraction and relaxation, which is why most electrolyte replacements contain all of these micronutrients.



Soccer, American football, and basketball players often cramp as well. Some research shows that football players who sweat out higher concentrations of sodium are more likely to cramp.



When it comes to the electrolyte hypothesis, one thing is clear: Drinking plain water does not reduce the occurrence of cramps. It increases it. 



When you drink only plain water while excreting significant amounts of sodium (salt) through sweat, you dilute your body’s sodium concentration. 




In a controlled environment, severe restriction of dietary sodium intake can result in hyponatraemia and may be associated with generalised skeletal muscle cramping in the absence of exercise.
Maughan RJ, et al.



Consider that statement in light of today’s salt-demonizing dietary recommendations.



If you severely cut back on salt intake or drink an excess of plain water, you can cause hyponatremia. Older adults often have pre-existing medical conditions or take medications that may disrupt their electrolyte balances. Following a low salt diet may lead to ongoing problems with cramping.



As an example, the use of low-sodium dialysis fluids in renal patients may trigger muscle cramps.



Though some research shows consuming electrolytes during intense physical activity reduces the occurrence of EAMC,