Nighttime leg cramps, often called charley horses, are sudden and painful muscle contractions that usually affect the calves, feet, or thighs. They tend to occur while resting or sleeping and can last from a few seconds to several minutes, sometimes leaving lingering soreness. Although they can feel alarming and disrupt sleep, they are generally harmless and quite common, especially as people age.

These cramps happen when a muscle involuntarily tightens and cannot relax properly. This may be linked to muscle fatigue, prolonged positions (like sleeping with toes pointed), or misfiring nerve signals. The exact cause is not always clear, but the result is a sharp, intense tightening that may leave the muscle tender afterward due to minor strain.

Several factors can increase the likelihood of leg cramps, including overuse of muscles, long periods of sitting or standing, dehydration, and age-related muscle changes. Pregnancy, certain medications, and conditions like diabetes or poor circulation can also contribute. Despite common belief, most people with cramps do not have serious electrolyte deficiencies.

Relief usually comes from gently stretching the affected muscle, massaging it, or walking briefly to restore circulation. Preventive steps include staying hydrated, stretching regularly (especially before bed), maintaining moderate physical activity, and avoiding prolonged inactivity. While most cases are harmless, frequent or severe cramps should be checked by a doctor.