Heat cramps are exertion-induced muscle contractions that occur during or after exertion in the heat.
Although exertion may induce cramps during cool weather, such cramps are not heat related and probably reflect lack of fitness. In contrast, heat cramps can occur in physically fit people who sweat profusely and replace lost water but not salt, thereby causing hyponatremia. Heat cramps are common among the following:
Cramping is abrupt, usually occurring in muscles of the extremities. Severe pain and carpopedal spasm may incapacitate the hands and feet. Temperature is normal, and other findings are unremarkable. The cramp usually lasts minutes to hours. Diagnosis is by history and clinical evaluation.
Cramps may be relieved immediately by firm passive stretching of the involved muscle (eg, plantar dorsiflexion for a calf cramp). Fluids and electrolytes should be replenished orally (1 to 2 L water containing 10 g [2 level tsp] salt or sufficient amounts of a commercial sports drink) or IV (1 to 2 L 0.9% saline solution). Adequate conditioning, acclimatization, and appropriate management of salt balance help prevent cramps.
Last full review/revision February 2010 by James P. Knochel, MD
Content last modified August 2010