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 Hyponatremia Hyponatremia is decrease in serum sodium concentration 136 mEq/L ( 136 mmol/L) caused by an excess of water relative to solute. Common causes include diuretic use, diarrhea, heart failure, liver... read more . Heat cramps are common among the following:
Cramping is abrupt, usually occurring in muscles of the extremities. Cramping can begin during or after exercise. 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.
(See also Overview of Heat Illness Overview of Heat Illness Heat illness encompasses a number of disorders ranging in severity from muscle cramps and heat exhaustion to heatstroke (which is a life-threatening emergency). Heat illness, although preventable... read more .)
Heat cramps may be relieved immediately by firm passive stretching of the involved muscle (eg, ankle dorsiflexion for a calf cramp). The patient should rest in a cool environment. Fluids and electrolytes should be replenished orally (1 to 2 L water containing 10 g [2 level teaspoons] salt or sufficient amounts of a commercial sports drink) or, for more rapid relief or when oral repletion is not possible, IV (1 to 2 L 0.9% saline solution). Adequate conditioning, acclimatization, and appropriate management of salt balance help prevent heat cramps.