Heat cramps are painful spasmodic muscle cramps that usually occur in heavily exercised muscles in hot and humid environments.
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 may be related to some combination of intravascular volume depletion (dehydration), electrolyte abnormalities (including hyponatremia when water but not salt is replaced orally during exercise), and fatigue (1). Heat cramps are common among the following:
Manual laborers (eg, engine room personnel, steel workers, roofers, miners)
Military trainees
Athletes
Cramping is abrupt, usually occurring in muscles of the extremities or abdomen. Cramping can begin during or after exercise. Severe pain and carpopedal spasm may incapacitate the hands and feet. Body temperature is normal, and other findings are unremarkable. The cramp usually lasts minutes to hours. Diagnosis is by history and clinical evaluation.
Reference
1. Casa DJ, DeMartini JK, Bergeron MF, et al. National Athletic Trainers' Association Position Statement: Exertional Heat Illnesses [published correction appears in J Athl Train. 2017 Apr;52(4):401. doi: 10.4085/1062-6050-52.4.07.]. J Athl Train. 2015;50(9):986-1000. doi:10.4085/1062-6050-50.9.07
Treatment of Heat Cramps
The patient should rest in a cool environment, if possible (1, 2). Fluids and electrolytes should be replenished with oral rehydration solution based on the World Health Organization “reduced osmolarity” formula, which is slightly hypotonic and commercially available (3), with other isotonic (or hypertonic) salt-containing solutions, or with sufficient amounts of a commercial sports drink. For more rapid relief or when oral repletion is not possible, intravenous isotonic saline solution may be used. Heat cramps associated with repetitive exercise of a specific muscle may be relieved immediately by firm passive stretching of the involved muscle (eg, ankle dorsiflexion for a calf cramp). Adequate conditioning, acclimatization, and appropriate management of salt balance help prevent heat cramps.
Treatment references
1. Eifling KP, Gaudio FG, Dumke C, et al. Wilderness Medical Society Clinical Practice Guidelines for the Prevention and Treatment of Heat Illness: 2024 Update. Wilderness Environ Med. 2024;35(1 suppl):112S-127S. doi:10.1177/10806032241227924
2. Casa DJ, DeMartini JK, Bergeron MF, et al. National Athletic Trainers' Association Position Statement: Exertional Heat Illnesses [published correction appears in J Athl Train. 2017 Apr;52(4):401. doi: 10.4085/1062-6050-52.4.07.]. J Athl Train. 2015;50(9):986-1000. doi:10.4085/1062-6050-50.9.07
3. Alam NH, Yunus M, Faruque ASG, et al. Symptomatic Hyponatremia During Treatment of Dehydrating Diarrheal Disease With Reduced Osmolarity Oral Rehydration Solution. JAMA. 2006;296(5):567–573. doi:10.1001/jama.296.5.567
