Heat illness

Heat illness includes heat cramps, heat syncope (fainting), heat exhaustion and exertional heat stroke, the four conditions ACSM groups under illnesses of hot environments.^{1Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 508.} Heat exhaustion is the most common: the client can’t keep exercising in the heat and develops prominent fatigue and progressive weakness without organ damage.^{2Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 509.}

Exertional heat stroke is life-threatening, with body temperature above 40.5 °C (105 °F), profound central nervous system dysfunction and multiple organ failure that can lead to delirium, convulsions or coma.^{2Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 509.} Signs include disorientation, irrational behavior, dizziness and vomiting.^{1Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 508.} ACSM calls for whole-body cooling in cold or ice water within 30 minutes; stopping cooling early risks complications or death.^{2Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 509.}

In practice

• For heat exhaustion, ACSM advises moving the client somewhere cool or shaded, elevating the legs and applying light cooling such as cold wet towels.^{2Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 509.} Give oral fluids only if the client is conscious, able to swallow and isn’t vomiting or having diarrhea.^{2Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 509.}
• Heat stroke risk rises with poor fitness, excess body fat, incomplete heat acclimatization, recent illness and stimulant-containing supplements.^{2Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 509.} High-intensity exercise, even in a weight room, can raise core temperature to dangerous levels in under 30 minutes in an unfit, overweight or unacclimatized client.^{3CSCCa and NSCA, Joint Consensus Guidelines for Transition Periods, p. 6.}
• Build heat exposure over 10 to 14 days of moderate exercise in the heat.^{4Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 511.}
• In hot, humid conditions, ACSM advises a heat plan developed with a medical professional: check wet bulb globe temperature, allow longer or more frequent breaks, train at cooler times and never restrict fluids.^{5Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 510.} Set emergency procedures with local medical professionals.^{5Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 510.}