Fluid and electrolyte disturbances in heat illness

Area of Science:

• Exercise Physiology
• Sports Medicine
• Environmental Health

Background:

• Traditional understanding of exercise-related heat illnesses, including heat cramps, heat exhaustion, and heat stroke, is based on outdated concepts.
• Current literature often misattributes these conditions to elevated body temperature or fluid/electrolyte imbalances, which lacks robust scientific evidence.

Purpose of the Study:

• To critically review exercise-related heat disorders.
• To evaluate the etiological role of fluid and electrolyte disturbances in these conditions.
• To provide an updated understanding for improved clinical management.

Main Methods:

• Literature review and critical analysis of existing studies on exercise-related heat illnesses.
• Examination of historical and modern evidence regarding the causes of heat cramps, heat exhaustion, and heat stroke.
• Assessment of the role of dehydration, heat production, heat loss, and physiological responses.

Main Results:

• Heat cramps and heat exhaustion are not primarily caused by elevated body temperature or specific fluid/electrolyte abnormalities.
• Exercise-induced heat stroke is a rare condition resulting from excessive heat production exceeding heat loss, requiring potent initiating factors beyond dehydration.
• Dehydration impairs heat loss and exercise performance but is not the sole or primary cause of heat stroke.

Conclusions:

• The terms 'heat cramps' and 'heat exhaustion' are misleading and require re-evaluation.
• Exercise-induced heat stroke is a distinct and infrequent condition with multifactorial causes.
• Clinical management of exercise-related heat disorders should be based on current scientific evidence rather than historical, often inaccurate, assumptions.