Dehydration and performance impairment

The reduction of physical performance resulting from dehydration has been established for centuries. A decrease in body water from normal levels provokes not only cardiovascular, thermoregulatory and metabolic changes, but it may also affect the central nervous system (visuomotor, psychomotor and cognitive functions) thereby increasing the risk of accidents. These changes progressively grow as dehydration worsens. The magnitude of decrements is higher when physical activity is performed in the heat compared to cooler conditions. More than 75 % of the energy generated by skeletal muscle substrate oxidation is liberated as heat. To prevent an excessive rise in body core temperature, blood circulation drives heat to the skin where it may be eliminated by different physiological mechanisms: direct conduction (swimming in cold water), air convection, radiation and mostly sweat evaporation