Page 80 - OHS, September 2024

HEAT STRESS
percent to –1 percent of body weight lost in fluid) allows the body to optimally thermoregulate and maintain cardiovascular function.
Normative Sweat Dynamics in Athletes
The amount of water and electrolytes (primarily sodium, Na+) lost due to thermoregulatory sweating during exercise can vary con- siderably within and among athletes. Even for the same individual, losses can vary greatly day to day.4 The reported range in sweating rate and sweat Na+ concentration ([Na+]) is ~0.5 to 2.0 L/h and ~10-90 mmol/L, respectively.5 Extrapolated for workers through- out a workday, this could result in multiple U.S. gallons of fluid lost in a day on the high end.
Effects of Dehydration
Proper hydration is essential, as even mild dehydration can de- crease physical performance by 2-3 percent6 and cognitive perfor- mance by up to 10 percent.
Dehydration elevates core temperature responses and negates the thermoregulatory advantages conferred by heat acclimatiza- tion. When dehydrated, similar core temperature responses7 were observed for both unacclimated and acclimated states.
The capacity to perform high-intensity exercise, which results in exhaustion within a few minutes, is reduced by as much as 45 percent8 by prior dehydration corresponding to a loss of only 2.5 percent of body weight.
Even mild dehydration can decrease physical performance by 2-3 percent and cognitive performance by up to
10 percent.
Exercise performance is impaired when an individual is dehy- drated by as little as 2 percent of body weight. Losses of more than 5 percent of body weight can decrease the capacity for work by about 30 percent.9
Fluid & Electrolyte Replenishment Guidelines
Appropriate fluid intake before, during and after exercise is impor- tant for health and optimal performance. Before exercise, athletes may achieve euhydration prior to exercise10 by consuming a fluid
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78 Occupational Health & Safety | SEPTEMBER 2024
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