Sweat, Page 3

The Exercise-Limiting Effect of Heat and Relative Humidity

The runner can lose useless metabolic heat by radiation, convection and sweat evaporation. Here is how those mechanisms participate at various air temperatures  in order to get rid of 80 kJoules of heat per minute:


                                      Radiation vs. Sweat losses of 80 kJ per min of heat.gif (4213 bytes)

Although heat loss by convection and radiation are very effective at low air temperatures, in typical US summertime afternoon temperatures these mechanisms hardly help at all, accounting for less than 20 kJ/min maximum heat loss. In these difficult conditions, heat loss by sweat evaporation becomes all-important.

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