ACSM Guidelines For Heat Stress And Long Distance Running

ACSM Position Statement On Prevention Of Heat Injuries During Distance Running

In 1975, the American College of Sports Medicine published a position statement on prevention of heat injuries during distance running. According to this statement, races greater than 10 miles should not be conducted when the WBGT exceeded 82.4°F. In 1984, the ACSM statement was revised to include races of any distance, along with specific recommendations for warning competitors of the relative risks of heat injury at various WBGT indices. This flag system for WBGT was devised:

Green Flag = Low Risk - <65°F  (Risk of heat exhaustion/heat stroke is low, but not 0.)

Yellow Flag = Moderate Risk, 65°F-73°F

Red Flag = High Risk - >73°-82°F ("Anyone who is particularly sensitive to heat or humidity probably should not run.")

Black Flag = Extreme Risk, >82°F ("Event Delay Threshold" = 82°F)

Dangerous = >90°F, a designation in line with the US Marine Corps standard. [Most recently, a WBGT "Event Delay Threshold" temperature for "Elite" events has been set at 87°F.]

The listing of “Dangerous” level >= 90°F was referenced in Table 3 in Martin, D: Climatic Heat Stress and Athletic Performance. Track Coach, Spring 1997, pp 4425-4452. This appears to have been based on the ACSM 1984 Position Stand plus extrapolation.

For the latest ACSM Position Stand (2007), click this link.