Effect of air temperature on the rectal temperature gradient at rest and during exercise

The purpose of the current study was to determine the effect of air temperature on the rectal temperature gradient at rest and during exercise. It was hypothesized that the rectal temperature gradient would be exacerbated in cold environments and attenuated in warm environments both at rest and during exercise. Each subject completed three exercise bouts on a motor driven treadmill at approximately 55% of their previously determined maximal oxygen uptake. Three different air temperatures (10, 22, 39°C) were used for the exercise bouts. Rectal temperature was measured at rest and every 5 min during each exercise bout using 4 temperature sensors affixed at 4, 7, 10 and 13 cm past the anal sphincter. Readings obtained from the 4-cm depth were significantly (p<0.05) lower than those obtained at deeper insertion depths both at rest and during exercise for all three air temperatures. Furthermore, the results showed that the rectal temperature gradient was exacerbated in cold environments and attenuated in warm environments both at rest and during exercise.