Thermal responses of men and women during cold-water immersion: influence of exercise intensity.

The influence of exercise intensity on thermoregulation was studied in 8 men and 8 women volunteers during three levels of arm-leg exercise (level I: 700 ml oxygen (O2).min-1; level II: 1250 ml O2.min-1; level III: 1700 ml O2.min-1) for 1 h in water at 20 and 28 degrees C (Tw). For the men in Tw 28 degrees C the rectal temperature (Tre) fell 0.79 degree C (P less than 0.05) during immersion in both rest and level-I exercise. With level-II exercise a drop in Tre of 0.54 degree C (P less than 0.05) was noted, while at level-III exercise Tre did not change from the pre-immersion value. At Tw of 20 degrees C, Tre fell throughout immersion with no significant difference in final Tre observed between rest and any exercise level. For the women at rest at Tw 28 degrees C, Tre fell 0.80 degree C (P less than 0.05) below the pre-immersion value. With the two more intense levels of exercise Tre did not decrease during immersion. In Tw 20 degrees C, the women maintained higher Tre (P less than 0.05) during level-II and level-III exercise compared to rest and exercise at level I. The Tre responses were related to changes in tissue insulation (I(t)) between rest and exercise with the largest reductions in I(t) noted between rest and level-I exercise across Tw and gender. For mean and women of similar percentage body fat, decreases in Tre were greater for the women at rest and level-I exercise in Tw 20 degrees C (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)