Influences of raised ambient temperature on cardiorespiratory performance in a 3-minute step test

We investigated the effects of raised ambient temperature on cardiorespiratory performance in a 3- min step test. Subjects repeatedly performed the step exercise under three ambient thermal conditions. A cardiorespiratory fitness index was computed from heart rate (HR) measurements during a recovery period after the exercise. Raised ambient temperature was associated with significantly increased HR not only during the rest period before exercise but also during the recovery period. The cardiorespiratory fitness index for the high temperature condition was significantly poorer than those for the moderate conditions. The variability of the pre-exercise HR among the three thermal condi- tions was highly correlated with the variability of the cardiorespiratory index. These results indicate that the 3-min step test should be performed under identical ambient thermal conditions and, if necessary, cardiorespiratory fitness evaluation based on HR recovery after the 3-min step exercise should be corrected for individual acclimation states or heat stress properties.