Evaluation of a temperate-environment test of heat tolerance in prior heatstroke patients and controls.

It has been reported that scores from a temperate-environment step test describe the heat-tolerance status of prior heatstroke patients (HP). This investigation evaluated the ability of this temperate-environment heat-tolerance test (HTT) to indicate altered heart rate (HR) and rectal temperature (Tre) responses of HP, after 7 days of heat acclimation. On day 1, ten male HP (61 +/- 7 days post-heatstroke) and five control subjects (C) bench-stepped (0.30 m high, 27 steps.min-1) for 15 min (25.8 degrees C dry bulb, 16.2 degrees C wet bulb). On days 2-8, subjects underwent heat acclimation (40.1 degrees C dry bulb, 23.8 degrees C wet bulb; treadmill, 90 min.day-1). Heat acclimation resulted in significant decreases in final HR (152 +/- 5 vs 130 +/- 3 beats.min-1, P less than 0.025) and final Tre (38.62 +/- 0.11 vs 38.13 +/- 0.07 degrees C, p less than 0.01) in HP. One HP but no C was defined heat intolerant, exhibiting inability to adapt to daily exercise in the heat. On day 9, HP repeated HTT, exactly as performed on day 1; mean group HTT scores did not change (day 1 = 39 +/- 6; day 9 = 48 +/- 6, P greater than 0.05). All physical characteristics and physiological responses of HP (days 1, 2, 7, 9) were statistically similar (P greater than 0.05) to those of C. In contrast to heat-acclimation data, HTT scores (score less than or equal to 30) indicated that four HP were heat intolerant on day 1 and two HP were heat intolerant on day 9.(ABSTRACT TRUNCATED AT 250 WORDS)