Fig. 1.

Mean arterial pressure at normothermia, heat stress, and the final 100 s before the end of the orthostatic challenge due to syncopal symptoms. Although data during the final 2 min of the orthostatic challenge were analyzed, 5 subjects experienced syncopal symptoms requiring test termination within a period of time between 100 and 120 s following the onset of the challenge. Thus only the final 100 s of data during the orthostatic challenge are presented to show average responses of all 46 subjects. Heat stress did not alter mean arterial pressure; however, blood pressure was reduced to 57 ± 9 mmHg at the termination of the orthostatic challenge. LBNP, lower body negative pressure. *Significantly different from normothermia; #significantly different from heat stress.