A Thermal Stress Treadmill Walk for Clinic Evaluation of Candidates for Hazardous Materials (HazMat) Duty

U.S. guidance for examining hazmat workers recommends stress testing be considered when heat stress is expected. However, the most common stress test—Bruce protocol treadmill electrocardiography (BPTE) wearing gym clothes—creates little thermal stress. Objective. Evaluate a novel thermal stress treadmill walk (TSTW). Methods. Body temperatures and heart rates during BPTE in 93 current and potential hazmat workers wearing gym clothes were compared with later values in 35 of these subjects while they were wearing thermally-restrictive “sauna suits” during a 45-min TSTW. Physiological strain index (PSI) was calculated from temperature and heart rate changes and compared with PSI values from hazmat simulations and climatic chamber exercises. Results. Tympanic temperature (TT) rose 0.5 °C (SD 0.5) during BPTE lasting 12.4 min (SD 2.9). PSI reached 6.0 (SD 1.3). TT rose 1.0 °C (SD 0.5) during TSTW, p < .01. PSI averaged 6.6 (SD 1.9) in 29 subjects who completed TSTW, versus 5.7 (SD 5.7) in the 6 subjects who did not. Ingested thermistor temperatures increased more than did TT during TSTW, yielding PSI of 7.0 (SD 1.5), equal to PSI values from climatic chamber exercises, i.e., 7.0 (SD 1.0). Conclusion. TSTW increased body temperature and PSI in 29 of the 35 subjects who completed it to levels matching those of operational simulations in climatic chambers and during hazmat exercises. This TSTW may be useful for evaluating candidates for hazmat duty.