Cooling rates of hyperthermic humans wearing American football uniforms when cold-water immersion is delayed

Context: Treatment delays can be contributing factors in the deaths of American football athletes from exertional heat stroke. Ideally, clinicians begin cold-water immersion (CWI) to reduce rectal temperature (T_rec) to,38.98C within 30 minutes of collapse. If delays occur, experts recommend T_rec cooling rates that exceed 0.158C/min. Whether treatment delays affect CWI cooling rates or perceptual variables when football uniforms are worn is unknown. Objective: To answer 3 questions: (1) Does wearing a football uniform and delaying CWI by 5 minutes or 30 minutes affect T_rec cooling rates? (2) Do T_rec cooling rates exceed 0.158C/min when treatment delays have occurred and individuals wear football uniforms during CWI? (3) How do treatment delays affect thermal sensation and Environmental Symptoms Questionnaire responses? Design: Crossover study. Setting: Laboratory. Patients or Other Participants: Ten physically active men (age ¼ 22 6 2 y, height ¼ 183.0 6 6.9 cm, mass ¼ 78.9 6 6.0 kg). Intervention(s): On 2 days, participants wore American football uniforms and exercised in the heat until T_rec was 39.758C. Then they sat in the heat, with equipment on, for either 5 or 30 minutes before undergoing CWI (10.68C 6 0.18C) until T_rec reached 37.758C. Main Outcome Measure(s): Rectal temperature and CWI duration were used to calculate cooling rates. Thermal sensation was measured pre-exercise, postexercise, postdelay, and post-CWI. Responses to the Environmental Symptoms Questionnaire were obtained pre-exercise, postdelay, and post-CWI. Results: The T_rec cooling rates exceeded recommendations and were unaffected by treatment delays (5-minute delay ¼ 0.208C/min 6 0.078C/min, 30-minute delay ¼ 0.198C/min 6 0.058C/min; P ¼ .4). Thermal sensation differed between conditions only postdelay (5-minute delay ¼ 6.5 6 0.6, 30-minute delay ¼ 5.5 6 0.7; P, .05). Environmental Symptoms Questionnaire responses differed between conditions only postdelay (5-minute delay ¼ 27 6 15, 30-minute delay ¼ 16 6 12; P, .05). Conclusions: Treatment delays and football equipment did not impair CWI's effectiveness. Because participants felt cooler and better after the 30-minute delay despite still having elevated T_rec, clinicians should use objective measurements (eg, T_rec) to guide their decision making for patients with possible exertional heat stroke.