Necessity of removing American football uniforms from humans with hyperthermia before cold-water immersion

Context: The National Athletic Trainers' Association and the American College of Sports Medicine have recommended removing American football uniforms from athletes with exertional heat stroke before cold-water immersion (CWI) based on the assumption that the uniform impedes rectal temperature (T_rec) cooling. Few experimental data exist to verify or disprove this assumption and the recommendations. Objectives: To compare CWI durations, T_rec cooling rates, thermal sensation, intensity of environmental symptoms, and onset of shivering when hyperthermic participants wore football uniforms during CWI or removed the uniforms immediately before CWI. Design: Crossover study. Setting: Laboratory. Patients or Other Participants: Eighteen hydrated, physically active men (age = 22 ± 2 years, height = 182.5 ± 6.1 cm, mass = 85.4 ± 13.4 kg, body fat = 11% ± 5%, body surface area = 2.1 ± 0.2 m²) volunteered. Intervention(s): On 2 days, participants exercised in the heat (approximately 40°C, approximately 40% relative humidity) while wearing a full American football uniform (shoes; crew socks; undergarments; shorts; game pants; undershirt; shoulder pads; jersey; helmet; and padding over the thighs, knees, hips, and tailbone [PADS]) until T_rec reached 39.5°C. Next, participants immersed themselves in water that was approximately 10°C while wearing either undergarments, shorts, and crew socks (NO_pads) or PADS without shoes until T_rec reached 38°C. Main Outcome Measure(s): The CWI duration (minutes) and T_rec cooling rates (°C/min). Results: Participants had similar exercise times (NO_pads = 40.8 ± 4.9 minutes, PADS = 43.2 ± 4.1 minutes; t₁₇ = 2.0, P = .10), hypohydration levels (NO_pads = 1.5% ± 0.3%, PADS = 1.6% ± 0.4%; t₁₇ = 1.3, P = .22), and thermal-sensation ratings (NO_pads = 7.2 ± 0.3, PADS = 7.1 ± 0.5; P > .05) before CWI. The CWI duration (median [interquartile range]; NO_pads = 6.0 [5.4] minutes, PADS = 7.3 [9.8] minutes; z = 2.3, P = .01) and T_rec cooling rates (NO_pads = 0.28°C/min ± 0.14°C/min, PADS = 0.21°C/min ± 0.11°C/min; t₁₇ = 2.2, P = .02) differed between uniform conditions. Conclusions: Whereas participants cooled faster in NO_pads, we still considered the PADS cooling rate to be acceptable (ie, > 0.16°C/min). Therefore, if clinicians experience difficulty removing PADS or CWI treatment is delayed, they may immerse fully equipped hyperthermic football players in CWI and maintain acceptable T_rec cooling rates. Otherwise, PADS should be removed preimmersion to ensure faster body core temperature cooling.