Temperate-water immersion as a treatment for hyperthermic humans wearing American football uniforms

Context: Cold-water immersion (CWI; 10°C) can effectively reduce body core temperature even if a hyperthermic human is wearing a full American football uniform (PADS) during treatment. Temperate-water immersion (TWI; 21°C) may be an effective alternative to CWI if resources for the latter (eg, ice) are unavailable. Objective: To measure rectal temperature (T_rec) cooling rates, thermal sensation, and Environmental Symptoms Questionnaire (ESQ) scores of participants wearing PADS or shorts, undergarments, and socks (NO_pads) before, during, and after TWI. Design: Crossover study. Setting: Laboratory. Patients or Other Participants: Thirteen physically active, unacclimatized men (age = 22 ± 2 years, height = 182.3 ± 5.2 cm, mass=82.5 ± 13.4 kg, body fat=10% ± 4%, body surface area = 2.04 ± 0.16 m²). Intervention(s): Participants exercised in the heat (40°C, 50% relative humidity) on 2 days while wearing PADS until T_rec reached 39.5°C. Participants then underwent TWI while wearing either NO_pads or PADS until T_rec reached 38°C. Thermal sensation and ESQ responses were collected at various times before and after exercise. Main Outcome Measure(s): Temperate-water immersion duration (minutes), T_rec cooling rates (°C/min), thermal sensation, and ESQ scores. Results: Participants had similar exercise times (NO_pads = 38.1 ± 8.1 minutes, PADS=38.1 ± 8.5 minutes), hypohydration levels (NO_pads = 1.1% ± 0.2%, PADS = 1.2% ± 0.2%), and thermal sensation ratings (NO_pads = 7.1 ± 0.4, PADS = 7.3 ± 0.4) before TWI. Rectal temperature cooling rates were similar between conditions (NO_pads = 0.12°C/min ± 0.05°C/min, PADS = 0.13°C/min ± 0.05°C/min; t12 = 0.82, P = .79). Thermal sensation and ESQ scores were unremarkable between conditions over time. Conclusions: Temperate-water immersion produced acceptable (ie, .0.08°C/min), though not ideal, cooling rates regardless of whether PADS or NO_pads were worn. If a football uniform is difficult to remove or the patient is noncompliant, clinicians should begin water-immersion treatment with the athlete fully equipped. Clinicians should strive to use CWI to treat severe hyperthermia, but when CWI is not feasible, TWI should be the next treatment option because its cooling rate was higher than the rates of other common modalities (eg, ice packs, fanning).