Investigating the Effects of Precooling on Recreationally Active Individuals during a Loaded Carriage Foot March in Heated Conditions

Introduction: Over the past 20 years, the literature has demonstrated that military members are prone to exertional heat illness due to a combination of heavy loads and physical exertion. Precooling is a relatively new idea where an individual ingests a substance preemptively to lower core temperature before an activity. Purpose: The aim of this study was to investigate the effects of a precooling protocol employing ice slurry (0±1°C) vs. cold water (4°C) on core body temperature and time to exhaustion during a simulated military full combat gear foot march in males aged 18 to 35 years. Methodology: The researchers used a precooling protocol of 7.5g/kg of bodyweight of both water (control) and ice-slurry (experimental) administered over a 30-minute period. Following the precooling protocol, the participants self-selected a pace from 3.0-4.0 MPH and walked for up to 90 minutes or until volitional fatigue inside a heat tent while wearing full Army combat gear. Core temperature, heart rate and RPE were collected every 5 minutes. Blood pressure was collected pre and post exercise. Results: There was no difference in time to exhaustion (p = 0.227), heart rate (p = 0.763) or core temperature (p = 0.876) between conditions. Conclusion: Precooling protocol was ineffective at lowering core temperature vs. control and thus did not increase time to exhaustion. Additional research on precooling with military equipment is needed to further elucidate the potential benefits of precooling on exercise performance and decreasing the risk of exertional heat illness.