Heat Mitigation Strategies Employed at the U.S. Air Force's Special Warfare Training Pipeline

Although the incidence rate of exertional heat stroke (EHS) in the U.S. military decreased from 2018 to 2022, a resurgence in 2024 highlights the importance of continued refinement of effective preventive measures. This study aimed to describe the burden of exertional heat illness (EHI) in the U.S. Air Force Special Warfare Training Wing (SWTW) from FY19 to FY24 and assess changes in annual external heat exhaustion (EHE) and EHS risk following implementation of mitigation strategies in 2019.

This descriptive epidemiology study analyzed 195 EHI cases among SWTW trainees from FY19 to FY24. Data on EHE and EHS were extracted from Military Health System records. Cumulative incidence (proportion of affected trainees per year) was calculated using the annual trainee population as the denominator. Mitigation strategies implemented in 2019 were assessed. Chi-square testing indicated that the distribution of EHS and EHE differed by fiscal year (χ2 = 12.92, P = .0241), reflecting year-to-year variation in case proportions. Historical weather data were reviewed to descriptively contextualize seasonal environmental conditions during periods of elevated EHI proportions.

During FY19 to FY24, there were 195 reported cases of EHI: 135 EHE and 60 EHS. EHE exceeded EHS annually from FY19 to FY23, with EHI peaking in FY22 (n = 45), declining in FY23 (n = 19), and resurging in FY24 (n = 36), driven by increased EHS (n = 19). EHE cumulative incidence (0.91%-1.90%) outpaced EHS (0.28%-0.79%) until FY24, when EHS rose to 1.80%, surpassing EHE (1.61%). A significant association was identified between EHI type and fiscal year (χ2 = 12.92, P = .0241) with an increased EHS rate in FY24 versus FY20 (P = .012) and FY23 (P = .045); FY22 versus FY20 (P = .039). No significant year-over-year variation in EHE was observed. The SWTW implemented various measures to mitigate heat injury.

Despite interventions at the SWTW, EHI remained prevalent to include an EHS proportion surge (1.80%) in FY24, indicating potential limitations and need for improved training adaptations, early detection, and risk management in high-intensity environments. Achieving zero EHI may not be feasible, thus, leadership must make decisions that acknowledge risk and apply evidence-based strategies to meet mission objectives. Seasonal patterns suggest tailored interventions may be necessary. Future studies should assess morbidity metrics, trainee fitness, and acclimatization to further evaluate and refine prevention strategies.