Rapid heat stress causes increased delta spectral power 24 h post-exposure and altered reaction time in firefighters by its dynamic ability to generate heat storage

Abstract

This experiment determined the duration that rapid heat stress (RHS) impacts neural function and reaction time. Previous research has discovered that RHS results in neural function changes immediately post-exposure. No studies have evaluated the duration that these variables are impacted. Additionally, research has not assessed the impact of RHS on reaction time. We hypothesized that RHS would lead to sustained electroencephalography (EEG) spectral power and reaction time changes. Twenty participants performed a treadmill protocol in an environmental chamber (35 °C; 45% humidity) in firefighter personal protective equipment until reaching a core temperature of 39 °C. The subjects performed a Go/No-Go (response inhibition) task (pre-, post-, 24, and 48 h post-RHS) while EEG and reaction time were recorded. Results from the Go/No-Go task revealed a difference between pre-RHS and post-RHS delta spectral power. These differences support previous literature. The first novel finding of this study is that delta power is still perturbed 24 h post-RHS exposure. The second novel finding is that reaction time is altered post-RHS, 24 h, and 48 h post-RHS. These cognitive changes could result in compounded consequences if two bouts of RHS occur in 24 h (e.g., two fires or other hyperthermic events), which could jeopardize critical life-saving missions.