Physiological and Cognitive Responses to Fast-Paced Load Carriage in the Cold

Physically demanding occupations, including the military, blue light services, and search and rescue organisations are often required to conduct load carriage activity concurrently with cognitive tasks whilst in austere environments. This study aimed to quantify changes in physiological and cognitive performance over time during a fast-paced load carriage (FLCP) task conducted in a cold environment. Fourteen participants (age: 26.1±7.8 years, stature: 1.85±0.08 m, body mass: 84.9±16.8 kg, estimated maximal rate oxygen uptake [V̇O2max]: 46.9±6.4 mL·kg-1·min-1) completed the FLCP in an environmental chamber (-10 °C, 50% RH) while carrying 16 kg of external load. Physiological variables (heart rate, rate of oxygen consumption, and core and skin temperatures), perceptual ratings (rating of perceived exertion, thermal comfort, and rating scale of mental effort [RSME]), and cognitive performance (Military-Specific Auditory N-Back Task [MSANT]) were recorded. Results demonstrated maintenance of cognitive performance (p = 0.344, Kendall’s W [W] = 0.080) and perceived mental effort (RSME) during the MSANT (p = 0.112, W = 0.128) across the FLCP. However, a significant main effect for time was shown for RSME during periods when participants were not undertaking the MSANT (p <0.001, W = 0.463), indicating that participants worked mentally harder as the protocol progressed. Physiological variables also increased, likely a result of the increasing exercise intensity through the FLCP. While maintenance of cognitive performance was evident, increased interim period RSME indicates a reduction in cognitive efficiency. Results can be applied to operational settings, informing decision makers of impaired cognitive efficiency when multiple stimuli are acting upon personnel.