The Effect of Two Acute Exercise Modalities on Performance, Physiology, and Cognition During Simulated Firefighting Tasks

Abstract

Evidence suggests exercise can transiently decrease occupational performance in firefighters. However, it is unclear how different modalities affect physiological and cognitive outcomes. We aimed to determine on-shift resistance and aerobic exercise’s impact on occupational performance and physiology during occupational tasks. Secondly, we aimed to understand the relationship between time- and frequency-domain heart rate variability (HRV) and cognitive function during occupational tasks. Lastly, we aimed to determine fitness metrics relevant to occupational performance. Thirty-two participants completed two baseline assessments. Three exercise sessions including resistance (RE), aerobic (AE), and control (CON) were completed followed by an occupational task assessment (OTA; 4 rounds of 10 deadlifts and 0.15-mile sandbag carry) and a cognitive Wisconsin Card Sorting Task (WCST) at 35 C, 50% humidity. RMANOVAs were used to compare differences by condition and a multiple-linear regression included fitness scores to predict performance and physiological strain. There were not differences in OTA time (p = 0.24). Heart rate, core temperature, and skin temperature were higher during OTA following AE and RE compared to CON, and higher after AE compared to RE (ps < 0.01). WCST errors and response time did not differ by condition (ps > 0.27). Time-domain HRV metrics did not differ by condition (ps > 0.05). All frequency-domain metrics, other than low-frequency power (p = 0.03), did not differ by condition (ps > 0.24). Low-frequency power was lower following AE compared to RE and CON (p < 0.01). This suggests job performance may not be impacted, but physiological strain may be elevated. This elevated core temperature could increase a firefighter’s risk for heat injury immediately following on-shift exercise, specifically aerobic exercise. An acute bout of on-shift aerobic or resistance exercise may not impact cognitive flexibility during subsequent occupational tasks, despite increased sympathetic drive following aerobic exercise. Multiple-linear regression results show a significant model for OTA time, RPE, skin temperature and blood lactate (ps < 0.02), but not core temperature, heart rate, ventilation, or WCST errors (ps > 0.06). Aerobic capacity, body composition, strength and power may be useful predictors of firefighter performance, perceived exertion, and physiological strain, but not cognition during simulated occupational tasks.