The Effect Of Two Acute Exercise Modalities On Physiology And Cognition During Firefighter Occupational Tasks

BACKGROUND: Evidence suggests exercise can transiently decrease occupational performance. However, it is unclear how different exercise modalities affect physiological and cognitive outcomes. We aimed to determine how resistance or aerobic endurance exercise impacts occupational performance, physiology, and cognition during occupational tasks. METHODS: 32 participants (M/F: 17/15; 25.2 ± 4.1 yrs; 173.8 ± 9.8 cm; 75.6 ± 13.2 kg; 23.3 ± 7.4% body fat) completed 3 experimental trials in semi-randomized order; resistance exercise (RE), aerobic high intensity interval training (AE), rested control (CON). Each trial was followed by an occupational task assessment (OTA; 4 rounds of 10 deadlifts (set to 85 or 135lbs) and a 0.15-mile 40 lb-sandbag carry) in an environmental chamber (35 °C; 50% humidity). After the second round, participants completed the Wisconsin Card Sorting Task (WCST) before completing two more rounds. Outcomes included WCST total errors and response reaction time. Equivital EQ02+ LifeMonitor provided heart rate, skin temperature, and estimated core temperature during the OTA. Additionally, time to complete the OTA was measured. Repeated measures ANOVAs were used to compare differences by condition. RESULTS: There was not a significant difference in time to complete the OTA (CON: 1134 ± 261, AE: 1198 ± 214, RE: 1212 ± 302 sec; p = 0.24). Average heart rate (CON: 148.5 ± 16.2 , AE: 166.3 ± 11.5, RE: 159.9 ± 13.0 bpm; p < 0.01), core temperature (CON: 37.56 ± 0.35, AE: 38.68 ± 0.26, RE: 38.44 ± 0.46 °C; p < 0.01), and skin temperature (CON: 36.33 ± 0.54, AE: 37.48 ± 0.58, RE: 36.87 ± 0.86 °C ; p < 0.01) were higher during OTA after AE compared to CON and RE. Post hoc analysis for each physiological variable showed AE and RE were higher than CON, and AE was higher than RE (ps < 0.01). WCST errors (CON: 8.2 ± 2.3, AE: 8.2 ± 2.2, RE: 8.9 ± 2.3; p = 0.27) and response reaction time (CON: 1445 ± 287 ms, AE: 1470 ± 296 ms, RE: 1415 ± 259 ms; p = 0.70) were not significantly different across conditions. CONCLUSIONS: Our findings suggest that while physical and cognitive job performance may not be impacted, physiological strain during occupational tasks may be elevated. This elevated core temperature could increase a firefighter’s risk for heat injury immediately following on-shift exercise, and more prominently following aerobic exercise.