The impact of training status on firefighter task performance after acute exercise
Authors: Agostinelli Philip , Bordonie Nicholas , Linder Braxton , Robbins Ann , Jones Parker , Reagan Lee , Mobley C Brooks 
Published: May 2024

Background: Though on-shift exercise provides firefighters structured time to maintain fitness levels needs for their job; many are concerned on-shift exercise may impair their readiness. It also remains unclear if their current fitness level is protective of potential exercise-induced decrements. Therefore, we aimed to determine if aerobic fitness and body composition impact occupational performance and physiological stress after acute exercise. Methods: 32 participants (17M/15F; 25.2 ± 4.1 yrs; 173.8 ± 9.8 cm; 75.6 ± 13.2 kg; 23.3 ± 7.4% body fat) completed 2 visits assessing fitness (VO2peak and %body fat (%BF)), and 3 experimental trials: resistance exercise (RE), aerobic exercise (AE), and 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 40lb-sandbag carry) in an environmental chamber (35°C; 50% humidity). Time to complete (TTC), blood lactate concentrations (BLC), and core temperature (CT) were assessed. Participants were split into tertiles based on high, moderate, and low VO2peak and %BF. Two-way ANOVAs were used to compare fitness level by exercise condition. RESULTS: There was a main effect of VO2peak on TTC (High VO2: 1094 ± 235; Moderate VO2: 1120 ± 200; Low VO2: 1365 ± 263 sec; p < 0.01). High VO2peak participants had a shorter TTC compared to moderate or low VO2max regardless of exercise prior (ps < 0.01). There was a main effect of VO2peak on CT (High VO2: 38.1 ± 0.6; Moderate VO2: 38.2 ± 0.6; Low VO2: 38.4 ± 0.5°C; p < 0.01). High VO2peak participants had a lower CT during the OTA compared to low VO2peak regardless of exercise prior (p < 0.01). There was a main effect of %BF on TTC (High %BF: 1029 ± 150; Moderate %BF: 1098 ± 210; Low %BF: 1399 ± 259 sec; p < 0.001). High %BF participants had a longer TTC compared to average or low %BF regardless of exercise prior (ps < 0.01). There was a significant main effect of %BF on BLC (High %BF: 6.6 ± 2.8; Moderate %BF: 7.6 ± 3.0; Low %BF: 9.9 ± 3.8 mMol/L; p < 0.01). Low %BF participants had lower BLC after the OTA compared to high %BF regardless of exercise prior (p < 0.01). CT were significantly higher following AE compared to RE and CON (AE: 38.7 ± 0.3; RE: 38.5 ± 0.5; CON: 37.6 ± 0.4°C; p < 0.01). All other interaction and main effects of TTC or physiological stress variables were not significantly different based on fitness (VO2peak and %BF; ps > 0.18). CONCLUSIONS: Our findings suggest fitness (VO2peak and %BF) impacts time to complete and physiological stress during occupational tasks. However, fitness did not influence the response to occupational tasks differently based on if acute exercise (aerobic or resistance) was performed beforehand. These findings contribute to our understanding of the impact of acute on-shift exercise methods and provide relevant metrics of fitness related to firefighter occupational performance. FUNDING DISCLOSURE: There are no funding sources to disclose. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.