(57) EXAMINING THE INFLUENCE OF AN 8-WEEK FIREFIGHTER-SPECIFIC INTERVAL TRAINING PROGRAM ON EMERGENCY CALL WORKLOADS

Traditional sport-athlete training load models have been utilized to quantify the objective work, or external load, and intrinsic responses to work, or internal load, in firefighters (FFs). Internal load is higher for FFs with lower aerobic capacity and greatest for emergency calls involving fire suppression. However, the responsiveness of these load measures to training in FFs remains unknown.

Purpose: To examine the influence of an 8-wk FF-specific interval training program on cardiovascular fitness and the external and internal load demands of call responses in active-duty FFs.

Methods: 27 (25 male, 2 female) FFs (36.07 ± 8.65 yrs, 179.28 ± 5.61 cm, 90.83 ± 14.14 kg) volunteered for this study. Participants were randomly assigned to a control (CTL) or intervention (INT) group. Before (T₁) and after (T₂), participants completed a maximal treadmill test to quantify peak aerobic capacity (VO_2PEAK) and wore a remote physiological strap that continuously measured acceleration and heart rate (HR) for 4-6 24-h shifts. Time-stamped call logs were utilized to post-hoc quantify the external load of each call response as impulse load (IMPULSE), the squared sum of triaxial acceleration scaled to gravity. The internal load for each call was quantified as Edward’s Training Impulse (ETRIMP), derived from time spent in 5 HR-based intensity zones. Calls were categorized as medical (MED), fire without suppression (FIRE0), or fire suppression (FIRE1). The IMPULSE and ETRIMP of each call type were averaged for a single observation per participant at T₁ and T₂ and change (Δ) scores were calculated. Separate RM ANCOVAs examined for group differences in ΔETRIMP for each call type while controlling for ΔIMPULSE. Bivariate Pearson correlations examined for relationships between ΔVO_2PEAK and ΔETRIMP for all call types. An alpha of p < 0.05 determined statistical significance.

Results: Non-significant RM ANCOVA group differences were identified for ΔETRIMP_MED (F_1,24 = .204, p = .655; Mean ± SE; CTL vs. INT; 1.361 ± 1.030 AU = .689 ± 1.069 AU), ΔETRIMP_FIRE0 (F_1,22 = 1.563, p = .224; .750 ± 1.733 AU = -2.521 ± 1.956 AU), and ΔETRIMP_FIRE1 (F_1,22 = 2.557, p = .124; -12.847 ± 12.991 AU = 17.258 ± 13.526 AU). ΔVO_2PEAK (-.028 ± 2.173 mL/kg/min) was significantly negatively related to ΔETRIMP_MED (1.037 ± 4.112 AU; r = -.429, p = 0.032) but non-significantly related to ΔETRIMP_FIRE0 (-.689 ± 7.17 AU; r = -.106, p = .629) and ΔETRIMP_FIRE1 (1.603 ± 97.56 AU; r = -.091, p = 0.681).

Conclusions: Following the intervention, both groups demonstrated non-significant trends of increased internal load for medical calls. However, smaller increases in internal loads were related to greater increases in aerobic capacity. For the trained group, non-significant trends of decreased internal load for non-suppression fire calls, and increased load for fire suppression calls, were exhibited and unrelated to aerobic capacity changes. PRACTICAL APPLICATION: Though an 8-wk interval training program did not significantly influence on-duty emergency call loads, the training group exhibited lower internal load trends for non-fire suppression call responses, suggesting practical enhancements of cardiovascular efficiency for lower intensity work. In contrast, the training group demonstrated increased trends in maximal internal load capacity that was unrelated to aerobic capacity. Future research should explore the contributions of other physiological systems on maximal workload responses.

Acknowledgements: Funding for this project was provided by a Doctoral Graduate Student Research Grant through the NSCA Foundation.