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Tactical Strength and Conditioning

(34) INFLUENCE OF CARDIOVASCULAR FITNESS ON EXTERNAL AND INTERNAL WORKLOADS OF FIRE EMERGENCY RESPONSES IN FIREFIGHTERS

Saturday, July 15, 2023
10:00 AM – 11:30 AM East Coast USA Time
Location: Milano III-IV
Abstract Details:

Introduction: 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, to minimize risk of over-exertional injury. Similarly, firefighters (FFs) are at risk for injury, with cardiac injury heightened following fireground operations, especially in FFs with lower cardiovascular fitness. To date, FF workload is generally defined as the number of calls responded to across a 24-hour shift. However, call volume measures do not quantify the objective work completed at a single emergency response, nor identify how intrinsic responses to fire tone calls may vary across individual fitness levels, which may support risk identification and injury prevention in FFs.

Purpose: To identify relationships between cardiovascular fitness and the external and internal load demands of fire tone call responses in active-duty FFs.

Methods: 33 (29 male, 4 female) FFs (36.46 ± 9.13 yrs, 179.92 ± 7.02 cm, 91.43 ± 12.75 kg) volunteered for this study. Participants completed a maximal treadmill test to quantify cardiovascular fitness as peak aerobic capacity (VO2PEAK). A remote physiological strap that continuously measured acceleration and heart rate (HR) was worn by each participant for 4-6 shifts. Time-stamped call logs were utilized to post-hoc quantify the external load of each fire tone call response as impulse load (IMPULSE), the squared sum of triaxial acceleration scaled to gravity. The physiological internal load for each call was quantified as Edward’s Training Impulse (ETRIMP), a metric derived from time spent in 5 HR-based intensity zones. Following call completion, participants provided a rating of perceived exertion from Borg’s CR-10 scale to quantify Foster’s Session Rating of Perceived Exertion (SRPE) and reflect perceived internal load. The external and internal loads for all calls were averaged for a single IMPULSE, ETRIMP, and SRPE observation per participant. Bivariate Pearson correlations examined for relationships between VO2PEAK and IMPULSE, ETRIMP, and SRPE. An alpha of p < 0.05 determined statistical significance.

Results: VO2PEAK (46.08 ± 6.21 mL/kg/min) was non-significantly related to IMPULSE (2394.20 ± 1211.69 N*s; r = -0.178, p = 0.321). VO2PEAK was significantly related to ETRIMP (34.30 ± 27.64 AU; r = -0.435, p = 0.011) yet non-significantly related to SRPE (246.92 ± 319.52 AU; r = -0.210, p = 0.250).

Conclusions: Cardiovascular fitness is unrelated to the external load completed by FFs for a fire tone call, suggesting that uniform amounts of work are completed by FFs of varying fitness levels. Cardiovascular fitness is also unrelated to the perceived internal load of the task, however, FFs with lower cardiovascular fitness levels elicit greater physiological internal loads to the work demands. PRACTICAL APPLICATION: The subjective measure of SRPE may allow individuals that elicit a greater cardiovascular response to job demands to reflect internal loads similar to those that required a lesser cardiovascular load. In turn, firefighters who have greater cardiovascular recovery needs and subsequently may have greater cardiovascular risk, including individuals with lower aerobic capacities, may go unnoticed. Utilization of a physiological internal load measure, such as ETRIMP, may more adequately reflect the intrinsic response to fire tone call demands and allow for enhanced identification of individual recovery needs.

Acknowledgements: None