(02) DOES YEARS OF SERVICE MEDIATE THE EFFECT OF AGE ON FIREFIGHTER FITNESS?

A unique aspect of the firefighting (FF) profession, as compared to other emergency responders, is that FF may enter the academy at any age, provided they pass entry requirements. Prior to entering the FF academy, individuals are required to pass the Candidate Physical Ability Test to assess ability to perform FF tasks. Thus, the biological age of a FF and their years of service (YOS) could potentially vary considerably between FF. Considering the numerous stressors associated with FF, injuries, and other health issues, one could assume that YOS may have an influence on fitness that could mediate some of the natural changes in fitness due to aging.

Purpose: To investigate the mediating effect of YOS on age and professional FF performance on common fitness assessments (FA).

Methods: A retrospective analysis was conducted on annual FF fitness testing from 2019-2021. Deidentified data from 1281 participants (M:1136, F:145, Age:39.18±9.34yr, YOS:10.98±7.26yr.) were included in the study. Fitness test data consisted of maximum pull-ups (PL), maximum push-ups within 60 seconds (PU), maximum curl-ups within 60 seconds (CU), and 3-minute step test to estimate peak oxygen consumption (VO₂). Descriptive statistics for FA were computed in means and standard deviations. A direct effect of YOS on age was assessed with Pearson’s correlation coefficient. A Path analysis was used to test the mediation effect of YOS on the relationship between age and FA. Model estimations were conducted with the Lavaan package using maximum likelihood estimates in R(p< 0.05).

Results: FF completed 5.58(5.10)PL, 35.10(12.55)PU, 42.91(17.35)CU, and had an estimated VO₂ of 45.12(8.54). There was significant direct effect between YOS and age (r=0.66,p< 0.001). The model was over identified (X² (df)=10.077(2)) and fit the data well (CFI=0.997, RMESA [95%CI]=0.056[0.025,0.093].The model revealed that the indirect effect of YOS significantly mediated the relationship between age and CU(b=-0.116, p< 0.001). YOS partially mediated the effect of age on performance of PL(b=-0.172,p< 0.001) and PU(b=-0.173,p< 0.001). YOS had no mediation effect on age(b=0.005,p >0.05) and VO₂(b=0.004,p >0.05).

Conclusion: Age-related reductions in fitness are well-documented, our findings suggest that YOS of FF may exasperate the decline specifically in core strength (measured by CU). Due to the rigor of FF, core strength can be a vital attribute for occupational performance (OP). The current evidence suggests that fire departments should consider YOS in addition to age when assessing OP of fitness FF.

PRACTICAL APPLICATION: Practitioners need to account for the potential of substantial variability in biological age and YOS when implementing assessments and periodized training programs for FF. The adoption of an annual fitness assessment by fire departments may be advantageous to objectively assess and monitor FF fitness longitudinally to attenuate compounding negative effects of age and YOS on FF OP.

Acknowledgements: None