Aerobic Capacity Protects Against Cardiometabolic Risk Independent of Occupational Tenure in Firefighters

Introduction: Cardiovascular disease (CVD) is a leading cause of on-duty mortality among firefighters, accounting for ~42% of duty-related fatalities. Aerobic capacity (V̇O 2 max ) is inversely associated with CVD risk. Whether these protective effects persist across the occupational lifespan (i.e., years of service) with cumulative exposure to firefighting hazards and lifestyle factors remains unclear. The purpose of this study was to examine differences in CVD risk indices between firefighters classified above and below an occupational aerobic capacity threshold (i.e., 42 mL·min −1 ·kg −1 ), while adjusting for years of service. Methods: A cross-sectional analysis was conducted on 144 career firefighters (143 male, 1 female; age 33.3 ± 8.6 yr). Participants were classified into low aerobic capacity (<42 mL·min −1 ·kg −1 ; n = 92) or high aerobic capacity (≥42 mL·min −1 ·kg −1 ; n = 52) groups based on estimated V̇O 2 max from treadmill stress testing. General linear models compared groups across dual-energy X-ray absorptiometry-derived body composition, blood lipid and glycemic biomarkers, and CVD risk scores, with years of fire service experience as a covariate. Results: The high AC group demonstrated significantly more favorable profiles across all cardiometabolic domains, including body fat, visceral adiposity, triglycerides, low-density lipoprotein cholesterol, atherogenic indices, fasting insulin, and homeostatic model assessment of insulin resistance (all P < 0.05), which persisted after adjustment for years of service. Adjustment strengthened several associations, with CVD risk scores reaching statistical significance. Clear separation was observed between groups based on the two aerobic capacity classifications. Conclusion: Higher aerobic capacity is associated with favorable cardiometabolic profiles in firefighters, independent of years of service. These findings support the use of occupationally derived, task-based aerobic capacity standards rather than age- and sex-adjusted population percentiles to determine fit-for-duty decisions. Fire departments should prioritize aerobic capacity assessment and maintenance programs to mitigate cardiometabolic risk across the occupational lifespan.