Resting heart rate, heart rate reserve, and metabolic syndrome in professional firefighters: A cross-sectional study

Background: Little is known about the associations of resting heart rate (RHR) and heart rate reserve (HRR) with metabolic syndrome (MetS) in firefighters. Methods: For each of 288 professional firefighters, HRR was calculated as the difference between measured RHR and estimated maximum HR. For comparison, VO₂ max based on a treadmill test was included. MetS was defined according to the NCEP/ATP III criteria. Results: The prevalence of MetS was 14.2%. The average of RHR was 61.5 beat/min. Only 5.8% of the firefighters had RHR of ≥80 beat/min. Between the firefighters in the lowest and highest quintiles, the prevalence ratios (95% confidence intervals) for MetS were 1.88 (0.71-4.94), 5.90 (1.74-20.02), and 8.03 (1.86-34.75) for RHR, HRR, and VO₂ max, respectively. Both HRR and VO₂ max, but not RHR, were significantly associated with MetS and its most component risk factors in middle-aged firefighters. Conclusions: HRR, a simple cardiovascular fitness measure, was inversely associated with MetS among middle-aged professional firefighters.