Objectives: We assessed the prospective association of resting heart rate (RHR) at baseline with peak oxygen uptake (VO2peak) 23 years later, and evaluated whether physical activity (PA) could modify this association. Background: Both RHR and VO2peak are strong and independent predictors of cardiovascular morbidity and mortality. However, the association of RHR with VO2peak and modifying effect of PA have not been prospectively assessed in population studies. Methods: In 807 men and 810 women free from cardiovascular disease both at baseline (1984-86) and follow-up 23 years later, RHR was recorded at both occasions, and VO2peak was measured by ergospirometry at follow-up. We used Generalized Linear Models to assess the association of baseline RHR with VO2peak, and to study combined effects of RHR and self-reported PA on later VO2peak. Results: There was an inverse association of RHR at baseline with VO2peak (p<0.01). Men and women with baseline RHR greater than 80 bpm had 4.6 mL·kg-1·min-1 (95% confidence interval [CI], 2.8 to 6.3) and 1.4 mL·kg-1·min-1 (95% CI, -0.4 to 3.1) lower VO2peak at follow-up compared with men and women with RHR below 60 bpm at baseline. We found a linear association of change in RHR with VO2peak (p = 0.03), suggesting that a decrease in RHR over time is likely to be beneficial for cardiovascular fitness. Participants with low RHR and high PA at baseline had higher VO2peak than inactive people with relatively high RHR. However, among participants with relatively high RHR and high PA at baseline, VO2peak was similar to inactive people with relatively low RHR. Conclusion: RHR is an important predictor of VO2peak, and serial assessments of RHR may provide useful and inexpensive information on cardiovascular fitness. The results suggest that high levels of PA may compensate for the lower VO2peak associated with a high RHR.
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