The Association Between Step Intensity and Cardiorespiratory Fitness in Adults

Abstract

Background: Cardiorespiratory fitness (CRF) is an independent predictor of morbidity and mortality risk. Physical activity is an established, modifiable determinant of CRF, and findings suggest that daily steps are positively associated with CRF. Whether step intensity is associated with CRF has not been rigorously investigated. Purpose: To examine the association between step intensity and CRF. Methods: Participants include 423 physically inactive adults (51.8 ± 8.6 years, 71.5% female) from two randomized controlled trials at Queen’s University. Step intensity (as indicated by average stepping rate, peak 1-min, and peak 30-min step rate) and daily steps were measured using a hip-worn accelerometer. CRF was assessed with a maximal treadmill test using open-circuit spirometry. Results: All step intensity metrics were positively associated with CRF in univariate analyses (p < 0.001). After controlling for age, sex, and daily steps, associations were attenuated: peak 1-min (partial R² = 0.02, p = 0.002) and 30-min step rate (partial R² = 0.01, p = 0.002) remained significant, while average step rate was not (p = 0.6). Daily steps remained associated with CRF independent of average step rate (R² = 0.02, p < 0.001) and peak 1-min step rate (partial R² = 0.01, p = 0.01), but not after adjusting for peak 30-min step rate (p = 0.22). Conclusion: Peak stepping intensity is associated with CRF beyond daily steps.