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The purpose of this study was to compare steps·d-1 between an accelerometer and pedometer in 2 free-living samples.
Data from 2 separate studies were used for this secondary analysis (Sample 1: N = 99, Male: n = 28, 20.9 ± 1.4 yrs, BMI = 27.2 ± 5.0 kg·m-2, Female: n = 71, 20.9 ± 1.7 yrs, BMI = 22.7 ± 3.0 kg·m-2; Sample 2: N = 74, Male: n = 27, 38.0 ± 9.5 yrs, BMI = 25.7 ± 4.5 kg·m-2, Female: n = 47, 38.7 ± 10.1 yrs, BMI = 24.6 ± 4.0 kg·m-2). Both studies used identical procedures and analytical strategies.
The mean difference in steps·d-1 for the week was 1643.4 steps·d-1 in Study 1 and 2199.4 steps·d-1 in Study 2. There were strong correlations between accelerometer- and pedometer-determined steps·d-1 in Study 1 (r = .85, P < .01) and Study 2 (r = 0.87, P < .01). Bland-Altman plots indicated agreement without bias between steps recorded from the devices in Study 1 (r = −0.14, P < .17) and Study 2 (r = −0.09, P < .40). Correlations examining the difference between accelerometer–pedometer steps·d-1 and MVPA resulted in small, inverse correlations (range: r = −0.03 to −0.28).
These results indicate agreement between accelerometer- and pedometer-determined steps·d-1; however, measurement bias may still exist because of known sensitivity thresholds between devices.
Behrens is with the Dept of Health Sciences, University of Colorado at Colorado Springs. Dinger is with the Dept of Health and Exercise Science, University of Oklahoma, Norman, OK.