Walk4Life MVP® Pedometer Accuracy to Assess MVPA During Treadmill Walking

There is much interest in physical activity (PA) assessment via pedometry. Concern arises regarding PA intensity with step counts. Are steps moderate-to-vigorous (MVPA) or lower intensity PA? Accelerometry, a pedometry alternative, is more expensive and time consuming. The Walk4Life MVP (W4L) pedometer assesses steps taken, distance, MVPA min and bouts of MVPA based on PA steps per min (spm; range 70-150) and minimum bout min (range 5-20 min), and total PA min.

Purpose

To determine W4L accuracy at a constant pace, with a known spm during MVPA (3.0 ≤ METs ≤ 6.0).

Methods

51 participants (23F; 28M) M age=22±3 yr completed a 32-min protocol of level treadmill walking at 3.4 mph (3.7 METs). Each participant wore W4L and Yamax pedometers. W4L and Yamax pedometers were randomly chosen from 10 and 5 available for each participant. Prior to the walk, individual stride length and spm at 3.4 mph were measured. MVPA bout length was set at 10 min and minimum spm at 2.5 mph (3.0 METs). Each participant completed 3 10-min bouts of MVPA in the 32-min protocol. Accuracy was determined by comparing W4L and Yamax step counts, comparison of W4L PA and MVPA min to the protocol time, and treadmill and W4L recorded distances. Comparison was made between W4L steps recorded and steps estimated from 32 mins * individual spm at 3.4 mph.

Analysis/Results

Two participants were excluded from analyses because the Yamax pedometer recorded ≤10 steps during 32 min walking, apparently due to placement. No W4L pedometer malfunctioned. The M difference between W4L and Yamax steps was 104 ± 233 (approximately 3800 steps). The M difference between spm estimated for 32 min and W4L steps was 72 ± 163. For 32 min of treadmill MVPA, the W4L recorded M=31:45 PA and M MVPA=31:44. The M distance difference between W4L and treadmill recorded miles was .11 ± .15. 39 (80%). W4L recorded 3 10-min bouts, 6 (12%) 2 bouts, 1 (2%) 1 bout, and 3 (6%) no bouts.

Conclusions

The W4L pedometer validly assessed group steps and PA and MVPA min during level treadmill walking at a constant MVPA speed. Individual variation was substantial in a small number of participants, but individual agreement was generally quite good (i.e., >85% of participants within 5% difference on most measures). Further evaluation is necessary for the W4L MVPA bout function and determination of W4L accuracy in non-constant, non-level, free-living PA.