College of Health

PURPOSE: To compare step outputs obtained from waist and wrist accelerometer attachment sites under laboratory and free-living conditions. METHODS: In the laboratory condition participants concurrently wore ActiGraph accelerometers at their waist and non-dominant wrist while walking/running at treadmill speeds between 14 m/min and 188 m/min. Visually counted steps served as a criterion standard. Participants then wore both accelerometers for 7 days. All accelerometer step data were processed applying both the manufacturer's default and low-frequency extension filters. Paired samples t-tests were used to evaluate mean differences in criterion steps/min and the four (attachment site X filter) estimates produced from the waist- and wrist-worn accelerometers in the laboratory study. Free-living differences in mean steps/day detected between the waist and wrist (considering both filters) were computed. RESULTS: Relative to visually counted steps, the waist attachment site generally out-performed the wrist attachment site at most speeds, regardless of the applied filtering process. Under free-living conditions, the waist-worn accelerometer detected 6,743 ± 2,398 (default filter) and 13,029 ± 3,734 (low-frequency extension) steps/day. The concurrently worn wrist accelerometer detected 9,301 ± 2,887 (default filter) and 15,493 ± 3,958 (low-frequency extension) steps/day. CONCLUSION: The wrist attachment site detected consistently fewer visually counted steps than the waist attachment site at most treadmill speeds during laboratory testing. In contrast, the wrist attachment site produced a higher average step count (ranging from approximately 2500 to 8700 more steps/day in free-living, dependent on filtering process applied) than the waist attachment site under free-living conditions. In conclusion, step outputs obtained from waist- and wrist-worn accelerometer attachment sites are generally not comparable in either laboratory or free-living conditions.