Effects of body mass index and step rate on pedometer error in a free-living environment.
Pedometers could provide great insights into walking habits if they are found to be accurate for people of all weight categories.


OBJECTIVE
the purposes of this study were to determine whether the New Lifestyles NL-2000 (NL) and the Digi-Walker SW-200 (DW) yield similar daily step counts as compared with the StepWatch 3 (SW) in a free-living environment and to determine whether pedometer error is influenced by body mass index (BMI) and speed of walking. The SW served as the criterion because of its accuracy across a range of speeds and BMI categories. Slow walking was defined as ≤80 steps per minute.


METHODS
fifty-six adults (mean ± SD: age = 32.7 ± 14.5 yr) wore the devices for 7 d. There were 20 normal weight, 18 overweight, and 18 obese participants. A two-way repeated-measures ANOVA was performed to determine whether BMI and device were related to number of steps counted per day. Stepwise linear regressions were performed to determine what variables contributed to NL and DW error.


RESULTS
both the NL and the DW recorded fewer steps than the SW (P < 0.001). In the normal weight and overweight groups, error was similar for the DW and NL. In the obese group, the DW underestimated steps more than the NL (P < 0.01). DW error was positively related to BMI and percentage of slow steps, whereas NL error was linearly related to percentage of slow steps. A surprising finding was that many healthy, community-dwelling adults accumulated a large percentage of steps through slow walking.


CONCLUSIONS
the NL is more accurate than the DW for obese individuals, and neither pedometer is accurate for people who walk slowly. Researchers and practitioners must weigh the strengths and limitations of step counters before making an informed decision about which device to use.
Tyo
Brian M
BM
Center for Physical Activity and Health, University of Tennessee, Knoxville, TN 37996, USA. btyo@utk.edu
Fitzhugh
Eugene C
EC
Bassett
David R
DR
John
Dinesh
D
Feito
Yuri
Y
Thompson
Dixie L
DL
D000293:Adolescent; D000328:Adult; D015992:Body Mass Index; D001835:Body Weight / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018670:Monitoring, Ambulatory / Q000295:instrumentation*; D019876:Sports Equipment; D016138:Walking / Q000502:physiology*; D055815:Young Adult