Precision and accuracy of an ankle-worn accelerometer-based pedometer in step counting and energy expenditure.
BACKGROUND
Walking is a widely used approach to increase physical activity levels in obese patients. In this paper, we investigate the precision and accuracy of an ankle-worn dual-axis accelerometer (Stepwatch) and investigate its potential application as a predictor of energy expenditure.


METHODS
Twenty healthy subjects (10 lean, 10 obese) wore spring-levered (Accusplit), piezoelectric (Omron HF-100), and Stepwatch pedometers. Subjects walked on a treadmill at 1, 2, and 3 mph and in a hallway at 1 and 1.85 mph, during which energy expenditure was measured.


RESULTS
The Stepwatch counted 99.7 +/- 0.67% (mean +/- SEM) of the manual counts. In comparison, the Omron pedometer counted 61 +/- 3.3% and the Accusplit counted 26 +/- 2.8% of the manual counts at 1 mph although all pedometers were accurate (> 98% of counts) at 3 mph. In repeated measures, the Stepwatch produced negligible variance (SD = 0.36) over all speed whereas the other pedometers showed a large amount of variance at all speed (SD = 4-13). Stepwatch counts were predictive of walking energy expenditure corrected by weight (r2 > 0.8).


CONCLUSIONS
The counts from the Stepwatch were virtually identical to the manual counts from a trained investigator and provided a reliable predictor of walking energy expenditure.
Foster
Randal C
RC
Endocrine Research Unit, Division of Endocrinology, Department of Internal Medicine, Mayo Clinic, Rochester, MN 55905, USA.
Lanningham-Foster
Lorraine M
LM
Manohar
Chinmay
C
McCrady
Shelly K
SK
Nysse
Lana J
LJ
Kaufman
Kenton R
KR
Padgett
Denny J
DJ
Levine
James A
JA
D000328:Adult; D000842:Ankle; D015992:Body Mass Index; D004734:Energy Metabolism / Q000502:physiology*; D019544:Equipment Failure Analysis; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008910:Minnesota; D008991:Monitoring, Physiologic / Q000295:instrumentation*; D016138:Walking / Q000502:physiology*