Elsevier

Preventive Medicine

Volume 41, Issues 3–4, September–October 2005, Pages 778-783
Preventive Medicine

Precision and accuracy of an ankle-worn accelerometer-based pedometer in step counting and energy expenditure

https://doi.org/10.1016/j.ypmed.2005.07.006Get rights and content

Abstract

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).

Conclusion.

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.

Introduction

Obesity is epidemic in the United States and Europe and is emerging as a major health concern in low- and middle-income countries (World Health Organization, 1997). Statutory bodies and expert committees have repeatedly emphasized the importance of increasing physical activity because of the broad-ranging health benefits of exercise, even in the absence of weight loss (US Department of Health and Human Services CfDCaP, National Center for Chronic Disease Prevention and Health Promotion, 1996). How best to successfully promote physical activity, however, remains elusive (US Department of Health and Human Services CfDCaP, National Center for Chronic Disease Prevention and Health Promotion, 1996). One approach has been through using step-counting devices or pedometers. Pedometers, which are readily available and generally inexpensive, can either be used as a means of monitoring physical activity or for exercise treatment (“10,000 steps per day program”) (Tudor-Locke et al., 2002, Speck and Looney, 2001). Data suggest, however, (Melanson et al., 2004) that such devices are frequently inaccurate independent of user error. This is important because if pedometers prove to be inaccurate, we should be cautious regarding their use in detecting and treating inactivity.

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. Our primary hypothesis was that the Stepwatch pedometer is an accurate and precise measure of walking steps in lean and obese individuals. Our secondary hypothesis was that walking energy expenditure can be accurately modeled using the Stepwatch pedometer.

Section snippets

Subjects

Twenty healthy adults of varying age (21–51 years), weight (56–120 kg), and body mass index (BMI) (19–43 kg/m2) were studied. Ten subjects (5 male and 5 female) were lean (BMI < 25 kg/m2) and 10 subjects (5 male and 5 female) were obese (BMI > 30 kg/m2).

Methods

Prior to the study, subjects provided informed verbal consent which was documented and all procedures were demonstrated and tested with the subject. The study was approved by the Mayo Clinic Institutional Review Board.

On the day of the study,

Results

All subjects completed all components of the study. The mean age, weight, and BMI (mean ± SD) for the lean group was 30 ± 13 years, 69 ± 11 kg, and 22 ± 2.0 kg/m2 and for the obese group (mean ± SD) 32 ± 7 years, 96 ± 12 kg, and 34 ± 4.0 kg/m2, respectively.

To address our primary hypothesis we compared the precision and accuracy of the pedometers against the gold standard of manual counting. First, there was almost perfect agreement between the two Stepwatches worn by each subject. The average,

Discussion

As obesity and inactivity are epidemic in many develop countries, we are challenged to develop accurate tools for evaluating and intervening in inactivity. Specifically, we evaluated an ankle-worn accelerometer-based step counter (the Stepwatch). We addressed two hypotheses, namely, that the Stepwatch is an accurate and precise measure of walking steps in lean and obese individuals. Our second hypothesis was that walking energy expenditure could be accurately modeled using the Stepwatch. Data

Acknowledgments

All authors declare no financial interest in any of the companies that manufacturer or distribute pedometers. The research was funded entirely by NIH DK56650, DK 63226, and DK66270.

References (15)

  • E.L. Melanson et al.

    Commercially available pedometers: considerations for accurate step counting

    Prev. Med.

    (2004)
  • C.E. Tudor-Locke et al.

    Pedometer-determined ambulatory activity in individuals with type 2 diabetes

    Diabetes Res. Clin. Pract.

    (2002)
  • D.R. Bassett et al.

    Accuracy of five electronic pedometers for measuring distance walked

    Med. Sci. Sports Exerc.

    (1996)
  • S.E. Crouter et al.

    Validity of 10 electronic pedometers for measuring steps, distance, and energy cost

    Med. Sci. Sports Exerc.

    (2003)
  • R.J. Gretebeck et al.

    Variability of some objective measures of physical activity

    Med. Sci. Sports Exerc.

    (1992)
  • J.O. Hill et al.

    Obesity and the environment: where do we go from here?

    Science

    (2003)
  • L. Lanningham-Foster et al.

    Labor saved, calories lost: the energetic impact of domestic labor-saving devices

    Obes. Res.

    (2003)
There are more references available in the full text version of this article.

Cited by (0)

View full text