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Medicine & Science in Sports & Exercise:
APPLIED SCIENCES: Physical Fitness and Performance

Accuracy and Reliability of 10 Pedometers for Measuring Steps over a 400-m Walk

SCHNEIDER, PATRICK L.; CROUTER, SCOTT E.; LUKAJIC, OLIVERA; BASSETT, DAVID R. JR.

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Abstract

SCHNEIDER, P. L., S. E. CROUTER, O. LUKAJIC, and D. R. BASSETT, JR. Accuracy and Reliability of 10 Pedometers for Measuring Steps over a 400-m Walk. Med. Sci. Sports Exerc., Vol. 35, No. 10, pp. 1779–1784, 2003.

Purpose: The purpose of this study was to determine the accuracy and reliability of the following electronic pedometers for measuring steps: Freestyle Pacer Pro (FR), Kenz Lifecorder (KZ), New Lifestyles NL-2000 (NL), Omron HJ-105 (OM), Oregon Scientific PE316CA (OR), Sportline 330 (SL330) and 345 (SL345), Walk4Life LS 2525 (WL), Yamax Skeletone EM-180 (SK), and the Yamax Digi-Walker SW-701 (DW).

Methods: Ten males (34.7 ± 12.6 yr) (mean ± SD) and 10 females (43.1 ± 19.9 yr) ranging in BMI from 19.8 to 33.6 kg·m−2 walked 400-m around an outdoor track while wearing two pedometers of the same model (one on the right and left sides of the body) for each of 10 models. Four pedometers of each model were assessed in this fashion. The actual steps taken were tallied by a researcher.

Results: The KZ, NL, and DW were the most accurate in counting steps, displaying values that were within ±3% of the actual steps taken, 95% of the time. The SL330 and OM were the least accurate, displaying values that were within ±37% of the actual steps, 95% of the time. The reliability within a single model (Cronbach’s alpha) was >0.80 for all pedometers with the exception of the SL330. The intramodel reliability was exceptionally high (>0.99) in the KZ, OM, NL, and the DW.

Conclusion: Due to the variation that exists among models in regard to the internal mechanism and sensitivity, not all pedometers count steps accurately. Thus, it is important for researchers who use pedometers to assess physical activity to be aware of their accuracy and reliability.

Prospective epidemiological studies support the belief that a physically active lifestyle can lower the risk of developing various chronic diseases such as coronary artery disease, Type 2 diabetes mellitus, hypertension, and obesity (1). With an emphasis on promoting a physically active lifestyle, numerous studies have examined the practicality and feasibility of using the pedometer as a tool for measuring physical activity levels (10,11,17,22,23,28,29). Pedometers are devices that are typically worn at the waist and are capable of counting steps. Some models also calculate distance and estimate energy expenditure. Pedometers are a means of objectively measuring ubiquitous, ambulatory activity as well as many types of structured physical activities (24).

The three main areas in which pedometer models may differ are cost, mechanism, and sensitivity of the device. There is considerable variation in the cost of a pedometer, which can range anywhere from $10 to $200. Given the wide range of costs of various pedometers, a less expensive pedometer becomes an attractive option for those wanting to do large-scale studies. Thus, it would be of interest to determine whether some of the less expensive pedometers are as accurate as some of the more costly versions. The internal mechanism is also a distinguishing point among the various brands and models of pedometers. There are three primary mechanisms by which pedometers function. The first type uses a spring-suspended horizontal lever arm that moves up and down in response to the hip’s vertical accelerations. This movement opens and closes an electrical circuit; the lever arm makes an electrical contact (metal-on-metal contact) and a step is registered. The second type of mechanism is a magnetic reed proximity switch. With this mechanism, a magnet connected to a spring-suspended horizontal lever arm within the pedometer moves up and down with each vertical acceleration of the hip. The magnetic field triggers a proximity switch encased in a glass cylinder and a step is counted. The third type uses an accelerometer-type mechanism consisting of a horizontal beam and a piezoelectric crystal. Pedometers using this particular mechanism can distinguish between differing intensities of exercise when estimating caloric expenditure. Finally, pedometers may also differ in their sensitivity, which is a function of the vertical acceleration “threshold” needed to trigger a step. Although this issue is related to the mechanism, the sensitivity of the internal mechanisms of different pedometers can vary as can the quality of the mechanism itself.

In general, pedometers are most accurate in counting steps, less accurate in calculating distance, and even less accurate at estimating energy expenditure (2,4). Because steps are the most direct expression of what the pedometer actually measures (25), most researchers recommend reporting pedometer data as steps (4,25). A previous study conducted by Bassett et al. (2) assessed the accuracy of five electronic pedometers in measuring distance walked and steps taken on a sidewalk course and found that pedometers varied significantly in the pedometer-calculated distance over 4.88 km. Due to the potential for such inaccuracies between pedometer models, it is essential that pedometers be tested for accuracy.

In addition to the variation that exists between models, it is possible for discrepancies to exist within a particular pedometer model (intramodel reliability). Given the potential for differences in manufacturing tolerances and design specifications, it is conceivable for devices of the same model to differ significantly in steps counted. Thus, it is evident that the reliability of pedometers within a particular model should be assessed.

Considering the fact that a great number of pedometer models have been introduced in recent years and that variability exists not only in the cost but also in the mechanism and sensitivity among pedometers, it would be beneficial to determine the accuracy of a variety of pedometers. In addition, the only multibrand comparison was carried out in 1996 (2), and none of the pedometers that were assessed at that time are currently available. Therefore, the purpose of this study was to determine the accuracy and reliability of 10 electronic pedometers for counting steps.

©2003The American College of Sports Medicine

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