Elsevier

Gait & Posture

Volume 52, February 2017, Pages 165-170
Gait & Posture

Full length article
StepWatch accuracy during walking, running, and intermittent activities

https://doi.org/10.1016/j.gaitpost.2016.11.035Get rights and content

Highlights

  • The StepWatch preprogrammed settings provide accurate step counts for walking, but not running, in able-bodied adults.

  • Modifying the cadence and sensitivity settings can improve accuracy in running and tennis.

  • The default settings enhance accuracy for able-bodied adults who perform light, intermittent lifestyle activities.

  • The modified settings enhance accuracy for able-bodied adults who perform running or vigorous sports.

Abstract

Introduction

The purpose of this study was two-fold: 1) to investigate effects of cadence and sensitivity settings for the StepWatch (SW3) on step count accuracy over a wide range of ambulatory speeds, and 2) to compare the preprogrammed “quick start” settings to modified settings during intermittent lifestyle activities.

Methods

Part 1: Fifteen participants (18–57 years of age) performed two trials of treadmill walking and running at ten speeds ranging from 26.8 to 268 m min−1 while wearing four SW3 devices. During the first trial, the cadence setting was maintained while sensitivity was varied; in the second trial sensitivity was maintained while the cadence setting was varied. Part 2: Fifteen participants performed four intermittent activities and drove an automobile while wearing two SW3 devices, one with preprogrammed settings and the other with the modified settings determined in Part 1.

Results

Part 1: The modified settings (cadence setting of 70% of default and sensitivity of 16) provided the greatest step counting accuracy across a wide range of speeds reporting 96.0–104% of actual steps between 53.6 and 268 m min−1. Part 2: The preprogrammed settings tended to have higher accuracy for light household tasks (recording 88% to 94% of actual steps) than the modified settings (recording 82% to 86% of actual steps) which showed a trend towards higher accuracy for tennis (recording 93% vs. 89% of actual steps) (p < 0.05).

Conclusion

The preprogrammed “quick start” StepWatch settings should be used with individuals who do not engage in running and vigorous sports. However, for individuals who engage in running and tennis, use of modified settings may result in improved step counting accuracy.

Introduction

Step counting has been performed for several centuries. Historically, it was used to estimate walking distances (based on an assumed stride length). More recently, however, it has been used to assess ambulatory physical activity in free-living humans. Tryon (1991) has noted that the step can be viewed as a preferred metric for physical activity assessment because it is a natural unit of ambulation. Step counting is an accepted measure of functional status of individuals, particularly at the lower end of the physical activity continuum where walking is the main activity performed and where physical activity questionnaires are less sensitive. For instance, increases in steps per day are viewed as a sign of improvement during the rehabilitation process and they are a valuable metric for discriminating physical activity levels in older adults [1], [2], [3]. Additionally, in healthy adult populations, step counters can serve to motivate clients and facilitate behavior change when coupled with a physical activity goal [4], [5]. However, these consumer-oriented step counters need to be compared against a more rigorously validated research grade device.

In previous studies, waist-worn pedometers have been found to be reasonably accurate for moderate or self-selected walking speeds (e.g. 80 m min−1). However, few studies have reported step count accuracy during running. Two studies report reasonable accuracy for running speeds including 160–215 m min−1, but accuracy at faster speeds and during intermittent activities is largely unknown [6], [7], [8]. Considering the slow speeds involved in intermittent activities of daily living (e.g. cleaning counter tops, vacuuming, and dusting) and high speeds involved in sport pursuits (e.g. tennis and basketball) a device that can accurately tally steps over a wide range of speeds is needed for assessing true daily step counts.

The StepWatch 3 (SW3; Modus Health, Inc., Washington, DC) is an ankle-mounted step counter originally developed for use in individuals with impaired functional status [1]. The SW3 is the most accurate pedometer ever constructed for walking, capturing 98% to 100% of all steps taken from 27 to 107 m min−1 [9]. Hickey et al. (2015) have shown the SW3 is also quite accurate for intermittent household activities, capturing 90% of steps taken while dusting and 102% of steps taken while cleaning a room. However, a serious limitation of this device is that it only captures 68% of steps during running at 161 m min−1 [7]. Other researchers have taken the approach of individualized calibration, adjusting the cadence and sensitivity settings until the device yielded results within 3% of directly observed steps [10], [11]. Using this approach, they were able to obtain accurate SW3 results for both walking and running in young children. However, no set rules for practical application were developed.

Clinicians and researchers can program the SW3 to account for the individual user’s step characteristics and gait speed. Specifically, the cadence and sensitivity settings preprogrammed into the device can be altered to account for these differences. The cadence setting is the length of time (cadence settings x 0.01 s) after a step is taken during which a subsequent step cannot be counted and sensitivity setting is the threshold acceleration that must be exceeded to register a step [12]. Determining the appropriate cadence and sensitivity settings for different speeds might improve the accuracy of the SW3 during running, while at the same time preserving its high accuracy for walking and intermittent lifestyle activities. Improving the accuracy of the SW3 in able-bodied adults could allow it to be used as a criterion for validating other step counters.

Thus, the purpose of this study was to examine the accuracy of the SW3 for determining steps taken by normal, healthy adults during walking, running, and intermittent lifestyle activities. In Part 1, the impact of the cadence and sensitivity settings on step counting error was explored for treadmill walking/running speeds ranging from 26.8 to 268 m min−1, in order to enhance the accuracy. In Part 2, the step count accuracy during intermittent, lifestyle activities was then investigated using the preprogrammed “quick start” settings and the modified settings developed in Part 1.

Section snippets

Participants

Twenty-five participants were recruited from the local community. Fifteen participants performed Part A, and five of them returned to complete Part B. Ten additional participants were recruited for Part B.

Individuals who were unable to run at 268 m min−1, who had lower limb injury or dysfunction, or who were diagnosed with cardiovascular disease were excluded from this study. The research protocol was approved by the local Institutional Review Board (IRB). All participants signed an informed

Results

A total of 25 participants with a mean (SD) age of 26 (8) years, height of 1.73 (0.10) m, body mass of 74.4 (13.8) kg, and body mass index of 24.7 (2.9) kg/m2 took part in this study. In Part 1, results from the one-way ANOVAs detected significant differences within all cadence and sensitivity settings at each speed (p < 0.05). Post hoc testing with Bonferroni adjustments revealed significant differences for several of the cadence and sensitivity settings used at each speed. Table 3, Table 4

Discussion

The main objective of this study was to explore the effects of the SW3 cadence and sensitivity settings on step count accuracy. This was done in order to develop modified settings that would allow for improved accuracy across a wide range of ambulatory speeds. A secondary objective was to compare the accuracy of the modified settings vs. the default settings, during intermittent, lifestyle activities.

To explore the accuracy of the SW3 settings at running speeds, the “Easy Start” selections in

Conflict of interest statement

All authors of this manuscript declare that they have no competing interests or conflicts of interest.

Funding

No financial support was received for the development and preparation of this manuscript.

Authors’ contributions

“Each of the authors has read and concurs with the content in the final manuscript. The material within has not been and will not be submitted for publication elsewhere except as an abstract.”

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