Step activity monitor: Increased accuracy in quantifying ambulatory activity

Abstract

This study compares the accuracy of a two-dimensional accelerometer worn on the ankle (a step activity monitor) with that of an electronic, digital pedometer worn on the belt line. Twenty-nine human subjects were evaluated while they briskly walked 400 M, slowly walked 10 M, and ascended and descended a flight of stairs. The step activity monitor had less error in all activities; its mean absolute error was 0.54%, whereas that of the pedometer was 2.82%. The difference was more pronounced in obese subjects (body mass index greater than 30), with an overall mean absolute error of 0.48% for the step activity monitor and 6.12% for the pedometer (nearly 13 times that of the step activity monitor). For subjects with a body mass index less than 30, the step activity monitor had an overall error of 0.56% and the pedometer had an overall error of 1.56% (less than 3 times that of the step activity monitor). The absolute error of the pedometer was positively correlated with body mass index (r = 0.792, p < 0.0001) and weight (r = 0.753, p < 0.0001), whereas the error of the step activity monitor was not significantly correlated with either. Neither device was significantly biased by age, gender, or the presence of a lower-extremity joint prosthesis. The accuracy and additional capabilities, including a real-time memory record of activity, of the step activity monitor make it well suited for objectively quantifying ambulatory activity, especially for obese subjects.

Reliability of daily step activity monitoring in adults with incomplete spinal cord injury

“…The SAM is a small, lightweight accelerometer that was developed in response to concerns regarding the accuracy and reliability of existing activity monitors when used by persons with gait dysfunction [28]. The SAM has been shown to demonstrate 95 percent accuracy and yield stable output during repeated testing (correlation range = 0.84 to 0.98) in persons with normal gait patterns [29]. In addition, Bowden and Behrman compared step counts obtained from the SAM to actual step counts registered during 10-meter and 6-minute walks and reported that the SAM displayed 97 percent accuracy among individuals with SCI [30].…”

Application of self-report and performance-based outcome measures to determine functional differences between four categories of prosthetic feet

“…Many methods can be implemented to monitor activity level, such as daily logs, pedometers, heart rate monitors, questionnaires, and accelerometers [32]. The step activity monitor (SAM), which is a device that measures long-term step activity, has demonstrated good reliability when measuring continuous activity [33] with varied surfaces and terrains [32]; footwear; body types [34]; gait styles [33]; and medical interventions and conditions, e.g., joint arthroplasty, lower-limb amputation, and diabetes mellitus [33][34].…”

The validity and reliability of a novel activity monitor as a measure of walking

“…This total may provide a person with a target to aim for but gives no indication as to when in the day the wearer was active, how long each walk lasted, or the intensity (for example, cadence) of the walk. Additionally, waist worn pedometer accuracy is compromised by slow walking speeds [7][8][9][10][11][12][13][14] and obesity. [15][16][17] The poor accuracy of waist mounted pedometers in recording slow walking may be a serious limitation when monitoring activity in patient groups such as the frail elderly.…”