PEDOMETER SENSITIVITY AND SPECIFICITY
Guy C. Le Masurier · Medicine & Science in Sports & Exercise · 2004
Dear Editor-in-Chief: Crouter et al. (1) provide a timely examination of the validity of 10 electronic pedometers. In terms of detecting steps taken, the authors recommended researchers choose from four pedometers that showed acceptable accuracy both at slow speeds (54 m·min−1) and at higher speeds. While I do not disagree with Crouter and his associates, I advise researchers to carefully consider sensitivity and specificity when selecting a motion sensor. For example, pedometers with greater sensitivity will be better able to detect lower stepping forces, thus making them more accurate at slower speeds. However, Le Masurier and Tudor-Locke (2) demonstrated that the CSA accelerometer (an accelerometer capable of counting steps taken) was more sensitive than a Yamax pedometer at slower walking speeds but also detected 17-fold more nonsteps during motorized travel, illustrating a lower specificity (i.e. ability to discriminate movements, including external agitation, that are not ambulatory in nature). In essence, increased motion sensor (pedometer or accelerometer) sensitivity to lower threshold forces can result in a significant overestimate of steps taken under such conditions. Of the four pedometers recommended by Crouter et al. (1) only the Yamax Corporation (Tokyo, Japan) publishes a sensitivity threshold for their pedometers (≤0.35 g). Lowering this sensitivity threshold would improve a pedometer’s ability to detect slow steps taken but would also lead to compromised specificity. Unfortunately, the optimal sensitivity threshold (i.e., one that maximizes sensitivity and minimizes specificity) is not known at this time, but it would be a useful indicator of motion sensor quality. Guy Le Masurier