Accuracy of a piezoelectric pedometer in persons with and without Down syndrome.

Background: Piezoelectric pedometers with a tri-axial accelerometer mechanism may effectively monitor physical activity in persons with Down syndrome (DS), but their accuracy has not been determined in this population.

Aim: To examine the accuracy of a pedometer with a tri-axial accelerometer mechanism in measuring steps at different walking speeds in persons with and without DS.

Methods: Eighteen persons with DS (8 women; age 25±7y) and 22 persons without DS (9 women; 26±5y) participated in this study. Participants completed six over-ground walking trials at the preferred speed and at 0.5, 0.75, 1.0, 1.25, and 1.5ms, each lasting 6min. The steps taken were measured with hand-tally and with the Walk4Life MVPa piezoelectric pedometer. Pedometer accuracy was assessed with absolute percent error and Bland-Altman plots.

Results: Absolute percent error did not differ between persons with and without DS across speeds. Error decreased with increased speed (p<0.001), but leveled off at ≥1.0ms. Pedometers underestimated steps at 0.5 and 0.75ms, but were highly accurate at the preferred walking speed and at speeds ≥1.0ms.

Conclusions: A piezoelectric pedometer with a tri-axial accelerometer mechanism measures steps with high accuracy at the preferred walking speed and at speeds ≥1.0ms in persons with and without DS. Accuracy, however, is compromised at slower speeds. Across speeds, pedometer error is similar between persons with and without DS.