Measuring step count: why it is important not to assume measures are reliable.

ABSTRACT

BACKGROUND: The validity and reliability of pedometer software Apps versus the previously investigated spring lever and piezoelectric pedometers is unknown. PURPOSE: To evaluate the validity and reliability (in adults aged 18-65) of two pedometer software Apps, the Walk Star and the Accupedo, with spring lever (Digi-Walker CW 700) and piezoelectric (Omron HJ-720ITC and Tanita PD-724) pedometers in the measurement of step count. The criterion for comparison was researcher tallied direct observation of step count using an electronic E3-EHT hand held tally counter. METHODS: Eighteen participants walked for 5minutes on a treadmill at slow (2miles per hour) moderate (3miles per hour) and fast walking (4miles per hour) speeds and on urban streets and upon grass at a perceived "comfortable" walking speed. RESULTS: Bland and Altman plots show wide limits of agreement observed for the Yamax CW 700, Accupedo App and Walk Star App, suggesting these pedometers are unsuitable for measuring step counts in individuals due to high random error (indicating low reliability). Narrow limits of agreement were observed for the Omron HJ-720ITC and the Tanita PD-724 pedometers compared against Tally count and were considered suitable for use. CONCLUSION: The validity and reliability of pedometers cannot be assumed but must be tested and ensured before use in measuring step count.