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

Area of Science:

• Biomechanics
• Wearable Technology
• Health Monitoring

Background:

• The accuracy of modern pedometer software applications (Apps) compared to traditional spring lever and piezoelectric pedometers remains unverified.
• Assessing the validity and reliability of step-counting devices is crucial for accurate physical activity monitoring.

Purpose of the Study:

• To compare the validity and reliability of two pedometer Apps (Walk Star, Accupedo) against established spring lever (Digi-Walker CW 700) and piezoelectric (Omron HJ-720ITC, Tanita PD-724) models.
• To determine the suitability of these devices for measuring step count in adults aged 18-65.
• To establish a benchmark for accuracy using direct researcher observation as the criterion measure.

Main Methods:

• Eighteen adult participants engaged in walking trials at varying speeds (2, 3, 4 mph) on a treadmill and at a self-selected pace on urban streets and grass.
• Step counts from two pedometer Apps and three physical pedometers were recorded.
• Direct researcher observation using an electronic hand tally counter served as the criterion measure for step count.

Main Results:

• Bland and Altman analyses revealed wide limits of agreement for the Yamax CW 700, Accupedo App, and Walk Star App, indicating significant random error and low reliability.
• The Omron HJ-720ITC and Tanita PD-724 pedometers exhibited narrow limits of agreement when compared to the criterion measure, suggesting suitability for step count measurement.
• Pedometer Apps and the spring lever model were found to be less reliable than the piezoelectric models tested.

Conclusions:

• The validity and reliability of pedometers, including software Apps, are not universally guaranteed and require empirical testing.
• Piezoelectric pedometers (Omron HJ-720ITC, Tanita PD-724) demonstrated superior accuracy and reliability compared to spring lever models and tested Apps.
• Researchers and individuals should verify the performance of any step-counting device before relying on its data.