Cell Phone Based Physical Activity Monitoring. A Validation Study

Background The study aim was to investigate whether it is possible to use the accelerometer of mobile phones as a valid and reliable tool for monitoring the physical activity.

Method A specific mobile phone application to gather and record time varying acceleration was developed. The accelerometer integrated within two mobile phones (HTC Wildfire and HTC Desire HD) was compared to a widely used accelerometer (ActiGraph GT3X). Seven healthy adults wore a waist belt with the devices attached over the right hip. Each participant performed a series of seven physical activities (e.g. Sitting/Standing, Walking, Running) for seven times. A metronome provided the intensity of the activities. The Reliability was evaluated using the Intraclass Correlation Coefficient (ICC) and the Coefficients of Variation (CVs). Concurrent validity was assessed through the Pearson correlation and the level of agreement.

Results All the devices have demonstrated excellent test retest reliability in all the activities. The ICC in both the phone devices ranged between 0.824 and 0.979. CVs, for assessing the inter instrument reliability, varied among the activities and the participants. CVs were relatively low in certain participants and in the activities with higher intensity. Both phones have shown good correlation and level of agreement to the ActiGraph in all the activities.

Conclusion Cell phone accelerometer may be used as a tool for measuring Physical Activity. Further studies are still required for its development and implementation.