Reliability and Validity of Activity Trackers

In order to examine the test-retest reliability and the validity of the ten trackers in a standardized situation, the participants walked for 30 min on a treadmill at a walking speed of 4.8 km/h. This walking velocity was similar to velocities used in previous treadmill studies and is based on an average walking speed [14 , 23 (link)]. During the treadmill test, the participants wore all ten activity trackers and the ActivPAL. The Optogait system on the treadmill was used as the gold standard. The primary outcome measure was the total number of steps measured within the duration of the 30 min treadmill test. All participants repeated this test one week later.