Accuracy of a new time-resolved step counter in children.

Most pedometers record cumulative steps, limiting ability to assess level of physical activity or nonwear periods. The SportBrain iStep X1 has potential to overcome this limitation by recording and storing step count data in 60-s epochs. We evaluated accuracy of this instrument in children and the duration of consecutive zero step count minutes that indicated nonwear time periods. Seventeen children walked or ran on a treadmill at 2, 3, 4 and 5 miles/hour and walked around a track while wearing the SportBrain and Digiwalker SW-701 pedometer. We compared percent error in step counts for each pedometers relative to observer counts. A subsample wore a SportBrain pedometer during up to 5 days of usual activity. The SportBrain pedometer performed with acceptable accuracy at all evaluated treadmill speeds and during self-paced walking, recording steps within an average of 4% of observed step counts. It outperformed the Digiwalker, especially at slower speeds and in overweight children. During normal wear only 1% of zero count periods were more than 60 min. We conclude that the SportBrain iStep X1 pedometer provides a valid measure of step counts in short averaging times useful for assessing patterns of physical activity in population studies and periods of nonwear.