Interinstrument Reliability of the Actigraph GT3X+ Ambulatory Activity Monitor During Free-living Conditions in Adults

Background: Currently, no studies have investigated inter-instrument reliability of the ActiGraph (AG) GT3X+ in free-living conditions. Methods: Nineteen adults (11 males, 8 females; aged 36.8 ? 11.9 years) wore a pair of AG?s (one on each hip), during all waking hours for one day. Raw outputs were generated for total counts, steps, wear time and mean counts per minute. Intensity outputs were derived for time (minutes) spent in 0.05). Conclusion: Reliability decreases beyond moderate intensities. MVPA displays superior inter-instrument reliability than individual intensity categories. Research question permitting, reporting time in MVPA may maximise reliability