Reliability and validity of wrist-worn activity monitors in healthy young adults

BACKGROUND: Wrist-Worn Activity Monitors(WWAMs) are low-cost, user-friendly devices which have become popular for monitoring physical activity. Their reliability and validity need investigation for accurate physical activity monitoring. We examined between-sessions and inter-device reliability of the WWAMs. In addition, we examined the criteria-related validity of the WWAMs against two gold standards, an Ankle-Worn Activity monitor (AWAM) and video. METHODS: Twenty volunteers participated in two sessions, one week apart. In each session, participants walked on a treadmill for five minutes at each of the three speeds: 0.89 m/s (slow),1.12 m/s (moderate) and 1.33 m/s (fast). Total step counts at each speed were obtained using one AWAM (stepWatch), three-WWAMs (Fitbit Flex) and video. The Intraclass Correlation Coefficient (ICC) was calculated to determine the reliability and validity of the WWAMs. RESULTS: The WWAMs exhibited moderate to excellent between-sessions reliability (ICC = 0.69-0.90). The WWAMs demonstrated excellent inter-device reliability at each speed across both sessions (ICC = 0.91-0.98). The criteria-related validity ofWWAMscompared to theAWAM, and video recording showed moderate to excellent agreement (ICC = 0.67-0.85) at each speed. CONCLUSIONS:WWAMs recorded steps consistently between-sessions and between-devices for treadmillwalking among healthy adults at each speed but exhibited limited agreement for recording steps at each speed compared to AWAMand video.