Measuring Reliability of Movement With Accelerometry: Fitbit^® Versus ActiGraph^®.

Area of Science:

• Biomedical Engineering
• Wearable Technology
• Movement Science

Background:

• Accelerometry is crucial for measuring upper extremity (UE) movement.
• Wearable devices like Fitbit offer accessible activity monitoring.
• Validating consumer-grade devices against research-grade monitors is essential for clinical utility.

Purpose of the Study:

• To compare the reliability of the Fitbit Flex with the ActiGraph wGT3X-BT for measuring UE movement.
• To assess the clinical utility of Fitbit accelerometry for UE activity.

Main Methods:

• Two studies involved healthy adults wearing both Fitbit Flex and ActiGraph monitors on wrists.
• Participants engaged in everyday activities for 24 hours (Study 1) or 4 hours during an active period (Study 2).
• Data from both devices were analyzed for correlation and differences in movement detection.

Main Results:

• A high positive correlation was observed between Fitbit and ActiGraph data.
• The Fitbit Flex recorded significantly fewer upper extremity movements compared to the ActiGraph wGT3X-BT.
• Despite correlation, sensitivity differences were noted.

Conclusions:

• The Fitbit Flex and ActiGraph demonstrate similar patterns in measuring UE activity.
• The Fitbit Flex is less sensitive than the ActiGraph in detecting movements.
• Findings provide insights into the clinical utility of Fitbit for UE activity monitoring.