A Validation Study of the Fitbit One in Daily Life Using Different Time Intervals

Area of Science:

• Wearable technology
• Human movement analysis
• Biomedical engineering

Background:

• Accelerometer-based wearables offer real-time user feedback.
• Minute-by-minute validity is crucial for accurate real-time feedback.
• Few studies have assessed this granular validity.

Purpose of the Study:

• To evaluate the Fitbit One's validity against the ActiGraph GT3x+.
• To assess physical activity metrics: steps and time in moderate-to-vigorous activity.
• To analyze validity across minute, hour, and day time intervals in young adults.

Main Methods:

• 34 healthy young adults participated.
• Wore both ActiGraph GT3x+ and Fitbit One for one week.
• Statistical analyses included mixed models, ICCs, and Bland-Altman for steps and activity intensity.

Main Results:

• Fitbit One systematically overestimated steps (0.82/min, 45/hr, 677/day) compared to ActiGraph.
• Strong correlations found for step counts (B=0.72-0.89).
• Weaker correlations found for moderate-to-vigorous physical activity time (B=0.39-0.57).

Conclusions:

• Fitbit One is valid for step activity assessment, including real-time monitoring.
• Device overestimates step counts but shows good agreement.
• Agreement and correlation for moderate-to-vigorous physical activity intensity were lower.