Systematic Review of Fitbit Charge 2 Validation Studies for Exercise Tracking.

Area of Science:

• Wearable technology validation
• Biomedical engineering
• Health informatics

Background:

• Research-grade devices like Polar chest straps (ECG) and ACTiGraph accelerometers are validated for heart rate (HR) and step count, respectively.
• Wearable activity trackers measuring HR and steps concurrently have shown conflicting validation results against research-grade equipment.

Purpose of the Study:

• To review validation studies of the Fitbit Charge 2 (FBC2) for accuracy in measuring HR and step count.
• To evaluate the FBC2's reliability for use by researchers and clinicians.

Main Methods:

• A systematic review was conducted following PRISMA guidelines.
• Eight eligible articles published between 2018-2019 were identified from multiple databases and hand-searches.
• Concordance correlation coefficients (CCC) and mean absolute percent error (MAPE) were used to assess agreement and error between the FBC2 and criterion devices.

Main Results:

• FBC2 HR monitoring agreement (CCC) ranged from 26% to 92%, decreasing with increased exercise intensity.
• Step count agreement (CCC) increased from 38% to 99% with higher exercise intensity.
• HR error (MAPE) ranged from 9.21% to 68%, increasing with exercise intensity.
• Step count error (MAPE) was 12% in healthy adults but 46% in older adults with heart failure.

Conclusions:

• The FBC2 demonstrates acceptable HR accuracy at low-to-moderate exercise intensities.
• Step count validation remains inconclusive, requiring further research with controlled testing.
• The FBC2 may be suitable for HR monitoring in specific populations but is not definitively validated for step counting in all users.