Comparing Methods to Identify Wear-Time Intervals for Physical Activity With the Fitbit Charge 2

Area of Science:

• Biomedical Engineering
• Public Health
• Wearable Technology

Background:

• Established methods for processing physical activity tracker data are lacking.
• Accurate data processing is crucial for interventions and analyses.

Purpose of the Study:

• To develop a standardized approach for defining valid wear time from physical activity trackers.
• To compare two distinct methods for processing Fitbit Charge 2 data.

Main Methods:

• Sixteen African American women wore Fitbit Charge 2 for 20 days.
• Method 1: Valid day defined as ≥10-hr wear time with heart rate data.
• Method 2: Excluded minutes without heart rate, low heart rate/step data, and nighttime.

Main Results:

• Method 1 yielded significantly more wear time (20.5 hrs) than Method 2 (16.3 hrs) (p < .0001).
• Step counts were similar between methods (7,436 vs. 7,298 steps/day, p = .64).
• Linear regression modeled daily and weekly step changes.

Conclusions:

• The proposed algorithm offers a novel way to standardize physical activity tracker data.
• Further research is needed to enhance the accuracy of physical activity data sets.
• This standardization is vital for reliable data in health interventions.