How valid are wearable physical activity trackers for measuring steps?

Area of Science:

• Biomedical Engineering
• Sports Science
• Human Movement Analysis

Background:

• Wearable activity trackers are widely used for monitoring physical activity.
• There is limited data on the validity of these devices for accurate step counting.

Purpose of the Study:

• To evaluate the accuracy and validity of 10 different wearable activity trackers in measuring step counts.
• To compare device performance across various activity conditions: treadmill, over-ground walking, and 24-hour free-living.

Main Methods:

• Thirty-five healthy participants engaged in three distinct activity protocols.
• Ten activity trackers were worn simultaneously during treadmill and over-ground trials.
• Three trackers were randomly selected for a 24-hour free-living assessment.

Main Results:

• Correlations between measured and observed steps were r=0.84 (treadmill) and r=0.67 (over-ground).
• Mean absolute percentage error (MAPE) was 8.2% (treadmill), 9.9% (over-ground), and 18.48% (free-living).
• Fitbit Zip and Withings Pulse demonstrated the highest accuracy across all conditions.

Conclusions:

• Wearable activity tracker accuracy for step counts varies significantly by device, speed, and activity context.
• Fitbit Zip and Withings Pulse are recommended for reliable step count monitoring.
• Further research is needed to understand the variability in tracker performance.