Accuracy of the vivofit activity tracker.

Area of Science:

• Sports Medicine
• Biomedical Engineering
• Wearable Technology

Background:

• Activity trackers are increasingly used for monitoring physical activity and energy expenditure.
• Accurate assessment of energy expenditure and step count is crucial for health and fitness applications.
• The vivofit is a popular consumer-grade activity tracker whose accuracy requires validation.

Purpose of the Study:

• To evaluate the accuracy of the vivofit activity tracker in measuring energy expenditure (EE) and step count.
• To compare vivofit's Basal Metabolic Rate (BMR) estimations with indirect calorimetry (IC).
• To assess vivofit's performance across different activity types and intensities, including treadmill walking and office-type activities.

Main Methods:

• Thirteen participants wore the vivofit for five days, engaging in 1-hour daily self-selected activities.
• On day four, participants underwent BMR assessment and a treadmill-walking task (TWT) in a lab setting.
• On day five, participants performed 1-hour of office-type activities to assess sedentary behavior tracking.

Main Results:

• Vivofit's BMR estimations showed no significant difference compared to IC measurements.
• The device significantly underestimated EE during treadmill walking but accurately detected changes in inclination.
• Step count was underestimated during level walking but accurately estimated during incline walking, with a strong correlation between EE and exercise intensity.

Conclusions:

• The vivofit activity tracker demonstrates comparable accuracy to similar devices for general physical activity tracking.
• Its BMR estimation is reliable, but users should be aware of potential underestimations in EE and step count during specific activities.
• The device's responsiveness to walking inclination suggests potential for use in varied terrain monitoring.