Table 1.

Technical specifications of the GT3X^® ActiGraph accelerometer and the Google Fit^® smartphone application.

Specification	ActiGraph GT3X®	Google Fit® smartphone application
Sample rate	30 Hz	Not available
Data storage	16 MB	16 GB
Battery life	31 days	17 h to 12.5 days
Accelerometer sensor	ADXL335 triaxial accelerometer (Analog Devices, USA)	MPU6515 triaxial accelerometer + gyroscope (Invense Inc., USA)
Registered range of acceleration	±3 g	Not available
Measured outcomes	Acceleration around three axes and vector magnitude	Acceleration around three axes
Estimated outcomes	Number of steps taken, energy expenditure (kcal), and duration of physical activity (min)	Number of steps taken, type of activity, traveled distance (miles or km), energy expenditure (cal), and duration of physical activity (min)