Table 3.

Challenges and solutions or strategies for utilizing the Fitbit physical activity (PA) tracker in health interventions at the intervention delivery stage.

Challenges		Strategies and solutions
Interaction between participants and app
	Syncing-related issues include risk of data loss due to study participants forgetting to sync their Fitbit tracker with the mobile app, participants not knowing or remembering how to sync, Bluetooth turned off, internet turned off; login issues include logging off accidentally and forgetting credentials.	Offer written step-by-step instructions on how often and how to sync their tracker with the Fitbit mobile app to minimize data loss; send weekly text messages reminding all participants to sync their Fitbits or target only those who have not synced periodicallya; email or text participants with step-by-step troubleshooting; contact the superuser; ask participants to write down login credentials in the manual or another place of easy access.
	Fitbit updates during the intervention	Notify participants about app updates; update the participants’ manual; determine how to handle the introduction of new features or behavior change techniques (eg, behavioral notifications about PA or CVb health) according to study needs.
	Accidental deletion of Fitbit app	Contact the superuser (eg, family member or research assistant).
Interaction between participants and tracker
	Broken Fitbit tracker (battery does not charge or broken or lost charger), lost Fitbit tracker	Ensure at least a 10% Fitbit and charger surplus to the study budget in case Fitbit needs to be replaced; have participants use a Bluetooth locator app to help find the device.
	Fitbit tracker aesthetics (width, color, discoloration of the band)	Offer multiple bands of different colors, sizes, and materials.
	Skin irritation and rashes caused by the Fitbit tracker	Purchase and offer hypoallergenic bands to participants that report skin irritation and rashes; suggest participants remove the tracker or wear the tracker on the other wrist for at least 1 hour per day.
	Adherence to Fitbit usage (Fitbit does not calculate wear time)	Choose a device with a heart rate monitoring feature to calculate an approximate wear time [24]; have research staff send messages if wear time <10 hours/day or build automated text message reminders to wear the Fitbit.

^aMost Fitbit trackers can save up to 7 days of intraday data and up to 31 days of cumulative data in their memory without syncing. After that time, data are erased from the tracker to create space for the new data. This creates a risk for potential data loss if study participants do not sync their tracker regularly.

^bCV: cardiovascular.