An interventional study of Mobile App Push Notification (Random Selection) and Mobile App Push Notification (Behavior Science Heuristics) in Sedentary Lifestyle, sponsored by Fitbit LLC. Completed at 1 site in United States. Open to participants aged 22 Years to 60 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-08-25.
Sponsored by Fitbit LLC · Not applicable, Interventional, and Other
To evaluate the impact of two personalized nudging strategies delivered as pop-up notifications via the Fitbit app on user step count. Specifically, to personalize the following parameters of the pop-up notification system: message content, and timing (hr of the day).
Phase 1 [Model calibration]: Recruit up to 1,000 Fitbit users for a 4 week pilot study. Nudge content and timing will be varied randomly in order to collect training data to prime the RL architecture prior to Phase 2.
Phase 2 [Performance evaluation]: Recruit up to 12,000 Fitbit users for a 60 day study in which they are randomized evenly between the following 4 arms:
[Control] No nudges Randomly selected nudges from the custom nudge library, delivered at constant time and frequency Behavior science (BS)-only nudge agent PEARL agent
Phase 3 [Micro-randomized Trial (MRT) \& LLM Feasibility]: Recruit up to 6,000 Fitbit users for a 60 day study in which they are randomized evenly between the following arms:
Behavior science Micro-randomized Trial (BS-MRT): Once per day users will be randomized across the below factors, and receive a message written by a behavior scientist (the same messages from Phase 1 \& 2).
COM-B Theme: 6 themes, and 1 control (no nudge) Time of day: 3 timeframes, and 1 control (no nudge) Large Language Model Micro-randomized Trial (LLM-MRT): Once per day users will be randomized across the below factors, and receive a message written by a large language model.
COM-B Theme: 6 themes, and 1 control (no nudge) Time of day: 3 timeframes, and 1 control (no nudge) Large Language Model + Reinforcement Learning (LLM-RL): Once per day, a reinforcement learning model will run to select the optimal COM-B theme and time of day (the same RL model from Phase 2 Arm 4). The nudges will be selected from a repository that is written by a large language model (LLM).
Primary Purpose:
Phase 1: Model calibration Phase 2: Evaluate performance on step count Phase 3: Micro-randomized Trial (MRT) \& LLM feasibility
1,273 studies on the registry are indexed under Sedentary Behavior; 300 are open to participants now.
This study's enrollment of 13,463 is above the median of 60 across 1,076 interventional studies indexed under Sedentary Behavior.
Browse Sedentary Behavior studies →Fitbit LLC is the lead sponsor of 7 studies on the registry; 2 are open to participants now.
Counted across the registry records on this site, refreshed daily.
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Exclusion Criteria:
Participants use Fitbit devices, without the addition of the nudge intervention.
Participants use Fitbit devices, with the addition of randomly deployed nudge interventions (random timing and theme).
Behavioral: Mobile App Push Notification (Random Selection)
Participants use Fitbit devices, with the addition of nudges deployed based on behavior science heuristics.
Behavioral: Mobile App Push Notification (Behavior Science Heuristics)
Participants use Fitbit devices, with the addition of nudges deployed based on a reinforcement learning algorithm.
Behavioral: Mobile App Push Notification (RL)
Participants use Fitbit devices, with the addition of randomly deployed nudge interventions (random timing and theme).
Also known as: Nudges
Participants use Fitbit devices, with the addition of nudges deployed based on behavior science heuristics.
Also known as: Nudges
Participants use Fitbit devices, with the addition of nudges deployed based on a reinforcement learning algorithm.
Also known as: Nudges
Change in step count from baseline.
The average daily step count during the final month minus baseline daily step count during one month before enrollment.
Time frame: One month prior to enrollment (Baseline) to the second month post-enrollment (60 days total enrollment).
Plan to share: No
Ran from Feb 2024 to primary completion in Aug 2024, 6 months.
Of 741 interventional studies with no phase under Sedentary Behavior, half reached primary completion within 14 months of starting (the median), counting those still running; a quarter within 6 and three quarters within 31. This study's 6 months is below that.
How these figures are worked out, and which studies are left out of them.
This study is completed, as verified in Aug 2026. You cannot join it, but the record below documents what was studied.
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