Sedentary LifestyleNCT07783724
Evaluating PEARL - a Personalized Exercise Assistant Using Reinforcement Learning (Walkmate Study)
A study testing Mobile App Push Notification (Random Selection), Mobile App Push Notification (Behavior Science Heuristics) and Mobile App Push Notification (RL) in people with Sedentary Lifestyle, run by Fitbit LLC at 1 site in United States.
Trial summary
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). Read more about this study
- Who is it for?
- Ages 22 to 60 yearsHealthy volunteers can take part
- Conditions the study is for
- Sedentary Lifestyle
- What is being tested?
- Mobile App Push Notification (Random Selection), Mobile App Push Notification (Behavior Science Heuristics) and Mobile App Push Notification (RL)
- Type of treatment
- Lifestyle or therapy programme
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 13,463 participants
- Where
- 1 siteUnited States
- Study dates
- 26 Feb 2024to 26 Aug 2024
- Phase
- Interventional
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 22 to 60 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Age 22-60 years
- [For Phase 2 \& 3] Daily average steps 1 month prior to recruitment is less than 8000
- Owns a Fitbit device \& smartphone with Fitbit app
- Willing to share a month of step count data prior to enrollment data
- Wear a Fitbit device regularly (user-reported)
Who cannot join
- Advised by a doctor to avoid exercising or limit physical activity
- Current employees of Alphabet
- [For phase 2] Have participated in Phase 1 of the study
- [For phase 3] Have participated in Phase 1 or 2 of the study
Trial locations and contacts
1 site in 1 country.
United States1 site
Google Office (Digital Study)
Mountain View, California, 94043
About this study
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).
Read the detailed description
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
- Conditions
- Sedentary Lifestyle
- Being tested
- Mobile App Push Notification (Random Selection), Mobile App Push Notification (Behavior Science Heuristics), Mobile App Push Notification (RL)
- Keywords
- activity, exercise, sedentary, artificial intelligence
- Medical subject headings
- Sedentary Behavior, Motor Activity
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Mobile App Push Notification (Random Selection)Behavioural
Also called Nudges
Participants use Fitbit devices, with the addition of randomly deployed nudge interventions (random timing and theme).
Mobile App Push Notification (Behavior Science Heuristics)Behavioural
Also called Nudges
Participants use Fitbit devices, with the addition of nudges deployed based on behavior science heuristics.
Mobile App Push Notification (RL)Behavioural
Also called Nudges
Participants use Fitbit devices, with the addition of nudges deployed based on a reinforcement learning algorithm.
| Study group | Role | What they receive |
|---|---|---|
| Control | No intervention | Participants use Fitbit devices, without the addition of the nudge intervention. |
| Random | Active comparator | Participants use Fitbit devices, with the addition of randomly deployed nudge interventions (random timing and theme). Receives: Behavioral: Mobile App Push Notification (Random Selection) |
| Behavior Science | Active comparator | Participants use Fitbit devices, with the addition of nudges deployed based on behavior science heuristics. Receives: Behavioral: Mobile App Push Notification (Behavior Science Heuristics) |
| Reinforcement Learning | Experimental | Participants use Fitbit devices, with the addition of nudges deployed based on a reinforcement learning algorithm. Receives: Behavioral: Mobile App Push Notification (RL) |
What is being measured
The primary outcome is the main question the study is designed to answer.
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.
Measured: One month prior to enrollment (Baseline) to the second month post-enrollment (60 days total enrollment).
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted25 Aug 2026
- Study start26 Feb 2024
- Primary completion26 Aug 2024
- Study completion26 Aug 2024
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Sedentary LifestyleStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Other
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Single blind
- Who is masked
- Participant
- Enrolment
- 13,463 participants (actual)
Sponsor and investigators
- Lead sponsor
- Fitbit LLC
- Sponsor type
- Industry (pharma, biotech, devices)
- Collaborators
- Google LLC.
- Responsible party
- Sponsor
- Investigators
- James A Taylor, MD, Principal investigator, Google LLC.
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07783724
- Sponsor's protocol ID
- PEARL-001
- Status last verified
- Aug 2026
- First submitted
- 21 Aug 2026
- Last updated
- 25 Aug 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 25 Aug 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Evaluating PEARL - a Personalized Exercise Assistant Using Reinforcement Learning (Walkmate Study)
- ClinicalTrials.gov ID
- NCT07783724
- Acronym / sponsor ID
- PEARL-001
- Conditions
- Sedentary Lifestyle
- Keywords
- activity, exercise, sedentary, artificial intelligence
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 13,463 participants (actual)
- Lead sponsor
- Fitbit LLCIndustry (pharma, biotech, devices)
- Collaborators
- Google LLC.
- Study start
- 26 Feb 2024 (actual)
- Primary completion
- 26 Aug 2024 (actual)
- Study completion
- 26 Aug 2024 (actual)
- First posted
- 25 Aug 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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).
Detailed description
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
Study design
- Primary purpose
- Other
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Single blind (participant)
- Number of arms
- 4
| Arm | Type | Receives |
|---|---|---|
| Control | No intervention | –Participants use Fitbit devices, without the addition of the nudge intervention. |
| Random | Active comparator | Behavioral: Mobile App Push Notification (Random Selection)Participants use Fitbit devices, with the addition of randomly deployed nudge interventions (random timing and theme). |
| Behavior Science | Active comparator | Behavioral: Mobile App Push Notification (Behavior Science Heuristics)Participants use Fitbit devices, with the addition of nudges deployed based on behavior science heuristics. |
| Reinforcement Learning | Experimental | Behavioral: Mobile App Push Notification (RL)Participants use Fitbit devices, with the addition of nudges deployed based on a reinforcement learning algorithm. |
Who may qualify
- Ages
- 22 to 60 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (5 listed)
- Age 22-60 years
- [For Phase 2 \& 3] Daily average steps 1 month prior to recruitment is less than 8000
- Owns a Fitbit device \& smartphone with Fitbit app
- Willing to share a month of step count data prior to enrollment data
- Wear a Fitbit device regularly (user-reported)
Key exclusion criteria (4 listed)
- Advised by a doctor to avoid exercising or limit physical activity
- Current employees of Alphabet
- [For phase 2] Have participated in Phase 1 of the study
- [For phase 3] Have participated in Phase 1 or 2 of the study
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Mobile App Push Notification (Random Selection)Also: NudgesParticipants use Fitbit devices, with the addition of randomly deployed nudge interventions (random timing and theme). | Behavioural | Random |
| Mobile App Push Notification (Behavior Science Heuristics)Also: NudgesParticipants use Fitbit devices, with the addition of nudges deployed based on behavior science heuristics. | Behavioural | Behavior Science |
| Mobile App Push Notification (RL)Also: NudgesParticipants use Fitbit devices, with the addition of nudges deployed based on a reinforcement learning algorithm. | Behavioural | Reinforcement Learning |
Primary outcome
Change in step count from baseline.
Time frame: One month prior to enrollment (Baseline) to the second month post-enrollment (60 days total enrollment).
The average daily step count during the final month minus baseline daily step count during one month before enrollment.
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 25 Aug 2026.
- Registration with Open Science Framework.Link provided by the sponsor.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
James A Taylor, MD principal investigator
Google LLC.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Mobile App Push Notification (Random Selection), Mobile App Push Notification (Behavior Science Heuristics) and Mobile App Push Notification (RL) in people with Sedentary Lifestyle, run by Fitbit LLC at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 5 inclusion and 4 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 25 Aug 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Change in step count from baseline. (time frame: One month prior to enrollment (Baseline) to the second month post-enrollment (60 days total enrollment).). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 25 Aug 2026.