LLM-Generated Coaching Prompts

January 21, 2026 updated by: Euan Ashley, Stanford University

Enhancing Physical Activity With LLM-Generated Coaching Prompts: A My Heart Counts Study

This pilot study aims to evaluate whether personalized coaching prompts generated by a large language model (LLM) can effectively increase physical activity levels among participants. The study will involve 50 participants who will receive daily text messages, either personalized by the LLM or generic, over a 14-day period. Participants will share their HealthKit data for analysis. The findings will inform the development of future versions of the My Heart Counts application, enhancing user engagement and health outcomes.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Estimated)

50

Phase

  • Not Applicable

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • Age: Participants must be 18 years or older.
  • Health Status: Participants must be healthy enough to engage in physical activity.
  • Language Proficiency: Participants must be able to read, understand, and consent in English or Spanish (dependent on which is being studied).
  • Device Ownership: Participants must possess an iPhone and an Apple Watch.
  • Data Sharing: Participants must be willing to share their HealthKit data via secure upload.

Exclusion Criteria:

  • Age: Participants under the age of 18.
  • Health Status: Participants who are not healthy enough to engage in physical activity.
  • Language Proficiency: Participants who cannot read, understand, or consent in English or Spanish.
  • Device Ownership: Participants who do not have both an iPhone and an Apple Watch.
  • Data Sharing: Participants unwilling to share their HealthKit data via secure upload.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Basic Science
  • Allocation: Randomized
  • Interventional Model: Crossover Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Personalized LLM-Generated Coaching Prompts
Behavioral: Pre-Generated Personalized LLM Coaching Impact
After the initial 7 days, participants will switch to the other type of prompting for another 7 days. This means that participants who initially received personalized LLM-generated prompts will then receive generic activity prompts, and vice versa. This crossover design allows for each participant to experience both types of interventions, providing a within-subject comparison of the effectiveness of personalized versus generic prompts in increasing physical activity levels.
Active Comparator: Generic Activity Prompts
Behavioral: Pre-Generated Personalized LLM Coaching Impact
After the initial 7 days, participants will switch to the other type of prompting for another 7 days. This means that participants who initially received personalized LLM-generated prompts will then receive generic activity prompts, and vice versa. This crossover design allows for each participant to experience both types of interventions, providing a within-subject comparison of the effectiveness of personalized versus generic prompts in increasing physical activity levels.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Time Frame
Physical Activity Levels
Time Frame: 14 days from enrollment
14 days from enrollment

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Stanford University

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

February 20, 2026

Primary Completion (Estimated)

July 30, 2026

Study Completion (Estimated)

December 1, 2026

Study Registration Dates

First Submitted

March 11, 2025

First Submitted That Met QC Criteria

March 11, 2025

First Posted (Actual)

March 17, 2025

Study Record Updates

Last Update Posted (Actual)

January 23, 2026

Last Update Submitted That Met QC Criteria

January 21, 2026

Last Verified

January 1, 2026

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 79946

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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