LLM-Generated Coaching Prompts

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.

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Key information

Conditions

Exercise Behavior Motor Activity

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

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.

Treatment and study plan

Pre-Generated Personalized LLM Coaching Impact

Behavioral

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.

Primary outcomes

Physical Activity Levels

Time frame: 14 days from enrollment

Sponsors and collaborators

Lead sponsor

Stanford University

Other

Registry information

Official study title

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

Important dates

Study start: 2027
Primary completion: 2027
Study completion: 2027
First posted: Mar 17, 2025
Registry last updated: Jul 23, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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