My Heart Counts Cardiovascular Health Study

My Heart Counts is a smartphone-based mobile cardiovascular health research study designed to collect data on physical activity and heart health across a broad population. This new version expands on the original study (IRB-31409) with several key improvements: inclusion of Android users alongside iOS, creation of a Spanish-language version, and, for future versions of the app, development of a platform architecture that can host multiple sub-studies.

The study will utilize smartphone sensors and connected devices to measure physical activity patterns, fitness levels through standardized tests (6-minute walk test, 12-minute run/walk test), and cardiovascular risk factors reported through health questionnaires. All data collection occurs remotely through participants' smartphones without requiring clinical visits.

A key component of the study is a 14-day randomized crossover trial evaluating the effectiveness of different physical activity coaching approaches.

Participants will experience both personalized coaching messages generated by a large language model and standard activity prompts, each for 7 days, in a randomly assigned order. The primary outcome will be the change in physical activity levels between intervention periods.

The study will serve as a digital biobank, with data made available to qualified researchers after appropriate de-identification. This platform approach will enable efficient recruitment for future cardiovascular health sub-studies without requiring development of new applications.