Digital Health and HeartSteps

Last updated on May 1, 2025

HeartSteps was the first-ever micro-randomized trial (MRT) designed to optimize a just-in-time adaptive intervention to increase physical activity among sedentary adults. In collaboration with study PI Predrag Klasnja, PhD and Susan A. Murphy, PhD, I served as the trial’s primary data analyst, and developed guidance for automating research-grade data for micro-ranodmized trials.

applied physical activity
Nicholas J. Seewald
Nicholas J. Seewald
Assistant Professor of Biostatistics

Assistant Professor of Biostatistics at the University of Pennsyvlania Perelman School of Medicine

Publications

Design considerations for preparation, optimization, and evaluation of digital therapeutics
This chapter offers a conceptual framework that ties together two domains of design decisions for digital therapeutics—those related to …
Shawna N. Smith, Nicholas J. Seewald, Predrag Klasnja
Cite Project DOI
Design considerations for preparation, optimization, and evaluation of digital therapeutics
Practical Considerations for Data Collection and Management in Mobile Health Micro-Randomized Trials
There is a growing interest in leveraging the prevalence of mobile technology to improve health by delivering momentary, contextualized …
Nicholas J. Seewald, Shawna N. Smith, Andy Jinseok Lee, Predrag Klasnja, Susan A. Murphy
Cite Project DOI arXiv PubMed
Efficacy of Contextually Tailored Suggestions for Physical Activity: A Micro-Randomized Optimization Trial of HeartSteps

BACKGROUND: HeartSteps is an mHealth intervention that encourages regular walking via activity suggestions tailored to the …

Predrag Klasnja, Shawna Smith, Nicholas J. Seewald, Andy Lee, Kelly Hall, Brook Luers, Eric B. Hekler, Susan A. Murphy
Cite Project DOI PubMed
Design Lessons from a Micro-Randomized Pilot Study in Mobile Health
Micro-randomized trials (MRTs) offer promise for informing the development of effective mobile just-in-time adaptive interventions …
Shawna N. Smith, Andy Jinseok Lee, Kelly Hall, Nicholas J. Seewald, Audrey Boruvka, Susan A. Murphy, Predrag Klasnja
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Design Lessons from a Micro-Randomized Pilot Study in Mobile Health
MRT-SS Calculator: An R Shiny Application for Sample Size Calculation in Micro-Randomized Trials
The micro-randomized trial (MRT) is a new experimental design which allows for the investigation of the proximal effects of a …
Nicholas J. Seewald, Ji Sun, Peng Liao
Cite Project arXiv