Adaptive Goals and Reinforcement Timing to Increase Physical Activity in Adults: A Factorial Randomized Trial

Marc A. Adams, Michael Todd, Siddhartha S. Angadi, Jane C. Hurley, Chad Stecher, Vincent Berardi, Christine B. Phillips, Mindy L. McEntee, Melbourne F. Hovell, Steven P. Hooker

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


Introduction: Potent lifestyle interventions to increase moderate-to-vigorous physical activity are urgently needed for population-level chronic disease prevention. This trial tested the independent and joint effects of a mobile health system automating adaptive goal setting and immediate financial reinforcement for increasing daily walking among insufficiently active adults. Study Design: Participants were randomized into a 2 (adaptive versus static goal setting) X 2 (immediate versus delayed financial incentive timing) condition factorial trial to increase walking. Settings/Participants: Participants (N=512 adults) were recruited between 2016 and 2018 and were 64.5% female, aged 18–60 years, 18.8% Hispanic, 6.1% African American, and 83% White. Intervention: Principles of reinforcement and behavioral economics directed intervention design. Main Outcome Measures: Participants wore accelerometers daily (133,876 day-level observations) that remotely measured moderate-to-vigorous physical activity bout minutes of ≥3 minutes/day for 1 year. Primary outcomes were between-condition differences in (1) engaging ≥1 bout of moderate-to-vigorous physical activity on each day and (2) on days with ≥1 bout, daily total moderate-to-vigorous physical activity minutes. Results: Mixed-effects hurdle models tested treatment group X phase (time) interactions using an intent-to-treat approach in 2021. Engaging in any ambulatory moderate-to-vigorous physical activity was greater for Adaptive than for Static Goal groups (OR=2.34, 95% CI=2.10, 2.60 vs OR=1.66, 95% CI=1.50, 1.84; p<0.001) and for Immediate than for Static Reinforcement groups (OR=2.16 95% CI=1.94, 2.40 vs OR=1.77, 95% CI=1.59, 1.97; p<0.01). The Immediate Reinforcement group increased by 16.54 moderate-to-vigorous physical activity minutes/day, whereas the Delayed Reinforcement group increased by 9.91 minutes/day (p<0.001). The combined Adaptive Goals + Immediate Reinforcement group increased by 16.52 moderate-to-vigorous physical activity minutes/day, significantly more than that of either Delayed Reinforcement group. Conclusions: This study offers automated and scalable–behavior change strategies for increasing walking among adults most at-risk for chronic diseases attributed to sedentary lifestyles. Trial Registration: This study is registered at ( Identifier: NCT02717663).

Original languageEnglish (US)
Pages (from-to)e57-e68
JournalAmerican journal of preventive medicine
Issue number2
StatePublished - Feb 2022

ASJC Scopus subject areas

  • Epidemiology
  • Public Health, Environmental and Occupational Health


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