Adaptive goal setting and financial incentives: a 2 × 2 factorial randomized controlled trial to increase adults’ physical activity

Abstract

BackgroundEmerging interventions that rely on and harness variability in behavior to adapt to individual performance over time may outperform interventions that prescribe static goals (e.g., 10,000 steps/day). The purpose of this factorial trial was to compare adaptive vs. static goal setting and immediate vs. delayed, non-contingent financial rewards for increasing free-living physical activity (PA).MethodsA 4-month 2 × 2 factorial randomized controlled trial tested main effects for goal setting (adaptive vs. static goals) and rewards (immediate vs. delayed) and interactions between factors to increase steps/day as measured by a Fitbit Zip. Moderate-to-vigorous PA (MVPA) minutes/day was examined as a secondary outcome.ResultsParticipants (N = 96) were mainly female (77%), aged 41 ± 9.5 years, and all were insufficiently active and overweight/obese (mean BMI = 34.1 ± 6.2). Participants across all groups increased by 2389 steps/day on average from baseline to intervention phase (p < .001). Participants receiving static goals showed a stronger increase in steps per day from baseline phase to intervention phase (2630 steps/day) than those receiving adaptive goals (2149 steps/day; difference = 482 steps/day, p = .095). Participants receiving immediate rewards showed stronger improvement (2762 step/day increase) from baseline to intervention phase than those receiving delayed rewards (2016 steps/day increase; difference = 746 steps/day, p = .009). However, the adaptive goals group showed a slower decrease in steps/day from the beginning of the intervention phase to the end of the intervention phase (i.e. less than half the rate) compared to the static goals group (−7.7 steps vs. -18.3 steps each day; difference = 10.7 steps/day, p < .001) resulting in better improvements for the adaptive goals group by study end. Rate of change over the intervention phase did not differ between reward groups. Significant goal phase x goal setting x reward interactions were observed.ConclusionsAdaptive goals outperformed static goals (i.e., 10,000 steps) over a 4-month period. Small immediate rewards outperformed larger, delayed rewards. Adaptive goals with either immediate or delayed rewards should be preferred for promoting PA.Trial RegistrationClinicalTrials.gov ID: NCT02053259 registered prospectively on January 31, 2014.

Erratum to: Adaptive goal setting and financial incentives: a 2 × 2 factorial randomized controlled trial to increase adults’ physical activity

“…Following publication of this article [1], it has come to our attention that in Fig. 5 the top and bottom panels were not presented in the correct order.…”

Evaluating the Carrot Rewards app, a population-level incentive-based intervention promoting step counts across two Canadian provinces: a quasi-experimental study (Preprint)

“…In this study, cash incentives worth about $11 US per week were contingent on reaching a weekly step target of 50,000 steps (a larger reward of $22 US was offered if a 70,000 step target was met). While this study was effective in promoting PA, the authors admit that the cost of the intervention (about $1 to $2 US per person per daymagnitude typically used to promote PA in these types of studies [15,20,[22][23][24][25] was likely too high for most third party payers. Additionally, the effect was not sustained six months after the incentives were discontinued.…”

“…According to behavioral economics, timely financial incentives leverage people's predictable tendency to act in favor of their immediate self-interest -a principal referred to as the "present bias" [10]. In the case of PA, the likelihood that someone will be more physically active should increase if a financial incentive is at stake -and the more immediate the incentive the stronger the nudge, according to this theoretical perspective [15].…”

Investigating Intervention Components and Exploring States of Receptivity for a Smartphone App to Promote Physical Activity: Protocol of a Microrandomized Trial (Preprint)

“…Personalized step goals are calculated daily for each participant based on the participant's activity over the past nine days employing the moving-window percentile-rank algorithm described by Adams and colleagues [10]. This adaptive goal-setting algorithm sets the daily step goal to the 60 th percentile of the participant's step count distribution of the past nine days meaning that the participant reaches her/his step goal 40% of the times when maintaining her/his recent activity level.…”

“…This adaptive goal-setting algorithm sets the daily step goal to the 60 th percentile of the participant's step count distribution of the past nine days meaning that the participant reaches her/his step goal 40% of the times when maintaining her/his recent activity level. Previous studies demonstrated that this adaptive goal setting outperforms static step goals [10,11]. To facilitate maintenance of behavior change, adaptive step goals are capped at 10,000 steps per day which approximates the WHO recommendations for physical activity [12,13].…”