Digital, Social Micro-Interventions to Promote Physical Activity Among Midlife Adults With Elevated Cardiovascular Risk: An Ambulatory Feasibility Study With Momentary Randomization

Abstract

Background: Although regular physical activity (PA) mitigates the risk for cardiovascular disease (CVD) during midlife, existing PA interventions are minimally effective. Harnessing social influences in daily life shows promise: digital micro-interventions could effectively engage these influences on PA and require testing.

Purpose: This feasibility study employed ecological momentary assessment with embedded micro-randomization to activate two types of social influences (i.e., comparison, support; NCT04711512).

Methods: Midlife adults (N = 30, MAge = 51, MBMI = 31.5 kg/m2, 43% racial/ethnic minority) with ≥1 CVD risk conditions completed four mobile surveys per day for 7 days while wearing PA monitors. After 3 days of observation, participants were randomized at each survey to receive 1 of 3 comparison micro-interventions (days 4-5) or 1 of 3 support micro-interventions (days 6-7). Outcomes were indicators of feasibility (e.g., completion rate), acceptability (e.g., narrative feedback), and potential micro-intervention effects (on motivation and steps within-person).

Results: Feasibility and acceptability targets were met (e.g., 93% completion); ratings of micro-intervention helpfulness varied by intervention type and predicted PA motivation and behavior within-person (srs=0.16, 0.27). Participants liked the approach and were open to ongoing micro-intervention exposure. Within-person, PA motivation and behavior increased from baseline in response to specific micro-interventions (srs=0.23, 0.13), though responses were variable.

Conclusions: Experimental manipulation of social influences in daily life is feasible and acceptable to midlife adults and shows potential effects on PA motivation and behavior. Findings support larger-scale testing of this approach to inform a digital, socially focused PA intervention for midlife adults.

Keywords: Cardiovascular risk; Ecological momentary assessment; Midlife; Mobile health; Physical activity; Social influence.

Fig. 1.

CONSORT flowchart.

Fig. 2.

Motivation to be physically active (Panel A) and steps in the following 3.5 hours during baseline observation (Days 1–3) and after distinct types of micro-intervention prompts (Days 4–7).

Fig. 3.

Patterns of change from person means in motivation to be physically active and steps in the following 3.5 hours during baseline observation (Days 1–3) and after distinct types of micro-intervention prompts (Days 4–7), displayed for 4 individual participants.