Among 92 adults over age 50 living with HIV (PWH), those receiving automated tailored text messages matched to daily reported exercise barriers — combined with motivational interviewing (MI) — maintained moderate-to-vigorous physical activity (MVPA) at ~30.5 min/day over 12 weeks, while the educational-control group declined to ~26.0 min/day (F(1,255)=5.76, p=.02, d=0.51). Tailored-message recipients also reported higher exercise self-efficacy and better perceived health. Crucially, tailored messaging effects appeared additive to MI alone.
PWH face accelerated cardiovascular aging, making sustained MVPA particularly consequential for this population — yet long-term adherence to exercise is notoriously difficult. A moderate effect size (d=0.51) from a low-cost, scalable SMS-based intervention is clinically meaningful; it suggests behavioral technology can extend the gains made during structured exercise programmes well beyond their formal end. The Two Minds Theory framework — targeting both reflective and automatic motivational systems — differentiates this from generic reminder apps.
Limitations are real: the sample is small, predominantly older, and HIV-specific, limiting generalisability. The 12-week sustainability window, while useful, leaves long-term durability untested. Attrition and the relatively high SD values suggest heterogeneous responses. Importantly, this is a preprint posted on medRxiv and has not yet been peer-reviewed, so findings and effect estimates may change. Nonetheless, the randomised design, objective actigraphy confirmation, and intent-to-treat analysis lend credibility. For healthy-aging researchers, this offers a transferable model for sustaining exercise in any high-risk middle-aged population.