Background Physical inactivity is a global public health concern. Systematic review evidence indicates interventions can increase short-term physical activity (PA) levels. However, long-term health benefits require sustained increases in PA levels, and evidence from interventions with objective PA measures beyond 12-months is lacking. This review aims to:

1. Identify and describe randomised controlled trials (RCTs) in adults with objective PA measures and long–term follow–up (beyond 12–months)

2. Evaluate the extent to which intervention effects are sustained beyond 12–months

Methods We systematically searched seven databases using MeSH headings and keywords to identify RCTs published after 01/01/2000. We included trials reporting long-term effects (≥ 12-months) on objective PA levels with community-based participants, aged ≥18 years, with no specific medical conditions. We conducted quality assessments and meta-analyses at different follow-up points.

Results Of 17233 unique records identified, 9 studies were included in the review, 5 in the meta-analyses. Long-term follow-up ranged from 12-months to 4-years. We observed increases in PA at 12-months for steps/day (mean difference (md)=554, 95% CI=383 to 724) and weekly minutes of moderate-to-vigorous PA (MVPA) (md=34.9, 95% CI=26.9 to 42.8). This increase was sustained up to 4 years for both steps/day (md=494, 95% CI 251 to 738) and weekly minutes of MVPA (md=25.2, 95% CI=13.3 to 37.1).

Conclusion There are few PA interventions with objective follow up beyond 12-months. This review provided evidence of sustained PA intervention effects beyond 12-months and up to 4-years for both steps/day and MVPA.