Effectiveness of interventions and behaviour change techniques for improving physical activity in young adults: A systematic review and meta-analysis.

Physical activity (PA) participation declines from adolescence to young adulthood. This review evaluates the effectiveness of interventions aiming to improve PA among healthy young adults (17-35 years), and the effectiveness of the behaviour change techniques (BCTs) used. Six electronic databases were searched up to December 2019, for randomized controlled trials aiming to achieve PA behaviour change among young adults. In total, 66 RCTs were included. Meta-analyses for moderate-vigorous PA (n = 11 studies), steps (n = 5 studies) and total PA (MET min/week, n = 11 studies) identified that intervention participants compared with control significantly increased PA at time points up to 3 months and >3 months. Narrative synthesis identified that 34 RCTs (52%) reported significant between group differences favouring the intervention for one or more PA outcome. BCTs with the highest effectiveness were material reward, valued self-identity and habit formation. However, the overall test of significance demonstrated no significant relationship between type or number of BCTs and effectiveness. This review identified interventions that improve steps, moderate-vigorous and total PA in young adults in the shorter-term, and BCTs associated with greater effectiveness. Further research is needed to determine strategies to achieve longer-term effectiveness of PA interventions in young adults.