Effectiveness of the Let's Move It multi-level vocational school-based intervention on physical activity and sedentary behavior: a cluster randomized trial.

Background: Low levels of physical activity (PA), more prevalent among those with low education, require effective interventions. Fewer trials have tested interventions to decrease sedentary behavior (SB). No school-based interventions have shown lasting effects on PA or SB in vocational schools.

Objective: To examine whether the Let's Move It intervention has effects on behavioral and clinical outcomes among vocational students after 2 and 14 months.

Methods: A cluster randomized trial in 6 school units in vocational education in Finland (N = 1112) (mean age 18.5 years, range 15-46). The multi-component intervention targeted in-class activity opportunities (eg, teacher-led activity breaks, equipment in classrooms), and students' motivation and self-regulation (eg, 6 group sessions, à 45-60 min, during the intensive intervention period of 2 months). Valid (≥ 4 days, ≥ 10 h/day) accelerometer data were obtained from 741 students at baseline, 521 (70.3%) at 2 months, and 406 (54.8%) at 14 months.

Results: No evidence of a significant intervention effect on the co-primary outcomes (moderate-to-vigorous PA, SB, breaks in SB) was found. Participants in the intervention arm reduced their total daily SB time by 32 min (95% CI, -43.2 to -20.8) on weekdays, compared with the control arm's reduction of 8.6 (95% CI, -19.5 to 2.3) and engaged in more accelerometer-measured light PA during school time. Few differences were found in secondary outcomes. The fidelity of intervention delivery was relatively good.

Conclusions: This school-based intervention did not affect leisure-time activity. Despite a positive outcome on school-time light PA, more comprehensive or intensive environmental changes may be needed to meaningfully improve vocational students' total activity.