How effective are physical activity interventions when they are scaled-up: a systematic review

Area of Science:

• Public Health
• Health Promotion
• Intervention Science

Background:

• Effective physical activity interventions are crucial for improving population health.
• Scaling up these interventions is necessary to achieve widespread health benefits.
• Understanding the effectiveness and adaptations of scaled-up interventions is vital.

Purpose of the Study:

• To systematically review the effectiveness of community-based physical activity interventions that have been scaled-up.
• To compare the effect sizes of scaled-up interventions with their pre-scale efficacy evaluations.
• To describe common adaptations made to interventions during the scale-up process.

Main Methods:

• Systematic literature search across six electronic databases, reference lists, and expert consultation.
• Inclusion criteria: interventions intentionally delivered at a larger scale than a preceding randomized controlled trial with a significant effect (p < 0.05).
• Quantified effect size differences between pre-scale and scaled-up interventions to identify potential 'scale-up penalties'.

Main Results:

• Ten studies were eligible, with six scaled-up interventions showing significant improvements in physical activity.
• Effect size differences ranged from 132% to 25%, with a median of 58.8%, indicating scaled-up interventions achieve less than 60% of their pre-scale effect.
• Adaptations, primarily in the mode of delivery, were common during scale-up.

Conclusions:

• Most scaled-up physical activity interventions remain effective but demonstrate markedly lower effects than in pre-scale trials.
• Intervention adaptations during scale-up may influence their effectiveness.
• Findings offer valuable insights for designing and scaling up effective health promotion interventions.