A Multi-component Physical Activity Intervention for Adolescent Girls

A four-arm randomised pilot trial involving: 1. Physical activity programme only - live exercise sessions, social support, standardised text messages 2. Individual behaviour change support only - regular one-to-one video calls with an activity mentor 3. Combined - Physical activity provision and individual behaviour change support 4. Usual care control All groups will be provided with a menu of physical activities. Objectives. To conduct a RE-AIM evaluation of a 6-month multi-component PA intervention for adolescent girls, through investigating: * Who the intervention reaches, how representative they are for the population (Reach, Adoption) and who is most likely to benefit from the intervention (Reach); * The extent to which the intervention is delivered as intended (Implementation), and factors that affect this (Adoption); * Preliminary impact on participants' PA, sedentary behaviour, cardiovascular fitness and psychological wellbeing at 3, 6 and 12 months (Effectiveness, Maintenance); * The qualitatively examine the acceptability of the intervention for adolescent girls, and identify necessary refinements; * To gather data to inform a sample size calculation for a main trail