A peer-led walking intervention for adolescent girls (the WISH study): a cluster-randomised controlled trial.

Background: Adolescent girls in the UK and Ireland fail to meet physical activity (PA) guidelines. PA behaviours track from childhood into adulthood. The effects of walking interventions on adult health are known; however, the potential of walking to promote PA in adolescents is less known. This study evaluated the effectiveness of a novel, school-based walking intervention aimed at increasing PA levels of adolescent girls.

Methods: In this cluster-randomised controlled trial, female pupils aged 12-14 years were recruited from 18 (mixed or single-sex) schools across the border region of Ireland and Northern Ireland. Schools were randomly assigned to either the control group (usual physical activity; n=9) or the intervention group (n=9) by independent faculty staff using an online randomisation tool (randomization.com). In intervention schools, female pupils aged 15-18 years were trained as walk leaders and led the younger pupils in 10-15 min walks before school, at break, and at lunchtime. Walks were in school grounds and pupils were encouraged to join as many walks as possible. The intervention was delivered for a full school year excluding holidays (for a total of 18-21 weeks). Accelerometers measured PA, and the primary outcome was total PA (counts per minute [cpm]). Ethics approval was granted by Ulster University Research Ethics Committee and written informed consent (parent or guardian) and assent (pupils) was obtained. This study is registered with the ISRCTN Registry, 12847782.

Findings: The study took place from Sept 1, 2021, to May 31, 2023. In total, 589 pupils were recruited (n=286 in intervention group; n=303 in control group). Median moderate-vigorous PA (MVPA) at baseline was 36·1 min/day (IQR 23·0) for the intervention group and 35·3 min/day (19·8) for the control group. Only 37 (15%) girls in the intervention group and 29 (10%) girls in the control group met PA guidelines (60 min/day of MVPA). The mean total PA after intervention was 676 cpm (SD 18·7) for the intervention group and 710 cpm (SD 17·7) for the control group. Post-intervention total PA did not differ between groups when adjusted for age, body-mass index, z-scores, and baseline PA (mean difference -33·5, 95% CI -21·2 to 88·1; p=0·213).

Interpretation: Scaling up PA interventions is challenging. Despite a promising feasibility study, the results of this fully powered trial indicate that in this context, the walking programme did not increase PA. Since the COVID-19 pandemic, school environments have changed, and although pupils enjoyed the programme, attendance at walks was low. There is a need to better understand the implementation of interventions such as this within schools.

Funding: Cross-border Healthcare Intervention Trials in Ireland Network (CHITIN).