The Green Prescription Program for Increasing Physical Activity in Adolescents

Regular physical activity during adolescence contributes to physical, mental, and social well-being. Despite well-established health benefits, many adolescents do not achieve recommended levels of physical activity. Schools provide an important setting for implementing behavioral interventions that encourage lifelong healthy habits.

The Green Prescription was a school-based behavioral intervention that incorporated health education to promote leisure-time physical activity among adolescents with insufficient physical activity. The intervention combined individualized written physical activity recommendations with health education and regular motivational support. Activity goals were tailored to each participant and were progressively increased throughout the intervention.

The study consisted of two sequential cohorts. Participants with insufficient physical activity were assigned to one of three intervention groups according to their primary risk factor: overweight or obesity, excessive screen time, or low perceived social support. Each intervention group followed the same Green Prescription framework while receiving recommendations and educational materials tailored to its primary risk factor. Adolescents with sufficient physical activity served as a comparison group and did not receive the intervention.

In the first cohort, the Green Prescription was delivered by a physical education teacher. In the second cohort, the intervention was delivered by a physical education teacher supported by an interdisciplinary team consisting of a dietitian, psychologist, special education teacher, and physiotherapist. Each cohort included three parallel intervention groups and one comparison group, allowing evaluation of both the effectiveness of the Green Prescription within each target group and the added value of the interdisciplinary delivery model.

Outcomes were assessed at baseline, immediately after the 12-week intervention, and six months after completion of the intervention. The study evaluated both the immediate and sustained effects of the Green Prescription on physical activity and related health outcomes.

General inclusion criteria

• Adolescents aged 15-17 years.
• Enrollment in a participating secondary school.
• Health status allowing participation in physical activity.
• Stable body weight during the month preceding enrollment (±1 kg).
• Written informed consent from the participant and a parent or legal guardian, as required by local regulations.

Intervention Groups (A-C)

Participants were eligible if they met all of the following criteria:

• Insufficient physical activity, defined as reporting fewer than 5 days during the previous week with at least 60 minutes of moderate-to-vigorous physical activity, assessed using the MVPA questionnaire.

and met one of the following group-specific criteria:

Group A - Overweight or Obesity

• Body fat percentage above the age- and sex-specific reference values.
• BMI ≥25 kg/m² (used as an auxiliary screening criterion). Group B - High Screen Time
• Recreational screen time ≥4 hours per day. Group C - Low Social Support
• Low perceived social support assessed using the Student Social Support Scale for Young People (SSYSS).
• Low psychological well-being assessed using the KIDSCREEN-52 questionnaire (boys <37.29; girls <42.64).

Comparison Group (Group D)

• Sufficient physical activity, defined as reporting at least 5 days during the previous week with at least 60 minutes of moderate-to-vigorous physical activity, assessed using the MVPA questionnaire.
• No participation in the Green Prescription intervention.

Exclusion criteria

• Secondary obesity.
• Acute or chronic medical conditions preventing participation in physical activity.
• Pregnancy or breastfeeding.
• Current psychological or psychiatric diagnosis requiring active treatment.
• Failure to provide written informed consent.