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.

• Green Prescription (Teacher-Led) (Behavioral): The Green Prescription is a school-based behavioral intervention incorporating health education to promote leisure-time physical activity among adolescents with insufficient physical activity. The intervention includes individualized weekly written physical activity recommendations, educational materials, and weekly motivational support, supplemented by additional support when required, delivered by a physical education teacher over a 12-week period. All participants follow the same Green Prescription framework, with group-specific objectives, physical activity recommendations, and educational materials tailored to their primary risk profile (overweight or obesity, excessive recreational screen time, or low perceived social support). Activities were adapted to group needs and recommended PA levels. Written recommendations and educational materials were delivered electronically.
• Green Prescription (Interdisciplinary) (Behavioral): The Green Prescription is a school-based behavioral intervention incorporating health education to promote leisure-time physical activity among adolescents with insufficient physical activity. The intervention includes individualized weekly written physical activity recommendations, educational materials, and weekly motivational support, supplemented by additional support when required, over a 12-week period. The intervention is delivered by a physical education teacher together with an interdisciplinary team consisting of a dietitian, psychologist, special education teacher, and physiotherapist. All participants follow the same Green Prescription framework, with group-specific objectives, physical activity recommendations, and educational materials tailored to their primary risk profile (overweight or obesity, excessive screen time, or low perceived social support). Written recommendations and educational materials were delivered electronically.

Primary outcomes

• Change in Moderate-to-Vigorous Physical Activity (MVPA) Screening Score [Baseline, immediately after the 12-week intervention, and 6 months after completion of the intervention.]: Self-reported physical activity was assessed using the MVPA screening measure. Participants reported the number of days on which they engaged in at least 60 minutes of moderate-to-vigorous physical activity (1) during the previous week (P1) and (2) during a typical week (P2). The MVPA screening score was calculated as the mean of the two responses: (P1 + P2) / 2, with a possible range of 0-7 days. Higher scores indicate a greater number of days with at least 60 minutes of MVPA.
• Change in Mean Daily Step Count (Huawei Watch Fit SE) [Baseline, immediately after the 12-week intervention, and 6 months after completion of the intervention.]: Objective physical activity assessed using Huawei Watch Fit SE. Participants wore the device for a 7-day baseline monitoring period, continuously throughout the 12-week intervention, for a 7-day post-intervention monitoring period, and for a 7-day monitoring period at the 6-month follow-up. The primary outcome is the mean daily step count derived from the monitoring periods used for outcome assessment.

Secondary outcomes

• Change in Body Mass Index (BMI) [Baseline, immediately after the 12-week intervention, and 6 months after completion of the intervention.]: Body Mass Index (BMI) was calculated from measured body weight and height as weight in kilograms divided by height in meters squared (kg/m²). Weight and height were combined to derive a single reported BMI value; the reported unit of measure was kg/m².
• Change in Waist Circumference [Baseline, immediately after the 12-week intervention, and 6 months after completion of the intervention.]: Waist circumference was measured in centimetres (cm) and reported as a single waist circumference value in cm at each assessment point.
• Change in Hip Circumference [Baseline, immediately after the 12-week intervention, and 6 months after completion of the intervention.]: Hip circumference measured in centimetres (cm).
• Change in Body Fat Percentage [Baseline, immediately after the 12-week intervention, and 6 months after completion of the intervention.]: Body fat percentage (FatP) assessed using Tanita bioelectrical impedance analysis.
• Change in Fat Mass [Baseline, immediately after the 12-week intervention, and 6 months after completion of the intervention.]: Fat mass (FatM) measured using Tanita bioelectrical impedance analysis.
• Change in Fat-Free Mass [Baseline, immediately after the 12-week intervention, and 6 months after completion of the intervention.]: Fat-free mass (FFM) measured using Tanita bioelectrical impedance analysis.
• Change in Total Body Water [Baseline, immediately after the 12-week intervention, and 6 months after completion of the intervention.]: Total body water (TBW) assessed using Tanita bioelectrical impedance analysis.
• Change in Predicted Muscle Mass [Baseline, immediately after the 12-week intervention, and 6 months after completion of the intervention.]: Predicted muscle mass (PMM) measured using Tanita bioelectrical impedance analysis.
• Change in Screen Time [Baseline, immediately after the 12-week intervention, and 6 months after completion of the intervention.]: Screen time was assessed using selected items from the Health Behaviour in School-aged Children (HBSC) questionnaire and average daily active screen time recorded from participants' smartphones.
• Change in Sleep Duration [Baseline (7-day monitoring period), immediately after the 12-week intervention (7-day monitoring period), and 6 months after completion of the intervention (7-day monitoring period).]: Sleep duration assessed using Huawei Watch Fit SE. The outcome is the mean total sleep duration derived from 7-day monitoring periods.
• Change in Perceived Social Support [Baseline, immediately after the 12-week intervention, and 6 months after completion of the intervention.]: Perceived Social Support assessed using the Short Scale of Youth's Social Support Assessment (SSYSS). Total scores range from 1.0 to 4.0, with higher scores indicating higher perceived support.
• Change in Health-Related Quality of Life [Baseline, immediately after the 12-week intervention, and 6 months after completion of the intervention.]: Health-related quality of life assessed using the KIDSCREEN-52 questionnaire. Total scores range from 23.3 to 100.0, with higher scores indicating better health-related quality of life.

Sex: All, ages: 15 Years to 17 Years, accepts healthy volunteers

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.

• Marlena Łopatka, Michał Bronikowski, Małgorzata Bronikowska, Agata Korcz, Maryna Khorkova, Dagny Adamczak, Jana Krzysztoszek; Physical activity recommendations for adolescents with overweight, high screen time, and low social support - A scoping review; Biomedical Human Kinetics; Volume 18 Issue 1; pp. 100-111. DOI: 10.2478/bhk-2026-0011

• Jana Krzysztoszek, PhD, DSc, Principal investigator, Poznan University of Physical Education