Online Physical Activity and Health Counseling for Survivors of Childhood Acute Lymphoblastic Leukemia (OPAC-ALL)- a study protocol

Survivors of childhood acute lymphoblastic leukemia face an elevated risk of treatment-related late effects, including reduced cardiorespiratory fitness, musculoskeletal impairments, and metabolic syndrome. Effective, accessible interventions are urgently needed to promote physical activity and improve long-term health outcomes in this population. This trial aims to evaluate the effectiveness of a 26-week online high-intensity functional training program combined with health counseling and access to a lifestyle education website on cardiorespiratory fitness. The study will also assess the long-term impact on physical activity compared with WHO’s physical activity guidelines. This single-center, two-arm randomized controlled trial will enroll 82 childhood ALL survivors aged 10–21 years who are at least one-year post-treatment and do not meet WHO physical guidelines. Participants will be randomized to an intervention group or a waitlist control group. The assessment time points for participants allocated to the intervention group will be at baseline and 26- and 78 weeks after baseline assessment. The assessment time points for participants allocated to the waitlist control group will be at baseline and at 26-, 52-, and 104 weeks after baseline assessment. The primary outcome is cardiorespiratory fitness. Secondary outcomes include physical activity levels, muscle strength, body composition, quality of life, fatigue, and markers of metabolic syndrome. Qualitative interviews will explore participant experiences and intervention feasibility. This trial will provide critical evidence on the efficacy and feasibility of a digitally delivered, multicomponent intervention for improving physical fitness and health in childhood ALL survivors. If effective, the OPAC-ALL program could be integrated into routine follow-up care to address unmet rehabilitation needs in this growing survivor population. ClinicalTrials.gov Identifier: NCT07042932. Registration date: 2025–06-17.