Effectiveness of a Physical Exercise Prescription Program in Primary Care to Improve Physical Fitness and Quality of Life in People over 65 in a Rural Basic Health Area—PREFIS-AP. A Randomized Clinical Trial Study Protocol

Background: Physical inactivity contributes substantially to morbidity, disability and premature mortality in older adults. However, physical activity counselling in primary care does not necessarily translate into structured, individualized exercise prescription. PREFIS-AP evaluates a standardized Exercise Prescription Program embedded in routine primary care for adults aged ≥65 years. Methods: PREFIS-AP is a pragmatic, parallel-group randomized controlled trial including 210 participants allocated 1:1 to an individualized exercise prescription program or usual care. The primary outcome is change in functional exercise capacity measured by the Six-Minute Walk Test (6MWT). Secondary outcomes include physical activity, health-related quality of life, muscle strength and lower-limb function, anthropometric measures, rectus femoris morphology assessed by point-of-care ultrasound, medication burden and safety. Analyses will follow the intention-to-treat principle, estimating between-group effects adjusted for baseline values. Discussion: PREFIS-AP will evaluate a reproducible model for integrating structured exercise prescription into routine primary care. Key strengths include electronic health record integration, standardized decision algorithms, individualized multicomponent exercise, objective functional and ultrasound assessment, and intervention-fidelity procedures. Limitations include its single rural setting, participation of an exercise professional, lack of participant and clinician blinding, and 12-week follow-up. If effective, the model could support scalable implementation of exercise prescription in primary care.