This study aims to validate a personalized physical activity algorithm for risk screening and individualized exercise prescription using a modified online Delphi process. International experts in physical activity and exercise will evaluate the algorithm's components over two rounds of questionnaires, with consensus defined as ≥70% agreement. If needed, a focus group will resolve any remaining disagreements. Validation of this algorithm may support safer, more effective autonomous exercise, promoting adherence, improved health outcomes, and population-level benefits.

Study Phases - eDelphi Validation of the APPA Algorithm

Phase 1 - Round 1 (Initial Online Questionnaire):

The first phase consists of an online survey in which international experts in physical activity and exercise will evaluate the components of the personalized physical activity algorithm for health risk screening and individualized exercise prescription. Experts will assess the relevance, clarity, and clinical appropriateness of each item. Feedback from this round will identify items requiring modification or clarification.

Phase 2 - Round 2 (Re-evaluation):

The second phase consists of a consecutive online survey round, in which experts will re-evaluate the revised algorithm components based on feedback from Round 1. Experts will have the opportunity to adjust their ratings. This phase aims to move items closer to consensus (≥70% agreement).

Phase 3 - Optional Focus Group (if needed):

If consensus is not reached on specific items after Round 2, an online focus group will be conducted to discuss and resolve remaining disagreements. This discussion will help refine the algorithm and ensure agreement on all components.

Inclusion Criteria

• Experts in Physical Activity and Exercise with recognized scientific or professional experience and a relevant doctoral degree.
• Availability to complete two rounds of the online modified Delphi questionnaire.
• Willingness to participate in an online focus group if consensus is not reached.
• Ability and willingness to provide informed consent.

Exclusion Criteria

• Individuals unable to provide informed consent.
• Individuals without access to a computer, smartphone, tablet, or other internet-enabled device necessary to complete the online survey.

The study population will consist of international experts in the field of Physical Activity and Exercise. Participants will be identified based on their recognized scientific or professional experience and possession of a relevant doctoral degree. Recruitment will be primarily via institutional email invitations, supplemented by personal contacts when needed. Eligible experts will voluntarily participate in two rounds of an online modified Delphi questionnaire and, if required, an online focus group to resolve any remaining disagreements. The targeted panel size is 9 - 18 experts to ensure representativeness and methodological robustness.