"Having a standardized way of measuring patient physical activity - and sharing those measurements - is an essential step to improving physical activity levels, both at an individual and at a population level. *Practitioners *need standard measures to: "
The items covered point to more stakeholders.
A defining list of stakeholders would help related to the main cycle picture.
For instance

• "patient" or more general individual wanting to stay healthy
• personal trainers
• population health specialists