The Product Owner is involved with the other Team Members throughout the Sprint, but after the Sprint Planning meeting is completed, the Product Owner cannot add to the scope of the work being done during the Sprint. New Product Backlog Items, no matter how high their priority, must be put onto the Product Backlog for the team to look at in the next Sprint. This restriction is meant to allow the team to truly be focused and committed to the work of the Sprint and to allow them to make commitments and learn to keep them, thereby building trust. The Product Owner can, of course, collaborate on the details of the PBIs the team has chosen for the Sprint. If the Product Owner does indeed force a team to take on extra work during the Sprint, it breaks the focus of the team and can lead to the team’s failure to complete the work they planned.
To learn more about Product Owners, visit the Scrum Team Assessment.