If you want to deactivate the automatic emails sent when you assign a workout plan go to the menu "Loyalty" and select "Communication Templates"
Find the template you would like to deactivate by searching by name and filtering by "Template Type" (push or email). In this case, we are looking for an email. When you have located the email click on the gear icon to the right.
This will take you to the template editor. Click on the "Configuration" drop down menu and select "Disabled". This will deactivate the automatic delivery of this email to your members.