To make a change - like adding Push ups to each work out. You will select Data > Make a change to a list of things and you will do a search for those clients and then you will select there workout fields. This will allow you to make a change to everyones workout program.

Looking up the workouts in a RG is something very similar. You make the Data Type = Workouts and for the Data Source you Do a search for those clients and select their Workout fields.

For this to make logical sense. You would need to have Workout as a Data Thing and Clients as a Data Thing and one of your fields in your Client data thing should have a field which has a field type = to Workout (The Data thing you created earlier)