during a workout video it would be very helpful if the instructor would pre-empt whether one of the exercises they are teaching was not good for someone with a specific injury or body problem and show a modification or just say to eliminate
it from the routine.

Thank you Anne. We'll keep that in mind when there is an obvious reason someone shouldn't be doing an exercise. Thank you.

conversely, the instructor could also say that the exercise is particularly good for a part of the body that needs attention. Does that make sense?