The incremental behavior is fixed in workouts. Awesome. But I do see this in challenges. Which are awesome!

As a new user, the distinction between "Manage workouts" and Manage exercises" is not clear.  So the app's first page the new user sees, no matter how attractive it is, is confusing.

And for the experienced user, the first page generally accomplishes nothing.  It's just an extra tap.

Suppose I, as a new user, decide to explore the two manage options.  I tap one and see Dr. Muscle and Custom.  So I go back and try the other.  Once again I see Dr. Muscle and Custom.  My little exploration showed me there is no difference.
So I decide to try again but deeper.  I try the first and Dr. Muscle.  I see Gym, Home gym, and Bodyweight.  That makes sense.  Then I back all the way out and try the second button and Dr. Muscle.  Wow!  All I see here is an overwhelmingly long list that with no obvious use.

So I back out again and this time look at the two Custom options.  The first has two blank lists headed "Workouts" and "Programs"  Then reflecting on the first buttons, they said Workouts and Exercises, now there are Programs also and I still don't know what any if them mean.  Plus, the main button said it's about managing workouts, and now it seems to be about managing programs too.

So I try the other and find I'm directed to create an exercise, and I still don't know what one is.  But I'm left with the puzzle of how these exercises are related to the other button's workouts, and where do programs fit in?

Unfortunately that over-long stream of consciousness pretty is much my initial (and current) impressions, so any suggestions I might have are probably wrong, but here goes anyway.

A manage button might display this operating explanation: "A workout is a group of exercises.  Select from this list of workouts or enter a name to create a new one ______."

(If a name is given, give the option of selecting from the list or entering   a name of their own creation.)  (this would be repeated until the user taps a Finish button. etc.

If I happened to have accurately described workouts and exercises, they appear to be so closely related that dividing them between two separate, top-level buttons only confuses their relationship.

I also suspect that few users will tweak beyond this.  My guess is that a Program is a collection of workouts.   While it might seem inconsistent to separate programs from workouts, but if most users don't create programs, separating it keeps it from cluttering up workout creation.

Regarding the second level of choice between Dr. Muscle and Custom, If I understand them correctly, separating them is artificial.    Every program, workout, or exercise should be equally available to the user who is building his own structure.  Separating them at a higher level prevents the user from building a program combining Dr. Muscle and his own workouts.

The settings interface isn’t compliant with simple user interface guidelines. The toggle switch is for optional selections, it’s not the correct button to use for mutually exclusive selections. Use radio buttons or a drop down for that. An example of this is the background. That should just be a single drop down with the one selection.

Click Manage Workouts — Dr Muscle — 

You’ll see or not see the Bodyweight button on the iPhone SE. 

Top half is there but it doesn’t show. It does work if you click. Takes you to manage body weight workouts. 

UI design bug

Finish a set say Bench Press.

I want to do it over.   Maybe I didn't get the machine I wanted.  Whatever.  If I go back to Bench Press, it sets me up in that session for the next workout.  But I want to edit the entire exercise, delete what I did and start over without it moving to the next session.

How do I erase after finishing that exercise and start over?

When we don't reach the number of reps asked for the first set, the app shouldn't ask us if it was hard or if we could have made more reps, it seems obvious it was too hard :)

Maybe some videos showing correct form  

I have swapped out some of the leg exercises to make the lower body work out more glute focused, I think it would be useful if there was a work out like this on the app.

Today I used version 2.5.20 for my workout. When I saved what I thought was the last set of the exercise (and the "All Sets Done" message displayed), the rest timer started again. This was confusing because it sent the mixed-message that I was supposed to do another set.

So I don't believe the rest timer should start running after saving the last set of an exercise.