Drop downs are a pain in the butt. Two ideas that are easy.
First, have a view that shows latest excersize entries chronologically . So if I did my squats last week, I can see that and click it to see my max etc.
Two, have a history filter that hides excersize a with no data. This is a view of history, I can't add to it here so why the heck are you cluttering my view. Terrible ux design.
App is just an HTML viewer so should be easy to make these changes on your server and improve the experience easily enough. I would estimate both changes could be done in less than eight hours total with two hours max for testing and qa .
You can expect to see an entirely new experience for entering results in the next year with the rebuild to the kiosk as well as the continued updates to the app.