I'm not sure if there is an IOS app for it but I use bodbot. It will give you a workout based on what you are wanting out of it. So if you are wanting to build muscle mass it'll organize routines based off that goal. I will say though that it's been a long while since I've utilized the free version. I paid for lifetime access some years back. Certain features were behind a pay wall that I wanted access too and I justified paying the rather hefty one time fee for it. You may not need those features so it may not be a big deal to you. Here check out their workout generator and see if this is what you are wanting.