The great thing about the TGU is it works a lot of major muscle groups and joints in one exercise so its hard to substitute another similar exercise and get the same benefits. I do work with an athlete who has a problematic shoulder and he does the TGUs with a sand bag on the shoulder eliminating the need to hold weight overhead then does another movement to work on shoulder strength and stability. (i.e. seated military press, TRX IYT etc)