Personally, I go on the ammount of weight and rep's. Presuming that rep speed and form are relatively equal. If you did 225 for 8 on your first set of your 1st exercise, and if youve achieved supercompensation then youll be able to do 9 or 10 w/ 225, or 7-8 w/235. If you cant then something went wrong. Sometimes its because you hit it again just a bit to soon, sometimes it could be cuz you underestimated caloric, or protien needs, or cuz you didnt sleep enough for a couple nights, or even cuz youve been stressed out over something unrelated to training. But if you pretty sure those things are in place, and that you havent been overtraining for months w/ no break, then its probably because you needed an extra day or so to grow. Not only will different styles of trainining require diffeerent recovery time's, but also certain times (ussually when the style is new and fresh to your body) you'll need different recovery lengths with the same style. Plus theres so many ways you could interpret a chest wkout consisting of 16 sets. You could take each set to positive failure, no more no less. You could pyramid, failing at gradually lower #'s of reps, or pyramid while going 1-2 reps shy of failure except for the last set of each excercise. Or add forced reps, ect,ect. IMO soreness is only a vague indicator for anything. You can get sore and eat well and sleep well and still not grow, or vice versa. And subsiding soreness after a wkout that got you sore, only gives you a sort of "ballpark" idea of when you can hit it again, and can at times be misleading. Thats why weight and reps is the only concrete statistical way of telling if you grew. The visible growth happens to slow most of the time, so you cant really tell. Unfortunately, even the weight/reps predictor has its limitations though. IE: it fails to account for strength increases attributable to improvements in neuro muscular efficiency (motor unit recruitment), and conective tissue strength building. Plus you cant keep having the same exercises in the same order forever.