Originally Posted by
Jordan Feigenbaum
You could really argue it both ways:
Way 1) In some phases of training you want to intentionally accumulate fatigue so that you can't recover between workouts so that you're, in effect, functionally (planned) overtraining/overreaching. By training sleep deprived/hungover/fatigued you're getting more stress, which depending on where you're at in your training and how well you'll recover from that increased stress may or may not lead to a more pronounced adaptation.
Way 2) Given the same load, volume, rest periods, etc. a "fresher" person will likely have better quality of reps, faster bar speed, and thus get better practice/technique development, motor pattern development, etc.
My thoughts: Sometimes you have to train when you feel like shit. Somedays those are awesome days and somedays you should've stayed home. The point is you show up, day in and day out and put the work in while trying to program as intelligently as possible.