I used to do the 3 a week IA SPBR split and would be totally gassed out by the last exercise. That's a pretty low volume routine with 5 lifts a day or so.
Now, I do 4 sessions a week, with higher frequency for the main lifts, 3-5 more worksets per session and higher volume on the assistance. I've also added 1 or 2 light cardio sessions a week. Of course, I felt like shit the first weeks switching over but over time I have adapted. I'm not entirely sure you should always listen to what your body is telling you about recovery. Granted, injuries are a bit different and should be allowed to heal properly before getting back on it, but the standard "feeling sore and beat up" after heavy lifting can be worked around. On some rest days I feel like total shit, sore all over, and I've noticed that I feel a lot better if I perform some kind of active recovery instead of just laying around. Being more active helps me a lot. Some days I've contemplated skipping the gym have turned out to be PR days.
I've read quite a lot lately about overtraning and higher frequency heavy training, like the Easterns Europeans. If I've got the time to be in the gym that frequently, I'd like to try it out at some point. I skipped the whole "full body high frequency SS style" programs when I was a beginner so I have no personal experience with it. I do know however that my main lifts are better now that I practice them more often and I wonder how I'd do squatting and benching 3 times per week (with regulated intensity).
Matt Perryman has written some interesting stuff on the subject:
Glenn Pendlay and John Broz also have some interesting stuff.
Edited by conceptionist - 10/11/13 at 1:16am