The following is taken from Chad Waterbury's "Branding Iron" column from Testosterone Magazine:
Soaring Through Soreness
Q: Once and for all, should a person train through soreness or wait until he's no longer sore before he trains that muscle group again?
A: In order to accurately answer this question I must first quantify soreness. Here?s how I do it.
Level I Soreness ? This is the type of soreness that's only felt/realized if the given muscle group is maximally contracted. In other words, you don't feel the soreness unless you flex hard. Level I soreness should always be worked through. At this stage of soreness, supercompensation will occur.
Level II Soreness ? This is the type of soreness that's felt all the time. In other words, if any flexion induces feelings of soreness, you're experiencing Level II. This type of soreness can be worked through, but only for one or two workouts. If it doesn't subside with your given program split, then allow for an extra day of rest between workouts.
Note: For some of my clients who spend their days protecting our country and sleeping with loaded Glocks, it's important to train the muscles to work through a state of Level II soreness. If you're merely trying to get big and strong, refer to my previous recommendation.
Level III Soreness ? If you're often heard screaming and cursing while brushing your teeth, opening your car door, or just moving through everyday life, you have Level III soreness. This type of soreness causes pain sensations even when your clothes are rubbing against the muscle!
This type of soreness should never be worked through unless it's an extremely light, high repetition, active recovery exercise. In fact, active recovery is a must at this point. Just remember what you did to cause this type of soreness and don?t do it again!
So to recap, subsequent strength training workouts should be performed as follows with regard to soreness of the given muscle group:
Level I ? Always
Level II ? Sometimes
Level III ? Never