3 in 1 Elite Athlete & World Champion Glory Fighter Mike Lemaire

From our friends at BodyBuilding.com 
The reality is that soreness is a very poor indicator if muscle growth is occuring. If you worked at a level that demonstrates overload you will cause muscle growth. In fact, muscle soreness on a consistent basis can be a sign of doing too much work and leading you down a path of overtraining. Many top athletes train without any desire to experience muscle soreness as it impedes their ability to perform. While I appreciate Arnold’s accomplishments as a bodybuilder his knowledge of the sciences is far more limiting.There are several factors that go into how often you train, mainly volume and intensity. Volume being calculated by load X sets X reps and intensity referring to the percentage of 1 repetition maximum. (Figure out your 1-rep max here.) If more volume exists the body is needing to restore it’s levels of energy components. The whole energetic theory is based upon the idea that suprecompensation of energy metabolites will occur resulting in increased muscle growth. If intensity is a high factor then time needs to be given primarly to the Central Nervous System to recover from such strenous work. If inadequate time is given no progress and sometimes backward progress results. There are some strength coaches that advocate very brief and intense training sessions be performed frequently during a day. However, this is more for strength development than muscle growth since volume is usually very low.

Source: http://www.bodybuilding.com/fun/henkin6yy.htm