Is Muscle Soreness necessary to gain strength and fitness ?

I encourage you to read the following brochure created by the American College of Sports Medicine, and updated by William Braun, Ph.D., and Gary Sforzo, Ph.D. This article explains the well known feeling of muscular pain usually occurring one or two days after a workout, called Delayed Onset Muscle Soreness. It also continues to explain that even though many people think, "no pain, no gain", it is NOT necessary to experience DOMS in order to increase muscle strength. However, DOMS is not something to worry about if the symptoms disappear within a few days. Should the pain be important, it is recommended to give the painful muscles a rest and go for a walk or a gentle swim to help loosen them up. 
 
Click on the link to read the full article :

http://www.acsm.org/docs/brochures/delayed-onset-muscle-soreness-(doms).pdf