Q: If I'm not sore after a strength-training  session, does it mean I didn't work hard enough?
A: This myth continues to live among the gym-going masses, as well as among some fitness professionals. The bottom line is that no, you don't have to be sore after a training session in order for it to be effective . In the world of exercise science, the soreness you feel after an intense workout is commonly referred to as exercise induced muscle damage (EIMD).
Whether or not this damage is a result of your training session depends on two key factors:
1. Did you do something new during your training session that your body isn't used to, like a new movement pattern?
2. Was there an increased emphasis on the eccentric phase (the "down" or "lowering" part) of a muscle action, like the descent portion of a squat?
EIMD is believed to be caused by a combination of both chemical and mechanical processes that occur within the body at a cellular level. In general, post-workout discomfort  will diminish once your body gets used to the same movement pattern. Does EIMD directly correlate to an increase in muscular size? According to a recent paper by fitness expert Brad Schoenfeld, M.Sc., C.S.C.S., published in the Journal of Strength and Conditioning Research, the jury is still out. If you're feeling too sore to complete your normal strength plan but don't want to lose your momentum, try this active recovery workout . It will help your muscles recover and prepare your body to accomplish even more next time you hit the weights.