How many times have you heard someone say, “Boy, I really feel my workout yesterday?”  What they are referring to is DOMS (delayed onset muscle soreness) or just “sore as hell” for short.  I’ll make this really simple: Soreness is not an indicator of the quality of your workout.   It is an indicator that you just did something your body isn’t used to doing.

Being sore can be caused by a few things.  You may be new to working out or you just added/changed exercises in your routine working muscles in a way that they haven’t been worked in a while.  It can also be caused by significantly upping the load on your normal lifts.  This is not, by any means, and exhaustive list of causes.

So, what really causes soreness?  Here is a great explanation from About.com

Delayed onset muscle soreness is thought to be a result of microscopic tearing of the muscle fibers. The amount of tearing (and soreness) depends on how hard and how long you exercise and what type of exercise you do. Any movement you aren’t used to can lead to DOMS, but eccentric muscle contractions (movements that cause muscle to forcefully contract while it lengthens) seem to cause the most soreness. 

You may be saying, “But it says soreness depends on how hard and long you exercise.”  This is where muscle adaptation comes in.  After doing an exercise for a period of time, your muscles become accustomed to it and the soreness is reduced.

Muscle adaptation is precisely the reason your workout should change every 4-6 weeks.  It is also the reason you should change your set/rep scheme periodically and continuously push yourself by increasing the load. 

Soreness is a sign that you may be experiencing muscle growth but it isn’t a requirement for muscle growth.  If you use your level soreness as a gauge to determine the quality of your workout, you would probably never finish a training program since the level of soreness would diminish significantly over a short period.  I’ve personally seen many people drop programs because they were no longer “feeling the pain”.  They jump from one workout to the next and their progress is very marginal.

In closing, the verdict on if this claim is fact or fiction?  Answer: Fiction.