by TheRealLurlock » Sat Mar 26, 2022 2:43 pm
DOMS is caused by eccentric stress (i.e. the lengthening of a muscle under load, as opposed to a contraction, or shortening) to which you are not adapted. The biology behind it is not well understood, but it is believed to be the result of cross-sectional damage to sarcomeres (basically the building blocks of muscle fibres). In any case, this is why descending, say down a flight of stairs, is always the most painful thing after you've developed DOMS - because it's the same thing that causes it: the eccentric loading of your quadriceps and other muscles as you control your descent down from one step to the next. This is also why if you take a strong track cyclist and make him squat a load of weight under a barbell, you will hospitalise him with soreness the next day. His legs are very well adapted to the concentric motion of cycling which means he can squat a heavy weight, but since cycling involves no eccentric loading whatsoever, he is completely unadapted to the controlled descent down into the bottom of the squat.
DOMS is not a marker of productive exercise and neither does its absence mean you haven't worked hard enough. If you are training or exercising regularly then you should never experience significant soreness beyond the first week or so (unless, of course, you are following some silly CrossFit-related principle of 'muscle confusion,' the aim of which is to make you constantly sore by cycling between movements to which you are unadapted all the time).