Eccentric movements and concentric movements can both lead to DOMS. Think of an eccentric movement as lowering the weight when doing a bench press, lowering the body in a pull-up, or lowering the body when doing a back squat. The concentric movement is pressing the barbell away from the body in a bench press, pulling the body to the bar in a pull-up, or standing up a squat. Doing a slow eccentric movement and then a concentric movement will typically lead to delayed onset muscle soreness from the slow eccentric.

There is some conflicting research. A lot of research in the ’90s, 00s, and the '10s even, was the slow eccentric work where we saw muscle tears or muscle breakdowns. There is some conflicting work now that says it can also occur during concentric work. Anecdotally, I typically see that when a slow eccentric is done athletes get sorer than if they are doing a higher speed eccentric. If you are looking to achieve some DOMS because liking the feeling of being sore, try some 6 to 10-second eccentric patterning which will lead to a large amount of strength but also soreness.

Cell swelling is another potential mechanism by which muscle damage can occur. So when we do high rep sets, muscles might be accompanied by an excess amount of proteins that accumulate inside of the muscle or myofiber. Cell swelling leads to tissue edema as Schoenfeld has pointed out in a couple of different research articles. In turn, the tissue edema leads to a type of cellular regulation based on the body’s overall cell swelling, thus another factor that can lead to delayed onset muscle soreness. This is similar to getting the pump. When you get the pump, there is a large amount of fluid inside of the muscle fiber and muscle cells which can alter the way the cells are working and lead to some sense of pain or discomfort.

Cell swelling can lead to a type of anabolism. It can lead to a decrease in protein degradation and an increase in muscle protein synthesis.

Muscle hypertrophy, which is essentially just getting swole, can occur from three different things. It will occur from mechanical tension (a load on the muscles), metabolic stress, and actual muscle damage. In regards to hypertrophy or getting swole, and the lens of DOMS occurring through new movements or movements that are confusing, a specific type of muscle damage can occur because the body is confused and not used to doing the movement. That muscle damage can then in turn lead to a form of hypertrophy. 

Many athletes in weightlifting don’t get sore per se. They’re constantly doing movements like snatches, cleans, jerks, squats, and pulls. They still don’t get that sore. Yes, they are fatigued, but they never are having the soreness that can be achieved in the pecs from an 80/60 drop set in the bench press. Weightlifters don’t feel that. It is mechanical tension that is the mechanism that leads to their gains in muscle mass, and their gains in hypertrophy. Meaning athletes don’t have to get sore, but athletes can still get swole from the mechanical tension. Better yet, athletes can gain strength because their neurological firing is improving when performing the difficult exercises of snatches and cleans.  

So is it horrible when the body gets sore? Will it negate the gains?

Nope.

Want to get sore? Use crazy movements with extreme rep ranges. Don’t want to get sore? Use familiar exercises with similar rep ranges that you are used to as well as similar rest periods. The body won’t be sore but the body will still have mechanical loading which will lead to that overall muscular hypertrophy.