There are three main ways that delayed onset muscle soreness can be stimulated;
- Micro-trauma to muscle tissue (mechanical damage)
- Oxidative stress
- Stress of the myelin sheath that encompasses our nerves
The first two may be things that we intentionally train to create in order to stimulate adaptations for growth or improvements in our cells’ energy production capabilities.
So how can our training cause these?
Mechanical damage occurs most readily when training a muscle in it’s lengthened range or during the eccentric portion of a rep, especially if the exercise is overloaded in the lengthened position. This can happen with a wide range of intensities and is more likely to occur in a greater degree of fatigue.
Oxidative stress occurs when our muscles are working at a rate that surpasses our mitochondria’s ability to produce energy. This typically requires longer time under tension and working at relatively lower intensities by the end of those sets.
The third, stress on the nerves themselves, is most often a byproduct of training in lengthened ranges and not something we directly try to achieve. It also doesn’t equate to a known adaptive response that compliments any physique or performance goals. This means that it is possible to acquire DOMS that is unrelated to a response that results in progress. Please keep this in mind for later.
All three of these have one thing in common. They all result in an inflammatory response. So in very simplistic terms, delayed onset muscle soreness is a sign of local inflammation. The soreness you “feel” is not the actual damage but is a result of inflammatory cytokines in the tissue that results in feedback to your nervous system. Just because you don’t “feel” sore, does not necessarily mean that there was no damage created.
Side Note: Inflammation is not necessarily a bad thing! Acute inflammation is a critical part of the body’s healing and repair process. So PLEASE avoid trying to take large doses of anti-inflammatory substances immediately after training that is designed to induce an inflammatory response. It may not only delay recovery but inhibit the growth and repair process that will lead to hypertrophy.
There is a time and place for some anti-inflammatory support, but right after training is usually not it.