Why do we get sore after exercise? Can stretching or something prevent it?
Delayed-onset muscle soreness (DOMS) is the soreness that we get 24-48 hours following exercise. In the past, it was thought that lactic acid was responsible for DOMS.
However, it has been shown that lactic acid or lactate is not responsible for this and there is more research accumulating that suggests it is actually our own immune system, or more specifically, neutrophils, that are responsible for this.
Neutrophils are the first white blood cell that reacts to an antigen, that is, a virus, bacterium or chemical that stimulates an immune response. These cells are armed with the ability to create several chemicals that could kill viral or bacterial infections, and they do a very good job at it.
Following intense exercise, there is literally damage to the muscle fibers, such that it does not “appear” as normal, healthy muscle. It is not this initial mechanical damage that causes any sort of DOMS. However, these structural changes trigger the inflammatory process – a cascading series of events that results in healing of the muscle. The neutrophils eventually become activated, and they respond to the structural damage in the same way as they would a bacterial or viral infection, multiplying in number in our circulation by a million-fold in 3 – 6 hours post-injury.
Unfortunately, when we perform new movements, whether they are faster, slower, heavier, or longer than what we are used to, the neutrophils become over stimulated. Their stimulation is correlated with the novelty of the movement and its intensity.
As the neutrophils travel throughout our circulation, they find the site of injury and they begin to adhere and infiltrate the muscle cell. Here, they not only release their onslaught of chemicals into the damaged muscle cells for repair, but also the surrounding healthy muscle. In other words, these same chemicals that were supposed to help us during an infection actually cause further damage to the already-injured muscle. This is referred to as secondary injury. This entire process may take 24 – 48 hours. Slides of exercise-induced muscle injury 24-48 hours appear more injurious after the initial mechanical injury that occurred initially after injury. At the same time, the neutrophil’s chemical onslaught causes our nerves to become more sensitive to pain.
Stretching pre-, during or post-exercise will not prevent this process from happening. The best option that we have is taking a non-steroidal anti-inflammatory drug, like ibuprofin, or naproxin BEFORE exercise, but I will not make any guarantees that it will always prevent any soreness.
Why don’t I get sore every time I exercise?
This refers to the “repeated bout effect” of exercise. Following one set of exercise involving muscle-lengthening contractions (such as lowering a bar to the chest during the bench press – the chest muscles are lengthening), a muscle will not be as sore during a second set of the same intensity.
Scientists have not determined the exact mechanism of why this happens. There are several theories out there. However, when referring to neutrophils, there is a significant decrease in circulating neutrophils and neutrophil infiltration into the muscle cell. For some reasons, neutrophils do not become as stimulated as before, so there is not any secondary muscle injury and improved muscle recovery.
This suggests that one of the best ways to get rid of muscle soreness is to continue to exercise the sore muscles in the same movement as the initial exercise pattern, but not at a higher intensity.
Therefore, continue exercising. Do not let the initial pain prevent you from continuing to pursue your fitness goals. In due time, you will be able to handle a series of random movements of various intensities continuously, transforming yourself into a well-rounded athlete.