It's decided, this year you're going to start running again. Laced shoes, headphones plugged in, you're ready. 15 kilometers later, and not even a stitch in your side, you're back home. But here it is, 2 days later, you can't go up the stairs, your calves are sore. However, before going to bed last night, it was fine, so what could have happened?
Complex mechanisms that remain to be elucidated
Muscle soreness refers to diffuse muscle pain that usually appears in the days following intense exercise and gradually disappears. As strange as it may seem for such a common phenomenon, the scientific community has not definitively determined the mechanisms underlying muscle soreness. Like any question that deals with the sensation of pain, understanding muscle soreness involves looking at complex biological processes.
Pain is primarily a subjective experience that results from the nervous system's interpretation of sensory signals, whether or not there are associated physical injuries. Many biological mechanisms have been proposed to explain the origin of muscle soreness, and the current consensus is that several phenomena are involved. And contrary to what you might have heard, "lactic acid" has nothing to do with it!
After intense and unusual exercise, and especially after eccentric contractions (contractions that involve resisting a stretch, for example when going down stairs), micro-lesions of the muscle can be observed at the smallest level of the contractile elements of the muscle: the sarcomeres.
But it is not these lesions themselves that are painful, because they are already present just after the effort while the muscle aches generally only appear 24 to 48 hours later.
On the other hand, these microlesions cause a cascade of physiological phenomena during the hours and days following intense or unusual physical exercise. Some of these phenomena are almost immediate, such as the leakage of components, including enzymes and proteins contained in the muscle cell that diffuse to the outside of damaged cell membranes. Others are later, such as inflammatory and immune reactions, which can spread over several days or even weeks.).
In addition to these physiological phenomena, microlesions also induce functional alterations, such as loss of strength, increased stiffness, or visible swelling of the muscle. However, none of these markers seem to be perfectly correlated with the sensation of pain. It is therefore likely that multiple mechanisms interact to give rise to muscle aches.
The nervous system itself also plays a central role in the onset of muscle soreness. The sensation of pain as such does not exist in the muscle. It results from the interpretation of nociceptive signals (warning signals) received by the brain. Furthermore, several mechanisms proposed to explain muscle soreness directly involve the various sensory sensors located in the muscle.
How to avoid muscle soreness?
Muscle soreness is not serious, and the pain usually disappears within a few days. However, functional deficits, such as loss of strength, can sometimes last a little longer (especially when the effort has been particularly hard), and the disappearance of muscle soreness is not necessarily a good indicator of muscle recovery.
The best solution to protect yourself from muscle soreness is to prepare for this unusual stress by being progressive in your training. Since the muscle is a very adaptable organ, having already been confronted with an exercise makes it much more resistant to muscle damage caused by other constraints in the future. Contrary to what you may hear, stretching before or after a session has no real impact on muscle soreness . And unfortunately, if it is too late and the muscle soreness is already there, no solution has really been proven to improve all the symptoms; the best thing is to remain patient. You can still continue to practice at lower intensities, this could even improve the symptoms a little.
This article is republished from The Conversation under a Creative Commons license.
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