Muscle Fatigue and Pain

Muscle Fatigue and Pain

Let’s experiment:  raise an arm to your side, palm facing up, and hold it for several minutes . . . I’ll wait . . ..

If you held your arm up for an extended length of time, you eventually felt pain before choosing to return it to its resting position, right?

If you actually did the experiment . . . move your shoulder up and down a few times now that your arm is in a resting position . . . does it still hurt?  Probably not.

This experiment demonstrates that muscle fatigue, and not tissue damage, could be the cause of musculoskeletal pain.

Which poses a dilemma . . . if it is actual tissue damage, some rest might be necessary for healing. If it is simply muscle fatigue, rest will eventually cause further atrophy . . . which may also present as pain. So, what to do?

The first thing is to determine whether actual tissue damage has occurred. When you know that there is no tissue damage . . . consider muscle fatigue.

It could also be a combination . . . conditions like arthritis and injuries that don’t fully heal can lead to muscle fatigue. So, it could be both/and.

To further complicate matters, the nervous system adapts its recruitment of muscles due to tissue damage and lifestyle habits and this can put multiple muscles in the same stressed position as your arm was, all at the same time, . . . meaning, due to compensations, multiple muscles can be in the same state as your extended arm was but the muscles are unable to return to a resting position when they feel pain so the pain becomes chronic.

It is difficult to identify all the adaptations made by the nervous system. And the nervous system itself can change in such a way that it considers the layered adaptations as normal, keeping the muscles in a state of fatigue and, therefore, consistent pain.  

What do I mean by adaptations and compensations?

The musculoskeletal system (bones/ligaments/muscles and the joints they create) is a complicated network of overlapping and interconnected tissues that allow for coordinated movement. These tissues are activated by the nervous system in a specific sequence, in order to carry out a movement. The organization of this sequence is called a strategy

For actions such as breathing, spinal extension, rolling, reaching, crawling, and squatting, our nervous system did not have to learn these strategies – they are inherent.  Walking is the culmination of an infant who has mastered the previous inherent movements. More complicated movements, such as throwing, golfing, driving, and using a tool, are strategies that the nervous system learns. This process requires blending of aspects of the inherent movements with new learned movements. 

It gets even more complicated but for the purposes of this post . . . when the normal strategy is unable to be used, the neuro-muscular system will adapt and compensate, which allows us to carry on with the planned activity.  This is not something we think about; it occurs unconsciously. 

Adaptation is helpful for an event like a twisted ankle. Our body will immediately adapt so we don’t fall down. We may limp for a few days and then as the ankle gets better, we resume normal walking. But, there are times when our system gets overwhelmed and it doesn’t adjust. A fractured ankle might result in the person falling to the ground and requiring assistance. So, there are times when our body is immediately overwhelmed and cannot accommodate.

Most musculoskeletal issues are not from a sudden injury, but minor changes and adaptations in the neuromuscular system that occur over time. Each change is apparently needed and occurs painlessly. However, when these adaptations and strategies either last too long or are too numerous, the muscles fatigue and cannot hold these changes any longer. This is when pain occurs. It can seem to occur suddenly, out of nowhere as a terrible muscle spasm or tendinitis . . . or . . . it could be a little discomfort that doesn’t go away or gradually gets worse.   

The result is that the pain is real and the location is specific but the cause is not specifically one cause. An x-ray might show arthritis, or the MRI could show a bursitis – but why did those develop? What types of adaptations and force re-distributions occurred resulting in arthritis and bursitis? There could be several layers of adaptations that occurred, making even this search impossible to find the one cause.

So, muscle pain can be caused by muscle fatigue which is caused by adaptations of the nervous system. Pain is not necessarily an indication of tissue damage; it could be an indication of muscle fatigue. And that is good news, because we can do something about muscle fatigue.

In this post, we discuss other potential reasons for pain . . ..

Muscle Fatigue in Crossed Syndromes