Practical Science on Movement and Pain
Practical Science on Movement and Pain
What is the first thing you do when a muscle is tight and sore? Stretch it right? The point of this post is to say: don’t do that. There is a good chance you will just make the problem worse, not better.
Before getting into why, I first want to define some terms which distinguish two concepts that are commonly used by physical therapists and trainers- structure and function. Structure means the actual physical hardware that we use for moving around – in short, the bones, muscle and connective tissue. Function means the ability to sense and control the physical structure, which is governed by the nervous system. You can think of structure as the hardware of the body and function as the software of the body.
So why do we care about the distinction? If you want to fix a problem with your computer, you might need to know whether to make changes to the software or the hardware. The same is true with the body. So imagine your hamstring feels stiff and sore when you run or bend over. Is this a problem with the hardware or software? Structure or function?
Let’s take the structural approach first, because this is the way we tend to think. From this perspective, the diagnosis is simple and mechanical. The hamstring feels stiff and sore simply because it is too short! The solution is also simple and mechanical. The hamstring can be made physically longer by stretching it. At first these length changes are elastic and therefore temporary, but if you stretch long and hard enough (and I mean longer and harder than anyone would ever want to) then it might become somewhat permanently longer by adding in some extra actual physical stuff (in the form of more fascia or extra contractile units) in the chain of muscle. So, now we have a longer hamstring. Have we solved the problem?
This depends on many things of course, but my guess is that we have made it worse. Let’s now look at the functional perspective to understand why stretching might not have been a good idea.
It is important to remember that the nervous system has complete control over how the hamstring feels and moves. The hamstring by itself is just a piece of meat. It is the nervous system that decides whether the hamstring will shorten or lengthen, and whether it feels stiff or painful when doing so. If you took a drug to take the nervous system out of the equation, such as a general anesthetic, you would be left with a hamstring that feels no pain and is far more flexible than you would imagine.
We should also remember that the main priority of the nervous system is to protect the body from tissue damage occasioned by falls, accidents, or other movements that could aggravate or cause injury, such as stretching your hamstring too far. Accordingly, we can safely assume that if your hamstring feels stiff and sore, the nervous system has concluded that stretching it is threatening to the safety of the body. The pain and stiffness are essentially protective mechanisms – ways to discourage you from lengthening it outside the perceived range of safety.
Why might the brain be concerned about lengthening the hamstring? There are endless possibilities. The most obvious would be that there is some existing tissue damage in the hamstring (maybe slightly torn and inflamed muscle tissue) that will be aggravated by a stretch. Or maybe the hamstring itself is fine, but it needs to be tense in order to protect the knee, which has been lacking in stability and coordination since an injury several years prior. Or maybe the hamstrings are tight to prevent certain movements in the hip or low back which the nervous system fears, avoids, or maybe has just forgotten how to make.
There is probably no way to know which of these factors is the true cause of the tight hamstring. But all of them have one thing in common – the nervous system is concerned that stretching the hamstring will cause damage. Therefore, in each case, we would expect that aggressive stretching of the hamstring will likely cause the threat level to rise even further, which will in turn cause even more pain and tightness in the hamstring. This is the problem with the structural approach – it treats the hamstring like a mindless piece of meat when in fact it is part of a living breathing nervous system that is trying to protect itself. The result is that a brute force stretching approach to a tight muscle is likely to make the problem worse, not better.
So what would a better solution look like? Again, the possibilities for a successful intervention are endless, but each one would have one critical factor in common – the solution would somehow reduce the level of threat that the nervous system perceives in regard to lengthening of the hamstrings.
With this in mind, we can devise some strategies. First, avoid movements that cause tension, stress or discomfort, such as … stretching the hamstring.
Second, realize that the nervous system will feel less threat in regard to a movement if it has more movement options and greater movement skill. For example, if the knee and low back are more coordinated, the hamstrings don’t have to be on lock down all the time to protect them. How do we get the knee, low back and other joints to become more coordinated? I have discussed some ways in previous posts, but I can summarize here by saying that you should explore as many movement possibilities in your body as possible, in a slow and mindful way that is non-threatening. Movements that are novel, curious and playful will turn on the nervous system’s ability to process information and learn. If you move while in pain or discomfort, the nervous system has no interest in repeating the new painful movements, only in finding out ways to prevent them from happening again in the future.
So, is stretching the hamstring always a bad idea? I think it’s probably never the best option but it sometimes can lead to a good outcome if done in a way that intelligently targets the nervous system instead of ignoring it. For example, PNF style stretching uses various techniques to “trick” the nervous system reflexes into allowing greater range of motion. Research shows that PNF is the most effective stretching technique to improve ROM (assuming for some reason you would care about ROM).
You might also gain benefit from stretching if you stretch in a very gentle, relaxing, and mindful way. Maybe you could also add in a supportive and nurturing environment, and perhaps some eastern spirituality, bamboo and incense, and other stuff that calms the nerves of white people. This is called a yoga class, and it can be an effective way to reduce pain to the extent that it reduces threat. If on the other hand, you approach your yoga class from the structural perspective, by, say, trying to deform your tissues into the approximate shape of Gywneth Paltrow, you can expect pain. So, take it easy in that power bootcamp core strength hot yoga class. Your nervous system might not like it.