Mesoderm vs. Ectoderm

August 24th, 2011

So, I was started writing an article about the differences between mesoderm and ectoderm, then I realized that my friend Todd Hargrove had already written a great article. Here it is:

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. This is called the mesoderm. Function means the ability to sense and control the physical structure. Function is governed by the ectoderm, which is basically 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? Do we treat the mesoderm or ectoderm?

Let’s take the mesodermal 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 ectodermal perspective to understand why the mesodermal approach might not have been a good idea.

First, the ectoderm or 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.

Second, 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 CNS 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 ham 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 mesodermal 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 mesodermal approach to a tight muscle is likely to make the problem worse, not better.

So what would a more sensitive, enlightened, ectodermal 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 CNS 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 as ectodermally (as opposed to mesodermally) as possible. 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 to the ectoderm. If on the other hand, you approach your yoga class from the mesodermal 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 ectoderm might not like it.


More on Pain

August 22nd, 2011

Research shows that understanding how your pain works helps you to manage it more effectively, and can actually decrease your pain level and distress.

(The IASP definition.)
“PAIN: An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.”

Pain is an OUTPUT of the Brain. This fact has only been discovered in recent decades and is still not fully appreciated by many healthcare professionals.
Pain expresses the brain‟s perception of THREAT. Incoming nerve signals from the tissues, called nociception, are best thought of as raw ”danger” signals. The brain interprets ALL the input (sensory, visual, memories, emotions, cognition) to determine how threatening the situation really is, and then will produce several outputs, one of which is PAIN. (This is not a conscious process).

If your brain decides that there is a significant threat, you WILL have pain. If your brain decides that there is no significant threat, you WILL NOT have pain.

This explains situations of people having severe pain despite minimal or no tissue damage, as well as some people with severe injuries who experience little or no pain at the time, because the brain decides that something else is more important (for example in emergencies demanding immediate action).

Sometimes pain indicates serious underlying pathology, but very often it does not, especially in chronic pain situations. Pain is a valuable warning system, but the system can malfunction.

One way to think about pain is that it is similar to thirst: If your body needs water the brain produces the sensation of thirst to motivate you to drink. If part of your body seems to be in danger of tissue damage, the brain produces the sensation of pain to motivate you to take action. This action could be withdrawing, guarding, resting, or moving.

Parts of the nervous system function both to alert the individual about potential danger to tissues (nociception) and to produce the pain perception. Throughout the tissues of the body there are peripheral nerve cells with various receptors. These are the sensory neurons. Some are responsive to mechanical stimuli (movement, pressure) some to chemicals, and others to temperature. These neurons produce signals in response to appropriate stimulation and these signals travel to the spinal cord, and on to the brain. There are neurons that respond to all types of stimuli at higher intensities likely to indicate tissue damage, and these are called nociceptive neurons. They send “danger” signals which can trigger the brain to output a pain experience.

“Remember that nociception is neither sufficient nor necessary for pain.” (Butler, Moseley 2003)

It is only after the brain evaluates the potential threat that the output of “PAIN” is produced. Signals from sensory neurons are transmitted to spinal cord neurons that bring the message up to specific brain areas. It is important to know that there is no “pain centre” in the brain. Many widely distributed areas are part of the network that produces the pain experience.

Acute pain, such as hitting your thumb with a hammer, often correlates quite well with the state of the tissues. When pain persists for a longer time it is no longer an accurate indication of the state of the tissues.

Remember: HURT does not equal HARM !

I have more to write, but no time…..to be continued

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