Hat tip to Chris Highcock for the video.

I have already written several articles on related subjects. But this is a very easily digestible review that includes discussion of a few concepts I haven’t touched on before, so I thought I would write a quick post on it. Do yourself a favor and get a full text copy of this paper and put it on your required reading list. Here’s a brief review of the contents with my some of my own thoughts.

“The brain responds to the perceived, not the actual reality”

The paper starts by noting one of the most important and now increasingly familiar ideas that has emerged in pain science, namely that:

Pain emerges from the brain according to the apparent danger to body tissues and the need for concerted response from the individual, not according to activity in nociceptive fibers or the actual state of the tissues.

The authors point out that that the failure to draw a distinction between tissue damage and pain is widespread in the treatment of pain. This confusion is likely to cause more problems in the case of persistent pain, which leads to changes in the brain that make the disconnect between pain and nociception that much greater.

Persistent pain and changes to the brain

Chronic pain is associated with sensitization of the spinal cord and supra-spinal centers, as well as “cortical disinhibition.” Excited neurons tend to excite other neurons, unless the spread of excitement is inhibited. Proper inhibition is what creates a meaningful pattern of neural activity as opposed to an undifferentiated explosion of neural activity such as an epileptic seizure. To use a simple example, imagine you are pricked on the arm by a needle. This will stimulate the cortical sensory maps for that part of the arm. The excitement will tend to spread to other areas unless it is inhibited. Without proper inhibition you would not be able to precisely locate where the needle prick occurred – you would feel it all over the arm.

Because people in chronic pain tend to have cortical disinhibition, they are less able to tell the difference between two different types of tactile stimulation. In other words, sensation (and pain) tend to spread inappropriately.

Telling left from right

The paper also discusses a very interesting relationship between chronic pain and the ability to tell left from right.

One way to measure whether the movement maps of a particular subject have been disrupted by chronic pain is to ask them to engage in a “left/right judgment task.” This means asking the subject to look at a picture of a hand or foot and determine whether the hand or foot is from the left or right side of the body. The determination requires the subject to mentally move his own limbs into the position shown in the picture, which requires use of the body maps. It has been shown that people with chronic pain are slower in performing these tasks, suggesting that their movement maps have been altered in some way as a result of the pain.

Lorimer Moseley and David Butler have developed an interesting therapeutic program called “recognize laterality” which attempts to treat chronic pain patients by having them practice the ability to identify pictures of right or left hands. There is at least some evidence to suggest that this practice can increase skills and reduce pain.

Harnessing neuroplasticity to treat pain

I like this line:

That pain emerges according to the apparent danger to body tissues and the need for concerted action, not according to the true danger or damage at a tissue level, means that anything that is detectable or accessible to the brain and relevant to the evaluation of danger to body tissue has the capacity to modulate pain

Well said. One of the optimistic conclusions that can be drawn about the role of the brain in creating pain is that it opens a wide range of potential treatment options.

Controlling pain

One primary strategy for pain reduction is based on cognitive behavioral work. The primary objective here is to reduce feelings of helplessness, establish a sense of control over pain and learn behaviors that reduce the impact of pain on quality of life. Pain education is part of the program here, as it is one way that such control can be given to the patient.

Normalizing sensory representations

The paper then discusses various strategies to correct the abnormalities in sensory maps that tend to occur in patients with chronic pain. I have written a lot about this subject before, arguing that novel movements can provide novel sensory feedback that can fill in gaps in sensory maps and thereby reduce associated pain and dysfunction.

The authors make a very important point in relation to this idea. In order for sensory feedback to result in meaningful changes in cortical sensory maps, the information must have “functional salience.” That is, it must be relevant in some way to the performance of a functional task.

This makes sense. The brain receives a tremendous amount of sensory information each day. Obviously it  is not going to completely change all of its sensorimotor maps each time a new piece of information comes to its attention. Instead it will ignore most of the information and only make a change when the information seems particularly interesting – for example, that it can assist the performance of a functional task.

This is illustrated by studies testing the use of sensory discrimination training as a means to reduce pain in patients with CRPS. As discussed above, chronic pain patients such as those with CRPS have a reduced ability to discriminate between two different types of tactile stimuli (for example the difference between a pen cap and a wine cork.) One study found that tactile discrimination training created significant reductions in pain and disability. But touch stimulation alone created no effect in the control group. The authors note that this is exactly what is predicted by the rule of functional salience.

The practical import of this information is that novel sensory stimulus alone is not likely to be therapeutic for pain. The stimulus must also suggest some solution to a functional problem. I see this rationale built into good movement programs such as the Feldenkrais Method, which uses movements not just as a way to entertain the brain with novelty, but to show it a more efficient way to move and solve physical problems.

Normalizing motor representations

The authors discuss a strategy called graded motor imagery, which involves three stages. The first stage is sessions of left/right limb judgments tasks. The second is imagining movements that normally cause pain. The third stage is mirror therapy, which involves moving the non-painful limb in a mirror box, which creates the illusion of non-painful movement in the painful limb. Each stage is essentially a method of activating motor areas without also activating the pain response, and thereby creating some neural differentiation between the two. I think slow gentle pain free movement is a good alternative for doing the same thing.

The paper also discusses the theory that sensory motor incongruence is a cause of chronic pain, which I have written about before. The basic idea is that inconsistency between motor output and sensory feedback is confusing and may even result in pain. The authors point out that evidence in support of this theory is conflicting. Which I find confusing and a little painful, but what can you do?

Well that’s about it. Make sure to pass this around and let me know if you have any thoughts in the comments.

In case you haven’t heard of Cook, he is a well-known physical therapist who developed the popular functional movement screen (FMS). Although I don’t agree with everything Cook has to say, and have some reservations about the FMS and some of the movements used in the screen, I have enjoyed the book so far and wanted to share some quotes that I thought were right on the money.

On the necessity of training for movement quality as a foundation for movement quantity:

Whenever possible, we must separate movement dysfunction from fitness and performance. Aggressive physical training cannot change fundamental mobility and stability problems at an effective rate without also introducing a degree of compensation and increased risk of injury.

…

Movement pattern corrective strategy is a form of exercise that focuses more on improving mobility, stability, basic motor control and whole movement patterns than the parameters of physical fitness and performance. Once established, the movement patterns create a platform for the general and specific parameters of fitness, including endurance strength speed agility power and task specificity.

As a Feldenkrais instructor, I noted that the following paragraph is quite consistent with Moshe’s ideas about global movement patterns:

Patterns and sequences remain the preferred mode of operation in biological organisms. Patterns are groups of singular movements linked in the brain like a single chunk of information. This chunk essentially resembles a mental motor program, the software that governs movement patterns. A pattern represents multiple single movements used together for specific function. Storage of a pattern creates efficiency reduces processing time in the brain, much as a computer stores multiple documents of related content in one file to better organize and manage information.

In regard to the issues of mobility and stability, I like Cook’s statement that mobility must come first. I also enjoyed his description of what would constitute good training for improved stabilization:

Common strengthening programs applied to muscles with the stabilization role will likely increase concentric strength but have little effect on timing and recruitment, which are the essence of stabilization.

…

Stabilizer training goes far beyond isometrics found in popular stability exercises such as side plank. In this isometric exercise model, conscious rigidity and stiffness are the goal, but true authentic stability is about effortless timing and the ability to go from hard from soft to hard to soft in a blink.

Stability is also confused with strength, where concentric and eccentric contractions build massive endurance. The muscles do become stronger and shortening lengthening, but again they lack the timing and control needed for true functional stabilization. We should train muscles in the way we use them. Stabilizers need to respond quicker than any other muscle group to hold position and control joint movement during loading and movement.

Well said.

Perhaps I will write more when I finish the book and hear what he has to say about the FMS. I don’t expect to be convinced that the FMS is the ideal way to correct movement patterns, but I do agree with his ideas about what good movement looks like, and the importance of prioritizing it as a training goal.

What do you think? Please share any thoughts you may have about the book or the FMS in the comments.

The study asked subjects to learn how to control movements of a cursor on a computer screen by manipulating a joystick and reaching with a robotic arm. While the participants performed the reaching movements, researchers collected data on arm muscle activation and overall energy expenditure.

Unsurprisingly, the subjects gained greater skill as they practiced, and this resulted in them using less muscular activity and less energy to perform the movements. The surprising thing is that the energy required to perform the movements continued to decline even after performance and muscular activity levels plateaued. One scientist remarked that “the results are very surprising and challenge the widely held assumption that muscle activity entirely explains changes in metabolic cost.” The study authors concluded that the continued decrease in the metabolic cost of the movement may be explained by greater efficiency in brain activity as opposed to muscle activity.

I think it is possible that there were muscular costs not accounted for in the data collection, which measured only muscular activity in the arms, and not in other muscles such as postural muscles which might have also learned to become more efficient in the task, and on a slower learning curve. However, I find the brain efficiency hypothesis to be very plausible in light of what we know from motor learning theory, which describes how learned movements move from the “cognitive” to the “automatic” stages of competence. And, more importantly, I find the whole idea to be very cool.

This would imply that even if two people are moving in a completely identical manner using the exact same muscle fibers to perform the exact same movements, one person might actually be using measurably less energy than the other, simply because his brain is working more efficiently to accomplish the same movements.

It also implies that even when you have completely peaked in terms of your performance of a particular skill, you still have room for improvement in reducing the amount of brain power it takes to perform the skill. This might be important in situations that require multitasking. For example, in soccer you may have to perform several skills at once, such as dribbling a ball while locating a teammate for a pass. So maybe you should continue to practice dribbling even if it never improves your actual dribbling, because it might still increase your mental reserves available to perform other activities while dribbling.

I am reminded that certain innovative trainers will challenge their athletes with purely mental tasks such as multiplication tables during the performance of sport specific skills. Perhaps they are finding ways of improving the mental efficiency of their athletes even if these drills do little for physical efficiency.

This also reminds me that the true virtuosos in any particular activity, whether that is music, sports or dance, are those  who have the ability to constantly practice fundamentals which they have already seemingly completely mastered. Perhaps they know that even if they are moving perfectly on the outside, there’s always room for improvement on the inside.

The arthrokinetic reflex defined

Arthro means joint. Kinetic means movement. Reflex means involuntary movement in response to a stimulus. Put them together and you have a term coined by researchers in the 1950s as a way to describe the idea that sensory input from joint movement can reflexively cause activation or inhibition of certain muscles.

This theory was proposed as way to explain the results of an experiment where scientists deactivated a cat’s brain but were still able to effect muscle tone changes in the legs by moving the knee. Similar results were found in a different study involving the muscles of the jaw. The researchers concluded that abnormal jaw positions resulted in mechanoreception that reflexively created abnormal (and dysfunctional) patterns of muscular activation.

The arthrokinetic reflex and strength

Dr. Eric Cobb, the creator of Z-Health, uses this term as a way to explain why joint mobility drills may be a quick and easy way to increase strength, flexibility or coordination. The idea is that moving a joint alters the mechanoreceptive information coming from the joint, which can reflexively alter the activation of the muscles attaching to the joint. For example, there is at least one study where hip mobilization led to immediate increases in hip abductor strength.

But is this the result of the arthrokinetic reflex or some other neural mechanism? I don’t know if there is any answer to this question, but personally I don’t care that much. Mechanoreceptive information might end up talking to many different areas of the spine and brain, all of which might have some sort of influence, reflexive or otherwise, on how the muscles around that area should be activated in the near future.

If the sensory information basically conveys the idea that movement in the joint is safe, we should expect the nervous system to loosen its governor on strength, speed and range of motion. If the information suggests that the movement in question involves danger, we should expect increased protective activity, such as stiffness, pain, weakness, and altered coordination.

Image via Wikipedia

Three new studies recently emerged that shed light on how gait changes our structure and function. I thought it would be interesting to discuss them all at the same time.

High heels are bad

It is known that wearing high heels tends to shorten the calf muscles and stiffen the achilles tendon. Shocker. Some researchers were curious what effects this might have on gait mechanics. So they recruited a group of women who wore high heels (more than 5cm) for at least 40 hours a week for two years. The control group rarely wore heels.

The women walked barefoot while the scientists collected data. Analysis revealed that the high heel group on average took shorter strides and did more work with the calf muscles to propel themselves forward. The low heelers used longer strides, stretched their achilles tendons further, and thereby gained more forward energy “for free” in the form of the release of the stored energy of the elastic tendons. Score one for low heels.

Minimal footwear is good?

In another recent study, Daniel Lieberman’s group recruited some people who habitually run with minimal footwear to run in their minimal footwear and then in normal running shoes. Guess what? Their gait was more efficient in the minimal footwear. This should be no major surprise. I would expect anyone to run most efficiently in the shoes they are accustomed to using. The study would have been more interesting if it included runners who wear mainstream running shoes. Would they have more or less efficient gaits than the minimal runners? Would they improve if they put on the Vibrams? We don’t know. But the study does show that footwear affects gait efficiency.

Running in circles

In the third study, researchers recruited a bunch of runners who spend a lot of time running around a track in the same direction. They found that the muscle reflexes were different from side to side. This was not found in the control group, so this was interpreted as an adaptation to the monotonous same direction running.

Conclusion

So what is the take away here? For me, it is that the structure and function of the body are always adapting to imposed stress in highly specific ways. Some of the adaptations will probably be harmless, and others will probably lead to problems (e.g. the high heels). But one way or the other, how you move will leave its mark.

Image via Wikipedia

I have previously written a series of articles about the study of adverse neural tension and nerve mechanics. If you are not familiar with the idea of adverse neural tension and you want to understand why somethings hurts, you should definitely give these a read.

Anyway, I just saw a study (hat tip to Michael Reoch) which relates to an important point from this series – namely that adverse neural tension may play a role in many pains that are commonly attributed to other sources (such as hamstring strain.)

Some background

In case you didn’t go back and read those old articles, here is a brief review of some basics concepts related to adverse neural tension, how it causes pain, and how to detect its presence.

The nerves of the body cross many joints as shown in the picture to the right. As such, they need to slide, bend, elongate and withstand compression as the body moves. This motion is normal and helps keep the nerves healthy.

However, many of these movements, particularly ones that elongate or compress the nerves, will restrict blood flow. This causes stress at low levels of intensity and duration, and damage at higher levels. Nerves can become sensitized to this stress under certain circumstances, such as the presence of  inflammation or preexisting physical damage. In this event, normal ranges of motion can cause pain, numbness, tingling or other signs of nervy distress – this is called adverse neural tension.

A great way to determine whether certain symptoms result from adverse neural tension or mechanical stress to some other structure is to use the process of “structural differentiation.” This basically involves using a movement to cause some sort of pain, then moving a joint far from the area of pain to relieve tension on the nerves in the painful area (but not other structures) and see if this eases the symptoms.

Here is an example you can do on yourself quite easily. Move into a forward bend to touch your toes while moving your head and neck to stare at your navel. This lengthens the continuous line of tension of the nerves from the head to the feet through the spinal cord and sciatic nerve. When you go low enough, you may feel a familiar pain at the back of the knee. Or perhaps you will feel some other undesirable symptoms elsewhere, such as the low back.

To determine whether these symptoms are the result of adverse neural tension, you can release tension on the nerves in the low back and hamstring area by moving the head to look upwards while keeping the rest of the body in the same place. If this relieves symptoms at the hamstrings, the inference is that they were caused by tensioning the nerves, because these are the only structures in the knee or low back that would have been affected by the head movement. You can play with moving your head up and down to feel how releasing and increasing tension on the nerves form above affects how you feel below. You may convince yourself that these are the true “anatomy trains.”

The study

With that background, let’s look at the study, which tried to determine the extent to which adverse neural tension was present in 14 rugby players previously diagnosed with grade one hamstring strain.

Researchers asked the players to do the slump test, which is fairly similar to the test described above. A little more than half of the players had positive tests, compared to zero players in the control group. Based on this result, it is reasonable to guess that adverse tension is likely to be present in someone previously diagnosed with hamstring strain.

This leads to some interesting questions about the causative relationship between neural and muscular pathology in the case of pain in the back of the thigh. First, was there ever any actual hamstring strain in the first place? If so, was it caused by preexisting issues with neural mobility? Or did damage to the hamstring and associated inflammation and fibrosis limit neural mobility? The study was unable to answer those questions, but it does make clear that people looking to fix “hamstring” issues should consider the possibility that the real issue is with neural mobility. For some basic ideas on how to increase neural mobility, see here.

Or, if you are old school and aren’t interested in this new fangled neurospeak, then watch the video below for an excellent demonstration of how a dynamic warmup can increase power, athletic performance, and help prevent “pulling a hammy.”

Some definitions

My definition of exercise is that you move in some way that puts the body under enough stress to provoke a compensatory adaptation, such as making a muscle bigger, or more capable of generating energy. The best exercise is simply the one that applies the right type and amount of stress to get the sort of adaptation you want without hurting yourself in the process.

Motor Learning means you move in some way that provides the brain with experiences that will teach it how to move the body with more skill, coordination or efficiency. This process is far more complex, subtle, and individual than exercise.

The purpose of this post is not to argue that one process is more important than the other. Of course each is a very valuable tool in helping you improve your physical function. My point is that understanding the differences between these two tools is a good way to decide which one is right for the job you have in mind.

Of course, the line between exercise and motor learning is not always totally clear, and most workouts will have elements of both. Doing pushups or pullups, or squats or lunges place the body under stress in a way that will stimulate adaptations in muscle performance. They will also place demands on good balance and coordination, so doing them will teach you something about how to move more efficiently. “Functional training” might be considered as an attempt to combine exercise with learning along these lines. But there are other approaches to physical training that try to keep learning and exercise as separate as possible. The rationale here is that there may be a tradeoff between the two, so that excessive focus on one will tend to compromise the other, and neither goal is accomplished very efficiently.

Feldenkrais: all learning no exercise

The Feldenkrais Method is concerned exclusively with learning and not exercise. That is why Feldenkrais referred to his work as “lessons” and his clients as “students.” One common feature of a Feldenkrais lesson is minimizing physical stress, because stress interferes with the learning process. Imagine how hard it would be to learn to play the piano if you were hitting the keys as hard as possible and jogging in place during practice sessions. Or to use a less ridiculous example, imagine trying to learn proper squat form with a weight heavy enough to hurt you if you make a little mistake. Not an optimal learning environment. So the movements in a Feldenkrais lesson are typically done as gentle and slow and easy as possible. Other similar training methods would include Alexander Technique and some forms of tai chi.

HIT: all exercise no learning

High Intensity “HIT” style weight training takes the complete opposite of this approach, focusing exclusively on safely stressing the muscles. This is done in part by minimizing the necessity of using any skill to perform the movements. This is why HIT advocates often prefer machines to the use of free weights or other exercises that require more skill and balance to perform. For example, in a squat or lunge you must use proper form, and you risk injury or even falling over if you don’t:

But on a leg press machine all your joints are stabilized and the path of movement is controlled by the machine. So all that’s left to do is focus on pushing as hard as possible – you are not distracted by concerns with safety, proper form, balance, etc. So you maximize the exercise stress by minimizing the skill demand.

The middle ground

As I said earlier, most forms of training fall somewhere in between these two extremes, incorporating elements of physical stress and skill acquisition in the same workout.

For example, running leans more toward exercise stress than motor learning. But running is also a lesson in efficient gait, perhaps especially so if you pay attention to form.

A yoga class leans more toward the development of good movement skill and body awareness, but some classes shift the focus more toward creating exercise stress (often at the expense of any beneficial learning).

Functional training done properly is a nice combination of skill and exercise stress. But sometimes it is biased too much in favor of developing (useless) movement skills, say balancing on a swiss ball while doing squats. In this event, it can degenerate into a circus act, where you have to choose between being safe and while using a tiny amount of weight, or using more weight and killing yourself in the process. Check this out:

The risk/reward here looks rather poor.

I think that part of the reason exercises such as squats, deadlifts, lunges, pullups and pushups have stood the test of time is that they are a nice combination of skill and stress, and a good way to get a large bang for your buck in the gym with a minimum of time and effort. Of course many people will not benefit from these exercises for one reason or another, and might be better served by a program that keeps skill training separate from exercise and vice versa.

What do you think? What type of training program do you prefer? Are these useful distinctions? Let me know in the comments.

The top pic is a cross section of the thigh of a 40 year old triathlete. The bottom is a triathlete at 70. The middle is a sedentary 74 year old man.

Notice any differences? I bet these legs look a LOT more similar on the outside.

The whole study is available for free here. Thanks to Alex for pointing this out.

Hell no. The brain is designed for movement, and movement is what wires it up. To grow a child’s brain, give them a safe place to play.

Here’s an amazing video of Charles-Edward, a nine month old boy who knows how to go to work. Check out what he does when given four hours to play in a room full of toys. Filmed and time lapsed down to two minutes by his father Francis:

Beautiful. Well done Charles, you are well on your way to world domination.

What may look like chaos here is actually a series of highly controlled movement experiments performed one after the other by a master scientist. Every second Charles is making a plan, checking the results, comparing the resulting data to expectation, and then making adustments for the next round of experiments.

Thanks to Francis for making this beautiful video and to Irene Gutteridge, the creator of the baby liv video for pointing it out.