Exploring the Links Between Human Movement, Biomechanics & Gait
What’s wrong with this picture?
The model is obviously well sculpted and hopefully will paid for the toll that this exercise will be taking on her nervous system overtime. Take a close look at the picture above on the left. Look carefully and what do you notice? Do you see it?
This exercise is neurologically incongruent. Her right arm is flexed at the same time as her right hip. When does this ever happen in gait?
Do you remember crossed extensor responses or tonic neck reflexes? If not, see here and here. When we walk the right arm and left leg or flexed while the left arm and right leg are extended. During a tonic neck response, and that is rotated to one side the upper and lower extremity (upper greater than lower) should extend on that side with flexion on the contralateral side.
During a tonic neck reflex, the head is rotated to one side the upper and lower extremity (upper greater than lower) should extend on that side with flexion on the contralateral side. In the picture above her torso is rotated to the left while looking straight ahead which is effectively right neck rotation and her extremities are flexed on that side.
In the picture above her torso is rotated to the left while looking straight ahead which is effectively right neck rotation and her extremities are flexed on that side.
Who thinks of these things? Certainly not folks that are paying attention to appropriate neurology and physiology! Oh yeah, and the ad was for massage cream. Jeez…
Taking advantage of the stretch reflex and reciprocal inhibition; or the “reverse stretch”
Reciprocal inhibition is a topic we have spoken about before on the blog (see here). The diagram above sums it up nicely. Note the direct connection from the spindle to the alpha motor neuron, which is via a Ia afferent fiber. When the spindle is stretched, and the pathway is intact, the uscle will contract. What kind of stimulus affects the spindle? A simple “stretch” is all it takes. Remember spindles respond to changes in length. So what happens when you do a nice, slow stretch? You activate the spindle, which activates the alpha motor neuron. If you stretch long enough, you may fatigue the reflex. So why do we give folks long, slow stretches to perform? Certainly not to “relax” the muscle!
How can we “use” this reflex? How about to activate a weak or lengthened muscle? Good call.
Did you notice the other neuron in the picture? There is an axon collateral coming off the Ia afferent that goes to an inhibitory interneuron, which, in turn, inhibits the antagonist of what you just stretched or activated. So if you acitvate one muscle, you inhibit its antagonist, provided there are not too many other things acting on that inhibitory interneuron that may be inhibiting its activity. Yes, you can inhibit something that inhibits, which means you would essentially be exciting it. This is probably one of the many mechanisms that explain spasticity/hypertonicity
How can we use this? How about to inhibit a hypertonic muscle?
Lets take a common example: You have hypertonic hip flexors. You are reciprocally inhibiting your glute max. You stretch the hypertonic hip flexors, they become more hypertonic (but it feels so good, doesn’t it?) and subsequently inhibit the glute max more. Hmm. Not the clinical result you were hoping for?
How about this: you apply slow stretch to the glutes (ie “reverse stretch”) and apply pressure to the perimeter, both of which activate the spindle and make the glutes contract more. This causes the reciprocal inhibition of the hip flexors. Cool, eh? Now lightly contract the glutes while you are applying a slow stretch to them; even MORE slow stretch; even MORE activation. Double cool, eh?
Try this on yourself. Now go try it on your clients and patients. Teach others. Spread the word.
The last few weeks , we have been talking about techniques to improve your (or your clients) stretching experience. 1st, we talked about reciprocal inhibition here. Next we talked about post isometric inhibition here. The we spoke about the symmetrical tonic neck reflex (response) here. If there is a symmetrical tonic neck reflex, then there must be an asymmetrical one as well, eh? That is the topic of todays discussion.
The asymmetrical tonic neck reflex was 1st described by Magnus and de Kleyn in 1912 (1). Like in the pictures above, when the head is rotated to one side, there is ipsilateral extension of the upper and lower extremity on that side, and flexion of the contralateral (the side AWAY from where you are rotating) upper and lower extremity. Take a few minutes to see the subtleness of the reflex in the pictures above. Now think about how this occurs in your clients/patients. The reflex is everywhere!
The reflex persists into adulthood (2) and is modulated by both eye movement and muscular activity (3). When there is neurological compromise, the reflex can be more prevalent, and it seems to arise from the joint mechanoreceptors in the neck and its connection to the reticular formation of the brainstem (4). It may modulate blood flow and cardiovascular activity as well (5).
So, how can we take advantage of this? We could follow in the footsteps of Berta Bobath (6) and incorporate these into our rehabilitation programs, which we have done, quite successfully. But rather than read a whole book, lets talk about how you could incorporate this into your stretching program.
Let’s say you want to stretch the right hamstring:
actively rotating the head to the right (see reference 3) facilitates the right tricep and right quadricep AND facilitates the left bicep and left hamstring
through reciprocal inhibition, this would inhibit the right bicep and hamstring AND left tricep and left quadricep
To get a little more out of the stretch, you could actively contract the right tricep and quadricep (MORE reciprocal inhibition), amplifying the effect
We encourage you to try this, both on yourself and your clients. It really works!
Wow, isn’t neurology cool? And you thought it was only for geeks!
The Gait Guys. Giving you info you can use in a practical manner, each and every post. Be a geek. Spread the word.
Before we talk about this next one, we need to give you a little background (neurologically speaking).
Take a look at the picture above and note the posturing of the baby in the 2 positions. These neurological reflexes (or postures) are called symmetrical tonic neck reflexes or responses (STNR’s for short) and were described in animals and men by Magnus and de Kleyn in 1912 (1). This work was later studied and reported by by Arthur Simons in 1916 (2) and later by Francis Walshe in 1923 (3). These were later made popular by Berta and Karl Bobath in the 70’s (who studied Walshes work), whom they are often attributed to (4).
You next question is “Do these persist into healthy adulthood”? and the answer is a resounding YES (5).
Take a look at the picture above again and note the following:
When the neck is flexed, the fore limbs flex (and the muscles facilitating that, bicep, brachialis, anterior deltoid are contracting) and the hind limbs are extending (relatively), with the glutes maximus, quadriceps, foot dorsiflexors contracting.
Note that when the head is extended, the forelimbs are extended and the hind limbs flexed. Think about the muscles involved. Upper extremity tricep, anconeus, posterior deltoid, lower back extensors, hamstrings and foot plantar flexors facilitated.
The reflex is based on the mechanoreceptors in the neck articulations and muscles and are frequently used by us and many others in the rehabilitation field. Generally speaking, looking up facilitates things which make you extend above T12, and flex below T12. Looking down facilitates flexion above T12 and extension below.
We would encourage you at this point to “assume” these positions and feel the muscles which are active and at rest.
So, how can we take advantage of these while stretching?
Think about your head position:
If you are standing up and hinging at the hips to stretch your hamstrings (notice we did not say “bent at the waist”; there is a BIG difference in shear forces applied to your lumbar spine) you would probably want your neck bent forward, as this would fire your quads which would in turn ALSO inhibit your hamstrings, in addition to the STNR inhibiting the hamstring.
If you were in a hip flexor stretch position, you would want you head up, looking at the ceiling to take advantage of the reflex.
We are confident you can think of many more applications of this reflex and trust that you will, as it can apply to both upper and lower extremity stretches. Just remember that this reflex is symmetrical and will affect BOTH sides. Of course, there are reflexes that only effect things unilaterally, but that is the subject of another post.
The Gait Guys. Helping make you better at what you do for yourself and others and assisting you on using the neurology that God gave you.
Simons A (1923) Kopfhaltung and Muskeltonus. Ges.Z. Neurol.Psychiatr. 80: 499-549.
Walshe FMR (1923) On certain or postural reflexes in hemiplegia, with special reference to the so-called “associated movements.” Brain 46: 1-37.
Janet M. Howle . Symmetrical Tonic Neck Reflex in Neuro-developmental Treatment Approach: Theoretical Foundations and Principles of Clinical Practice. NeuroDevelopmental Treatment, 2002 p 341 ISBN 0972461507, 9780972461504
While I was making linguine and clam sauce for my family, one of my favorite foods that I haven’t had in quite some time( and listening to Dream Theater of course) I was thinking about this post. Then I remembered about voice recognition on my iMac. Talk about multitasking!
What do you agree that stretching is good or not, you or your client still may decide to do so possibly because of the “feel good” component. Make sure to see this post here on “feel good” part from a few weeks ago.
If you do decide to stretch, make sure you take advantage of you or your clients neurology. There are many ways to do this.One way we will discuss today is taking advantage of what we call myotatic reflex.
The myotatic reflex is a simple reflex arc. The reflex begins at the receptor in the muscle (blue neuron above) : the muscle spindles (nuclear bag or nuclear chain fibers). This sensory (afferent) information then travels up the peripheral nerve to the dorsal horn of the spinal cord where it enters and synapses in the ventral horn on an alpha motor neuron. The motor neuron (efferent) leaves the ventral horn and travels back down the peripheral nerve to the contractile portion of the myfibrils (muscle fiber) from which the the sensory (afferent) signal came (red neuron above). This causes the muscle to contract. Think of a simple reflex when somebody taps a reflex hammer on your tendon. This causes the muscle to contract and your limb moves.
Nuclear bag and nuclear chain fibers detect length or stretch in a the muscle whereas Golgi Tendon organs tension. We have discussed this in other posts here. With this in mind, slow stretch of a muscle causes it to contract more, through the muscle spindle mechanism.
Another reflex that we should be familiar with is called reciprocal inhibition. It states simply that when one muscle (the agonist) contracts it’s antagonist is inhibited (green neuron above). You can find more on reciprocal inhibition here.
Take advantage of both of these reflexes? Try this:
do a calf stretch like this: put your foot in dorsiflexion, foot resting on the side of the doorframe.
Keep your leg straight.
Grab the the door frame with your armsand slowly draw your stomach toward the door frame.
Feel the stretch in your calf; this is a slow stretch. Can you feel the increased tension in your calf? You could fatigue this reflex if you stretched long enough. If you did, then the muscle would be difficult to activate. This is one of the reasons stretching seems to inhibit performance.
Now for an added stretch, dorsiflex your toes and try to bring your foot upward. Did you notice how you can get more stretch your calf and increased length? This is reciprocal inhibition at work!
There you have it, one neurological tool of many to give you increased length.The next time you are statically stretching, take advantage of these reflexes to make it more effective.
The Gait Guys. Teaching you more about anatomy, physiology, and neurology with each and every post.
We have all had injuries; some acute some chronic. Often times injuries result in damage to the joint or articulation; when the ligament surrounding a joint becomes injured we call this a “sprain”.
Joints are blessed with four types of mechanoreceptors. We have covered this in many other posts (see here and here). These mechanoreceptors apprise the central nervous system of the position (proprioception or kinesthesis) of that body part or joint via the dorsal column system or spinocerebellar tracts. Damage to these receptors can result in a mismatch or inaccuracy of information to the central nervous system (CNS). This can often result in further injury or a new compensation pattern.
Joints have another protective mechanism called arthrogenic inhibition (see diagram above). This protective reflex turns off the muscles which cross the joint. This was described in a few great paper by Iles and Stokes in the late 80’s an early 90’s (vide infra). Not only are the muscles inhibited, but it can also lead to muscle wasting; there does not need to be pain and a small joint effusion can cause the reflex to occur.
If the muscles are inhibited and cannot provide appropriate afferent (sensory) and efferent (motor) information to the CNS, your brain makes other arrangements to have the movement occur, often recruiting muscles that may not be the best choice for the job. We call this a “compensation” or “compensation pattern”. An example would be that if the glute max is inhibited (a 2 joint muscle, with a larger attachment to the IT band and a smaller to the gluteal tuberosity; it is a hip extender, external rotator and adductor of the thigh), you may use your lumbar erectors (multi joint muscles; extensors and lateral rotators of the lumbar spine) or hamstrings (2 joint muscles; hip extenders, knee flexors, internal and external rotators of the thigh) to extend the hip on that side, resulting in aberrant mechanics often observable in gait, which may manifest itself as a shortened step length, increased vertical displacement of the pelvis, lateral shift of the pelvis or increase in step height, just to name a few. Keep this up for a while and the new “pattern” becomes ingrained in the CNS and that becomes your new default for that motion.
Now to fix the problem, you not only need to reactivate the muscle, but you need to retrain the activity. Alas, the importance of doing a thorough exam and thorough rehab to fix the problem.
Often times, the fix is much more involved than figuring out what the problem is (or was). Take your time and do a good job. Your clients and patients will appreciate it!
We get a lot of interest in our posts on stretching. Seems like this is a pretty hot subject and there is a lot of debate as to whether it is injury preventative or not. Are you trying to physically lengthen the muscle or are you trying to merely bring it to its physiological limit? There’s a big difference in what you need to do to accomplish each of these goals. Lets take a look at each, but 1st we need to understand a little about muscles and muscle physiology.
Muscles are composed of small individual units called sarcomeres. Inside of these “sarcomeres” there are interdigitating fibers of actin and myosin (proteins) which interact with one another like a ratchet when a muscle contracts. Sarcomeres can be of various lengths, depending on the muscle, and are linked and together from one end of the muscle to the other. When a muscle contracts concentrically (the muscle shortening while contracting) the ends of the sarcomere (called Z lines or Z discs) are drawn together, shortening the muscle fiber over all (see the picture above).
Signals are sent from the brain (actually the precentral gyrus of the cerebral cortex areas 4, 4s and 6) down the corticospinal tract to the spinal cord to synapse on motor neurons there. These motor neurons (alpha motor neurons) then travel through peripheral nerves to the muscles to cause them to contract (see picture above).
The resting length of the muscle is dependent upon two factors: The physical length of the muscle 2. The “tone” of the muscle in question.
The physical length of the muscle is determined by the length of the sarcomeres and the number of them in the muscle. The “tone” of the muscle determined by an interplay of neurological factors and the feedback loops between the sensory (afferent) receptors in the muscle (Ia afferents, muscle spindles, Golgi tendon organs etc.), relays in the cerebellum and basal ganglia as well as input from the cerebral cortex.
If you’re trying to “physically lengthen” a muscle, then you will need to actually add sarcomeres to the muscle. Research shows that in order to do this with static stretching it must be done 20 to 30 minutes per day per muscle.
If you were trying to “bring a muscle to its physiological limit” there are many stretching methods to accomplish this. Pick your favorite whether it be a static stretch, contract/ relax, post isometric relaxation etc. and you’ll probably be able to find a paper to support your position.
Remember with both not to ignore neurological reflexes (see above). Muscle spindle loops are designed to provide feedback to the central nervous system about muscle length and tension. Generally speaking, slow stretch activates the Ia afferent loop which causes causes physiological contraction of the muscle (this is one of the reasons you do not want to do slow, steady stretch on a muscle in spasm). This “contraction” can be fatigued overtime, causing the muscle to be lengthened to it’s physiological limit. Do this for an extended period of time (20-30 mins per day) and you will physically add sarcomeres to the muscle.
Next time you are stretching, or you were having a client/patient stretch, think about what it is that you’re actually trying to accomplish because there is a difference.
We are and remain The Gait Guys. Bald, good-looking, and above-average intelligence. Spreading gait literacy with each post we publish.
thanks to scienceblogs.com for the corticospinal tract image