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.

More Tricks for stretching, part 3

We have been talking about ways to enhance stretching, talking about taking avvantage of reciprocal inhibition (please see part 1 here) and autogenic  (or post isometric) inhibition (please see part 2 here). 

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. 

  1. http://www.worldneurologyonline.com/article/arthur-simons-tonic-neck-reflexes-hemiplegic-persons/#sthash.6QS3Eat3.dpuf 
  2. Simons A (1923) Kopfhaltung and Muskeltonus. Ges.Z. Neurol.Psychiatr. 80: 499-549.
  3. Walshe FMR (1923) On certain or postural reflexes in hemiplegia, with special reference to the so-called “associated movements.” Brain 46: 1-37. 
  4. 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
  5. Bruijn SM1, Massaad F, Maclellan MJ, Van Gestel L, Ivanenko YP, Duysens J. Are effects of the symmetric and asymmetric tonic neck reflexes still visible in healthy adults?Neurosci Lett. 2013 Nov 27;556:89-92. doi: 10.1016/j.neulet.2013.10.028. Epub 2013 Oct 21.

Making your stretching more effective. 

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 arms and 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. 

image from :www.positivehealth.com

More thoughts on stretching

   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

Why does it feel so good to stretch? 

We are sure you have read many articles, some written by us, about the good the bad and the ugly about stretching.  Regardless of how you slice the cake, we think we can all agree that stretching “feels” good. The question of course is “Why?”

Like it or not, it all boils down to neurology. Our good old friends, the Ia afferents are at least partially responsible, along with the tactile receptors, like Pacinian corpuscles, Merkel’s discs, Golgi tendon organs, probably all the joint mechanoreceptors and well as a few free nerve endings. We have some reviews we have written of these found here, and here and here.

What do all of these have in common? Besides being peripheral receptors. They all pass through the thalamus at some point (all sensation EXCEPT smell, pass through the thalamus) and the information all ends up somewhere in the cortex (parietal lobe to tell you where you are stretching, frontal lobe to help you to move things, insular lobe to tell you if it feels good, maybe the temporal lobe so you remember it, and hear all those great pops and noises and possibly the occipital lobe, so you can see what you are stretching.

The basic (VERY basic) pathways are:Peripheral receptor-peripheral nerve-spinal cord-brainstem-thalamus-cortex; we will call this the “conscious” pathway:  and peripheral receptor-peripheral nerve-spinal cord-brainstem-cerebellum- cortex; we will call this the “unconscious” pathway.

Of course, the two BASIC pathways cross paths and communicate with one another, so not only can you “feel” the stretch with the conscious pathway but also know “how much” you are stretching through the unconscious pathway. The emotional component is related through the insular lobe (with relays from the conscious and unconscious pathways along with collaterals from the temporal lobe to compare it with past stretching experiences) to the cingulate gyrus and limbic cortex,  where stretching is “truly appreciated”. 

As we can see, there is an interplay between the different pathways and having “all systems go” for us to truly appreciate stretching from all perspectives; dysfunction in one system (due to a problem, compensation, injury, etc) can ruin the “stretching experience”. 

Hopefully we have stretched your appreciation (and knowledge base) to understand more about the kinesthetic aspect of stretching. We are not telling you to stretch, or not to stretch, merely offering a reason as to why we seem to like it.

The Gait Guys