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

A little neuro, anyone?

Welcome to Monday, and yes, it is a NEURO day. In fact, if you got up this morning, you too are having a NEURO day. Dr Allen thinks it’s all about the ORTHOPEDICS, but without NEURO, there would not be any orthopedics : )

A dialogue from one of our avid readers, Dr. Ryan.

Dr. Ryan: Hey Ivo,

I just read this article on Mercola’s site which is an interview with Dr. Craig Buhler who does muscle activation techniques.  Can you check this for accuracy?  This must be a mistake b/c I always thought spindle activation will facilitate the muscle to contract.  Also, I always wondered why the O/I attachment points are tender in muscles that are inhibited.  Does his description sound right to you.  If not, do you have a better explanation?

“Your muscle system and nervous system relate to each other from within tiny muscle fibers called spindle cells, which monitor stretch. If your muscle is overloaded too rapidly, the spindle cells will temporarily inhibit the muscle. The next time you contract the muscle, it will fire again. Similarly, cells within your tendons called Golgi tendon organs also measure and monitor stretch. If your tendon is stretched too rapidly or exceeds its integrity, the Golgi tendon organs will temporarily inhibit the muscle. But the next time the muscle fires, it will again fire appropriately.

“But there’s a fail-safe system,” Dr. Buhler explains. “It’s where the tendon attaches into the periosteum of the bone and the little fibers there are called Sharpey’s fibers. Those fibers are loaded with little receptors that monitor tension. And if the integrity of those fibers are exceeded, they inhibit the muscle, just like a circuit breaker would inhibit an electrical circuit.

Once that happens, the muscle will still fire under passive range of motion. But if you load the muscle, it gives way. If you continue to load the muscle, your body creates pain at the attachment points to protect you. What the central nervous system does at that point is compute an adaptive strategy by throwing stress into the muscle next to it. Other tissues begin to take on more of the load for the muscle that’s been injured.”

Here is a link to the entire article if you want to check it out:

http://fitness.mercola.com/sites/fitness/archive/2013/01/04/advanced-muscle-integration-technique.aspx?e_cid=20130104_DNL_art_1

Dr Ivo: Thanks Dr. Ryan.

Spindles monitor length and GTO’s monitor tension. My understanding is spindles, when activated, stimulate the alpha motor neuron(at the cord) and cause contraction of that muscle or motor unit. GTO’s, when activated, cause inhibition of the muscle they are associated with. I am not aware of them being inhibitory, only GTO’s. They are believed to be GABAnergic synapses. The impulse (at least in cats) can be smaller or inhibited if the muscle is held in contraction for an extended period of time (see attached)

Perhaps he is talking about spindle dysfunction, where the intrafusal portion of the spindle (which is innervated by a gamma motor neuron) is either excited or inhibited. The gamma’s are more of a slave to the interneuronal pool (in the cord), which would be the sum total of all excitatory and inhibitory input to that area (ie the central integrated state). This not only reflects local receptor input but also cortical information descending (from areas 4s and 6 in the precentral gyrus) AND descending information from the caudal reticular formation.

Based on what you sent, I do not agree with the 1st 2 sentences. I was not aware about increased receptor density of Sharpeys fibers. I did a quick search and found this: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2100202/  , which eludes to it and here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3098959/. I will have to dive in more when I have time.

Not sure why O/I attachments are tender in inhibited muscles. I find them tender in most folks. Maybe because inhibited muscles ave altered receptor function and that preloads the nociceptive afferent pathway or at least that neuronal pool? Are they closer to threshold for some reason? Not sure. LMK what you find.

Thanks for getting me jazzed about sharpeys fibers!

for those of you who need to know YES, there will be a forthcoming Sharpeys fibers article

Dr. Ryan: That’s what I thought.  Thanks for looking into it and I will check out those links.  You have jazzed me plenty of times over the years.  Glad I could jazz you up for a change.  Have a great weekend.


Yes, Dr Ivo is definitely an uber neuro geek, especially when he spends time on the weekend talking about spindles!



all material copyright 2013 The Homunculus Group/ The Gait Guys. All rights reserved. Please as before you lift our stuff.

A little neuro, anyone?

Welcome to Monday, and yes, it is a NEURO day. In fact, if you got up this morning, you too are having a NEURO day. Dr Allen thinks it’s all about the ORTHOPEDICS, but without NEURO, there would not be any orthopedics : )

A dialogue from one of our avid readers, Dr. Ryan.

Dr. Ryan: Hey Ivo,

I just read this article on Mercola’s site which is an interview with Dr. Craig Buhler who does muscle activation techniques.  Can you check this for accuracy?  This must be a mistake b/c I always thought spindle activation will facilitate the muscle to contract.  Also, I always wondered why the O/I attachment points are tender in muscles that are inhibited.  Does his description sound right to you.  If not, do you have a better explanation?

“Your muscle system and nervous system relate to each other from within tiny muscle fibers called spindle cells, which monitor stretch. If your muscle is overloaded too rapidly, the spindle cells will temporarily inhibit the muscle. The next time you contract the muscle, it will fire again. Similarly, cells within your tendons called Golgi tendon organs also measure and monitor stretch. If your tendon is stretched too rapidly or exceeds its integrity, the Golgi tendon organs will temporarily inhibit the muscle. But the next time the muscle fires, it will again fire appropriately.

“But there’s a fail-safe system,” Dr. Buhler explains. “It’s where the tendon attaches into the periosteum of the bone and the little fibers there are called Sharpey’s fibers. Those fibers are loaded with little receptors that monitor tension. And if the integrity of those fibers are exceeded, they inhibit the muscle, just like a circuit breaker would inhibit an electrical circuit.

Once that happens, the muscle will still fire under passive range of motion. But if you load the muscle, it gives way. If you continue to load the muscle, your body creates pain at the attachment points to protect you. What the central nervous system does at that point is compute an adaptive strategy by throwing stress into the muscle next to it. Other tissues begin to take on more of the load for the muscle that’s been injured.”

Here is a link to the entire article if you want to check it out:

http://fitness.mercola.com/sites/fitness/archive/2013/01/04/advanced-muscle-integration-technique.aspx?e_cid=20130104_DNL_art_1

Dr Ivo: Thanks Dr. Ryan.

Spindles monitor length and GTO’s monitor tension. My understanding is spindles, when activated, stimulate the alpha motor neuron(at the cord) and cause contraction of that muscle or motor unit. GTO’s, when activated, cause inhibition of the muscle they are associated with. I am not aware of them being inhibitory, only GTO’s. They are believed to be GABAnergic synapses. The impulse (at least in cats) can be smaller or inhibited if the muscle is held in contraction for an extended period of time (see attached)

Perhaps he is talking about spindle dysfunction, where the intrafusal portion of the spindle (which is innervated by a gamma motor neuron) is either excited or inhibited. The gamma’s are more of a slave to the interneuronal pool (in the cord), which would be the sum total of all excitatory and inhibitory input to that area (ie the central integrated state). This not only reflects local receptor input but also cortical information descending (from areas 4s and 6 in the precentral gyrus) AND descending information from the caudal reticular formation.

Based on what you sent, I do not agree with the 1st 2 sentences. I was not aware about increased receptor density of Sharpeys fibers. I did a quick search and found this: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2100202/  , which eludes to it and here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3098959/. I will have to dive in more when I have time.

Not sure why O/I attachments are tender in inhibited muscles. I find them tender in most folks. Maybe because inhibited muscles ave altered receptor function and that preloads the nociceptive afferent pathway or at least that neuronal pool? Are they closer to threshold for some reason? Not sure. LMK what you find.

Thanks for getting me jazzed about sharpeys fibers!

for those of you who need to know YES, there will be a forthcoming Sharpeys fibers article

Dr. Ryan: That’s what I thought.  Thanks for looking into it and I will check out those links.  You have jazzed me plenty of times over the years.  Glad I could jazz you up for a change.  Have a great weekend.


Yes, Dr Ivo is definitely an uber neuro geek, especially when he spends time on the weekend talking about spindles!



all material copyright 2013 The Homunculus Group/ The Gait Guys. All rights reserved. Please as before you lift our stuff.

Understanding Neuroreceptors: Movement Concepts

For all you inquiring minds out there, here is a question on one of our YOUTUBE videos we though was worth making into a post.

Question: “Dr Waerlop says that GTO’s (golgi tendon organs) inhibit muscle tension and muscle spindle apparatuses (MSAs) increase muscle tension. But then he says to treat the attachments (GTOs) to increase the tension and the bellies (MSA’s) to decrease. Seems counterintuitive. What is the modality of tx, acupuncture? Massage?…..What is your modailty for treating these? And does that modality inhibit those neurosensors or stimulate them?”

Answer: GTO’s are high threshold receptors that actually modulate muscle activity through inhibition  (Ib afferents) and Spindles are lower threshold receptors receptors that modulate overall activity, particualrly length. Think of the GTO’s as responding to tension and the spindles as responding to muscle length. Spindles are more in the belly of the muscle and GTO’s at the musculo tendonous junctions. By treating the origin and insertion of the muscles, you can modulate both, whereas treating the belly of the muscles, seems to affect the spindles more.

By treating the origin and insertion of the muscles, you can modulate both, whereas treating the belly of the muscles, seems to affect the spindles more.

The modality can be manual or acupuncture stimulation of the origin/ insertion of the muscle that tests weak.We find that acupuncture seems to work bestbut manual methods work just fine as well. We believe we are normalizing function, rather than specifically inhibiting or exciting. Like Chinese medicine, we are balancing the Yin and the Yang, creating homeostasis.

The Gait Guys: Making it real. Making it understandable. Making it happen : )

The information you have been waiting for. How do you facilitate a muscle? How do you defacilitate a muscle? Do you already know how? Do you know the mechanism?

Fear not… In this weeks Neuromechanics, Dr Waerlop simplifies the function of Golgi Tendon Organs. Clinical correlations are made throughout the presentation with his usual sense of humor. Neuro and foot geeks around the world are rejoicing…

Wow, we really are geeks!