Exploring the Links Between Human Movement, Biomechanics & Gait
Manipulation and Mechanoreceptors
Do YOU do joint manipulations or mobilizations? Could you explain how they are working and accomplishing what you think (or say) they are accomplishing?
All of this information applies to ANY articulation, not just the spine. This is essential information that all folks performing manipulations or mobilizations should know.
What ARE the different types of mechanoreceptors and how do they work? How does that relate to manipulation and its effects? How can mechanoreceptors inhibit pain and influence muscle tone? Dr Ivo answers these questions and more in this video, excerpted from a recent seminar.
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 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.
On the topic of endurance training (which we discussed on this weeks PODcast, forthcoming in the next day or so; we have both been extraordinarily busy in our clinics); if you are a well trained athlete (ie endurance junkie), how might this effect your running gait?
So, you run 103 miles with an elevation change of over 31,000 feet, how do you think you would fare? These folks were tested pre and 3 hours post race on a 22 foot long pressure walkway at about 7.5 miles per hour. Here’s how this group of 18 folks did:
increased step frequency
decreased “aerial” time
no change in contact time
decrease in downward displacement of the center of mass
decrease in peak vertical ground reactive force
increased vertical oscillation
leg stiffness remained unchanged
So what does this tell us?
wow, that is a lot of vertical
holy smokes, that is really far
don’t know how I would do with a race like that
they are fatigued (1, 2, 6)
they are trying to attenuate impact forces (2, 3, 4, 5, 7)
The system is trying to adapt the best it can. If you were to do a standard hip screen test (like we spoke about here) you would probably see increased horizontal drift due to proprioceptive fatigue. Remember that proprioception (our bodies ability to sense its position in space) makes the world go round. Proprioception is dependent on an intact visual system (see our post yesterday) , an intact vestibular system and muscle and joint mechanoreceptors functioning appropriately). We would add here that central nervous system fatigue (ie central processing both at the cord and in the cortex) would probably play a role as well.
The take home message? The human machine is a neuro mechanical marvel and much more complex than having the right shoe or the right running technique. Training often makes us more competent and efficient, but everything has it limits.
The Gait Guys. Making it real with each and every post.
all material copyright 2013 The Gait Guys/ The Homunculus Group
Université de Lyon, F-42023 Saint-Etienne, France. firstname.lastname@example.org
Changes in running mechanics and spring-mass behavior due to fatigue induced by a mountain ultra-marathon race (MUM, 166km, total positive and negative elevation of 9500m) were studied in 18 ultra-marathon runners. Mechanical measurements were undertaken pre- and 3h post-MUM at 12km h(-1) on a 7m long pressure walkway: contact (t(c)), aerial (t(a)) times, step frequency (f), and running velocity (v) were sampled and averaged over 5-8 steps. From these variables, spring-mass parameters of peak vertical ground reaction force (F(max)), vertical downward displacement of the center of mass (Δz), leg length change (ΔL), vertical (k(vert)) and leg (k(leg)) stiffness were computed. After the MUM, there was a significant increase in f (5.9±5.5%; P<0.001) associated with reduced t(a) (-18.5±17.4%; P<0.001) with no change in t(c), and a significant decrease in both Δz and F(max) (-11.6±10.5 and -6.3±7.3%, respectively; P<0.001). k(vert) increased by 5.6±11.7% (P=0.053), and k(leg) remained unchanged. These results show that 3h post-MUM, subjects ran with a reduced verticaloscillation of their spring-mass system. This is consistent with (i) previous studies concerning muscular structure/function impairment in running and (ii) the hypothesis that these changes in the running pattern could be associated with lower overall impact (especially during the braking phase) supported by the locomotor system at each step, potentially leading to reduced pain during running.
As we have discussed in other posts, proprioception is subserved by cutaneous receptors in the skin (pacinian corpuscles, Ruffini endings, etc.), joint mechanoreceptors (types I,II,III and IV) and muscle spindles (nuclear bag and nuclear chain fibers) . It is both conscious and unconscious and travels in two main pathways in the nervous system.
Conscious proprioception (awareness of where a joint or body part is in space or action) arises from the peripheral mechanoreceptors in the skin and joints and travels in the dorsal column system (an ascending spinal cord information highway) to ultimately end in the thalamus of the brain, where the information is relayed to the cerebral cortex.
Unconscious proprioception arises from joint mechanoreceptors and muscle spindles and travels in the spino-cerebellar pathways to end in the midline vermis and flocculonodular lobes of the cerebellum.
Conscious proprioceptive information is relayed to other areas of the cortex and the cerebellum. Unconscious proprioceptive information is relayed from the cerebellum to the red nucleus to the thalamus and back to the cortex, to get integrated with the conscious proprioceptive information. This information is then sent down the spinal cord to effect a response in the periphery. As you can see, there is a constant feed back loop between the proprioceptors, the cerebellum and the cerebral cortex. This is what allow us to be balanced and coordinated in our movements and actions.
The ACL is blessed with type I, II and IV mechanoreceptors (Knee Surgery, Sports Traumatology, Arthroscopy Volume 9, Number 6) We remember that type I mechanoreceptors exist in the periphery of a joint capsule (or in this case, the periphery of the ACL) and are largely tonic in function (ie: they fire all the time) and type II are located deeper in the joint (or deeper in the ACL) and are largely phasic (ie they fire with movement). Type IV mechanoreceptors are largely pain receptors and anyone who has injured his knee can tell you all about them.
The article does a great job reviewing the importance of proprioception and how it relates to knee function and concludes “A higher physiological sensitivity to detecting a passive joint motion closer to full extension has been found both experimentally and clinically, which may protect the joint due to the close proximity to the limit of joint motion. Proprioception has been found to have a relation to subjective knee function, and patients with symptomatic ACL deficiency seem to have larger deficits than asymptomatic individuals.” Bottom line, never quit on the rehab and training of an ACL deficient knee until the absolute best outcome has unequivocally been achieved with certainty that no further improvement can be achieved…… absolute certainty. Too many stop shy of certainty, and your brain will know it. And it will show it in small gait, running and athletic skills.
Yup, this is some heavy stuff, but hey…you’re reading it, right? If we didn’t explain it in detail you might not believe that WE are The Gait Guys ……. more than just foot and shoe guys. After all, there is a brain attached to the other end calling the shots.
Sorting it out so you don’t have to…We remain…The Gait Guys
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This week, we conclude the mechanoreceptor journey……