Neuromechanics?  This early in the morning?

It has been a while since we have done a neuromechanics post. While doing some research for one of our PODcasts, We ran across this paper: http://www.ajronline.org/content/184/3/953.full

It’s title?

Midbrain Ataxia: An Introduction to the Mesencephalic Locomotor Region and the Pedunculopontine Nucleus

Yikes! What a mouthful!

What’s the bottom line?

The paper review a condition called “gait ataxia”. In plain English this means “aberrant or unsteady” gait. Things which usually cause gait ataxia originate in an area of the brain called the cerebellum, which coordinates all muscle activity. If you drink to much alcohol, it affects your cerebellum and you have a “wobbly” gait : ).

This paper looks at another area of the brain called the midbrain. It is the top part of the brainstem and contains an important gait integration and initiation center called the “midbrain locomotor nucleus”. The paper looks at 3 different cases and has some cool MRI images to see, along with alot of fancy neurological words and pathways.

Whenever we see gait ataxia, we think of impaired proprioception (look here for a bunch of posts on that, or at this post specifically).

There are many factors to consider when evaluating ataxic (or wobbly) gait, and this just gives us all one more place to look.

The Gait Guys. Making you smarter every day!

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 : )

Proprioceptive effects of aging: It’s all in the details

Here is a brief video of a gentleman that presented to us with neck discomfort and limited range of motion. Step through it several times before proceeding.

Hopefully, you noted the following:

Increased arm swing on the right (or, decreased on Left)

Pelvic shift to the left on Left stance phase

Decreased step length on the left

Hip hike on Left during Right stance phase

The patient does not have a leg length deficiency.

We remember that there are 3 systems that keep us upright in the gravitational plane:

1. vision

2. vestibular system

3. proprioceptive system

We also remember that as one of these systems become impaired, the others will usually increase their function to help maintain homeostasis. All these systems are known to decline in function with aging. So we have 3 systems breaking down simultaneously.

Did you also note the head forward posture, to move the center of gravity forward? How about the subtle head tilt to the right and “bobble” right and left? Motions which have to do with the head are functions of the vestibular system. He is attempting to increase the input to these areas (by exaggerating movements) to increase input.

How about the glasses? Presbyopia (hardening of the lens) makes it more difficult to focus. Movement (detected largely by rods in the eyes have a much higher density than cones, which are for visual acuity). By moving the head, he provides more input to the visual (and thus nervous system)

Amplified extremity movements provide greater input to the proprioceptive system (muscle spindles and golgi tendon organs (GTO’s), as well as joint mechanoreceptors).

Think of the cortical implications (and effects on the cerebellum, the queen of motor activity and important component for learning).  You are witnessing the cognitive effects of aging playing out on the ability to ambulate and its effect on gait.

 So what do we do?

Improve quality of joint motion, whether that is mobilization or manual methods to improve motion where motion is lost. Perhaps acupuncture to help establish homeostasis and improve muscular function. There are many options.

Postural advice and exercises

Core work

Proprioceptive exercises (like head repositioning accuracy, heel to toe and heel to shin)

Gait retraining

 You get the idea. Providing some of that increased input for him and helping the system to better process the information will be the key to improving his function and helping to counteract and maybe slow the effects of aging on the locomotor system.

We are the Gait Guys. Two geeks, giving you the info so we can all make a difference, every day

Special thanks to RM, who allowed us to use this video for this discussion.


Copyright 2012 , The Gait Guys/Homunculus Group

Materials and content cannot be used, copied or distributed without proper author credit /reference or without prior written consent.

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Neuromechanics Weekly: How does appropriate movement diminish pain?

We talk about proper (or should we say appropriate) movement (including gait) inhibiting or diminishing pain. So, how does that happen?

Above on the left is a great diagram that we will…

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The nervous system often takes the path of least resistance. Gait compensations are similar. What you are sometimes are seeing is the “least common denominator” with regards to compensation and conservation of energy.  Here is an article that exemplifies this finding.AbstractWhen sharing load among multiple muscles, humans appear to select an optimal pattern of activation that minimizes costs such as the effort or variability of movement. How the nervous system achieves this behavior, however, is unknown. Here we show that contrary to predictions from optimal control theory, habitual muscle activation patterns are surprisingly robust to changes in limb biomechanics. We first developed a method to simulate joint forces in real time from electromyographic recordings of the wrist muscles. When the model was altered to simulate the effects of paralyzing a muscle, the subjects simply increased the recruitment of all muscles to accomplish the task, rather than recruiting only the useful muscles. When the model was altered to make the force output of one muscle unusually noisy, the subjects again persisted in recruiting all muscles rather than eliminating the noisy one. Such habitual coordination patterns were also unaffected by real modifications of biomechanics produced by selectively damaging a muscle without affecting sensory feedback. Subjects naturally use different patterns of muscle contraction to produce the same forces in different pronation-supination postures, but when the simulation was based on a posture different from the actual posture, the recruitment patterns tended to agree with the actual rather than the simulated posture. The results appear inconsistent with computation of motor programs by an optimal controller in the brain. Rather, the brain may learn and recall command programs that result in muscle coordination patterns generated by lower sensorimotor circuitry that are functionally “good-enough.”J Neurosci. 2012 May 23;32(21):7384-91.

The nervous system often takes the path of least resistance. Gait compensations are similar. What you are sometimes are seeing is the “least common denominator” with regards to compensation and conservation of energy.  Here is an article that exemplifies this finding.

Abstract
When sharing load among multiple muscles, humans appear to select an optimal pattern of activation that minimizes costs such as the effort or variability of movement. How the nervous system achieves this behavior, however, is unknown. Here we show that contrary to predictions from optimal control theory, habitual muscle activation patterns are surprisingly robust to changes in limb biomechanics. We first developed a method to simulate joint forces in real time from electromyographic recordings of the wrist muscles. When the model was altered to simulate the effects of paralyzing a muscle, the subjects simply increased the recruitment of all muscles to accomplish the task, rather than recruiting only the useful muscles. When the model was altered to make the force output of one muscle unusually noisy, the subjects again persisted in recruiting all muscles rather than eliminating the noisy one. Such habitual coordination patterns were also unaffected by real modifications of biomechanics produced by selectively damaging a muscle without affecting sensory feedback. Subjects naturally use different patterns of muscle contraction to produce the same forces in different pronation-supination postures, but when the simulation was based on a posture different from the actual posture, the recruitment patterns tended to agree with the actual rather than the simulated posture. The results appear inconsistent with computation of motor programs by an optimal controller in the brain. Rather, the brain may learn and recall command programs that result in muscle coordination patterns generated by lower sensorimotor circuitry that are functionally “good-enough.”
J Neurosci. 2012 May 23;32(21):7384-91.

Muscle coordination is habitual rather than optimal.

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“It was suggested that the most important criteria in the selection of running shoes are fit and comfort. Running shoes that meet these criteria are likely to provide optimal levels of cushioning and stability.”www.med.nyu.eduMore evidence that perception is reality; just like one of our other posts about a persons perception of what the shoe will do and what it actually does. Looks like the brain may know best!The Gait Guys

Shoes and Shoe fit

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