The effects of aging on the proprioceptive system

When the nervous system breaks down, there are predictable patterns that we can see. Aging isn't that much different in the grand scale of things than some neurological disorders. 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; giving you the info so we can all make a difference, every day

We will be talking about some principals of proprioceptive rehabilitation along with 2 cases of neurological disorders Wednesday evening for our "3rd Wednesdays" talk on online.com: Biomechanics 321. 5 PST, 6MST, 7CST, 8EST

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

This simple screening test becomes a form of exercise.

Today we look at a simple CNS screen for your “central pattern generators” or “CPG’s”. If you do not pass, then the exercise becomes the rehab exercise. If you (or your client) does not have good coordination between the upper and lower extremity, then they will not be that efficient, physiologically or metabolically. 

The “cross crawl” or “step test” looks at upper and lower extremity coordination, rather than muscular strength. If performed for a few minutes, it becomes a test that can look at endurance as well. 

It is based on the “crossed extensor” response, we looked at last week. That is, when one lower limb flexes, the other extends; the contralateral upper limb also flexes and the ipsilateral upper limb extends. It mimics the way things should move when walking or running. 
 

• Stand (or have your client stand) in a place where you will not run into anything.
• Begin marching in place.
• Observe for a few seconds. When you (or your client) are flexing the right thigh, the left arm should flex as well; then the left thigh and right arm. Are your (their) arms moving? Are they coordinated with the lower extremity?
• What happens after a few minutes? Is motion good at 1st and then breaks down?
• Now speed up. What happens? Is the movement smooth and coordinated? Choppy? Discoordinated?
• now slow back down and try it with your (their) eyes closed

If  movement is smooth and coordinated, you (they) pass

If movement is choppy or discoordinated, there can be many causes, from simple (muscle not firing, injury) to complex (physical or physiological lesion in the CNS).

• If movement is not smooth and coordinated, try doing the exercise for a few minutes a day. You can even start sitting down, if you (they) cannot perform it standing. If it improves, great; you were able to help “reprogram” the system. If not, then you (they) should seek out a qualified individual for some assistance and to get to the root of the problem.

The Power of Facilitation: How to supercharge your run.

While running intervals this crisp, cool 19 degree morning, something dawned on me. My left knee was hurting from some patellar tracking issues, but only on initial contact and toe off. I generally run with a midfoot strike. I began concentrating on my feet, lifted and spread my toes and voila! my knee pain instantly improved. Very cool, and that is why I am writing this today. 

Without getting bogged down in the mire of quad/hamstring facilitation patterns, lets look at what happened.

I contracted the long extensors of the toes: the extensor digitorum longus and the extensor hallicus longus; the short extensors of my toes: the extensor digitorum brevis, the extensor hallucis brevis: as well as the dorsal interossei.the peroneus longus, brevis and tertius were probably involved as well.

Do you note a central theme here? They are all extensors. So what, you say. Hmmm… 

Lets think about this from a neurological perspective:

In the nervous system, we have 2 principles called convergence and divergence. Convergence is when many neurons synapse on one (or a group of fewer) neuron(s). It takes information and “simplifies” it, making information processing easier or more streamlined. Divergence is the opposite, where one(or a few) neurons synapse on a larger group. It takes information and makes it more complicated, or offers it more options.

In the spinal cord, motor neurons are arranged in sections or “pools” as we like to call them in the gray matter of the cord. These pools receive afferent information  and perform segmental processing (all the info coming in at that spinal cord segment) before the information travels up to higher centers (like the cerebellum and cortex). One of these pools fires the extensor muscles and another fires the flexor muscles.. 

If someone in the movie theater keeps kicking the back of our seat, after a while, you will say (or do) something to try and get them to stop. You have reached the threshold of your patience. Neurons also have a threshold for firing.  If they don’t reach threshold, they don’t fire; to them it is black and white. Stimuli applied to the neuron either takes them closer to or farther from threshold.  When a stimulus takes them closer to firing, we say they are “facilitating” the neuron. If it affects a “pool” of neurons, then that neuronal pool is facilitated. If that pool of neurons happens to fire extensor muscles, then that “extensor pool” is facilitated.

When I consciously fired my extensor muscles, two things happened: 1. Through divergence, I sent information from my brain (fewer neurons in the cortico spinal pathway) to the motor neuron pools of my extensor muscles (larger groups of motor neurons) facilitating them and bringing them closer to threshold for firing and 2. When my extensor muscles fired, they sent that information (via muscle spindles, golgi tendon organs, joint mechnoreceptors, etc) back to my cerebellum, brain stem and cortex (convergence) to monitor and modulate the response.

When I fired my extensor muscles, I facilitated ALL the neuronal pools of ALL the extensors of the foot and lower kinetic chain. This was enough to create balance between my flexors and extensors and normalize my knee mechanics.

If you have followed us for any amount of time, you know that it is often “all about the extensors” and this post exemplifies that fact.

 Next time you are running, have a consciousness of your extensors. Think about lifting and spreading our toes, or consciously not clenching them. Attempt to dorsiflex your ankles and engage your glutes. It just may make your knees feel better!

The Gait Guys. Facilitating your neuronal pools with each and every post.

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