Podcast 137: Running: Limitations in thoracic spine function matter

We cover many aspects of human movement on this podcast, the topics are broad ranging on today's show, but they are worthy of your time in our opinion.

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Key words:
arm swing, thoracic extension, scapular retraction, arch height, rear foot posting, forefoot loading, ankle dorsiflexion, ankle rocker, shoulder extension, SSEP, F-wave, EMG/NCV testing, gait ataxia
 
Here are some key quotes from today's show:


You may have the range of motion, but are you actually able to use it?
You haven't truly injured yourself, you've just lost your ability to compensate.

And we discuss a case study today, where the following paragraph is germane.

"Abnormal gait changes might be the first signs of an early slow cooking neurologic disorder. Most, not all, pathology is afferent, yet most (not all) EMG/NCV testing is geared towards the efferent pathology (motor end organ disease, not sensory compromise), hence, testing can miss your client's pathology.  We discuss a classic case where the client clearly had the beginnings of a neurologic disorder on our exam (clonus and joint position sense changes and clear ataxic gait) yet the testing "that was done" showed a normal study of this client.  Much pathology is afferent, the input is the problem, so you need to consider requesting Sensory nerve action potentials, SSEP and F-wave testing, because they are difficult to elicit and good technique is paramount. Hence these extra components of the test are not done, and you need to ask for this in your testing.  "Maybe it's not there because you are not looking".  We have much more on this topic, come listen to Podcast 138 and get the full monty."

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Proprioceptive afferent inputs can control the timing and pattern of locomotion. When disease is present, or when injury has compromised the neuro-biomechanical linkages, slow postural responses can trump what timely responses are necessary to ensure for smooth locomotion.
 
When many people think of balance and locomotion, the cerebellum is often a top topic for it is important for movement control and plays a particularly crucial role. Thus, a most characteristic sign of cerebellar damage is walking ataxia. It is not known how the cerebellum normally contributes to walking, although recent work suggests that it plays a role in the generation of appropriate patterns of limb movements, dynamic regulation of balance, and adaptation of posture and locomotion through practice. (1)
Reflex pathways exist which regulate the timing of the transition from stance to swing, and control the magnitude of ongoing motoneuronal activity. During locomotion there is a closely regulated feedback from the various sensory receptors in the skin, joints, muscles, tendons, ligaments and other tissues, this is referred to as afferent feedback. When there is damage to these sensory “organs”, or the pathways into, or out of, the central nervous system locomotion becomes difficult.  We can see this in the video case above. This is a case of Chronic Inflammatory Demyelinating Polyradiculopathy (CIDP). It is an immunne-mediated inflammatory disorder of the peripheral nervous system whereby the myelin sheath of neurons is slowly eroded and as a result, the affected nerves and pathways fail to respond well rendering numbness, paresthesias, pain and progressive muscle weakness along with loss of deep tendon refexes. Obviously this will render locomotion fatiguing and difficult. Falls are not uncommon as you can see in the video.
 
Timing and coordination is everything in gait. When a portion of the system is compromised from injury or neurologic deficit, locomotion becomes strained.  There is an intricate balance between the extensor and flexor muscles.  We found this quote by Lam and Pearson particularly relevant to today’s discussion and video.

“Proprioceptive feedback from extensor muscles during the stance phase ensures that the leg does not go into swing when loaded and that the magnitude of extensor activity is adequate for support. Proprioceptive feedback from flexor muscles towards the end of the stance phase facilitates the initiation of the swing phase of walking. Evidence that muscle afferent feedback also contributes to the magnitude and duration of flexor activity during the swing phase has been demonstrated recently. The regulation of the magnitude and duration of extensor and flexor activity during locomotion is mediated by monosynaptic, disynaptic, and polysynaptic muscle afferent pathways in the spinal cord. In addition to allowing for rapid adaptation in motor output during walking, afferent feedback from muscle proprioceptors is also involved in longer-term adaptations in response to changes in the biomechanical or neuromuscular properties of the walking system.” (2)

Gait and any form of locomotion are highly complicated with many pieces necessary to achieve clean, smooth, coordinated motion.  Failure in only one piece of the puzzle can result in profound unhinging of the entire system because of the entangled nature of the feedback loops.  
Nothing dramatic today gang, just some thoughts that came to us after seeing this client and doing some reading to keep up on things.  We thought this would be a nice follow up to Monday’ blog post on proprioception.
Shawn and Ivo
the gait guys
References:
1. Neuroscientist. 2004 Jun;10(3):247-59.

Cerebellar control of balance and locomotion.

2. Adv Exp Med Biol. 2002;508:343-55.

The role of proprioceptive feedback in the regulation and adaptation of locomotor activity. Lam T1, Pearson KG.

The awkward runner ?: Gait Ataxia, another cause.

Vitamin B12 deficiency: Another cause of Gait Ataxia.

Here is where our clinical background gives us another slight edge on those in the gait and movement fields. Once again we need to bring to the table another cause of gait problems.  This problem can manifest as a gait, running or simply a mild impairment of muscular coordination patterns.  There are so many people out there these days providing “care” to athletes and those that want to stay physically fit. Many of these care givers however are not in the medical field. They might be a coach, trainer, massage therapist, physical therapist, or God forbid someone you are taking advice from over the internet. The problem in giving health advice or treatment is that it is easy to do and often, if you are without a medical license, fraught with the “you cannot be aware of something that you do not know exists”.  So, if you are one of those who trains or coaches people, offers nutritional advice, stretches, massages, “activates” or uses other means without a medical license, you had best be aware that you could be missing things.  And, even if you do have a license, failure to get results is sometimes a result of something being missed diagnostically, not a failure to treat enough or not using the right techniques or therapy. This is not a dig at anyone or their passion, it is just a fact, without a medical background you just might not be exposed to the gamut of things to be aware of.  Thus, it is quite possible that “interventions” are not working because other things are lurking below the surface, things one just might not be aware of. On this note, It is never a bad idea to ask your athlete if they have had some blood work and chemistry workups in the last 12 months, especially if they are not progressing or are having some of the early subtle signs or symptoms of something bigger lurking systemically. Read on.

You will recall from our last talk on movement impairments from organic or systemic nutritional complications (Nov 10th, Gluten Gait Ataxia) that there are several metabolically driven gait and ataxia disorders. The one we are going to talk about today is Vitamin B12 deficiency ataxia (we are going to downplay the pernicious anemia thing for now to stay focused).

You will recall that the definition of ataxia is pretty broad.  Ataxia refers to an inability to coordinate bodily movements, especially movements of the muscles. Thus ataxia can manifest as a possible aberrant motor pattern, lack of coordination or subtle gait impairments such as early balance difficulties.

Vitamin B12 (aka cobalamin) is a water soluble vitamin that has a paramount role in the normal function of the central nervous system and blood formation. It is one of 8 B vitamins. Vit B12 deficiency is nothing to shrug off.  In its most severe unaddressed form it can potentially cause irreversible central nervous system damage (for you doctor-types out there you will fondly recall the long lectures on SCD (subacute combined degeneration of the spinal cord and CNS) from your favorite neurophysiology professors).  At subacute B12 levels softer symptoms can range from fatigue, depression, dizziness, memory loss, confusion, anxiety and other neurocognitive problems as well as altered executive function, ataxia (unsteady gait, balance impairment) peripheral limb or circumoral numbness or tingling.  The vagueness of these symptoms often lead to untimely diagnosis.   

Vitamin B12 occurs naturally in most animal products, but if you are one of millions of people who cannot absorb B12 efficiently, then you can begin experiencing symptoms of vitamin B12 deficiency.  And yes, to remind you once again, the symptoms are soft and vague at the start.  They are vague because it takes time for gradual degradation of the nerve’s myelin sheath, the place where Vit B12 has its impact. It is this myelin, the conductive coating on a nerve, that is necessary for accurate and timely communication between the central nervous system and muscles and organs.  And it is here that gait ataxia truly begins.  The nerves of your spinal cord rely on a steady in and outflow of information from your nerve sensors throughout your body.  Messages to and from the nerves in your limbs are conducted along the spinal cord (particuularly in the spino cerebellar and dorsal column tracts: See Dr Ivo’s neuromechanics lectures for a review of these here ) and to the brain, thus controlling gross and fine motor tasks such as running, walking, dancing, climbing, skipping, or tapping your feet.  Nerve damage causes these signals to become misinterpreted, resulting in poor coordination, or gait ataxia.

Here are some signs and symptoms of gait ataxia:

  • Unsteady gait, difficulty walking without stumbling
  • Difficulty staying balanced on one leg
  • Trembling awkward movements, clumsiness
  • Muscular weakness in the legs and arms
  • impaired motor tasks
  • Spasticity
  • Hypotension (low blood pressure)
  • Vision problems
  • Numbness / tingling; particularly around the mouth


So that is our little talk on gait ataxia and its relation to Vit B12.  It is a quite in-depth topic to be honest but we want to keep this concise.  In terms of recommendations, we are not going to make any here today.  The recommended daily allowances are easy to find on the internet.  Two things you can do,  you should improve your diet (we all can) and get yearly blood work studies.  If you are vegan (unless you are a lacto-ovo vegetarian) or do not consume much in the way of animal based food products you need to consider B12 supplementation (that or start eating termites - B12 rich !).  You should also be aware that there are many things that can alter Vit B12 absorption /integration such as birth control pills, alcohol consumption, nicotine, medications, antibiotics and many others. These are consumables that increase your risk of B12 problems and thus risk for gait ataxia and the other B12 related issues.  Most of the time, ataxia is a difficult diagnosis to make (unless a copious single event of alcohol consumption at the local pub is the culprit). 

Bottom line.  There is so much more to Vitamin B12 deficiency but this was not meant to be that forum.  Ataxia and gait alterations are nothing to dismiss, especially in the elderly.  There are many causes of ataxia and this is just another that we wanted to bring to light.  The nervous system and muscular systems have some definite source needs and Vit B12 is one of them.  Without the right fuel these systems will begin to show impairments, soft impairments at first which could be the difference in a high level athlete’s performance.  If your parents, patients, athletes or those you know are expressing some vague and subtle symptoms, educate them. Better yet, send them off to their doctor if symptoms persist, rather than handing them a bottle of Gatorade and casually telling them they are probably just dehydrated, anemic from low iron or low on electrolytes …. as it so often occurs.

Shawn and Ivo, The Gait Doctors