Observing motor control and movement quality

Purpose:
Describe how GRIP Approach evaluates movement quality based on physics and motor control.

Think about the basic activity of transitioning from sitting position to standing. Clinicians, therapists, and trainers may have 2 main pathways of observing this movement critically.

Observation Path # 1

• Can the person transition from sitting to standing position without help?
• Can he/she do so with or without experiencing pain?
• Can he/she do so several times?

Observation Path # 2

• Does the person have proper movement quality during the transition from sitting to standing?
• What position are the joints in?
• What is the firing order of the musculature?
• Does the body have to work around a structural barrier to achieve the movement?
• Etc., Etc.,
• Can I increase demand to this transition without negatively altering movement quality?

Observation path # 1 is all most clients care about and is a fine observational path. Most current rehabilitation methodology focuses on observation path # 2, noting one cannot perform sitting to standing several times for a lifetime without appropriate movement quality. This is also a fine observational path as certain movements have been associated with a higher occurrence of injury.

We get in trouble in a few areas. 

I'd like to redefine pain as the personal experience in response to nociception or perceived danger. Essentially pain is entirely subjective for everyone and can be in response to real tissue damage and danger as reported to the brain by stimulation of nociceptors or in response to perceived danger such as a knee that is still painful to bend because it previously was inflamed stimulating nociceptors to send afferent information to the brain which was then interpreted as pain (even in an injury that is 20 years healed). Subjective pain is not an accurate way of judging movement quality. We'd like to shelve the subjective experience of pain to talk in terms of function and physics. For more on pain, Lorimor Moseley and Gregory Lehman have a few articles below:

https://theconversation.com/explainer-what-is-pain-and-what-is-happening-when-we-feel-it-49040
http://www.greglehman.ca/2015/01/04/smudging-pain-neurotags-and-cortical-body-maps-explaining-the-weirdness-of-pain/

The whole concept of movement quality also poses some concrete challenges, most notably, defining adequate or proper moment quality. These definitions tend to focus on specific positions, movements, and firing patterns based on averages that the observer deems to be ideal. It leaves me searching for the beautiful specificity of each person. Where does specific anatomy, training, and previous patient experience squeeze into the picture. Here is where GRIP comes in.

Theory: 'Optimal' motor control can be observed in individuals based on evaluation of the balanced recruitment of musculature surrounding a joint or region in question. This is specific to the individual but follows predictable patterns outlined in developmental kinesiology and respects anatomical variations.

Choice of muscle - Does your brain think you need the monster truck or the unicycle?

Phasic musculature?  

               Postural musculature?

When we look at the design elements of muscles a few things jump out:

Cross-sectional area of skeletal muscle is proportional to muscle strength. Sarcomeres generate contractile force - the greater the sarcomere count the greater force can be generated by the tissue.

The further away the the muscle is from your center of mass and the rotational reference point that it controls, the greater compression force is generated. If we use the lumbar spine for example, the iliocostalis can generate a greater force on the spine than the multifidus with same contractile effort due to the greater moment arm of the iliocostalis (perpendicular distance from the muscle to the point of rotation)

 

Thank you Aaron Swanson for the diagrams!

So if we look at the design of muscles, we see that big muscles near the surface of our body are both the strongest and the most capable of generating compressive force on our joints. These muscles are most capable of meeting huge increases in demand. GRIP's assumption is that your brain (specific, I know!) recruits more units and those units of greater cross-sectional area further from the rotational axis in response to perceived need/increased demand.



So if our bodies were infinitely durable or could be replaced easily, the most effective system of movement and postural control would be primarily these phasic muscles near the surface that are large. The two issues with this are that 1) these muscles tend to cross multiple joints making them less capable of skilled movements and that 2) the body is not insanely durable. Pavement holds up better to unicycles than monster trucks.

If activities like sitting, standing, and walking can be performed with adequate motor recruitment (rather than excessive) we greatly reduce the compressive and shearing forces at the joint. When a demanding activity requires extensive motor recruitment, we expect synergy and balance to provide a centrated position, essentially centering the compressive force for the benefit of a neutral force dispersement.

If there is excessive motor recruitment and a clenching/compression strategy in the basic activities of sitting, standing, and walking it becomes infinitely more difficult to produce an adequate response of synergy and balance when demand increases. I always say in my courses, “your program of control, wether clenching or expanding, is going to increase and spread throughout the body when you increase demand”. We see this in every day examples. Stand up and actively squeeze the toes of your feet together to grip the ground. Take a few steps. Notice how this creates a small clenching response at the knee, hamstrings, and throughout the rest of the kinematic chain. Now spread and elongate your toes and notice how the motor recruitment changes. The clenching dissipates. The breath relaxes. This is an example of how the motor control of stabilization spreads throughout the body with increased demand. Now, in this simple example of walking with a concentric/superficial strategy of stabilization vs an elongation/expansion strategy, we observe and hypothesize a difference in shearing and compressive forces at the joint.

So, am I saying we need to turn in our monster trucks for unicycles? No, absolutely not! These surface muscles are our prime movers and are positioned well for power. We need to use them, train them, strengthen them, but to be cognizant of their ability to generate insanely high compressive and shearing forces on the joints of the body. These tissues need to be recruited appropriately and balanced around the joint to disperse the force transmitted. This is where we see the curve of a spinal segment being less clinically significant to an injured disc in question than strategy of stabilization around that joint.

Bringing it all home here: When there is a perceived increase in demand (poor joint position, posture, increased external load, etc.) we recruit the big surface muscles to meet the demand. When there is less perceived demand we recruit less superficial musculature. When over-recruitment of these phasic muscles are used as a primary stabilization strategy we generate adverse compressive and shearing forces. This is poor motor control and can be seen in those with brain injuries, cerebral palsy, central developmental disturbances, and at varying degrees with all of our patients.

So how can we apply this observation to our clinical model on a daily basis? Evaluate the individual in their necessary movements of life and in your favorite screens for the balance of musculature around a joint in question, the appropriate level motor recruitment recruitment, absence/presence of a clenching/compression stabilization strategy, and their ability to maintain this balance with increased external load.


To explore these concepts with practical clinical and performance applications sign up for a course at www.GRIPapproach.com