This article is a continuation from Part 2....
Kinematic redundancy is the ability of the kinetic chain to complete a movement task using numerous combinations of joint motions and levels of contribution from various muscles. This is evident even in a motion as repetitive as walking. If we were to evaluate sophisticated gait analysis data (ground reaction forces, EMG, joint angles and displacement), we would see that no two sequential strides are exactly alike. There are patterns and ranges within the data, but they will not be exactly alike. Interestingly, those ranges could involve desirable kinematics or undesirable kinematics. Just because a motion falls with a given kinematic range does not mean that it’s the range we want.
With kinematic redundancy, the more variables (i.e., joints) involved, the greater variability in the muscle activation pattern and greater variability of motion at the involved joints. A standing one arm cable row with lunge, for example, could produce different responses on each repetition at both ankles, knees, hips, lumbar spine, thoracic spine, scapulo thoracic joint, gleno-humeral joint, elbow joint, radio-ulnar joint, wrist and even the interphalangeal joints.
This presents a challenge for the fitness professional who assumes the client is engaging the appropriate muscle groups at the optimal time in the movement sequence with the optimal force contribution. In the one arm cable row, the goal would be to extend the ankle, knee and hip of the front leg prior to extending the lumbar spine. This allows the gluteus maximus to fire and contribute to force closure, along with the contralateral latissimus dorsi of the S.I. joint. The preferred firing sequence of the involved muscles produces the desired movement sequence.
If the lumbar spine extends prior to the hip, the desired stability from the gluteus maximus is late. Lumbar extension prior to hip extension increases lumbar stresses and places the lumbo-sacral region at greater risk of injury. If the fitness professional is not accurately assessing these motions during the exercise, the “functionality” of the exercise is questionable.
Another biomechanical consideration is that of limited motion in a link of the involved chain. Limitations in motion of one joint in the involved chain will transfer the responsibility to another joint, and motion will occur first in a more flexible joint. The body will produce motion at the more mobile segments in the chain first. For example, in our cable row, if the client is kyphotic, during the eccentric phase of the exercise, the thoracic spine will flex prior to the hips and lumbar spine. This decreases the mechanical line of pull of the thoracic extensors with tendinous attachments on the lumbar spine and thereby reduces their contribution to lumbar stability. It then increases stress on the passive soft tissue structures of the lumbar spine as the flexion moment is more concentrated in the lumbar spine because there is no flexion left to give in the thoracic spine.
A corrective exercise program that addresses these dysfunctions by improving thoracic extension and proprioceptive awareness of spine/hip motion can enhance the overall quality of the more integrated movement.
The gluteus maximus is linked with the contralateral latissimus dorsi via the thoraco-dorsal fascia making up the Posterior Oblique System. The Posterior Oblique System is one of multiple myofascial slings present in the human body. Recent advancements in the understanding of force transmission through muscle, fascia bone, tendons and ligaments have shed new light on how the body maximizes mechanical efficiency through these slings. Thomas Myer’s book “Anatomy Trains” is an excellent resource on this topic.
A myofascial sling is formed when any of the previous mentioned structures (i.e., muscle, fascia, etc.) lie in series and parallel to one another. They are anatomically connected and functionally related. Myofascial slings can cross multiple joints and can be “active” during certain movements and “inactive” during other movements based on the relationships of the body parts during the given movement. They allow the body to store kinetic energy from ground reaction forces in motions like walking or the above cable row example when the trunk and arm are rotated in one direction and the contralateral hip and pelvis are rotated in the opposite direction. When they contract, they act as one continuous muscle. This provides the body with an enormous advantage for stability and force production. The Posterior Oblique System literally connects the hip and opposite shoulder. Other myofascial slings throughout the body will be active in the sagittal plane, frontal plane and transverse plane motions.
The structures that give myofascial slings a mechanical advantage may also contribute to disruption of normal movement patterns. Any dysfunction in one part of the sling will have an effect on the rest of the sling. For example, we often see clients with shoulder girdle issues that are directly related to hip issues on the opposite side of the body.
In our cable row, if the dysfunction in the posterior hip was not addressed prior to performing this exercise, the resulting muscle activation patterns would be much different at the shoulder girdle than expected. This would stress the lumbar spine as previously mentioned but would also increase stress on the entire upper extremity of the rowing arm due to poor ground reaction force transfer from the lack of contralateral hip stabilization.
Corrective Exercise Application
I use corrective exercises prior to introducing the cable row to promote the desired movement sequence and minimize an environment for compensation. The number one purpose behind using corrective exercises is to improve the quality of overall movement, not to isolate joint movement or a muscle or produce artificial movement. Cognitive processing is used to reinforce movement patterns by accessing another part of the brain during the execution of the exercise.
Corrective exercises create the road map for the body to follow on its route to producing improved movement patterns. The fundamental goals of the corrective exercise program to enhance movement are:
- Activate latent muscles
- Release hypertonic muscles
- Create proprioceptive awareness of enhanced segmental motion
- Improve postural alignment and the body’s center of gravity
- Improve osteokinematics and the path of the instantaneous center of rotation of the joints
- Functionally integrate the responses across multiple segments in the kinetic chain
- Create a baseline for improved movement strategies
This methodology of corrective exercise follows the well established motor learning approach of "segmentation." Segmentation consists of taking a complex movement and practicing it in small parts. The small parts are progressively linked together, producing the more complex skill. Segmentation is similar to Keel’s Gearshift Analogy. When learning to drive a stick shift, initially each of the individual actions are independent motor tasks. With practice, similar tasks are linked together, decreasing the overall number of tasks. Eventually, the process is automatized and becomes one independent motor task, allowing the driver to add other tasks involved with driving (i.e., turn signals, climate control, etc.)
When working with clients and athletes that have active symptoms or chronic injuries, corrective exercises allow the fitness professional to progress the client safely. Corrective exercises avoid end range loading of joints and exceeding tissue tolerance thresholds. Exercises are progressed as the client successfully meets the objectives within the exercise program. If a client is apprehensive, unable to perform an exercise or the exercise produces pain, the exercise can be changed with less chance of injury.
In a more comprehensive and loaded exercise from the FR, there is a much smaller “buffer” zone. If an unsafe exercise is mistakenly given, the risk of injury is much higher. If a client has been asked to do a transverse plane lunge with an ankle level reach and their lumbar facets didn’t cooperate, the damage would be done if the client could not control the acceleration of his body. You can’t “un-ring” the bell. If an unsafe corrective exercise is mistakenly given, the movements are slow enough and the ROM is controlled enough to allow the client to stop the exercise before any damage is done.
All exercise is about manipulating the environment to produce a desirable change in the client or athlete. Sometimes that requires going backwards to ultimately move forward. We cannot mistake being effective for being efficient. Corrective exercises are functional because they are part of the safest and most influential continuum for many clients and athletes.
We should be cautious in adopting a single thought process that is applied to all our clients and athletes all of the time. And we should be equally cautious not to discount the value of other thought processes being used by others. Because one will soon discover that the process that they have become dogmatic about, will not work for all of the people all of the time. The true craftsman always chooses the best tool for the job... not his favorite tool.
Corrective exercises should not be left out of the conversation on “function” just because at first glance they don’t look like an activity of daily living or an athletic movement. If the result of a corrective exercise sequence is transferable to improvements in activities of daily living or athletic movements, then there is a functional result. And a functional result is the ultimate goal.
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