Just wanted to share my thought on a discussion our group was having about "Imbalances in the Human Movement System"
By, Brian Van Hook, CSCS
I believe we would all agree that the body will compensate for any imbalances in the Human Movement System caused by injury, poor posture or muscular imbalance. A tight muscle stuck in a shortened state may alter joint position, setting off a chain reaction that will worsen an imbalance and leave the body functionally weak. In the human movement system the muscular, skeletal, and nervous systems will work together to allow optimal function. If any component of the system is out of balance, it will lead to dysfunction. Muscles work most efficiently in specific positions. They will have an ideal length-tension or position from which they can produce the most amount of force. If a muscle is stuck in a lengthened or shortened position, force production can decrease. Muscles and joints have receptors that are constantly sending feedback to the central nervous system. When the muscles are at the right length and the joints are moving correctly, the CSN receives the correct information to allow for the best possible performance. However, if muscles are too short or too long, they change the position of the joints to which they are attached.
An altered kinesthetic awareness leads to synergistic dominance, reciprocal inhibition, arthrokinetic inhibition and decreased flexibility. Muscles will work together to produce force, reduce force, and dynamically stabilize the kinetic chain during function. If one muscle is too overactive or to underactive, then other muscles in the chain will become over dominate.
I was thinking about the squat in a early post so I would like to use that as an example, If a person has proper flexibility, balance, core strength, functional strength, and neuromuscular efficiency, then they should be able to squat to parallel or below without compensating at the foot/ankle, knee, lumbar spine, or upper extremity. However, if they have altered length-tension relationships, weakness of a primary muscle with compensation from a secondary synergist, or joint hypomobility, then you will see abnormal movements. These are easily picked up during the movement pattern. During the squat a trainer/coach may notice bilateral external rotation of the feet and eversion of the foot. This demonstrates tightness in the lateral gastrocnemius, soleus, peroneals, and biceps femoris, they may also find weakness in the anterior tibialis, posterior tibialis and medial gastrocnemius. Another problem a trainer/coach may uncover during the squat is the athlete’s knee adducted and internally rotated. This may suggest a tightness in the adductor complex and may also be a weakness in the gluteus medius. Weakness in the gluteus medius may lead to dominance of the adductor complex and tensor fascia latae. Functionally, these combined deficits can cause several problems.
So what all this means is an imbalance in any form from a specific muscle or kinetic chain may lead to problems in other areas of the body and a decrease in performance. Many of my H.S. athletes may enjoy performing the bench press, but dislike any type of latissimus dorsi or rhomdoideus exercises, I always have to remind them for every push, we must do a pull.
I am more of an application type of person, so I am sure I missed a few muscles/imbalances along the way, so feel free to add.