What happens to the Human Movement System with injury, poor posture, and muscular imbalance?
To understand what happens under dysfunctional circumstances, it is important to understand how the Human Movement System functions under ideal circumstances.
Keep in mind, however, that given the way society is with technology, sedentary jobs and even how fitness centers are set up predominantly with uni-planar, sagittally dominant machines, that everyone will at some point develop some sort of movement impairment and Kinetic Chain imbalance. It’s only a matter of time.
What does a “functional” Human Movement System look like?
The Human Movement System is composed of 3 interrelated systems:
1. Muscular System: Length-Tension Relationships of soft tissues (muscle balance between length & strength)
2. Nervous System: Force-Couple Relationships (recruitment of muscle synergies during movement)
3. Articular System: Arthrokinematics (functional joint motion)
The Muscular System
The Muscular System consists of soft tissue structures (i.e. muscles, tendons, ligaments and fascia). Muscles and joints have typically been viewed from a structural (i.e. origin, insertion, action) rather than functional perspective.
The structural or orthopedic approach focuses on the pathology of static structures and emphasizes diagnosis based on localized evaluation and special tests.
A functional approach recognizes the function of all processes and systems within the body, rather than focusing on a single site of pathology or dysfunction.
The structural approach is necessary and valuable for acute injury or exacerbation, the functional approach is preferable when addressing chronic musculoskeletal pain and dysfunction.
Functionally, muscles can have different classifications:
- Agonists– prime movers e.g. Gluteus Maximus during hip extension
- Antagonists – act in direct opposition to prime movers e.g. Psoas and Gluteus Maximus during hip flexion/extension
- Synergists – assist prime movers during functional movement patterns e.g. Hamstrings and Gluteus Maximus during hip extension
- Stabilizers- support or stabilize the body while the prime movers and the synergists perform the movement patterns e.g. TVA, Internal oblique and multifidus
- Neutralizers- Counteract unwanted action of other muscles e.g. anterior and posterior deltoids during shoulder abduction
Muscles move in different planes (i.e. sagittal, transverse and frontal). This is important to understand as many injuries occur in the transverse plane (rotation). Most exercise programs focus on sagittal movements.
A muscle may be a prime mover (agonist) acting concentrically in one plane and an antagonist, neutralizer or stabilizer acting eccentrically or isometrically in another.
Muscles can be further classified into two distinct, yet interdependent systems enabling our bodies to properly stabilize as well as ensure efficient force distribution during movement. These systems are the Local Muscular System (Stabilization System) and Global Muscular System (Movement Systems).
The Stabilization System is prone to weakness and inhibition. It is less activated in most functional movement patterns and fatigues easily during dynamic activities.
The Global System is prone to developing tightness. It is readily activated during most functional movements and overactive in fatigue situations or during new movement patterns.
Arthokinematics refers to joint motion.
As mentioned above, the structural or orthopedic approach focuses on the pathology of static structures and emphasizes diagnosis based on localized evaluation.
When looking at the Human Movement System however, it is important to consider that each joint is part of a chain and that the areas above and below a joint are influential. In fact, there is evidence that in some cases, areas that are seemingly unrelated and located distal or proximal to the joint in question, may be the cause of dysfunction. This has been termed Regional Interdependence.
A good example of functional biomechanics is looking at what happens throughout the kinetic chain during pronation: The foot and ankle complex dorsiflexes and abducts. This causes the knee and subsequently the hip, to flex, adduct and internally rotate. As a result, the pelvis will be pulled into an anterior pelvic tilt. This in turn places tension on the thoraco-lumabar-dorsal fascia, which will lead to over activity of the latissimus dorsi, causing dysfunctional movement at the shoulder complex. Based on this example, it is not hard to see that shoulder pain can be exacerbated by walking with a pronated foot/ankle.
Gray Cook, in his text Movement, talks about the major joints in the body alternating between needing mobility or stability. His observation, along with others is as follows:
“The joints alternate between mobility and stability. The ankle needs increased mobility, and the knee needs increased stability. As we move up the body, it becomes apparent the hip needs mobility. The process goes up the chain as a basic alternating series of joints”.
Joint — Primary Need
Ankle — Mobility (sagittal)
Knee — Stability
Hip — Mobility (multi-planar)
Lumbar Spine — Stability
Thoracic Spine — Mobility
Scapula — Stability
Gleno-humeral — Mobility
Middle/lower cervical- Stability
Upper Cervical- Mobility
These insights are valuable when performing a movement screen and then determining what corrective exercises would be best to use (i.e. mobility or stability).
The nervous system, in particularly the CNS, enables the Human Movement System to operate functional and synergistically in all three planes of motion. It does this through sensations and perceptions and through mechanoreceptors located throughout the body, that relay proprioceptive information. Through motor behavior (Motor control, motor learning and motor development), muscle synergies and movement patterns are “grooved” into the nervous system.
Just like your body can learn a skill or technique, it can also learn faulty and dysfunctional movement patterns that result in injuries or chronic pain. These dysfunctional patterns can be undone through manual therapies and corrective exercises.
The Human Movement System (HMS) under normal circumstances has optimum length-tension relationships in the muscular system, optimal force-couple relationships controlled by the nervous system and optimal arthokinematics. The end result is optimum neuromuscular efficiency, or “the ability of the neuromuscular system to allow agonists, antagonist, synergists and stabilizers to work synergistically to produce, reduce and dynamically stabilize the HMS in all three planes of motion”.
But what about dysfunction?
Take a look at some statistics:
Foot/Ankle Injuries: There are more than 1 million doctor visits per year for Plantar Fasciitis. Ankle Sprains are the most common sports related injury, with lateral sprain creating a high risk for developing chronic ankle instability. Ankle sprains can decrease activation to the gluteus medius and maximus, affecting frontal plane stability.
Shoulder Injuries: 21% of general population report shoulder injuries, with 40% lasting at least 1 year, and with Shoulder impingement being the most common. This can increase the risk for osteoarthritis over time. In my experience, shoulder impingement is often a result of the Upper Crossed Syndrome (Over active pecs, and lats and under active posterior scapular stabilizers)
Low Back Pain: Affects nearly 80% of adults. 1/3 of all work injuries involve trunk and 60% involve the lower back. The average injury cost approximately 9 days per episode and annual costs associated with low back pain is greater than $26 billion. Many people spend a significant part of their work and after work time sitting, which can result in “gluteal amnesia” (Overactive hip flexors, underactive glutes and synergistic dominance of the erector spinae and hamstrings). In addition, chronic sitting has been linked to obesity.
Knee Injuries: 80-100,000 anterior cruciate ligament (ACL) injuries occur annually in general population, with 70-75% being non-contact injuries (Think transverse plane and poor biomechanics). Osteoarthritis occurs at 10x greater rate with ACL injury. Females are 4-6x more likely than males to have knee injuries (possibly due to the Q-angle). Many of these injuries occur in the transverse plane during deceleration (i.e. eccentric rotary movements). For those “cross fitters” out there, next time you are partaking in the WOD, take a look around at the other participants. How is their form when they jump? Do their knees cave in? Are they sacrificing form for time?
What happens to the Human Movement System with injury, poor posture, and muscular imbalance?
As you can see, the simple answer would be INJURIES. But how/why do these injuries occur?
Imbalance and dysfunction.
Some common causes of these imbalances can include: Pattern overload, aging, decreased recovery and regeneration following an activity, repetitive movement, lack of core strength, immobilization, cumulative trauma, lack of neuromuscular control, and postural stress.
When there is HMS impairment, there is dysfunction that is characterized by:
1. Altered length-tension relationships
2. Altered force-couple relationships
3. Altered arthrokinematics
This results in altered sensorimotor integration, altered neuromuscular efficiency and tissue fatigue and break down (cumulative injury cycle).
The Cummulative Injury Cycle is where an injury will induce inflammation, muscle spasm and adhesion, altered neuromuscular control and muscle imbalances.
Muscle imbalances lead to predictable postural distortion patterns. These are characterized by:
Altered Reciprocal Inhibition– The process whereby a tight or overactive agonist inhibits its functional antagonist, resulting in altered force couple relationships and synergistic dominance, faulty movement patterns and poor neuromuscular control (e.g. an overactive psoas causes decreased neural drive to its functional antagonist the gluteus maximus)
Synergistic Dominance-The process whereby synergists compensate for a weak or inhibited prime mover in attempts to maintain force production and functional movement patterns. (e.g. The erector spinae and hamstrings compensating for an inhibited gluteus maximus. Should you stretch the hamstrings in this case?)
Arthrokinetic Dysfunction– A biomechanical dysfunction in two articular partners, resulting in abnormal joint movement (arthrokinematics) and proprioception.
Any restriction in movement will lead to relative flexibility, where the body seeks the path of least resistance (e.g. deceased dorsiflexion at the ankle resulting in forward leaning during an overhead squat assessment).
Janda, a Czech physiatrist was one of the first to notice these predictable patterns in his patients, through observation and EMG testing. He named these patterns:
1. Upper Crossed Syndrome
2. Lower Crossed Syndrome
3. Lower extremity postural distortion
In all patterns, Janda observed that “There was a chain reaction that evolves in which some muscles shorten and others weaken, in predictable patterns of imbalance.”
Upper Crossed Syndrome
Characterized by: Rounded shoulders and a forward head posture. This pattern is common in individuals who sit a lot or who develop pattern overload from uni-dimensional exercise.
Common injuries: Rotator cuff impingement, shoulder instability, biceps tendonitis, thoracic outlet syndrome, headaches.
Lower Crossed Syndrome
Characterized by: Increased lumbar lordosis and an anterior pelvic tilt.
Common injuries: Hamstring strains, anterior knee pain, low back pain.
Lower extremity postural distortion
Characterized by: Excessive foot pronation, genu valgus and poor ankle flexibility.
Common Injury Patterns: Plantar fasciitis, Posterior tibialis tendonitis (shin splints), anterior knee pain, low back pain.
Janda also noticed the effects of over active calf’s on low back pain- Is your low back pain due to tight calf’s?
When the calf’s become tight, one’s center of mass shifts anteriorly, causing the thoracolumbar paraspinal muscles to become overactive, thereby increasing the lumbar lordosis to maintain erect posture during standing and walking. This creates stress and abnormal tension in the low back muscles. In addition, the upper body over compensates for this weight shift.
Full ankle dorsiflexion and full knee flexion are necessary for squatting and lunging patterns. This cannot happen with restricted or tight calf muscles.
The Human Movement System provides a functional understanding of how the neuromusculoskeletal system should work under optimum circumstances as well as what occurs with dysfunction.
Evaluating the HMS through a movement screen, range of motion and muscle testing and palpation, and then correcting imbalances through exercise and manual therapies, can be extremely effective and rewarding for rehabilitation, injury prevention and/or performance enhancement.