This is the second in a series of blogs asking what makes movement good or bad—what are our principles of optimal movement. The first two were alignment and conservation of energy. This blog addresses appropriate distribution of movement andproportional use of synergists.
The emerging rehabilitation principle of regional interdependence is defined as “seemingly unrelated impairments in remote anatomical regions of the body may contribute to and be associated with a patient’s primary report of symptoms.” (See excellent article in J. of Man. & Manip Ther. A regional interdependence model of musculoskeletal dysfunction: research, mechanisms, and clinical implications. Sueki D, Cleland J, Wainner S).
In other words, bodies are integrated—body parts don’t work independently or in isolation, but in relationship to one another. When relationships are sub-optimal, dysfunctional or invariant, tissue strain and breakdown occur. These relationships can be skeletal or muscular—or both.
Inappropriate Distribution of Movement
Limitation of movement in one region necessitates too much movement in another region—Shirley Sahrmann has coined the term ‘relative flexibility’ to describe this phenomenon. Too much movement in one place creates hyper-mobility stresses, and joint instabilities occur.
There are several examples of this distribution of movement principle from the spinal system. Places of common spinal hypermobilities are the lower neck and lower lumbar areas. Conversely, the thoracic spine and hips (which is where the spine starts) are commonly hypomobile. Cause and effect or cosmic coincidence?
There are ample examples in the literature linking reduction of neck pain with thoracic manipulation or mobilization and many examples linking lack of hip movement (or muscle strength) with low back pain. Lack of hip flexion leads to too much lumbar flexion.
Hip extension or rotation limitation leads to too much lumbar extension or rotation. Substitute thoracic for hip and cervical for lumbar and the same mechanisms apply. Observe the way babies link the intension to look with thoracic and pelvic movement. We know this, but tend to think that if we prescribe an exercise or apply a manual intervention to improve hip or thoracic mobility it will automatically result in improved cervical and lumbar health.
Other examples of this hypermobility/hypomobility pair principle are:
- Ankle dorsi-flexion vs. foot pronation when walking.
- Hip flexion vs. knee flexion on stairs.
- Hip external rotation vs. knee external rotation when cutting.
- Thoracic extension vs. gleno-humeral extension when reaching overhead.
We Can Do Better
This is a leap of faith—just because something has the ability to move more doesn’t necessarily mean the habit-driven nervous system will utilize that movement in daily activities. Exercise needs to simultaneously train mobilization of hypomobile and stabilization of hypermobile areas while facilitating proprioceptive awareness of how/when to apply to functional context (looking, bending, lifting, swinging a golf club, etc.). This is what makes specific motor control exercise.
Disproportionate Use of Synergists
Lack of muscle contribution in one region necessitates too much effort in muscles of another region; hyper-tonicity stresses and muscular over-use syndromes result. Proportional use of synergists is closely related to the distribution of movement principle. Habitually insufficient muscle use somewhere necessitates too much effort elsewhere—muscle hyper-tonicity syndromes.
Additionally, habitual overuse of one muscle creates agonist pair imbalances—reciprocal-inhibition-driven antagonist weakness. All the dominoes tumble and the whole system slides into dysfunction:
- Insufficient psoas use in sitting leads to overuse of abdominals and inhibition of back extensors.
- Habitual disuse of hip extensors in standing necessitates too much lumbar extensor use, which in turn inhibits the abdominal muscles.
- Insufficient thoracic extensor use riding a bike leads to overuse of cervical extensors.
- Under-utilization of hip extensors means lumbar extensor overuse when lifting.
Knowing How the Body ‘Should’ Move Informs Our Assessment and Choice of Exercise
We can train ourselves to recognize sub-optimal movement relationships, articulate how that movement contributes to or perpetuates musculoskeletal dysfunction, train our charges to recognize the error of their ways, and prescribe integrated corrective exercise. Embracing the role of movement teacher, we then need to decide what style of integrated movement we want to teach, Static or Dynamic (topic of next blog).