Do you think about symmetry?
No baby, baby: Salt N Peppa haircuts irked me...
So it's little wonder that I grew up to work in physical rehabilitation and sports performance. Much of my time deals in the business of symmetry; identifying and minimizing musculoskeletal asymmetry.
On the other hand, all brains that ponder symmetry have two halves; with hands and brain halves each being quite asymmetrical. While I'd like to be able to make a neat fold between the the two "m"s, even the form of the word "symmetry" hints of an ideal. It's hard to deny the different structures in each half of the body suited to take on different demands.
So maybe we shouldn't get too caught up in symmetry. And I mean that with all my left sided heart, which itself is larger on the left.
Asymmetry often rules the details. Some is explained by this thing we call "dominance." For a number of reasons, the body settles into a preferred or dominant patterns that favors one arm, leg, ear, eye, etc.
The dominant patterns are often task specific and they may be consistent or mixed. That is, an individual could be right handed with scissors but a lefty stirrer. They could be left footed and right eyed. In terms of muscle size and performance, like jumping, up to 15% difference between the right and left sides is considered normal.
Much of the asymmetry that I deal with in the clinic is simply the result of the body gradually adapting to the demands placed upon it. Sometimes this proves to be unproblematic while in other areas the asymmetry is a warning sign. For example, asymmertry in shoulder flexibility is a fairly good predictor of pitching injuries while an uneven resting posture of the scapula is not. Asymmetry of hip movement has proven to be relevant in the diagnosis and treatment of knee and low back problems, while anywhere from 2 to 6 millimeters is an acceptable difference in leg length.
There’s some evidence that folks can usually fill their left lung easier than their right. The right diaphragm uses the liver for “leverage.” This results in some of the right ribs having a subtle rotation, which in turn affects thoracic and scapula position.
Scientists have found that healthy runners show about the same amount of asymmetry as injured runners. The fact that injured runners have increased joint loading forces as compared to healthy runners suggests that high impact loading is the primary problem, with asymmetry simply influencing the side on which injury first appears.
Some asymmetry is due to trauma and developmental issues. My right pointer- and pinky fingers have been fractured and now turn inward, giving that hand a semblance of the tower of Orthanc. But they don't hurt, at least not yet. Just don't ask me to point out the guilty party in a line of suspected criminals.
And so it seems that body symmetry is often an ideal with no hard and fast rules. Yet there's something about symmetry.
Despite dominance, structural adaptations, and subtle deviations, it does appear that we're balanced through the integration of whole system imbalances. Yes, symmetrical asymmetry! Plus, a truly amazing ability to adapt.
The torso, for example, is balanced with a liver on the right and a heart on the left. Extremity dominance is balanced through reciprocal function; the left arm moves with right leg and vice versa. Fine coordination on one side of the body often appears with more absolute strength on the other. Dad taught me to throw righty and bat lefty, and now that's just what I do.
Identifying structural or movement asymmetry is a relatively straightforward process. Trained therapists recognize these imbalances and typical patterns. The challenge is determining whether or not an asymmetry is modifiable and worth modifying.
I've found that moving toward symmetry helps. It helps a ton. I witness this reality on a daily basis. I'm often surprised when a patient with right hip bursitis has never noticed how "flat" their left foot is; or fails to relate their right side neck pain to leaning on the left elbow when driving.
It makes sense that if exposure to repeated loading in the same direction does indeed cause microtrauma, movement dysfunction, and eventual pain, why would you not at least try to redistribute the strain? Why shouldn't athletes bring their weakest link up to snuff for both injury prevention and peak performance?
Uneven structure can often be accommodated or improved with specific corrective exercises, if not "fixed" to be perfectly even. Even partial reversal of habitual postures and ingrained movement strategies is often enough to allow healing of weakened or overworked tissues.
Reversing mechanical forces. Modifying movement patterns. Lengthening restricted joints and strengthening/stabilizing weak tissues. Do you understand why lasting relief for your painful spine or unstable knee is rarely a matter of simply cracking that baby back "in?"
In conclusion, instead of aiming for symmetrical movement, we should technically be aiming for more symmetrical movement. And a PT guy is fulfilled when he attempts to unite truth with beauty, and in doing so, helping someone along their way.
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