In every sense that matters, nobody’s perfect. Not physically. Everyone’s body is slightly asymmetrical. We have to keep that in mind when we train: those asymmetries are natural, and we should take them into account. Trying to create the “perfect” body—a body that is perfectly symmetrical—will mean that our bodies are less functional, because part of our biological systems will be devoted to maintaining those artificial symmetries.
A recent article discusses this at length, from the perspective of CrossFit. It makes the point that a lot of CrossFit injuries occur because of too much symmetrical training with an asymmetrical body: since we have a dominant side (larger, more powerful, more easily trained) and a non-dominant side (smaller, less powerful, less easily trained), training both sides “equally”—say, by doing barbell squats that load both sides equally—we are actually contributing to our body’s asymmetry.
We should train our non-dominant side more than our dominant side: when we get tired during a marathon, our form will collapse first on our non-dominant side. Then our dominant side will be forced to pick up the slack. Even if our dominant side is super strong, the mechanical energy is no longer translating properly from our bodies into the ground (and vice versa), eventually leading to injury.
But there’s more to this than just training. Lateral differences in people’s bodies have important effects on how mechanical energy is translated into the ground. When we run, it’s important to push off with the foot tripod (a.k.a the entire foot, with the weight on the first and second metatarsal). However, in order for both feet to do this when we have two different-sized left and right legs, the muscles of one leg need to work differently from those of the other: muscular asymmetries must be created in order to balance out skeletal asymmetries.
A right-dominant person’s right side is typically larger than their left. In the case of their hip bones this means that the right hip will be wider and longer than the left. (Their right femur is further away from the body’s centerline than their left femur). This means that the right foot is prone to evert (rotate outwards) more than the left. Supposing that the right foot pushes off correctly (with the entire foot tripod firmly planted), the left foot is likely to naturally underpronate during the swing phase, which means that this foot is likely to push off with more weight on the outer metatarsal bones.
In order to make the pronation (and therefore the pushoff) equal between the left and the right foot, the relevant hip muscles (usually hip abductor muscles) at the left hip, leg, and lower leg must be correspondingly stronger than those on the right side.
You see this happen in a lot of elite athletes, from Buzunesh Deba’s right leg swing to Haile Gebrselassie’s right arm swing (seen best at 1:47). During the swing phase, Deba’s right leg rotates inward slightly more than her left leg (and her right hip is consistently higher than her left). Similarly, Haile’s right arm ends the upswing with his hand just above the collarbone, while his left hand ends up just below. (These asymmetries are very slight because both these athletes have a very clean gait). Possibly, these athletes’ muscles are pulling asymmetrically in order to compensate for slight asymmetries between their right and left sides. These seeming imbalances allow their legs and feet to translate the mechanical energy generated by their bodies into the ground in the most efficient way possible. Trying to “correct” these asymmetries would likely result in a reduced athletic output.
Deba’s and Gebrselassie’s bodies are quite simply done pretending that they’re symmetrical. Neurologically, muscularly, and skeletally, their bodies are quite in touch with their own imperfections.
I’m making a case for self-awareness and self-acceptance. And I’m certainly not saying that self-acceptance will magically grant you good biomechanics. But biomechanical acceptance isn’t that far removed from the physical acceptance we need when we look at our bodies in the mirror. Not really.
None of this means that “perfect” symmetry is the ideal situation. Dominance is something that happens naturally, in order for us to be able to move the body asymmetrically. Having a dominant hand is far from a drawback: it allows us to write, paint, or to throw a javelin. Neurologically speaking, dominance lets both hemispheres of the brain provide greater computing power to a single extremity, resulting in much finer movement, and much greater skill.
Furthermore, the organs of the body aren’t arranged perfectly symmetrically: the heart is slightly on the left side, and the liver is on the right, for example. Because of how the body is organized, weight is distributed in odd places. More blood reaches some parts of the body than others, and dominance means that the touch, and proprioceptive receptors of some areas of the body are getting far more stimulation than others. The body grows differently in different places, and that’s a good thing.
But some of the most important movements we can make harness the body’s symmetry: running and walking. We somehow need to reconcile the need for symmetry with the need for asymmetry. Because each of us are different in different ways, we each reconcile those needs differently.
It’s not easy to reconcile these things. When we don’t have a lot of experience moving our bodies, our neuromuscular system makes the computationally simplest assumption: that both sides of our body are identical in length, width, height, and weight. It takes the brain a lot of data mining (from a lot of training) for our mental map of our bodies to include our biomechanical quirks and musculoskeletal idiosyncracies.
Training isn’t just about self-improvement. I believe that, above all, athletic excellence is about self-knowledge. Firsthand knowledge of our bodies leads to better, safer, and more efficient training. But it can also lead to a much better athletic experience, with much greater personal satisfaction.