Credit: Doug Mills (New York Times)
In a recent NY Times article (NYT) about Usain Bolt’s running form, it notes that his right leg appears to produce 13% more peak force than his left leg and that his left leg stays on the ground 14% longer than his right leg. Antti Mero, an exercise physiologist at the University of Jyvaskyla in Finland, noted in the article that the degree of asymmetry between runners’ legs (elite sprinters) is typically between 1-7% – so Bolt’s asymmetry is notable.
The article notes that the most feasible reason for Bolt’s running asymmetry is the effects of his scoliosis (his right leg is functionally 1/2 inch shorter than his left). Bolt does have a history of injury – specifically his back and hamstrings, which logically could be the result of his scoliosis and therefore his asymmetric running gait.
As the study in the NYT article is not completed, it is not clear if Bolt’s asymmetry enhances his performance or if he had a more symmetrical stride, he could run even faster.
What can be clearly extrapolated from the article is that 100% symmetry is extremely rare. Therefore, perfect symmetry should not be the goal when working with a runner. Assuming that Bolt’s scoliosis plays some role in his asymmetric gait, it teaches us coaches a valuable lesson that you MUST look at the whole body when looking to alter one’s biomechanics. In Bolt’s case, if someone were to try to make Bolt’s stride symmetrical, it would likely not only slow him down, but also increase the chance for injury. Therefore, when performing a visual assessment of an athlete in regard to their form, do not assume that asymmetry is bad. As a side note, if you suspect your client has a substantial asymmetry in their gait, it is advised to refer them to a specialist such as a physical therapist.
As has been noted in other studies, the body is able to alter its mechanics to take into account internal and external factors. Therefore, asymmetries may be the result of the body compensating for these internal or external factors (i.e., worn shoes, running in sand) versus a runner simply having “bad form.”
So the main takeaway from the NYT article is that most runners have asymmetries and even if they are substantial, it does not mean that they cannot perform well. They might even win Olympic Gold!