First, your right achilles begins bothering you after a long run. A few weeks later, your right hamstring starts nagging you in the middle of a faster track workout. Three months pass, and then you begin having some pain on the front of your right knee a few miles into each run. "What is going on?" you ask yourself. "Why do I develop injuries only on my right side?"
Runners who ask themselves this question likely have gross or specific asymmetries. In other words, one side of the body is stronger or more flexible than the other side....not necessarily at the site of the injury. For instance, the runner in the above scenario might have weaker gluteal muscles and a slightly tighter calf on the right side when compared to the left. Think of the human body as a kinetic chain: one chink in the chain can lead to a multitude of overuse injuries. As a result, when a runner becomes injured, he or she (or the health care professional) needs to consider the significant effect an asymmetry can have on the body when it is subjected to a high training load. I will even go one step further by saying that we should address asymmetries before an injury even surfaces.
Now, are asymmetries only tight or weak muscles? Absolutely not. We need to think about the way we move, sit, and perform basic tasks in everyday life. Let's say that you squat to the floor to pick a piece of paper off the ground. Do you notice that you bear more of your body weight on one side versus the other? Does one heel come off the floor while the other remains flat? How about the position of your knees -- are they both over your toes, or is one of them collapsing in? Being able to perform a basic, yet complex movement like a squat with proper technique and body symmetry is an important factor for keeping injuries at bay.
Asymmetries are not the only factors that contribute to running injuries, however. Training error (aka too much, too soon), poor running biomechanics, and symmetrical muscular imbalances (aka inactive or weak gluteal muscles) can all lead to a gradual onset of pain in one or more locations. Therefore, the key to running injury prevention and recovery is identifying such deficiencies so that they can be addressed earlier rather than later.
