Identify & Fix Muscle Imbalances & Injury Risks 

**Andy Galpin** (0:00)
The science and practice of enhancing human performance for sport, play and life.
Welcome to Perform.
I'm Dr. Andy Galpin, I'm a professor and scientist and the executive director of the Human Performance Center at Parker University. I want you to imagine for a second that I could increase your best race time ever by seven or eight seconds, by only increasing your ankle range of motion by a single degree. You don't have to actually run that exercise because that's been done scientifically and it turns out to be true. To put this in context a little bit, that seven seconds might be what it takes for you to finally cross below that 24-minute mark if you're an elite male running your best 8K time. Or maybe you're a woman and you're trying to finally get below 20 minutes in that 6K.
But remember, that's only for a single degree change.
Imagine how much you could improve if we got two or three or even four degrees difference in that ankle range of motion. See, this is not just about ankle range of motion. In this particular case, what we're talking about is reducing the asymmetry or the difference in range of motion between the two legs. Most of you have seen this classic Vitruvian man, right? Leonardo da Vinci's perfect symmetry between the human body. And it's romantic for us to think about that. And in fact, in the early 1900s, we thought that the symmetrical puman was the perfect thing to be. If you looked at an athlete, you would pick the one who is the most symmetrical to be the most successful in all sports. But that turned out to not be true. In fact, the wonderful writer David Epstein, if you've ever read his tremendous book, The Sports Gene, outlined and talked about how the body type explosion happened recently. After that, when we started to realize some sports and activities require asymmetry and in fact are given a huge advantage when limbs aren't the same length and when the body doesn't work exactly the same way on all sides. Today, we're going to dive into this because there's also the reality that shows people that have asymmetries, particularly in their lower body, increase their injury risk by as much as 35%.
So which is it? Do asymmetries help us or do they hurt us? We all have them. The most common one is what we call handedness. You're right handed or you're left handed. That exists in every human, well, at least about 98% of us. That other 2% can use both sides pretty equally. For over 5000 years, we've been acknowledging the fact that we at least have some different skill on one side of our hand versus the other side. And the general rule of thumb you're going to hear is 10%.
I want you to remember this number because we're going to come back to this over and over and over again today. The difference between one side of your body, front and back, top to bottom, left or right, as long as it's within about 10%, then you're fine. But we actually know scientifically that's not the case. And in fact, if you look at the research on this, one recent review came out that looked at over 6000 athletes and found that across 30 studies, about a third of the research found that asymmetries led to more injury. About a third of the studies found it was irrelevant. And then about a third of the studies said, we actually don't know. Could be somewhere in between. People are really confused right now. Right, we see these other studies. One of my favorite ones in this entire field looked at almost 300 Jamaican kids. Jamaica, of course, being arguably the most dominant sprinting country in the world, despite being really small. And it found that symmetry, specifically just the size of things like their wrist, the size of their ankle and their knees, predicted not only was faster in the 100 meter dash, but who was also faster 14 years later. And so we have this confusion. What's going on? Should I be symmetrical? Should I not? If so, how much is too small? How much is too big? And what in the world is going on with symmetry and imbalances? And so we're really left with two confusing points. One, when does an asymmetry become dysfunctional or problematic and get us in that injury case? And is it normal or potentially even advantageous? And then the second major question that comes along with this is, okay, if I have a problem, what do I do about it? If you were to Google this right now, how do I correct asymmetries or muscle imbalances?