 So, I'm Tim Hewitt and I'm the Director of Biomechanics and of Sports Medicine Research at Mayo Clinic in both Rochester and Minneapolis, Minnesota. And the reason I came to this injury prevention symposium is to present our latest findings on both primary and secondary prevention. But I also would like to point out that maybe that prevention is a bit of a misnomer. Basically it's injury reduction. So what we're trying to do is reduce the relative risk of injury in a population. So if you could actually prevent an injury, you'd actually have to be able to predict the injury was going to happen, which we can't really do. Basically what we do is test athletes and we risk stratify athletes. We put them in high, moderate, low risk strata categories. And then from there we can design interventions that are geared toward their relative risk level. So I think risk reduction rather than prevention and risk stratification rather than prediction are more scientifically valid terms. So we've been the last 25 years studying the anterior cruciate ligament, trying to figure out what puts that ligament at risk. And basically we've found four modifiable neuromuscular imbalances that are ligament dominance, quadriceps dominance, leg dominance, and trunk dominance. And basically what we've done is put interventions that target those specific neuromuscular imbalances in individuals. So for example, if an individual has all those imbalances, they're going to be a high risk individual. They're going to target an intervention toward all the imbalances that they demonstrate, show that we can alter their risk profile, change their risk stratification level, and increase their neuromuscular control and decrease their relative risk of a future injury. And we've done this over multiple trials over many years, and we're just putting out in the Journal of Orthopedic Research, it's supposed to come out any day. We did a meta-analysis of meta-analyses, which we call an umbrella analysis, where we show there's been over 15 randomized controlled trials now, and there have been over eight meta-analyses. And what we demonstrate is we can reduce the risk of an ACL injury, any ACL injury, or any lower extremity injury by 50% with targeted neuromuscular training, and we can reduce the risk of those non-contact ACL injuries, which are, again, neuromuscular and modifiable in nature by two-thirds. And we actually published a study back in 1999 where we showed the exact same numbers. This was the first randomized controlled trial where we looked at the efficacy of targeted neuromuscular training and demonstrated we could reduce the risk of any ACL injury or any lower extremity injury by half and any non-contact ACL injury by two-thirds. So what we do know is this risk reduction is possible, it's highly efficacious. You can't necessarily risk stratify, you can't do this testing at home. We have, like you all have here, we have at Mayo Clinic, a biomechanics lab, where we test for these relative neuromuscular imbalances of ligament dominance, quadriceps dominance, leg dominance, and trunk dominance, and then can develop a risk stratification profile and then develop a targeted intervention to reduce relative risk of an ACL injury. There are some simple tests you can do, a drop-down test off a foot-high box, just to look and see. For example, an athlete that has a lot of valgus or inward hip and knee collapse is at greater risk. We know that. So if you have a valgus landing profile, you're at greater risk. If you are more asymmetric, if you really load one side or really favor one side relative to another, you're at relative risk. If you have underdeveloped posterior chain, your glutes, your hamstrings, you're at relative risk. So firing up that posterior chain with exercises like Russian hamstring curls reduces your risk. And again, just overall using your musculature to absorb these high-ground reaction forces because landing a ski jump can be 20 times your body weight when only three to four times your body weight can tear your ACL. So you really have to use that musculature to absorb and dissipate those forces and don't allow them to go to the joint or to the ligament and end up in a rupture. No, there is really no perfect athlete. What you have to think about is years and years of training in elite athletes actually creates neuromuscular imbalance because you're developing your body to perform specific athletic tasks in an optimal way. Obviously, all you have to do is look at an elite tennis player. They're actually quite asymmetric. That increases their risk of injury, and that's why you see an elite athlete some of the highest risk of injury. And that's why it's important that they work with their physicians, their athletic trainers, their physical therapists to rehab to develop greater balance along with that great elite performance level.