Monday, June 11, 2018

Assessing Risk - Is It Possible Part V

During the last couple of weeks, we looked at a recent study published by Wren et al J Orth Sports Phy Ther 2018.  In this study the authors looked at hop distance symmetry as a predictor of lower limb biomechanics.  The authors found hop distance is not a predictor of biomechanics and that the athletes tend to compensate on the non-involved leg.  As we began our discussion we talked about how this happens in our athletes and what we must do to prevent.

Last week, we began discussing mental compensation (kinesiophobia) and lack of training as a potential cause for this being a pattern that athletes continue with even when they return to play or post rehabilitation.  It is suspected or hypothesized this could be one reason that athletes continue to be at greater risk of re-injury (Wiggins et al Am J Sports Med 2016) or osteoarthritis 12 years later (Holm et al Am J Sports Med 2012).  As a physical therapist, athletic trainer or strength coach, there is a lot that we can do to change these odds.  First, we have to know what to look for.

In our last series, we discuss the Johnson et al Am J Sports Med 2018 paper where the authors identified the mechanism for non-contact ACL injuries in professional football players.  This led the authors to suggest there was a need to develop programs that assess and assist athletes to control this dynamic valgus position.  Although this is relevant for NFL players, is this also relevant for our younger college and high school players?  Owusu_Akyaw et al Am J Sports Med 2018 looked at the mechanism of injury in male and female athletes ranging from 15-30 years old.  Although the authors did not have video analysis available for all injuries, they were able to identified the position of the articular surfaces at the time of the injury by evaluating the bone bruising that was present on the surfaces.  Based on biomechanical models, this reveals a similar dynamic valgus position at the time of injury.



Considering, we must then assess this.  There are a lot of ways to do this.  You can do with a variety of movements and variety of technologies.  For our athletes, we use the ViPerform AMI (powered by DorsaVi) due to the fact that it has a progressive routine of single limb tests.  This assesses the ability to stabilize in single limb and it is measured with an inertial measurement unit and video.  The IMU provides accuracy of measurement within 3% of a Viacom system and the video provides a medium for providing feedback to the athlete.


As we mentioned in the previous blog, assessing both the magnitude of motion and speed of motion is critical when looking at risk.  Keep in mind, the ACL is about the size of your pinky.  It takes 21.5 N of torque (rotation) to rupture and 250 kg of force.  In a closed kinetic chain, the more valgus that occurs at your knee the more torque that is imparted to the ACL (with larger degrees of valgus comes internal rotation in a closed kinetic chain).  In addition, force is determined by both the amount of motion that occurs and the speed at which that motion occurs.  Therefore, assessing only the amount of motion is only half the picture, you must also look at the athlete's ability to control the speed at which that motion occurs.  With IMUs, you can capture not only the amount of motion that occurs but also the speed at which that motion occurs.

Why is video feedback so important?  Agresta et al J Ortho Sport Phy Ther 2015 performed a systematic literature review looking at common movement patterns present in runners that predisposed to injury and effective ways at which change that.  What this study found was that providing video feedback helped the athlete make immediate changes to their running patterns.  What we have found is that video helps in several ways:


  1. Showing an athlete how they move on video is a very effective tool to helping them understand the complexity of and relation to impact on sport
  2. Showing them a video of them moving has an immediate impact on their buy in to what you are telling them and their overall compliance.  

So, this was a really long way around approaching how we can use this in our training.  Providing video feedback is critical first step in training the athlete.  It starts with the assessment.  Showing the athlete how they move during single limb performance and during fatigued state.  This will assist in the immediate buy in and help the develop a better kinetic sense of the movement.   In addition, this will also assist in further training down the road when we are cuing them on correctives.  They will be able to correct the movement faster without the need for external visual input since they got this earlier in the rehabilitation or training routine.

Next week, we will continue our discussion on use of video in our assessment as well as how to address athletes subconsciously avoiding that involved side.  Please make sure to check out our new website at www.iceperform.com where our goal is to help you help others.  #ViPerformAMI


Dr. Nessler is a practicing physical therapist with over 20 years sports medicine clinical experience and a nationally recognized expert in the area of athletic movement assessment.  He is the founder | developer of the ViPerform AMI, the ACL Play It Safe Program, Run Safe Program and author of a college textbook on this subject.  Trent has performed >5000 athletic movement assessments in the US and abroad.  He serves as the National Director of Sports Medicine Innovation for Select Medical, is Vice Chairman of Medical Services for USA Obstacle Racing and movement consultant for numerous colleges and professional teams.  Trent is also a competitive athlete in Brazilian Jiu Jitsu.