Monday, January 9, 2017

Innovations in Movement - Blending Movement Science with Technology - Part II

Last week, we started this series to look at how we can leverage what we know in the movement sciences with technology.  The intent of this series is to share with you the various technologies we have encountered as well as some of the benefits and challenges of these.  Considering this, during this series we are going to touch on several different aspects.

  1. Technologies to assess movement
  2. Technologies to treat movement
  3. Training technologies to train proper movement
Last week, we looked at the use of 3D technologies to assess human movement.  This week, we will continue looking at 2D technologies and some specific technologies that are available on the market for doing this.  Before we do that, we should discuss the challenges associated with use of 2D.  These can be mitigated but we must be aware of in order to control.  Remember, we are attempting to make 3D interpretation off a 2D image.  Sometimes that 2D image may appear to show something that is truly not there in a 3D environment.  

Some things to consider when performing movement assessments using 2D technology.

  1. Camera orientation - in order to get a true picture of frontal plane movement of lower kinetic chain, you must have the camera directly infront of the athlete perpendicular to the orientation of the athlete (depicted here).  If the camera orientation is slight off (off to the right or left of the athlete) then this will result in seeing a valgus or varus that is not really there.  If the camera is tilted down or up, then again you will see motion that may not actually be there.  As common knowledge as this sounds, I attend a lot of conferences with some very reputable companies presenting on 2D analysis showing adduction at the knee during a movement and the orientation of the camera to the athlete is way off to the side.  This can all be avoided by ensuring the camera orientation is perpendicular to the athlete.
  2. Angles - most of the 2D technologies out there offer the ability to measure angles.  When measuring human movement, the difference between 5 degrees and 15 degrees can mean the difference between an athlete at risk and one that is not at risk.  What we know is that when you measure angles on 2D, there is an inter and intrarater reliability of +/- 10 degrees.  So, did you really improve that frontal plane motion by 10 degrees or that supination by 5 degrees or did you simply put your starting point at a different spot.  If you are going to use the angle function on these technologies, you can reduce some of this error by palpating the bony landmarks on the athlete, placing markers on those anatomical references and use those when reviewing the video.
  3. Tracking - although this is a really cool capability of some of these technologies, use of tracking with a 2D technology is done via pixels and relies on color.  That being said, if you have an athlete in dark colors against a dark surface, the tracking capabilities will be very limited.  If you are going to use this capability, there must be some significant contrast in colors to have increased accuracy of the tracking.  In addition, the slower the movement is the more accurate the tracking will be.
  4. Stability - this one goes without saying and most control for this.  But attempting to assess movement using 2D video without use of a tripod is very difficult.  This is more common with the use of the smart phone or Ipad for assessing movement.  Again, if not controlled, you will see movement that may not be accurate.  
  5. Frames per second - for any 2D analysis, it is important to know what the fps your camera is.  Optimal is to have a camera with 120 fps or >.  Using cameras with 30-90 fps will result in videos that will be choppy when you are analyzing them in slow motion.  This will often lead to missing the pathological movement you are looking to assess.
For 2D assessment, there is 2 basic types.  Desktop software and Apps.  

Desktop software:

Two of the most common desktop software companies are Dartfish and Kinovea.  Dartfish is a Switzerland based company that was originally used by high performance coaches in professional and Olympic athletics.  Dartfish developed "stromotion" which allowed coaches to see how athletes are moving through all the phases of athletic performance.  This allowed coaches to capture minor nuances throughout the extremely high speed motions in order to create more coachable opportunities.  For me, Dartfish was instrumental in my ability to truly assess and understand movement.  It allowed me to slow down movement to the point that I could capture pathological movement patterns form which I could train athletes to improve and use it to educate them about their movement.  
Although we did not use this to put angles on movement, what we did find is much more accurate way of quantifying frontal plane motion with this technology.  By simply using plumb lines and specific anatomical landmarks, we found that this had a high correlation to frontal plane motion captured via Viacom system.  So we could not only objectively measure frontal plane motion but also objectively quantify improvements in that motion.  

Kinovea is a French based company that offers a 2D video technology that looks and functions very similar to Dartfish.  Although this software is free, it should not be mistaken that there are some fundamental differences in Kinovea and Dartfish.  First off is reliability of the software itself.  There is nothing worse than capturing data on over 30 players and having the system corrupt the videos as you are doing your analysis on later (speaking from experience).  Although some of the functionality is similar, it does not offer the same level of capabilities of Dartfish.  If you are just starting out in movement assessment, this is a good and cheap alternative to start to get your feet wet.  But if you are doing a lot of movement capture, spending the money on Dartfish is money well spent.


There are a lot of different apps that are offered out there for assessing human movement and too many to mention them all.  In this section, we will talk about some of the most common ones.  Most have the ability to function on IOS and Android.  

  1. Hudl - this is a 2D app that offers some versions for free and some upgraded versions offered at minimal cost.  This app allows you to capture movement, perform slow motion and draw lines on the video.
  2. Dartfish Express - this comes to us from Dartfish and includes some of the capabilities that are available in the software.  It allows some of the same functionality of the others but the quality and functionality of this app seems to have a step ahead.  It is available for minimal cost.
  3. Coaches Eye - this is another 2D app that initially started as a tool for coaches to assess players motion during athletic competition or practice.  The application to movement assessment is obvious and it also offers some of the same functionality of the previous two.  
This is by no means an all inclusive list but just a list of the ones we have had the most experience with.  We hope you found this helpful and next week, we will be discussing some movement technologies we can use with treatment.  

Dr. Nessler is a practicing physical therapist with over 17 years sports medicine clinical experience and a nationally recognized expert in the area of athletic movement assessment.  He is the developer of an athletic biomechanical analysis, is an author of a college textbook on this subject  and has performed >3000 athletic movement assessments.  He serves as the National Director of Sports Medicine Innovation for Select Medical, is Chairman of Medical Services for the International Obstacle Racing Federation and associate editor of the International Journal of Athletic Therapy and Training. 

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