Archive for category Motion Analysis
The Limitations of Two-Dimensional Kinematic Analysis
Posted by Kyle in Mechanics, Motion Analysis on June 15, 2011
A clip on YouTube that has gotten a fair amount of press is this SOMAX Sports clip of Tim Lincecum. There are a lot of assumptions that are made in this video with regard to training and flexibility that I’m not going to get into at this time, but I would like to address this very obviously wrong portion of the video.
Tim Lincecum at MER
The measurement on the still frame to the left is not mine, it is what SOMAX believes Lincecum’s maximum external rotation is – taken straight from their YouTube video analysis.
This is very incorrect and is immediately obvious to anyone who has taken a high school physics course. Attempting to measure the degree of an angle when your line of sight is not directly perpendicular to the angle being measured is a serious error in physics called parallax error. SOMAX makes this very elementary mistake when attempting to analyze Tim Lincecum’s motion.
If you were to adjust the camera to be perpendicular to Lincecum’s acromial line, you would quite obviously get a reading near 90 degrees (MER is usually measured with the shoulder internally rotated at 90 degrees per ASMI’s standards, so this would really be 180 degrees) and not 65 degrees like SOMAX believes.
This is yet another reason why two-dimensional kinematic analyses are spotty when not properly controlled for (as in most game situations), and why serious analysis should rely on multiple high-speed cameras used to reconstruct a three-dimensional model of a pitcher.
I wouldn’t trust any “sports performance institute” that relied on video-based coaching tools if they couldn’t properly adjust for a simple error that a 9th grade physics student could probably pick out, but that’s just me.
THT Article: The Velocity Loss Phenomenon
Posted by Kyle in Links, Motion Analysis on June 7, 2011
I know everyone here reads my Hardball Times articles – and is subscribed to my THT RSS feed – right, right?
Well, just in case you forgot that I write there, you can check out my latest article titled The Velocity Loss Phenomenon. My article talks about Trevor Bauer, Dylan Bundy, and their “unorthodox” training methods that got them to where they are – and why it scares big league teams off.
In the near future, look for an article on crude biomechanical analysis as applied to the 2nd pick overall in the 2011 MLB Draft: Danny Hultzen of the Seattle Mariners (formerly the University of Virginia).
Here’s the teaser image:
Danny Hultzen - Maximum Knee Height
But you have to subscribe to my RSS feed or pay close attention to THT for it!
Our Motion Capture Lab: The Overview
Posted by Kyle in Motion Analysis, Notes on June 6, 2011
Since the weather’s gotten a bit better, we’ve decided to do our high-speed biomechanical analysis filming outside. Matthew (my research assistant) and I took the equipment outside where we continued progress on our three-dimensional filming model.
Taking it outside
Today, we filmed a few different movement patterns:
- Baseball pitching off a mound
- Shot put throw
- Baseball swing off a tee
For those unaware of how it works, we reconstruct our control object of precisely known size and put it where we want to capture the motion.
Control Object
We then chalk the corners of the object, indicating the boundaries of where we can film. After that, we film the cube from the number of high-speed cameras we’ll be using. By doing this, each camera is then calibrated with the specific locations of the cube. The cameras will not move from these positions while the trials are being filmed.
Filming Area
We then film the subject performing whatever motion we want to analyze, using all of our high-speed cameras.
And lastly, we’ll digitize the two-dimensional video files, creating a three-dimensional model from the video files. We then have kinematics we can store in a database for future analysis and a three-dimensional skeletal model we can use for coaching and training purposes for the athlete.
Sample Lab Results
We’ve improved the process a number of times, making setup much quicker. We can deploy the motion capture lab at a mobile site in under an hour, and then film test subjects all day. This makes our lab setup ideal for filming pitchers in competition without being intrusive – no external markers are necessary on the athlete.
Interested? Look into our biomechanical video analysis services, and contact us today.
Biomechanics and Me?
Posted by Kyle in Links, Mechanics, Motion Analysis on March 21, 2011
I made a guest FanPost titled Biomechanics and Me? over at Lookout Landing, a very popular (and great) Seattle Mariners blog in the SB Nation network. It talks about my history of building our biomechanics lab.
Even prior to Graham’s post, I had been working on building a low-cost biomechanical analysis laboratory in Seattle. For those unaware, high-speed cameras were basically unavailable at reasonable price points in 2008 until the Casio Exilim EX-F1 came out for $1000. Even then, these cameras weren’t enough to do the advanced biomechanical analysis required to even shine a light on the “mechanics” of throwing a baseball. It would require multiple cameras, off-the-shelf software that could solve for kinematics/kinetics (and provide a digitization solution), custom algorithms that could solve the synchronization issue between these consumer-grade cameras (commercial ones do this automatically), and a precisely measured control object.
Commercial packages are available, but cost $15-17k for a two-camera setup that is not sufficient for working with movements that occur in all three planes so rapidly – like baseball pitching. You’re looking at $25-30k at the bare minimum with off-the-shelf packages, plus customization and training.
Head over there and take a look if it interests you!
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Kyle’s Hardball Times Articles- Fastball mechanics: The hardest and softest throwers October 7, 2011
- Jason Vargas, the twist, and the intent to throw hard September 13, 2011
- How baseball failed Steve Delabar September 12, 2011
- A pitcher breaking the mold August 13, 2011
- The science of scouting: A biomechanical look at Gerrit Cole August 11, 2011
