Validating optical motion capture assessments of
First, a graph – this is a comparison of pronation/supination at the elbow using a marker-based system vs. Second, a statement from a biomechanist who works in an academic lab: You got me thinking again about the issues/problems with accuracy in measuring internal shoulder rotation…with markerless/digitizing, it comes down to carrying angle of the elbow screwing up the cross-product of upper and forearm (which is how shoulder IR/ER has to be tracked if going markerless).After exposing him to a minimal Plyo Care throwing program to smooth out some mechanical deficiencies and to just give him a lower-volume throwing program to replace some days of his long toss program, his velocity went from 87-90 MPH to 92-95 MPH touching 96-97 MPH!He carved up AAA and was in the big leagues shortly thereafter, where he remains as his velocity has settled more into the low-90s as a starting pitcher.Marker-based biomechanics systems are incredibly precise AND accurate, while markerless systems typically lack the validation required to even make firm conclusions about precision.At Driveline Baseball, we are pushing markerless technology forward by planning hundreds of test cases of marker-based situations vs.What I slowly began to realize – and how we use biomechanical data at Driveline Baseball now – is that this data is part of a larger thumbprint, an increasingly vital part of an athlete’s assessment.Today, we use this data for amazing purposes, and every day that goes by that we put assessments into our machine learning-enabled backend software, we learn more and more about injuries, performance, and the human body simply by doing our jobs. But before we delve too deep into the actionable part of the data – which we talk about all the time on our blog and on social media – let’s talk about pitfalls of biomechanical analyses and the misuse of science that I see on a regular basis.
He needs high-intensity training like throwing 3 ounce underload baseballs 116 MPH, because if he doesn’t keep the intensity up, he loses fastball velocity very quickly, something he found out in 2013 when he was tinkering with his programming.
Ah, well, I guess we need to factor in calibration of the cameras, accounting for optical errors as well, so use this formula too: And of course, DLT reconstruction is just a few steps away: Got it?
Off you go – set up some cameras, record some markers on the human body, and you too will start solving for kinematics (mechanics) and kinetics (forces/torques) soon enough! Believe it or not, the above equations are how I got started in analyzing biomechanics.
Comparatively, there are athletes with low arm speed that we see in our biomechanical reports.
These athletes can probably tolerate higher workloads to develop velocity, due to lower stresses at the elbow and shoulder.For example, a common issue that we have found that is a marker for injury is high angular velocity at the elbow and shoulder combined with low ball velocity.