Pitching Accuracy
Let’s take the motion capture lab to your phone. I wrote a post on our website last month, talking about our solution PitchAI – and how it was used to be a reliable method of capturing data in the field. But – how accurate would this data be compared against the gold standard motion capture lab?
We collected data with our team at Brock University – but we also worked with our partners at Driveline Baseball to get even more paired data between cell phone video and the motion capture lab. In total, we had over 100 pitches to compare against, and close to 50 pitchers to analyze. This would be our most representative sample of how accurate PitchAI could be – which has huge implications for the use of the tool for injury prevention, performance improvement, and rehabilitation.
While more granular results will be available soon – we intend on publishing these data in a peer-reviewed journal shortly – to give you a summary of how things looked, PitchAI reports back on 15 metrics – Elbow Flexion, Shoulder Abduction, Horizontal Abduction, and External Rotation for the throwing arm and the glove arm, Trunk Twist, Trunk Flexion, and Trunk Tilt, Pelvis Twist, and the Knee Flexion of the trail leg and lead leg.
Statistically, we used a correlation on the full signal analysis between the motion capture system and PitchAI, as well as error % – which represented the error as a factor of the full range of motion exhibited by each pitcher.
Here are a few examples – take a look at external rotation of the throwing arm:
And, Trunk Twist.
And finally, hip to shoulder separation
In summary, take a look at the averages for the throwing arm, glove arm, trunk, and knee metrics for both correlation and error.
| Throwing Arm | GloveArm | Legs | Trunk | Average | |
| r2 | 0.94 | 0.87 | 0.98 | 0.97 | 0.89 |
| Error | 10% | 18% | 14% | 4% | 12% |
Where the meat of the analysis is being performed (between foot strike and ball release), the average error across all 15 of our metrics, is less than 10 degrees.
The easiest way to see what is happening from PitchAI is this video – the blue lines are the motion capture system. The white lines are from our single camera iPhone capture.
The number that sticks out the most – on average, 12% error. 12% error across all pitchers (and we included pros, college, and high school arms in this validation). Instead of needing to go into a motion capture lab to get an accurate biomechanics assessment – you can just pitch. This is Corey Kluber pitching in a game back in March – now complete with a biomechanics assessment.
It is now that easy to get a biomechanics assessment done – at any time, on any player. That ergonomics model for understanding player performance and injury risk? Just wait for the data to roll in. With a great research team consisting of Dr. Colin McKinnon, Ryan Bench, Dr. Mike Holmes, and the Biomechanics team at Driveline Baseball (including Anthony Brady and Kyle Boddy), we can’t wait to share what we’re working on next.