Preprint / Version 2

Validation of PITCHAI Markerless Motion Capture Using Gold Standard 3D Motion Capture


  • Tyler Dobos Department of Kinesiology, Faculty of Applied Health Sciences, Brock University, St. Catharines, ON, Canada
  • Ryan Bench Department of Kinesiology, Faculty of Applied Health Sciences, Brock University, St. Catharines, ON, Canada
  • Colin McKinnon 3MotionAI, Oakville, ON, Canada
  • Anthony Brady Driveline Baseball LLC, Kent, WA, USA
  • Kyle Boddy Driveline Baseball LLC, Kent, WA, USA
  • Mike Holmes Brock University
  • Michael Sonne 3MotionAI, Oakville, ON, Canada



Kinematics, Baseball, Pitching, Motion Capture


Kinematic assessments in baseball pitchers have previously been determined using marker-based motion capture systems. No current research exists on the feasibility of single camera markerless motion capture technology for kinematic pitching analysis. This study sought to compare and validate pitching kinematics (joint angles, summary metrics) from a markerless motion capture solution with a gold standard, 3D optical marker-based solution. 38 elite-level healthy pitchers threw 1-3 maximum effort pitches while concurrently using marker-based optical capture and pitchAITM smartphone based (markerless) motion capture. Measures were compared using Pearson's R (R), R Squared (r2), and root mean square error (RMSE). Kinematics were evaluated at foot plant, maximal shoulder external rotation, ball release, and for descriptive metrics. For full time-series angles, pelvis and trunk averaged r2 of 0.92, and 6.0 ± 1.1° of RMSE. Knee angles averaged an r2 of 0.87 ± 0.08, and 8.8 ± 3.6° of RMSE. Throwing arm averaged an r2 of 0.88 ± 0.03, and 12.3 ± 4.2° of RMSE.  Glove arm averaged an r2 of 0.81 ± 0.09, and 14.1 ± 4.5° of RMSE. Most metrics were comparable to the gold standard. pitchAITM can be recommended as a markerless alternative to marker-based motion capture for pitching kinematic analysis. 


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2022-01-12 — Updated on 2022-02-25