The purpose of this study was to measure baseball pitching kinematics with a marker-less motion capture system and compare the results against marker-based measurements. A sample of 114 pitches were captured at 240 Hz simultaneously with a 9-camera marker-less system and a 12-camera marker system. The pitches were thrown by nine baseball pitchers (age 17.0 ± 4.0 yrs). For each trial, the data were time-synchronized between the two systems using the instant of ball release. Coefficient of Multiple Correlations (CMC) were computed to assess the similarity of waveforms between the two systems. Paired t-tests were used to compare differences between the two systems for 3 temporal and 18 kinematic measurements. The CMC for all eight time series analyzed were excellent, ranging from 0.90 to 0.99. Timing of events between the two systems varied by two frames (0.0083 s) or less. Angular positions differed between the two systems up to 14 degrees. Thus, the marker-based and marker-less motion capture systems produced similar patterns for baseball pitching kinematics. However, based on the variations between the systems, it is recommended that a database of normative ranges should be established for each system individually.
Fleisig, Glenn; Slowik, Jonathan S.; Wassom, Derek; Bishop, Jasper; and Diffendaffer, Alek Z.
"COMPARISON OF MARKER AND MARKER-LESS AUTOMATED MOTION CAPTURE FOR BASEBALL PITCHING BIOMECHANICS,"
ISBS Proceedings Archive: Vol. 39:
1, Article 5.
Available at: https://commons.nmu.edu/isbs/vol39/iss1/5