Analyzing the Reliability and Precision of Fast-Pitch Softball Kinematics Using Markerless Motion Capture

There is limited research the kinematics of the softball pitching motion, especially with markerless motion capture. Objective: Determine the test-retest and intersystem reliability of OpenCap when analyzing stride length, knee flexion, trunk flexion, trunk lateral flexion, and trunk rotation at stride leg foot contact. Participants: 9 softball pitchers with college pitching experience. Methods: This study examined the test-retest and intersystem reliability with which OpenCap can measure kinematics in a softball pitching motion. Subjects completed 2 sessions of 5 successful fastballs measured by two OpenCap systems running concurrently. Results: Variables were measured with moderate to excellent reliability with ICC values ranging from 0.614-0.987. All variables were significant (p<0.05) except for test-retest reliability of trunk rotation. Conclusion: The results illustrate that OpenCap can be used to reliably measure some kinematic variables during a softball pitching motion. This technology could be used for injury prevention and performance enhancement. More research needs to be done to determine the full extent of its use.