Reliability and Validity of Quantitative Video Analysis of Baseball Pitching Motion

Abstract

Video recordings are used to quantitatively analyze pitchers' techniques. However, reliability and validity of such analysis is unknown. The purpose of the study was to investigate the reliability and validity of joint and segment angles identified during a pitching motion using video analysis. Thirty high school baseball pitchers participated. The pitching motion was captured using 2 high-speed video cameras and a motion capture system. Two raters reviewed the videos to digitize the body segments to calculate 2-dimensional angles. The corresponding 3-dimensional angles were calculated from the motion capture data. Intrarater reliability, interrater reliability, and validity of the 2-dimensional angles were determined. The intrarater and interrater reliability of the 2-dimensional angles were high for most variables. The trunk contralateral flexion at maximum external rotation was the only variable with high validity. Trunk contralateral flexion at ball release, trunk forward flexion at foot contact and ball release, shoulder elevation angle at foot contact, and maximum shoulder external rotation had moderate validity. Two-dimensional angles at the shoulder, elbow, and trunk could be measured with high reliability. However, the angles are not necessarily anatomically correct, and thus use of quantitative video analysis should be limited to angles that can be measured with good validity.

Trunk Lean During a Single-Leg Squat Is Associated With Trunk Lean During Pitching

“…13 Excellent reliability has been established for two-dimensional video analysis of angular measures of lateral trunk lean in high school pitchers at maximum external rotation (ICC 2,k = 0.90; SEM= 3.2°). 15 Statistical analyses were performed using SPSS software (version 22; SPSS Inc., Chicago, IL, USA), with an alpha level set a priori at p ≤ 0.05. A Pearson correlation coefficient was calculated to determine the relationship between trunk lean in the SLS and lateral trunk lean in pitching.…”

“…A sample size of 29 participants was needed to achieve 80% power to determine if a correlation coefficient differs from zero, with an effect size 0.77 15 , and an alpha level of 0.05.…”

Simple Assessment of Height and Length of Flight in Complex Gymnastic Skills: Validity and Reliability of a Two-Dimensional Video Analysis Method

“…Video analysis is common in elite sports and covers different areas of application. In individual sports, especially acrobatic sports, video analysis is used to compare and improve complex skills [1]. For quantifying biomechanical aspects of such skills, such as score-relevant kinematic variables of vaults in artistic gymnastics, 3D motion capture (3D video analysis) is used.…”

“…Two-dimensional video analysis (2D analysis), if sufficiently accurate, could offer a more practical alternative for measuring kinematics during training, especially since advancements in smartphone and tablet technology are continually making high-definition video capture and analysis more convenient. Aside from convenience while capturing motion, 2D video is faster, cheaper, and requires less prior knowledge compared to 3D analysis [1,7]. Nonetheless, although multiple studies showed moderate validity compared to 3D motion capture and high intrarater reliability of 2D analysis when examining joint angles during simple movements, such as single-leg squats and running [1,[5][6][7], the validity and reliability of 2D video analysis for complex skills in acrobatic sports are unclear and must be scientifically assessed before this method can be recommended for gymnastics.…”

“…Aside from convenience while capturing motion, 2D video is faster, cheaper, and requires less prior knowledge compared to 3D analysis [1,7]. Nonetheless, although multiple studies showed moderate validity compared to 3D motion capture and high intrarater reliability of 2D analysis when examining joint angles during simple movements, such as single-leg squats and running [1,[5][6][7], the validity and reliability of 2D video analysis for complex skills in acrobatic sports are unclear and must be scientifically assessed before this method can be recommended for gymnastics. The validity and reliability of 2D analysis were deemed sufficient for measuring the flight time and height of vertical jumps, when compared to optical measurement systems (Opto Jump, Microgate, I) [8] or to a force plate [9].…”