Markerless Motion Capture in the Crowd

This work uses crowdsourcing to obtain motion capture data from video recordings. The data is obtained by information workers who click repeatedly to indicate body configurations in the frames of a video, resulting in a model of 2D structure over time. We discuss techniques to optimize the tracking task and strategies for maximizing accuracy and efficiency. We show visualizations of a variety of motions captured with our pipeline then apply reconstruction techniques to derive 3D structure.Comment: Presented at Collective Intelligence conference, 2012 (arXiv:1204.2991

Determining Relationships Between Kinematic Sequencing and Baseball Pitch Velocity Using pitchAITM

Professional baseball pitchers have consistently been increasing pitch velocity since 2008 (the first year of automated pitch tracking and classification at all 30 MLB stadiums) and increasing the number of pitches thrown over 95mph (Sullivan, 2019). Fastball velocity is a primary risk factor for elbow injuries as there is a general linear relationship with increased elbow torques (Aguinaldo & Chambers, 2009; Chalmers et al., 2016; Slowik et al., 2019). The kinematic sequence has been referred to as the order and magnitude of joint angular velocities during the pitch delivery and has been associated with pitch velocity and elbow torque (Nicholson et al., 2022a, 2022b; Scarborough, Leonard, et al., 2021). The purpose of the research was to identify kinematic sequence metrics associated with pitch velocity and use them to predict pitch velocity using pitchAITM (Dobos et al., 2022). A total of 80 pitchers (187.2 ± 8.2 cm, age 20.1 ± 3.3 years) ranging in skill level from high school to professional baseball participated in this study. Video for pitchAITM, player height and weight were collected at 2 baseball training facilities. Extracted pitchAITM data included the peak magnitudes and relative timings of pelvis rotation velocity, trunk rotation velocity, elbow extension velocity, and shoulder internal rotation velocity. Average pitch velocity in the data set was 85.3 ± 5.7 mph or 38.1 ± 2.5 m/s. Pitch velocity was predicted using both a multilinear regression, as well as a custom neural network model. The multilinear regression generated a significant prediction for pitch velocity with an R2 = 0.368 and p < 0.01. Pitcher weight (β = 0.535, p < 0.001), peak pelvis rotational velocity timing (β = -0.157, p = 0.001), peak elbow extension timing (β = 0.122, p = 0.006), and peak shoulder internal rotation timing (β = -0.113, p = 0.018), were significant contributors to the multilinear model. The neural network model significantly predicted velocity with an R2 = 0.372, p < 0.01. Actual and predicted velocity were not significantly different (p = 0.353). In conclusion, pitchAITM kinematic sequencing can predict pitch velocity using both a multilinear regression and custom neural network

Kinetic and Kinematic Variables Related to Medial Elbow Joint Space in Collegiate Baseball Pitchers

The ulnar collateral ligament (UCL) is a prime stabilizer in the elbow against valgus force. It is also a commonly injured structure in the overhead-throwing athlete. The majority of literature to date assesses the medial elbow by adding a valgus stress or evaluates the elbow after injury has occurred. The purpose of this dissertation is to explore static changes to the medial elbow and the relationship with the overhead throw. The first investigation sought to determine if there was a bilateral difference in the medial joint space of the elbow in general population college-aged students. There was no significant difference bilaterally; suggesting that the magnitude of stress applied to the elbow by daily activities is not substantial enough to produce an anatomical change to the connective tissue. However, there was a significant gender effect with males exhibiting larger joint spaces. The second study investigated the bilateral difference in the medial joint space of the elbow in male and female overhead athletes with the same protocol from the previous study. In this study, there was a significant difference between the dominant and non-dominant arms. The third study measured the medial joint space of collegiate baseball pitchers before, after, and 48 hours following the throwing of a simulated game. This study also included measures of grip strength and ball kinematics, in order to investigate a relationship between kinetic and kinematic factors and the changes in the medial joint space. There were no significant changes in the medial joint space following pitching a simulated game, although interestingly, grip strength increased following pitching. Ball kinematics did not indicate a relationship with the changes in the medial elbow joint space

Tommy John Surgery: Potential Risk Factors and Causes in Major League Pitchers

Since 1974, over 270 Tommy John surgeries have been performed on pitchers at the major league level. Thousands more surgeries have been performed on minor league, college, high school and youth pitchers. As more biomechanical and statistical research has been conducted over the past few decades, a clearer picture of some of the risks and causes that lead to serious elbow injuries in pitchers have been found. This paper explores the research surrounding several of those factors, including pitching mechanics, pitch velocity, and pitch type. Using a data set comprised of major league pitchers that have undergone Tommy John surgery between 2008 and 2018, a significant difference in velocity was seen between the Tommy John group and a control group of pitchers. No major differences in pitch type or spin rate were seen between the groups