LAUSR

Objectives: The advent of motion and kinematic analysis of athletes during sport-specific activities has shed light on mechanical factors associated with improved athletic performance. This is especially true in baseball, where motion analysis has provided a nuanced understanding of the pitching motion. Previously, information from motion analysis has been used to identify risk factors for injury, such as to the medial elbow. However, there is less information regarding modifiable mechanical factors associated with increased performance that are safe and do not place the athlete at increased risk for injury. Identification of such variables would allow medical professionals to counsel pitchers on safe and effective ways to improve performance without risking injury. The goal of this study was to identify modifiable mechanical factors that were specific to pitchers throwing with above average fastball velocities. Methods: All participants were recruited from NCAA Division I and III collegiate baseball programs and all participants were currently pitching for their teams and had no history of injury in the preceding 6 months. Participants pitched from a 10-inch mound towards a target with a designated strike zone 60 feet 6 inches away. Each participant pitched the pitch types that they felt most comfortable pitching in a game setting, and pitches were thrown in random order to simulate a game setting. Motion data were collected at 250 Hz using a Vicon 512, 12-camera motion capture system (Vicon Motion Systems, Los Angeles, CA) using previously described methods. A single fastball pitch was randomly selected from each participant for analysis. The average ball velocity was used to place participants into either the ‘high velocity group’ (above average fastball velocity) or ‘low velocity group’ (below average ball velocity). A two-tailed unpaired t-test was performed to determine statistical significance of the variables measured during motion analysis to determine which mechanical differences between the two groups were associated with increased fastball velocity. Results: 99 pitchers (avg. age 19.9 +/- 1.4) were enrolled in the study. The average velocity was 70.2 miles per hour (range 49.1 - 80.9). There were 57participants in the high velocity group and 42 participants in the low velocity group. Variables that were statistically different between the two study groups are listed in Table 1. A The high fastball velocity group showed decreased glenohumeral coronal angle at ball release (more ‘side arm’), increased anterior thoracic tilt at ball release, increased anterior pelvic tilt at ball release, increased pelvic obliquity at maximum glenohumeral external rotation (pelvis tilting up towards throwing arm), increased hip abduction at lead foot contact, and increased knee flexion at lead foot contact. Conclusion: The results indicated a number of modifiable variables that were significantly different between the two study groups. Using this information pitchers can look to modify their pitching motion to improve their performance as defined as increased fastball velocity. This information also provides a foundation for future work to determine which of these performance variables are also associated with increased medial elbow stresses that could lead to an increased risk of injury. Using this data could then allow coaches to optimize training regiments to focus on improving performance while minimizing risk of injury. Table 1: Variables associated with high velocity pitchers and low velocity pitchers with associated p-values. BR = ball release; MER = maximal glenohumeral external rotation; FC = foot contact. Variable High Velocity Low Velocity P Value Pitching Mechanics associated with increased Velocity Glenohumeral Coronal Angle at BR 64.7° 72.1° 0.01 A more ‘side arm’ position at BR Thoracic Tilt at BR 32.3° 25.3° <0.0001 Thorax leading towards home plate at BR Pelvic Tilt at BR 43.5° 38.0° <0.0001 Pelvis leading towards home plate at BR Pelvic Obliquity at MER 4.8° 0.9° <0.0001 Pelvis tilting up towards the throwing arm at late cocking phase Lead Hip Coronal Angle at FC 37.0° 33.8° 0.03 Increased lead hip abduction at FC Lead Knee Sagittal Angle at FC 43.6° 40.3° 0.03 Increased lead knee flexion at FC