Kinematic Sequence Classification and the Relationship to Pitching Limb Torques

Abstract

Purpose The kinematic sequence (KS) during a baseball pitch provides insight into an athlete’s ability to efficiently transfer energy and develop segmental velocities, to assess the quality of body segment position and control. Study purposes were 1) to introduce the four-category Kinematic Sequence Classification System and 2) to compare elbow and shoulder torques and shoulder distraction force across the KS categories performed during the fastball pitch. Methods Thirty baseball pitchers (20.0 ± 3.1 yr) underwent 3D biomechanical pitch analyses of 249 fastball pitches. Seventeen distinct KS patterns were identified and assigned into four categories: 1) The proximal-to-distal (PDS) group includes the KS closest to theoretical ideal order of the five body segments (pelvis → trunk → arm → forearm → hand). The other categories were defined based on the segment where the first out-of-sequence peak angular velocity occurred: 2) distal upper extremity (DUE), 3) proximal upper extremity, and 4) pelvis/trunk. Throwing limb shoulder distraction force and shoulder and elbow torques were calculated. Linear mixed model analyses compared variables across KS categories. Results Average elbow valgus torques differed significantly across all categories, P = 0.023, and were greater for the DUE (73.99 ± 20.84 N·m) than the PDS (61.35 ± 16.79 N·m), P = 0.006. Shoulder external rotation torques were significantly different, P = 0.033, across categories. Conclusion The PDS group demonstrated less mechanical stresses on the throwing shoulder and elbow but was observed in only 12% of pitches. The DUE group was the most common and generated the greatest elbow valgus and shoulder external rotation torques. The KS can inform coaches and sports medicine clinicians where the greatest torques are incurred by a pitcher. A KS classification system may serve as a screening tool or target pitching instruction for injury avoidance.

Comparison of Kinematic Sequences During Curveball and Fastball Baseball Pitches

“…The previously described Kinematics Sequence Classification groups the observed KSs to better understand the influences that altered sequences have on the pitcher's body. Each group is named relative to the first body segment that demonstrates peak angular velocity out-of-sequence from the targeted proximal-to-distal sequence (Scarborough et al, 2021 ). The groups described previously include: (1) the proximal-to-distal (PDS) group which also includes the closest to the ideal sequence where the forearm and the hand segments' peak angular velocities peak simultaneously, (2) the altered distal upper extremity (DUE) group, and (3) the altered proximal upper extremity (PUE) group and the altered pelvis/trunk (CORE) group (Scarborough et al, 2021 ).…”

“…Performance of this efficient transfer of segmental angular velocity is reported to reduce stress on musculoskeletal structures and thus the probability of injury while also maximizing ball velocity (Putnam, 1993 ; Seroyer et al, 2010 ; Chalmers et al, 2017 ; Scarborough et al, 2020 ). Recent investigations on a sample of fastball pitches performed by a group of high school, collegiate, and professional pitchers revealed that there are at least 17 distinct observable KS patterns (Scarborough et al, 2021 ). Out of the 17 observed patterns, none displayed the most efficient proximal-to-distal KS desired.…”

“…Influenced by the power and timing of trunk movement, torque developed during shoulder rotation is correlated to elbow valgus torque and subsequent injury risk (Chalmers et al, 2017 ; Aguinaldo and Escamilla, 2019 ). The proper execution of the proximal to distal kinematic sequence leads to less torque production across the shoulder and elbow yet contributes to increased ball speed (Putnam, 1993 ; Seroyer et al, 2010 ; Scarborough et al, 2021 ). Certain kinematic sequences result in greater shoulder and or elbow torques than other KS patterns (Aguinaldo and Escamilla, 2019 ; Scarborough et al, 2021 ).…”

“…The proper execution of the proximal to distal kinematic sequence leads to less torque production across the shoulder and elbow yet contributes to increased ball speed (Putnam, 1993 ; Seroyer et al, 2010 ; Scarborough et al, 2021 ). Certain kinematic sequences result in greater shoulder and or elbow torques than other KS patterns (Aguinaldo and Escamilla, 2019 ; Scarborough et al, 2021 ). Specifically, torques increase among KS patterns where the trunk reaches peak rotational velocity prior to the peak pelvis velocity (Seroyer et al, 2010 ; Aguinaldo and Escamilla, 2020 ).…”

Association of Pitch Timing and Throwing Arm Kinetics in High School and Professional Pitchers

“…In a mixed cohort of players ranging from high school (HS) to PRO, those who followed a proximal-to-distal sequence of segmental velocities demonstrated decreased elbow varus torque and shoulder internal rotation torque. 30,31 Additional studies have validated the importance of the temporal phases of the pitching motion. In collegiate and PRO pitchers, those who initiated trunk rotation before lead foot contact had significantly higher elbow varus torque compared with those who rotated after foot contact.…”