Influence of biomechanical models on joint kinematics and kinetics in baseball pitching

Xavier Gasparutto, Erik van der Graaff, Frans van der Helm, Dirkjan Veeger

In baseball pitching, biomechanical parameters have been linked to ball velocity and potential injury risk. However, although the features of a biomechanical model have a significant influence on the kinematics and kinetics of a motion, this influence have not been assessed for pitching. The aim of this study was to evaluate the choice of the trunk and shoulder features, by comparing two models using the same input. The models differed in thoraco-humeral joint definition (moving or fixed with the thorax), joint centre estimation, values of the inertial parameters and computational framework. One professional pitcher participated in the study. We found that the different features of the biomechanical models have a substantial influence on the kinematics and kinetics of the pitchers. With a fixed thoraco-humeral joint the peak average thorax angular velocity was delayed and underestimated by 17% and the shoulder internal rotation velocity was overestimated by 7%. The use of a thoraco-humeral joint fixed to the thorax will lead to an overestimation of the rotational power at the shoulder and will neglect the power produced by the forward and upward translation of the shoulder girdle. These findings have direct implications for the interpretation of shoulder muscle contributions to the pitch.

Keywords: Inverse dynamicsmodellingoverhand throwshouldertrunk

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Knee Angle and Stride Length in Association with Ball Speed in Youth Baseball Pitchers

Bart van Trigt, Wouter Schallig, Erik van der Graaff, Marco Hoozemans, Dirkjan Veeger

The purpose of this study was to determine whether stride length and knee angle of the leading leg at foot contact, at the instant of maximal external rotation of the shoulder, and at ball release are associated with ball speed in elite youth baseball pitchers. In this study, fifty-two elite youth baseball pitchers (mean age 15.2 SD (standard deviation) 1.7 years) pitched ten fastballs. Data were collected with three high-speed video cameras at a frequency of 240 Hz. Stride length and knee angle of the leading leg were calculated at foot contact, maximal external rotation, and ball release. The associations between these kinematic variables and ball speed were separately determined using generalized estimating equations. Stride length as percentage of body height and knee angle at foot contact were not significantly associated with ball speed. However, knee angles at maximal external rotation and ball release were significantly associated with ball speed. Ball speed increased by 0.45 m/s (1 mph) with an increase in knee extension of 18 degrees at maximal external rotation and 19.5 degrees at ball release. In conclusion, more knee extension of the leading leg at maximal external rotation and ball release is associated with higher ball speeds in elite youth baseball pitchers.

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Elite Athlete Motor and Loading Actions on The Upper Limb in Baseball Pitching

Xavier Gasparutto, Erik van der Graaff, Dirkjan Veeger

In baseball, pitchers are the players that are most prone to injury. Most injuries occur at the elbow and shoulder of the throwing upper limb. It is widely accepted that understanding the loading in the joints during pitching is a key factor to prevent injuries. To deepen the understanding of the joint actions this study proposes to split the net joint actions into two part: the motor actions and the stability actions representing respectively the actions generating the joint motion and the actions maintaining the joint integrity. The actions represent the actions applied on the distal segment of the joint. Eight youth elite pitchers participated the study and performed 5 fastball pitches while equipped with skin markers. Three pitches per pitchers were used to compute the joint actions with an inverse dynamics method. The results indicate at the elbow a maximal elbow stability moment in adduction (52±5Nm) on the lower arm at maximal external rotation and a motor action in flexion (38±10Nm) during the acceleration phase. At maximal internal rotation the maximal stability shoulder loading occurred, with a pulling force of 520±80N, a downward force of -290±95N and a depression moment of 65±17Nm. The motor actions at the shoulder were mainly a forward force (93±46N) and an exorotation moment (24±12Nm) during the arm acceleration phase. This study suggest that the main action of the shoulder is to stabilise the joint, with a maximal load at maximal internal rotation, and that the main action at the elbow is avoiding hyperextension, with a critical phase at maximal external rotation. Further study is needed to link the stability actions to injury risk.

    Keywords: pitching, baseball, joint loading, joint moment, elbow, shoulder

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    The role of pelvis an thorax rotation velocity in baseball pitching.

    Erik van der Graaff, Marco Hoozemans, Martijn Nijhof, Michael Davidson, Merel Hoezen, Dirkjan Veeger
    The objective of the present study was to examine the relative timing of pelvis and thorax rotations in achieving high throwing velocities in baseball pitching. During the preseason, a kinematic analysis was performed on eight pitchers. Peak angular velocities of the pelvis and thorax were determined and separation, defined as the time between the moments of maximal rotation velocity of the pelvis and thorax, was calculated. By themselves, maximal pelvis and thorax rotation velocity were not associated with throwing velocity. Separation was positively and significantly associated with throwing velocity. Results indicate that the relative timing of pelvis and thorax peak rotation velocity in pitching fastballs in baseball is a determinant of throwing velocity in skilled pitchers.

    Keywords: biomechanics; kinematics; performance; pitching; separation

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    Longitudinal changes in shoulder ROM and strength in association with ball-throwing speed in elite youth baseball pitchers.

    Femke van Dis, Marco Hoozemans, Erik van der Graaff, Dirkjan Veeger
    The purpose of this prospective study was to examine the longitudinal changes in shoulder ER ROM and relative IR strength in elite youth baseball pitchers over one year and to determine their associations with changes in ball speed for throwing fastballs. One hundred and five Dutch elite youth baseball pitchers were measured three times over a period of one year. Statistical analyses of the data revealed that changes in ER ROM and relative IR strength were not significantly associated with changes in ball-throwing speed.

    Keywords: baseball; pitching; performance; screening; prospective study

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    Shoulder joint velocity during fastball pitching baseball.

    Xavier Gasparutto, Erik van der Graaff, Frans van der Helm, Dirkjan Veeger
    The purpose of this study was to assess the rotation and translation velocity of the shoulder complex during fastball pitching in baseball. 8 pitchers from the Dutch AAA team performed each 3 fastball pitches. Their motion was recorded by an opto-electronic device. Kinematic computation was performed using the quaternion algebra. The results showed that the endo-rotation, depression and backward rotation velocity of the humerus at ball release are initiated by a translation of the scapular girdle in the forward and upward direction before ball release.

    Keywords: baseball; pitching; upper limb; shoulder; velocity

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    Asymmetry and evolution over a one-year period of the upward rotation of the scapula in youth baseball pitchers

    Erik van der Graaff , Bengt Kom, Femke van Dis, Xavier Gasparutto, Marco Hoozemans & Dirkjan Veeger

    The pitching motion is an asymmetric action by which coordination of scapular rotation in the dominant arm might be affected in time and in comparison with the non-dominant arm. The study aimed to compare asymmetry and the evolution of scapular upward rotation over a one-year period. Data were collected twice, before and after a one-year period, from 92 participants (age = 15.1 SD 1.4 years, body height = 177.3 SD 10.9 cm, body weight 69.2 SD 14.5 kg). Scapular motion was tracked at different glenohumeral angles of elevation in the scapular plane: anatomical position (0°), 45°, 90° and 135°. Scapular upward rotation was calculated as the angle between the spinae scapula and the spine. Scapular upward rotation of the dominant arm was 5.1° (95% CI: 2.1°−8.1°) more compared to the non-dominant arm. Age group or glenohumeral angles of elevation did not affect this difference. Scapular upward rotation of the dominant arm decreased 1.9° (95% CI: −0.5° to 4.3°) after a one-year period, however, neither this observation, nor the interaction with age group or elevation angle was significant. These findings may indicate that pitchers could be at risk to develop shoulder injuries especially those that have been associated with scapular asymmetry.

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