Intersegmental dynamics of 3D upper arm and forearm longitudinal axis rotations during baseball pitching

Upper body contributions to pitched ball velocity in elite high school pitchers using an induced velocity analysis

Interest in joint and segment contributions to pitched ball velocity has been dominated by inverse dynamic solutions, which is limited in ascertaining complex muscle/joint interactions. Our purpose was to use induced velocity analysis to investigate which joint(s) made the largest contribution to the velocity of a pitched ball. Pitching data were collected from six elite high school-aged pitchers with no history of arm injury. Participants threw a fastball pitch from the windup on flat ground. Data were collected using seven Vicon 612 cameras (250 Hz) and three AMTI force platforms (1000 Hz). A 14-segment biomechanical model (feet, legs, thighs, pelvis, a combined thorax-abdomen-head, i.e., trunk, upper arms, forearms, and hands) was implemented in Visual3D as a dynamic link library built using SD/Fast (PTC) software. Model-generated induced velocity of the ball was validated against ball velocity obtained from a calibrated radar gun. Velocity induced torques at the shoulder just prior to release, and elbow during the cocking phase, contributed 31.0% and 18.1%, respectively, to forward ball velocity. The centripetal/Coriolis effects from the upper arm and forearm velocities made the largest contribution to ball velocity (average 57.8%), but the source of these effects are unknown. The lower extremities and trunk made little direct contribution to pitched ball velocity. These results may have implications with regard to pitching performance enhancement and rehabilitation.

The influence of upper-body mechanics, anthropometry and isokinetic strength on performance in wrist-spin cricket bowling

Delivering a cricket ball with a wrist-spin (WS) bowling technique is considered one of the game's most difficult skills. Limited biomechanical information exists for WS bowlers across skill levels. The purpose of this study was to compare biomechanical, isokinetic strength and anthropometric measures between elite (12) and pathway bowlers (eight). Data were collected using a motion analysis system, dynamometer and a level-two anthropometrist. A regression analysis identified that performance was best explained by increased wrist radial deviation torque and longitudinal axis rotational moments at the shoulder and wrist. From back foot impact (BFI) to ball release (BR), elite bowlers rotated their trunks less, experienced less trunk deceleration resulting in a more front-on position and increased pelvis rotation angular velocity. They also displayed an increased shoulder internal rotation moment as the upper arm moved from external into internal rotation and was a major contributor in the subsequent differences observed in the distal segments of the bowling limb. Anthropometric differences were observed at the wrist and finger joints and may be used to form the basis for talent identification programmes. This study highlights the important contribution to bowling performance of the musculature responsible for producing long axis rotations of the bowling limb.

Segmental Power Analysis of Sequential Body Motion and Elbow Valgus Loading During Baseball Pitching: Comparison Between Professional and High School Baseball Players

Background:

Pitching-related elbow injuries remain prevalent across all levels of baseball. Elbow valgus torque has been identified as a modifiable risk factor of injuries to the ulnar collateral ligament in skeletally mature pitchers.

Purpose:

To examine how segmental energy flow (power) influences elbow valgus torque and ball speed in professional versus high school baseball pitchers.

Study Design:

Descriptive laboratory study.

Methods:

A total of 16 professional pitchers (mean age, 21.9 ± 3.6 years) and 15 high school pitchers (mean age, 15.5 ± 1.1 years) participated in marker-based motion analysis of baseball pitching. Ball speed, maximum elbow valgus torque (MEV), temporal parameters, and mechanical power of the trunk, upper arm, and forearm were collected and compared using parametric statistical methods.

Results:

Professional pitchers threw with a higher ball speed (36.3 ± 2.9 m/s) compared with high school pitchers (30.4 ± 3.5 m/s) (P = .001), and MEV was greater in professional pitchers (71.3 ± 20.0 N·m) than in high school pitchers (50.7 ± 14.6 N·m) (P = .003). No significant difference in normalized MEV was found between groups (P = .497). Trunk rotation time, trunk power, and upper arm power combined to predict MEV (r = 0.823, P < .001), while trunk rotation time and trunk power were the only predictors of ball speed (r = 0.731, P < .001). There were significant differences between the professional and high school groups in the timing of maximum pelvis rotation velocity (42.9 ± 9.7% of the pitching cycle [%PC] vs 27.9 ± 23.4 %PC, respectively; P < .025), maximum trunk rotation (33 ± 16 %PC vs 2 ± 23 %PC, respectively; P = .001), and maximum shoulder internal rotation velocity (102.4 ± 8.9 %PC vs 93.0 ± 11.7 %PC, respectively; P = .017).

Conclusion:

The power of trunk motion plays a critical role in the development of elbow valgus torque and ball speed. Professional and high school pitchers do not differ in elbow torque relative to their respective size but appear to adopt different patterns of segmental motion.

Clinical Relevance:

Because trunk rotation supplies the power associated with MEV and ball speed, training methods aimed at core stabilization and flexibility may benefit professional and high school pitchers in reducing the injury risk and improving pitching performance.

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

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.

The Effect of Stride Length and Lateral Pelvic Tilt on Elbow Torque in Youth Baseball Pitchers

High elbow torque during a pitch may contribute to injury risk. Our objective was to determine the pitch mechanics associated with elbow varus torque in youth baseball pitchers. Eighteen male youth pitchers (age = 15.5 ± 1.6 years) threw 3 fastballs and 3 change-ups from a windup position while undergoing 3-dimensional kinematic analysis. Independent variables included ball release point distance, stride length, lateral pelvic tilt, and ball velocity. Two multiple regression models, separated by pitch type (fastball, change-up) were used to determine the association of independent variables with peak varus torque at the elbow. Fastball and change-up regression models indicated that stride length (β = 0.301, p = .015; β = 0.46, p < .001, respectively) and lateral pelvic tilt (β = −0.50, p < .001; β = −0.25, p = .04, respectively) were significantly associated with peak elbow varus torque. During fastballs, pitch velocity was significantly associated with peak elbow varus torque (β = 0.38, p = .002), while release point distance was significantly associated with peak elbow varus torque during change-ups (β = −0.33, p = .015). Youth pitchers with longer strides and less lateral pelvic tilt demonstrated greater elbow torque regardless of pitch type, while the association of ball velocity and release point to elbow varus torque was dependent on pitch type.

Contribution of interaction torques during dart throwing: Differences between novices and experts

We examined if experts and novices show different utilization of the torque components impulses during dart throwing. Participants threw darts continuously at a dartboard aiming for the centre (target bull's eye). The upper-limb joint torque impulses were obtained through inverse dynamics with anthropometric and motion capture data as input. Depending on the joint degree of freedom (DOF) and movement phase (acceleration and follow-through), three main strategies of net torque (NET) impulse generation through joint muscle (MUS) and interaction (INT) torque impulses were highlighted. Firstly, our results showed that the elbow flexion-extension DOF leads the movement according to the joint leading hypothesis. Then, considering the acceleration phase, the analysis revealed differences in torque impulse decomposition between expert and novices. For the glenohumeral (GH) joint abduction-adduction and for wrist flexion, the INT torque impulse contributed positively to NET joint torque impulse in the group of experts unlike novices. This allowed to lower the necessary MUS torque impulse at these DOFs. Also, GH axial rotation was actively controlled by muscle torque impulse in the group of experts. During the follow-through, the experts used the INT torque impulse more proficiently than novices to break the elbow extension. The comparison between experts and novices through inverse dynamics document the link between the exploitation of interaction torques impulses and expertise in dart throwing for which the main objective is precision rather than velocity.

Long-latency reflexes of elbow and shoulder muscles suggest reciprocal excitation of flexors, reciprocal excitation of extensors, and reciprocal inhibition between flexors and extensors

Postural corrections of the upper limb are required in tasks ranging from handling an umbrella in the changing wind to securing a wriggling baby. One complication in this process is the mechanical interaction between the different segments of the arm where torque applied at one joint induces motion at multiple joints. Previous studies have shown the long-latency reflexes of shoulder muscles (50-100 ms after a limb perturbation) account for these mechanical interactions by integrating information about motion of both the shoulder and elbow. It is less clear whether long-latency reflexes of elbow muscles exhibit a similar capability and what is the relation between the responses of shoulder and elbow muscles. The present study utilized joint-based loads tailored to the subjects' arm dynamics to induce well-controlled displacements of their shoulder and elbow. Our results demonstrate that the long-latency reflexes of shoulder and elbow muscles integrate motion from both joints: the shoulder and elbow flexors respond to extension at both joints, whereas the shoulder and elbow extensors respond to flexion at both joints. This general pattern accounts for the inherent flexion-extension coupling of the two joints arising from the arm's intersegmental dynamics and is consistent with spindle-based reciprocal excitation of shoulder and elbow flexors, reciprocal excitation of shoulder and elbow extensors, and across-joint inhibition between the flexors and extensors.