Comparison of kinematics in skilled and unskilled arms of the same recreational baseball players

Effects of a Simulated Game and Doubleheader Inning on Peak Kinetics in Softball Pitching Across Pitch Types

BACKGROUND

Softball pitchers frequently pitch at high volumes. Previous research has demonstrated changes in mechanics, range of motion, and perceived levels of fatigue and pain at high workloads. To date, little research has assessed changes in kinetics at high workloads across pitch types to understand the injury risk.

PURPOSE

To examine changes in peak kinetics of the shoulder, elbow, and wrist of the pitching arm throughout a simulated game and doubleheader inning.

STUDY DESIGN

Descriptive laboratory study.

METHODS

A total of 19 high school softball pitchers (mean age, 15.1 ± 1.5 years; mean height, 1.6 ± 0.2 m; mean weight, 76.3 ± 16.9 kg) participated. Pitchers threw 4 innings of 25 randomly assigned pitches to mimic a game's high pitch count. Participants then rested for 30 minutes before subsequently proceeding to pitch the first inning of a doubleheader. Each pitcher threw a fastball, drop ball, curveball, and changeup. Peak shoulder, elbow, and wrist kinetics were compared across the first, last, and doubleheader innings and pitch types.

RESULTS

Compared with the first inning, significant decreases in kinetics were observed at the shoulder, elbow, and wrist in the last (P < .016) and doubleheader (P < .016) innings, particularly for shoulder and elbow compression force during the drop ball and curveball pitch types and wrist net force for all pitch types but the changeup. Significant decreases in elbow and wrist kinetics were observed during the changeup between the last and doubleheader innings (P < .016). Furthermore, differences in kinetics were observed between pitch types (P < .008); notably, the changeup had reduced kinetics compared with the fastball and breaking ball pitch types (drop ball, curveball) across innings.

CONCLUSION

Across innings, attenuations in select joint kinetics of the pitching arm occurred that were specific to the pitch type. Across pitch types, peak kinetics was often greater during the fastball, while the changeup displayed the lowest peak kinetics.

CLINICAL RELEVANCE

The joints examined in this study are common sites of overuse injuries in pitchers. This work adds to previous findings on decrements in neuromuscular function as well as self-reported fatigue and pain with tournament-style pitching that may increase the injury risk. Collectively, these findings support developing a protocol combining functional testing and player-reported outcomes to aid sports specialists' decisions for pitchers to continue to pitch or return to play, which may help prevent musculoskeletal injuries and time loss from sports participation.

Effort-dependent effects on uniform and diverse muscle activity features in skilled pitching

How do skilled players change their motion patterns depending on motion effort? Pitchers commonly accelerate wrist and elbow joint rotations via proximal joint motions. Contrastingly, they show individually different pitching motions, such as in wind-up or follow-through. Despite the generality of the uniform and diverse features, effort-dependent effects on these features are unclear. Here, we reveal the effort dependence based on muscle activity data in natural three-dimensional pitching performed by skilled players. We extract motor modules and their effort dependence from the muscle activity data via tensor decomposition. Then, we reveal the unknown relations among motor modules, common features, unique features, and effort dependence. The current study clarifies that common features are obvious in distinguishing between low and high effort and that unique features are evident in differentiating high and highest efforts.

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.

Development and Validation of Robot Patient Equipped with an Inertial Measurement Unit and Angular Position Sensors to Evaluate Transfer Skills of Nurses

To more efficiently enhance the patient transfer skills of nursing students, this study aims to integrate a transfer skills evaluation system and a robot patient. The evaluation parameters, namely, the translational acceleration of the waist, rotational speed of the chest, and joint angles of the shoulder, hip, and knee, were selected on the basis of the pre-experimental results obtained with a simulated patient acted by the human individuals. To measure these parameters, inertial measurement unit (IMU) and angular position sensors were installed on the robot patient. An experiment was conducted with four nursing teachers to verify whether the robot patient could distinguish the incorrect methods of the transfer skills, determined to be a common mistake made by the nurses. According to the results, most transfer steps had the same effect on the simulated patient and the robot patient, which demonstrates that the robot patient is a suitable substitute for an actual patient. However, in certain steps, the robot patient was not able to distinguish between the correct and incorrect methods using the chosen parameters owing to the differences being insignificant. These insignificant differences were mostly attributed to the passive joint design of the robot patient.

Translational Acceleration, Rotational Speed, and Joint Angle of Patients Related to Correct/Incorrect Methods of Transfer Skills by Nurses

Currently, due to shortages in the nursing faculty and low access to actual patients, it is difficult for students to receive feedback from teachers and practice with actual patients to obtain clinic experience. Thus, both evaluation systems and simulated patients have become urgent requirements. Accordingly, this study proposes a method to evaluate the nurse’s transfer skill through observation from the patient. After verifying the proposed method, it will be integrated with a robotic patient as a future work. To verify if such an evaluation is practical, a checklist comprising 16 steps with correct and incorrect methods was proposed by the nursing teachers. Further, the evaluation parameters were determined as translational acceleration, rotational speed, and joint angle of patient. Inertial sensors and motion capture were employed to measure the translational acceleration, rotational speed, and joint angle. An experiment was conducted with two nursing teachers, who were asked to carry out both correct and incorrect methods. According to the results, three parameters reveal the difference for a patient under correct/incorrect methods and can further be used to evaluate the nurse’s skill once the thresholds are determined. In addition, the applicability of inertial sensors is confirmed for the use of robot development.

Interlimb differences in coordination of unsupported reaching movements

Previous research suggests that interlimb differences in coordination associated with handedness might result from specialized control mechanisms that are subserved by different cerebral hemispheres. Based largely on the results of horizontal plane reaching studies, we have proposed that the hemisphere contralateral to the dominant arm is specialized for predictive control of limb dynamics, while the non-dominant hemisphere is specialized for controlling limb impedance. The current study explores interlimb differences in control of 3-D unsupported reaching movements. While the task was presented in the horizontal plane, participant's arms were unsupported and free to move within a range of the vertical axis, which was redundant to the task plane. Results indicated significant dominant arm advantages for both initial direction accuracy and final position accuracy. The dominant arm showed greater excursion along a redundant axis that was perpendicular to the task, and parallel to gravitational forces. In contrast, the non-dominant arm better impeded motion out of the task-plane. Nevertheless, non-dominant arm task errors varied substantially more with shoulder rotation excursion than did dominant arm task errors. These findings suggest that the dominant arm controller was able to take advantage of the redundant degrees of freedom of the task, while non-dominant task errors appeared enslaved to motion along the redundant axis. These findings are consistent with a dominant controller that is specialized for intersegmental coordination, and a non-dominant controller that is specialized for impedance control. However, the findings are inconsistent with previously documented conclusions from planar tasks, in which non-dominant control leads to greater final position accuracy.

Shooting motion in high school, collegiate, and professional men's lacrosse players

The purposes of this research were to quantify the kinematics of the lacrosse shot, based on arm dominance and player experience level. Male players (N = 39; 14-30 years; high school [n = 24], collegiate [n = 9], professional [n = 6]), performed overhead shots using dominant and non-dominant sides. Motion was captured using a high-speed, 12-camera optical system and high-speed filming. Body segment rotational velocities and joint angles were determined at key points in the shot cycle from foot contact (0% of shot) to ball release (100% of shot). All players shot with less anterior trunk lean, less transverse shoulder rotation, and slower trunk-shoulder rotational velocities with the non-dominant side than the dominant side (all p < 0.05). Professional players produced crosse angular velocities 21% faster than high school or collegiate players (p < 0.05). Transverse shoulder rotation range of motion on both dominant and non-dominant and trunk rotation sides was highest in the professional players (p < 0.05). These kinematic features enable professional players to produce faster ball speeds than younger players (138 ± 7 km/h vs. 112 ± 15 km/h, respectively; p < 0.05). Less anterior lean or suboptimal rotation sequence could increase proximal shoulder forces that could contribute to injury as in other throwing sports.

A kinematic comparison of the overhand throw and tennis serve in tennis players: how similar are they really?

Tennis coaches often use the fundamental throwing skill as a training tool to develop the service action. However, recent skill acquisition literature questions the efficacy of non-specific training drills for developing complex sporting movements. Thus, this study examined the mechanical analogy of the throw and the tennis serve at three different levels of development. A 500 Hz, 22-camera VICON MX motion capture system recorded 28 elite female tennis players (prepubescent (n = 10), pubescent (n = 10), adult (n = 8)) as they performed flat serves and overhand throws. Two-way ANOVAs with repeated measures and partial correlations (controlling for group) assessed the strength and nature of the mechanical associations between the tasks. Preparatory mechanics were similar between the two tasks, while during propulsion, peak trunk twist and elbow extension velocities were significantly higher in the throw, yet the peak shoulder internal rotation and wrist flexion angular velocities were significantly greater in the serve. Furthermore, all of these peak angular velocities occurred significantly earlier in the serve. Ultimately, although the throw may help to prime transverse trunk kinematics in the serve, mechanics in the two skills appear less similar than many coaches seem to believe. Practitioners should, therefore, be aware that the throw appears less useful for priming the specific arm kinematics and temporal phasing that typifies the tennis serve.

Complex hand dexterity: a review of biomechanical methods for measuring musical performance

Complex hand dexterity is fundamental to our interactions with the physical, social, and cultural environment. Dexterity can be an expression of creativity and precision in a range of activities, including musical performance. Little is understood about complex hand dexterity or how virtuoso expertise is acquired, due to the versatility of movement combinations available to complete any given task. This has historically limited progress of the field because of difficulties in measuring movements of the hand. Recent developments in methods of motion capture and analysis mean it is now possible to explore the intricate movements of the hand and fingers. These methods allow us insights into the neurophysiological mechanisms underpinning complex hand dexterity and motor learning. They also allow investigation into the key factors that contribute to injury, recovery and functional compensation. The application of such analytical techniques within musical performance provides a multidisciplinary framework for purposeful investigation into the process of learning and skill acquisition in instrumental performance. These highly skilled manual and cognitive tasks present the ultimate achievement in complex hand dexterity. This paper will review methods of assessing instrumental performance in music, focusing specifically on biomechanical measurement and the associated technical challenges faced when measuring highly dexterous activities.

Biomechanical strategies for accuracy and force generation during stone tool production

Multiple hominin species used and produced stone tools, and the archaeological record provides evidence that stone tool behaviors intensified among later members of the genus Homo. This intensification is widely thought to be the product of cognitive and anatomical adaptations that enabled later Homo taxa to produce stone tools more efficiently relative to earlier hominin species. This study builds upon recent investigations of the knapping motions of modern humans to test whether aspects of our upper limb anatomy contribute to accuracy and/or efficiency. Knapping kinematics were captured from eight experienced knappers using a Vicon motion capture system. Each subject produced a series of Oldowan bifacial choppers under two conditions: with normal wrist mobility and while wearing a brace that reduced wrist extension (∼30°-35°), simulating one aspect of the likely primitive hominin condition. Under normal conditions, subjects employed a variant of the proximal-to-distal joint sequence common to throwing activities: subjects initiated down-swing upper limb motion at the shoulder and proceeded distally, increasing peak linear and angular velocities from the shoulder to the elbow to the wrist. At the wrist, subjects utilized the 'dart-thrower's arc,' the most stable plane of radiocarpal motion, during which wrist extension is coupled with radial deviation and flexion with ulnar deviation. With an unrestrained wrist, subjects achieved significantly greater target accuracy, wrist angular velocities, and hand linear velocities compared with the braced condition. Additionally, the modern wrist's ability to reach high degrees of extension (≥28.5°) following strike may decrease risk of carpal and ligamentous damage caused by hyperextension. These results suggest that wrist extension in humans contributes significantly to stone tool-making performance.

Descending corticospinal control of intersegmental dynamics

To make an accurate movement, the CNS has to overcome the inherent complexities of the multijoint limb. For example, interaction torques arise when motion of individual arm segments propagates to adjacent segments causing their movement without any muscle contractions. Since these passive joint torques significantly add to the overall torques generated by active muscular contractions, they must be taken into account during planning or execution of goal-directed movements. We investigated the role of the corticospinal tract in compensating for the interaction torques during arm movements in humans. Twelve subjects reached to visual targets with their arm supported by a robotic exoskeleton. Reaching to one target was accompanied by interaction torques that assisted the movement, while reaching to the other target was accompanied by interaction torques that resisted the movement. Corticospinal excitability was assessed at different times during movement using single-pulse transcranial magnetic stimulation (TMS) over the upper-arm region of M1 (primary motor cortex). We found that TMS responses in shoulder monoarticular and elbow-shoulder biarticular muscles changed together with the interaction torques during movements in which the interaction torques were resistive. In contrast, TMS responses did not correlate with assistive interaction torques or with co-contraction. This suggests that the descending motor command includes compensation for passive limb dynamics. Furthermore, our results suggest that compensation for interaction torques involves the biarticular muscles, which span both shoulder and elbow joints and are in a biomechanically advantageous position to provide such compensation.

Distinct Inter-Joint Coordination during Fast Alternate Keystrokes in Pianists with Superior Skill

Musical performance requires motor skills to coordinate the movements of multiple joints in the hand and arm over a wide range of tempi. However, it is unclear whether the coordination of movement across joints would differ for musicians with different skill levels and how inter-joint coordination would vary in relation to music tempo. The present study addresses these issues by examining the kinematics and muscular activity of the hand and arm movements of professional and amateur pianists who strike two keys alternately with the thumb and little finger at various tempi. The professionals produced a smaller flexion velocity at the thumb and little finger and greater elbow pronation and supination velocity than did the amateurs. The experts also showed smaller extension angles at the metacarpo-phalangeal joint of the index and middle fingers, which were not being used to strike the keys. Furthermore, muscular activity in the extrinsic finger muscles was smaller for the experts than for the amateurs. These findings indicate that pianists with superior skill reduce the finger muscle load during keystrokes by taking advantage of differences in proximal joint motion and hand postural configuration. With an increase in tempo, the experts showed larger and smaller increases in elbow velocity and finger muscle co-activation, respectively, compared to the amateurs, highlighting skill level-dependent differences in movement strategies for tempo adjustment. Finally, when striking as fast as possible, individual differences in the striking tempo among players were explained by their elbow velocities but not by their digit velocities. These findings suggest that pianists who are capable of faster keystrokes benefit more from proximal joint motion than do pianists who are not capable of faster keystrokes. The distinct movement strategy for tempo adjustment in pianists with superior skill would therefore ensure a wider range of musical expression.

Throwing darts utilizes the interaction torque of the elbow joint

Acquiring the skillful movements of experts is a difficult task in many fields. If we find quantitative indices of skillful movement, we can develop an adaptive training system using the indices. We focused on throwing darts in our previous study. It was found that optimization criteria of sum of squared joint torque changes over time was negatively correlated with subject's scores, suggesting that the experts optimally controlled the shoulder elevations and rotation around the elbow joint in terms of dynamics. In this study, we investigate the relationship between the skill level of subjects and their utilization joint torque components such as the muscular torque, interaction torque and gravity torque. It is shown found that the sum of squared joint torque components of the subjects correlates with their scores, suggesting that the subjects who can take higher scores utilize the interaction torque of the elbow joint without shoulder displacement.

Kinematics of arm joint rotations in cerebellar and unskilled subjects associated with the inability to throw fast

Cerebellar subjects and unskilled throwers cannot produce fast arm movements when throwing. We investigated the arm movement kinematics associated with this lack of skill. Cerebellar subjects and matched controls, and skilled throwers throwing with their skilled (dominant) and unskilled (nondominant) arms, were instructed to make slow, medium, and fast 3-D overarm throws from a sitting position. Only the fast throws were analyzed in detail. Joint motions were computed from angular positions of arm segments recorded with search coils. When throwing, both the cerebellar group and the unskilled-arm group had slower arm movements, and slower elbow extension and wrist flexion velocities than their reference groups. They also had similar magnitudes of many kinematic parameters, e.g., both cerebellar and unskilled groups had similar elbow extension and wrist flexion velocities. Compared to their reference groups, both the cerebellar and unskilled-arm groups also had a smaller elbow extension acceleration, a smaller shoulder adduction deceleration, and the absence of a large elbow extension deceleration before ball release. Similar decreases in joint velocities and in joint accelerations and decelerations in the cerebellar and unskilled groups are consistent with the idea that the absence of the skill of throwing fast in both groups is associated with an inability to exploit interaction torques.

Pickup of Essential Kinematics Underpins Expert Perception of Movement Patterns

In a series of 3 experiments, the authors examined the ability of badminton players of different skill levels (12 experts and 12 nonexperts) to anticipate the direction of badminton strokes. Participants viewed either film or point-light displays under a range of temporal or spatial occlusion conditions. World-class players were able to consistently pick up useful predictive information from the advance (precontact) kinematics of both the lower body and the racquet when the motion of those features was presented in isolation, whereas recreational players' use of the same information depended on the concurrent presence of linked segments. Participants' information pickup closely matched key biomechanical changes in the movement pattern being viewed, although, contrary to a common-coding view of perception and action (e.g., W. Prinz, 1997), some important differences were evident between the characteristics of the experts' movement prediction and those of expert movement production.

Roles of proximal-to-distal sequential organization of the upper limb segments in striking the keys by expert pianists

Roles played by the proximal-to-distal sequencing (PDS) of the multi-joint limb in a relatively slow target-aiming task by the arm were investigated using keystroke motion on the piano. Kinematic recordings were made while experts (N=7) and novices (N=7) of piano players performed an octave keystroke at four linearly-scaled loudness levels with a short tone production (staccato) technique. The temporal relationship of the peak angular velocity at the shoulder, elbow and wrist joints showed a clear PDS organization for the experts, but not for the novices. The result thus confirmed that the PDS occurred in a slow and skilled multi-joint movement. The summation effect of segmental speed in terms of increment of the peak segmental angular velocity was equal for both groups. Similarly, no group difference was found for the total kinetic energy produced by the upper limb during keystroke. The role of the PDS in piano keystroke thus cannot be explained by the exploitation of speed-summation effect and mechanical efficiency. Compared to the novices, the experts had a longer period and a greater magnitude of deceleration at the shoulder and elbow joints while their adjacent distal joints were accelerating. These results indicated that greater inertial forces had been generated to descend the forearm as well as the hand for the experts. A dominant role of the PDS in pianists can therefore be to effectively exploit motion-dependent interaction torques at the forearm and hand, and thereby reducing muscle-dependent torques to make the keystroke more physiologically efficient.

Control of 3D Limb Dynamics in Unconstrained Overarm Throws of Different Speeds Performed by Skilled Baseball Players

This study investigated how the human CNS organizes complex three-dimensional (3D) ball-throwing movements that require both speed and accuracy. Skilled baseball players threw a baseball to a target at three different speeds. Kinematic analysis revealed that the fingertip speed at ball release was mainly produced by trunk leftward rotation, shoulder internal rotation, elbow extension, and wrist flexion in all speed conditions. The study participants adjusted the angular velocities of these four motions to throw the balls at three different speeds. We also analyzed the dynamics of the 3D multijoint movements using a recently developed method called “nonorthogonal torque decomposition” that can clarify how angular acceleration about a joint coordinate axis (e.g., shoulder internal rotation) is generated by the muscle, gravity, and interaction torques. We found that the study participants utilized the interaction torque to generate larger angular velocities of the shoulder internal rotation, elbow extension, and wrist flexion. To increase the interaction torque acting at these joints, the ball throwers increased muscle torque at the shoulder and trunk but not at the elbow and wrist. These results indicates that skilled ball throwers adopted a hierarchical control in which the proximal muscle torques created a dynamic foundation for the entire limb motion and beneficial interaction torques for distal joint rotations.