THE INFLUENCE OF AGE-RELATED FACTORS ON THE VARUS/VALGUS MOMENT CAPACITY OF THE ELBOW MUSCLES OF BASEBALL PITCHERS

The purpose of this study was to investigate how age-related factors may influence the capacity of the muscles to protect the ulnar collateral ligament during baseball pitching. Three-dimensional marker position data from 30 pitchers (across three age groups) were incorporated into a musculoskeletal modeling framework, using OpenSim software. The effect of pitcher size, strength, and mechanics were represented by independent implementations of scaling factors, isometric muscle force values, and joint angles, resulting in 27 model combinations. For each combination, the maximum isometric varus/valgus moments that could be produced by all of the muscles were calculated and evaluated. While we found minimal age-related changes in joint angles, varus/valgus moments were highly sensitive to muscular strength and pitcher size

KINEMATIC AND KINETIC COMPARISON BETWEEN AMERICAN AND JAPANESE COLLEGE PITCHERS

The purpose of this study was to investigate the kinematic and kinetic differences between American and Japanese baseball pitchers. Kinematic and kinetic data were analyzed for 11 American pitchers (21±2 y, 190±6 cm, 93±9 kg) and 11 Japanese pitchers (21±1 y, 180±6 cm, 81±7 kg) using 3D motion capture (480 Hz). The American pitchers generated faster ball velocities and increased throwing arm kinetics. At foot contact, the Japanese pitchers had longer stride length, greater shoulder external rotation, and greater elbow flexion. At the instant of maximum shoulder external rotation, American pitchers had less elbow flexion and greater pelvis rotation velocity. The kinematic and kinetic differences seen here may suggest a difference in pitching styles or training between cultures

COMPARISON OF MARKER AND MARKER-LESS AUTOMATED MOTION CAPTURE FOR BASEBALL PITCHING BIOMECHANICS

The purpose of this study was to measure baseball pitching kinematics with a marker-less motion capture system and compare the results against marker-based measurements. A sample of 114 pitches were captured at 240 Hz simultaneously with a 9-camera marker-less system and a 12-camera marker system. The pitches were thrown by nine baseball pitchers (age 17.0 ± 4.0 yrs). For each trial, the data were time-synchronized between the two systems using the instant of ball release. Coefficient of Multiple Correlations (CMC) were computed to assess the similarity of waveforms between the two systems. Paired t-tests were used to compare differences between the two systems for 3 temporal and 18 kinematic measurements. The CMC for all eight time series analyzed were excellent, ranging from 0.90 to 0.99. Timing of events between the two systems varied by two frames (0.0083 s) or less. Angular positions differed between the two systems up to 14 degrees. Thus, the marker-based and marker-less motion capture systems produced similar patterns for baseball pitching kinematics. However, based on the variations between the systems, it is recommended that a database of normative ranges should be established for each system individually

What is the true evidence for gender-related differences during plant and cut maneuvers? A systematic review

Purpose Female athletes have a significantly higher risk of sustaining an anterior cruciate ligament (ACL) injury than male athletes. Biomechanical and neuromuscular factors have been reported as the main cause. The purpose of this review was to critically review results of the published literature on gender differences regarding biomechanical and neuromuscular movement patterns during plant and cutting maneuvers. Methods MEDLINE (1966 to December 2008), EMBASE (1947 to December 2008) and CINAHL (1981 to December 2008) searches were performed. The seven studies meeting the inclusion criteria were analyzed. Results Biomechanical gender differences were of questionable clinical relevance. Quadriceps dominance was not found in women. Conclusion The question raises whether ACL injuries during plant and cutting maneuvers are purely gender related and whether women do have to move like men in order to reduce injury risk? Caution is warranted in making inferences as studies were heterogeneous in terms of subject and study characteristics and had low statistical power as a result of insufficient number of subjects. It is advised that future research moves beyond the isolated gender comparison and that larger sample sizes will be included. This review may aid in improving experiments to draw valid conclusions, in order to direct future ACL injury prevention programs, which might need to be more individualized

BASEBALL PITCHING BIOMECHANICS AFTER SURGERY

Baseball pitchers with and without histories of elbow or shoulder surgery were tested with a 240 Hz automated 3D motion capture system. No differences were found between pitchers with history of UCL reconstruction and matched controls. Pitchers tested shortly after returning from UCL repair demonstrated reduced elbow extension, elbow velocity, and shoulder velocity compared to a control group, but it is unknown whether these few kinematic differences resolve with time. Pitchers with a history of SLAP repair produced less shoulder horizontal abduction, shoulder external rotation, and forward trunk tilt than matched controls. The Thoracic Outlet Syndrome case report demonstrated significantly more shoulder abduction after surgery. Thus the ability to return to normal pitching biomechanics after injury depends upon the type of surgery

Physical activity when young provides lifelong benefits to cortical bone size and strength in men

The skeleton shows greatest plasticity to physical activity-related mechanical loads during youth but is more at risk for failure during aging. Do the skeletal benefits of physical activity during youth persist with aging? To address this question, we used a uniquely controlled cross-sectional study design in which we compared the throwing-to-nonthrowing arm differences in humeral diaphysis bone properties in professional baseball players at different stages of their careers (n = 103) with dominant-to-nondominant arm differences in controls (n = 94). Throwing-related physical activity introduced extreme loading to the humeral diaphysis and nearly doubled its strength. Once throwing activities ceased, the cortical bone mass, area, and thickness benefits of physical activity during youth were gradually lost because of greater medullary expansion and cortical trabecularization. However, half of the bone size (total cross-sectional area) and one-third of the bone strength (polar moment of inertia) benefits of throwing-related physical activity during youth were maintained lifelong. In players who continued throwing during aging, some cortical bone mass and more strength benefits of the physical activity during youth were maintained as a result of less medullary expansion and cortical trabecularization. These data indicate that the old adage of “use it or lose it” is not entirely applicable to the skeleton and that physical activity during youth should be encouraged for lifelong bone health, with the focus being optimization of bone size and strength rather than the current paradigm of increasing mass. The data also indicate that physical activity should be encouraged during aging to reduce skeletal structural decay

Biomechanical Basis of Interval Throwing Programs for Baseball Pitchers: A Systematic Review

# Background Interval throwing programs are used in rehabilitation of throwing injuries, especially ulnar collateral ligament injuries. Athletes who are rehabilitating begin by throwing on flat ground progressing through increasing distances, number of throws, and intensity of throwing. If the athlete is a baseball pitcher, the flat-ground throwing phase is followed by pitching on a mound at progressively increased effort. The goal is to build back arm strength and capacity with an emphasis on proper mechanics. # Purpose To determine whether interval throwing progressively builds joint kinetics (specifically, elbow varus torque) to the level required during full-effort baseball pitching. A secondary purpose was to examine the kinematics produced during interval throwing compared to those seen during baseball pitching. # Study Design Systematic Review # Methods Following PRISMA guidelines, PubMed, Embase, Web of Science, SPORTDiscus, and Google Scholar were systematically searched for biomechanical studies of flat-ground throwing and partial-effort pitching in baseball between 1987 and 2023. Studies that reported the biomechanics of either flat-ground throwing, or partial-effort pitching were included in this review. The AXIS tool was used to assess study quality. # Results Thirteen articles met the inclusion criteria. Ten studies were determined to be of moderate quality, while three studies were deemed high quality. Elbow varus torque during partial-effort pitching was less than during full-effort pitching. Elbow varus torque for most flat-ground throws did not exceed full-effort pitching torque. While most studies showed increased elbow varus torque with increased flat-ground throwing distance, the distance at which elbow varus torque matched or exceeded full-effort pitching elbow varus torque was not consistent. As flat-ground throwing distance increased, shoulder external rotation angle and shoulder internal rotation velocity increased. Arm slot (forearm angle above horizontal) decreased as flat-ground throwing distance increased. For varied effort pitching, shoulder external rotation angle, shoulder internal rotation velocity, elbow extension velocity, and ball velocity increased as effort increased. While the front knee extended slightly from foot contact to ball release in full-effort pitching, the front knee flexed slightly during partial-effort pitching. # Conclusions An interval throwing program progressively builds elbow varus torque up to levels produced in full-effort baseball pitching. While differences exist between interval throwing kinematics and pitching kinematics, the patterns are similar in general. # Level of Evidence