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In baseball pitchers, the association of fatigue with overuse injury and decline in pitching performance has been discussed frequently, but the scientific data concerning their interrelationships have been inconsistently reported. The purpose of this narrative review is to summarize and explore the evidence regarding acute changes in pitching biomechanics and performance from repetitive throwing motions among baseball pitchers. Muscle fatigue from repetitive throwing not only decreases muscle output but also disturbs the kinetic chain of baseball pitching. In addition, repetitive throwing can impair the proprioceptive and kinesthetic functions needed for accurate joint position sense in the shoulder and elbow. Consequently, these changes negatively affect ball velocity and pitching accuracy, two critical aspects of overall pitching performance. Moreover, the cumulative loading caused by fatigue contributes to the high prevalence of overuse injuries, particularly in the elbow and shoulder joints. Thus it is important to comprehensively understand the relationships among changed pitching mechanics, deteriorated performance, and musculoskeletal injury originating from muscle fatigue due to repetitive pitching., (© 2023 American Academy of Physical Medicine and Rehabilitation.)

Context: Compared to shoulder and elbow functions, the hip functional characteristics of baseball pitchers have not been fully investigated. Therefore, little is known about the relationship between hip function and pitching performance., Objective: The purpose of this study was to evaluate the characteristics of hip flexibility and strength, focusing on their influences on the ball velocity in baseball pitchers., Design: Descriptive laboratory study., Setting: Laboratory and university baseball facility., Participants: Twenty-three college baseball pitchers., Interventions: Passive hip range of motion (ROM) and isometric hip muscle strength were bilaterally measured. The pitchers threw 20 fastballs at an official pitching distance., Main Outcome Measures: Bilateral hip ROM and strength in flexion, extension, abduction, adduction, and external and internal rotation; the maximal ball velocity., Results: The pivot side showed smaller hip external rotation ROM (P < .01), larger hip internal rotation ROM (P = .03), and greater hip adduction strength (P = .03) than the stride side. The hip extension ROM on the stride side had a negative correlation with the maximal ball velocity (r = -.58, P < .01). The maximal ball velocity (135.3 [4.1] km/h) positively correlated with the hip extension (r = .59, P < .01), flexion (r = .57, P < .01), abduction (r = .55, P < .01), and adduction (r = .55, P < .01) strength on the pivot leg, and the hip flexion (r = .53, P = .01), abduction (r = .67, P < .01), and adduction (r = .46, P = .03) strength on the stride leg., Conclusions: These findings suggest that baseball pitchers do not have marked side-to-side differences in hip flexibility and strength, and that an important fitness factor for increasing ball velocity is not the hip flexibility but the hip muscle strength of both legs.

Aim: The purposes of present study were to investigate quantitatively using functional MR imaging the effect of a series of throwing activities on rotator cuff muscles and to compare the effect of pitching with that of all-out shoulder external rotator exercise as the targeted external rotator muscle group (the infraspinatus and the teres minor)., Experimental Design: MRI measurements after 135 baseball pitches or all-out shoulder external rotator exercise (concentric mode) in each subject's nondominant shoulder., Participants: 6 amateur baseball pitchers., Measures: serial T2-weighted images of rotator cuff muscles were obtained before pitching (or shoulder exercise) and immediately, 30, 60 min, 24, 48, 96 hrs after pitching (or shoulder exercise). T2 relaxation times (T2) at each measurement time were calculated for the rotator cuff muscles., Results: Both the supraspinatus and the external rotator muscle group showed significant T2 elevations until 96 hrs after pitching. The subscapularis also showed significantly increased T2 until postpitching 48 hrs. On the other hand, a significant T2 elevation continued until 60 min after shoulder exercise, but thereafter returned towards the value at rest over the next 24 hrs., Conclusion: Long lasting T2 elevations in rotator cuff muscles would be associated with an increase in each intramuscular water content, and may be attributed to the muscle damage that resulted from eccentric contraction during pitching. This information should serve as a useful complement to shoulder injury prevention for baseball pitchers.

Aim: The purpose of this study was to investigate the effects of various therapeutic measures on the shoulder range of motion (ROM) and muscle cross-sectional area (mCSA) of rotator cuff muscles after baseball pitching., Experimental Design: a mode of therapeutic measures was classified in 4 groups; the control (CON), ice treatment (IT), light shoulder exercise (LSE) and ice treatment with LSE (ILSE) groups. Each therapeutic measure was performed after pitching., Participants: 7 healthy, skilled baseball pitchers., Measures: ROM and mCSA were measured before pitching, immediately after pitching, at the time of the therapeutic measure, and 24 hours after pitching. Shoulder ROM at 90 inverted exclamation mark of abduction included internal rotation (IROM), maximum internal rotation (IMROM), external rotation (EROM) and maximum external rotation (EMROM)., Results: In all groups, both IROM and IMROM were significantly decreased after pitching compared with the pre-exercise values and conversely both EROM and EMROM were significantly increased. The mCSA of all rotator cuff muscles were increased significantly after pitching. For IMROM, ILSE showed a significant recovery at the post-therapeutic measure compared with the others and at 24 hours after pitching compared with IT, respectively. For IROM, both LSE and ILSE showed significant recovery compared with CON at the post-therapeutic measure. For the mCSA of external muscles, ILSE showed a greater decrease at the post-therapeutic measure than the others, and at 24 hours after pitching than CON., Conclusion: This study suggested the possibility that ILSE was more effective to recover ROM and decrease mCSA than the other methods.

Aim: This study was intended as an investigation of the effects of various therapeutic measures on the shoulder strength and muscle soreness after baseball pitching., Experimental Design: participants threw 98 pitches in a simulated single game. The mode of the therapeutic measures after pitching were classified into 4 groups; the control group (CON), the ice treatment group (IT), the light shoulder exercise group (LSE) and the ice treatment with LSE group (ILSE). Each therapeutic measure was applied to the dominant shoulder immediately after pitching., Participants: 7 healthy, skilled baseball pitchers., Measures: both shoulder strength and muscle soreness were measured before pitching, immediately after pitching (Post-P), at the time of the therapeutic measure (Post-TM), and 24 hours after pitching (Post-24 h)., Results: All 4 groups showed shoulder strength losses in shoulder abduction, internal/external rotation with no shoulder abduction or with the shoulder abducted to 90 degrees immediately after pitching. ILSE had greater recovery from Post-P values at Post-TM or Post-24 h than the other methods in all 5 shoulder strengths. On the other hand, the soreness in shoulder internal rotation was increased significantly from Post-P and continued by Post-24 h. Both IT and ILSE had beneficial effects on reducing the shoulder muscle soreness at Post-TM or Post-24 h., Conclusion: The findings of this study suggested that ILSE was the optimal therapeutic measure against decreased shoulder strength or increased shoulder muscle soreness resulting from the repetitive baseball pitching.

The purpose of this study was to investigate the morphology of rotator cuff muscles and shoulder isokinetic strength in adolescent baseball players. Junior high school baseball players were divided into a skilled group (SG, 6 players) and an unskilled group (USG, 6 players), according to their baseball history. The maximal anatomical cross-sectional area, and the volume of the rotator cuff muscles (supraspinatus, external rotators: infraspinatus and teres minor, and subscapularis) were mesured on both sides of their shoulders using magnetic resonance imaging. In addition, isokinetic shoulder internal and external rotation strength (180 and 300°/sec) were measured with the shoulder abducted 90° and the elbow flexed 90° on both sides. The external/internal strength ratio was also calculated. The paired and unpaired t-tests were used to analyze the difference between the throwing and nonthrowing sides and between both groups, respectively. Although the maximal cross-sectional area and the volume of each muscle in the SG tended to be greater than those in the USG on both sides of the shoulder, both groups showed significantly greater subscapularis on the throwing side, regardless of their baseball history. Concerning the shoulder strength and the strength ratio, there were no significant differences between the throwing and nonthrowing sides in each group, or between groups. However, there was a significant correlation between the maximal cross-sectional area of the external rotators and the shoulder external rotational strength (180 and 300°sec) on both sides of the shoulder. This study suggests that remakable characteristics of repetitive throwing activities were not found in the morpholgy of the rotator cuff muscles and the shoulder rotation strength in junior high school baseball players. [ABSTRACT FROM AUTHOR]