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The following is a summary of “Examining the changes in strength and mechanical property of dynamic stabilizers of the medial elbow joint through repetitive pitching,” published in the August 2024 issue of Surgery by Ishigaki et al.

The flexor-pronator muscles (FPM) and their common tendon (CT) play a critical role in safeguarding the medial ulnar collateral ligament (MUCL) from elbow valgus stress during the pitching motion, which is particularly demanding in baseball players. This study aimed to explore the impact of repetitive pitching on the strength of the FPM and the stiffness of the CT, which are vital for maintaining elbow joint stability. Researchers recruited fifteen healthy male participants, averaging 21.8 ± 1.3 years, all of whom had over five years of baseball experience. The participants were subjected to a rigorous pitching protocol of 100 full-effort fastball pitches. Investigators measured grip strength to assess the effects of this repetitive motion. They isolated the digital flexion strength of the second, third, and fourth digits before and after the pitching session. The decline in muscle strength was quantified as the rate of change in strength post-pitching relative to the baseline measurements. 

Additionally, CT stiffness was evaluated using a hand-held myotonometer at rest and during grip motion at 50% of maximum voluntary contraction (MVC). Compared to the resting state, the augmentation rate of CT stiffness during grip motion was calculated to determine the tendon’s response to muscle contraction. Statistical analyses were conducted to compare the variations in grip strength, digital flexion strength, and CT stiffness due to the pitching activity. The study also compared the reduction rates among different strength variables and examined correlations between the augmentation rate of CT stiffness and the reduction in muscle strength. The results demonstrated a significant decrease in both grip and isolated digital flexion strengths following the pitching exercise (P < 0.01), with a more pronounced decline observed in the isolated digital strengths compared to grip strength (P < 0.05). Although CT stiffness increased with grip motion relative to rest both before and after pitching (P < 0.001), no significant change in CT stiffness was detected as a direct result of pitching (P > 0.05). However, a moderate correlation was found between a lower augmentation rate of CT stiffness after pitching and a greater reduction in the second digital flexion strength (r = 0.607, P = 0.016). 

This finding suggests that the flexor digitorum superficialis, particularly its influence on the second digit, is pivotal in enhancing CT stiffness, thereby contributing to elbow stability. The study underscores the importance of digital flexion strength in the functional integrity of the FPM, especially in the context of high-demand activities such as pitching.

Source: sciencedirect.com/science/article/abs/pii/S1058274624005767