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The following is a summary of “Influence of Flexor Pronator Muscle Contraction on Medial Elbow Joint Space Distance in High School Baseball Players: A Cross-Sectional Study,” published in the February 2025 issue of Journal of Shoulder and Elbow Surgery by Suzuki et al. 

The flexor pronator muscles (FPMs) play a critical role in stabilizing the elbow joint, particularly for baseball players who repeatedly perform high-intensity throwing motions. However, the specific impact of various types of FPM contractions on the medial joint space (MJS) in high school baseball players remains underexplored. This study sought to investigate the effects of individual and combined contractions of the FPMs—including the flexor carpi ulnaris (FCU), flexor digitorum superficialis (FDS), pronator teres (PT), palmaris longus, and flexor carpi radialis (FCR)—on the MJS in this population. The hypothesis was that certain muscle contractions, particularly those involving the FDS, PT, and FCR, would lead to a narrowing of the MJS. The study included 36 high school baseball players who completed nine different contraction tasks involving the FPMs, including a resting state, in a randomized order. 

The MJS was measured using ultrasound imaging and compared with the measurements taken during the resting state. To analyze the data, the Friedman test, a repeated-measures one-way analysis of variance (ANOVA), was performed, followed by Steel’s test for multiple comparisons. All statistical analyses were conducted using EZR software, with a significance level set at 5%. The results of the repeated-measures one-way ANOVA and the Friedman test revealed significant differences among the nine contraction tasks (p < 0.001). Using Steel’s test, a notable reduction in the MJS was observed compared to the resting state (mean ± SD = 4.8 ± 1.2 mm). Specifically, contraction tasks involving the PT (mean ± SD = 4.0 ± 1.0 mm, p = 0.017), the combination of FDS and PT (mean ± SD = 4.0 ± 1.1 mm, p = 0.007), and the combination of FCU, FDS, and PT (mean ± SD = 4.0 ± 1.1 mm, p = 0.008) demonstrated significant reductions in MJS. 

These findings highlight that the contraction of the PT, in particular, plays a significant role in reducing the MJS, emphasizing its critical involvement in elbow joint stability. This study contributes to understanding the biomechanical impacts of FPM contractions on the elbow joint in baseball players and underscores the potential importance of PT in maintaining elbow integrity. Future research is warranted to explore whether these findings can be applied in developing effective injury prevention and rehabilitation strategies for high school baseball players, particularly for those at risk of elbow-related injuries.

Source: linkinghub.elsevier.com/retrieve/pii/S1058274625000990