ABSTRACT
Introduction: Trunk and shoulder strength are consistently shown to be involved in performance limitations, as well as contributing to stability, power output, and reducing the risk of injury. Although their biomechanical interaction is a critical aspect for athletes, there is limited research on the relationship between trunk and shoulder strength in sports where upper body mechanics are critical for optimal performance. Purpose: This study examined the differences and relationships between trunk rotational strength and shoulder rotational strength among athletes participating in mixed martial arts (MMA), tennis, swimming, and baseball. Methods: Maximal voluntary contraction tests were performed to evaluate strength of 39 professional adult male athletes from disciplines of MMA (n = 6), tennis (n = 11), swimming (n = 11) and baseball (n = 11). Peak force data were used in sports comparison and relationship analysis between trunk and shoulder rotation strength parameters. Results: The findings revealed a complex and significant relationship between trunk and shoulder strength, with unique patterns for each athletic discipline. Tennis players exhibited a strong correlation between trunk bilateral differences and internal shoulder rotation, while other disciplines demonstrated a more balanced use of trunk asymmetry. Swimmers displayed the best interactions between trunk and shoulder overall, emphasizing the aquatic environment's biomechanical demands. In MMA, the strongest correlation was between shoulder internal and external rotation with the trunk, mainly due to the number of defensive movements in addition to offensive ones. Baseball pitchers showed a significant correlation between internal/external shoulder rotation strength ratio and trunk asymmetry. Conclusion: While no differences in peak force variables were found, unique relationships between trunk and shoulder rotational performance were discovered. The results suggest a long-term sport-specific adaptation of the trunk-shoulder interaction in sports that require upper limb power movements. It seems, that the relationship between the various parameters of trunk and shoulder was influenced by the movement stereotype of each sport. Therefore, recognition of sport-specific interactions is critical to the development of effective training programs that enhance performance and potentially reduce injury risk in different sports. Researchers and practitioners should focus on longitudinally monitoring fluctuations in TRS and SRS relationships throughout each sport season and examining potential associations with injury incidence.
ABSTRACT
In light of previous research highlighting the prevalence of asymmetries in soccer players and possible links to injury risks, there is a crucial gap in the biomechanical understanding of complex relationships between lower extremity and trunk asymmetries in elite soccer players. The purpose of this study was to investigate the level, relationships, and differences among twelve different parameters of strength, morphological, and neuromuscular asymmetries in elite soccer players. Methods: Elite male soccer players (n = 25, age 21.7 ± 3.9 years) were tested in the following tests: bilateral fluid distribution, hip flexor range of motion, postural stability, isokinetic strength of knee extensors and flexors, isometric lateral trunk rotation strength, eccentric strength of knee flexors, isometric bilateral strength of hip adductors, and vertical ground reaction force in counter-movement jump-free arms, counter-movement jump, squat jump, and drop jump tests. One-way ANOVA, Pearson's coefficient (r), and partial eta squared (η p 2) were used for data analysis. Results: Significant differences in asymmetries were found in elite soccer players (F11,299 = 11.01, p < .01). The magnitude of asymmetry over 10% was in postural stability and drop jump parameters. The lowest magnitudes of asymmetries were in the fluid distribution of the lower limbs and the vertical ground reaction force during the take-off phase in squat jumps. The highest asymmetries between the dominant and non-dominant sides were found in postural stability and drop jump. A total of eleven significant correlations (p < 0.05, r = 0.41-0.63, R2 = 0.17-0.40) were detected between the analyzed asymmetries in elite soccer players. The lateral trunk rotation asymmetries were significantly correlated to vertical ground reaction force asymmetries and knee extensors. Conclusion: Long-term exposure in elite soccer leads to unilateral biomechanical loading that induces abnormal strength and morphological adaptations in favor of the dominant side while linking lower limb and trunk strength asymmetries. By unraveling these complex relationships, we strive to contribute novel methods that could inform targeted training regimens and injury prevention strategies in the elite soccer community. The data should encourage future researchers and coaches to monitor and develop trunk strength linked to lower body kinematics.
