Abstract / Summary
Regional body composition is associated with athletic performance, but the relative explanatory contributions of trunk and lower-limb lean mass to multi-joint strength and power remain insufficiently understood. This study examined the associations of trunk and lower-limb lean mass with leg-press performance and evaluated their unique and shared explanatory contributions in professional male soccer players. Fifty-one professional male soccer players underwent standardized preseason assessments. Segmental bioelectrical impedance analysis was used to estimate total body fat-free mass, trunk segment lean mass, and lower-limb lean mass. Maximal bilateral leg-press strength and peak mechanical power were assessed using a pneumatic resistance system. Primary analyses included bivariate correlations and two-predictor linear regression models containing trunk and lower-limb lean mass. Because incremental R2 depends on predictor-entry order, reversed-order hierarchical regression, commonality analysis, and dominance analysis were performed as secondary analyses. Additional sensitivity analyses included models adjusted for body-size indicators, combined club/tier grouping and playing position, and log-log allometric models. Total fat-free mass, lower-limb lean mass, and trunk segment lean mass were positively correlated with maximal strength and peak power (all p < 0.001). Bivariate correlation magnitudes did not differ significantly between trunk and lower-limb lean mass for maximal strength (p = 0.498) or peak power (p = 0.067). The two-predictor models explained 48.2% of the variance in maximal strength and 55.8% of the variance in peak power. For maximal strength, the unique contributions of trunk and lower-limb lean mass were 6.9% and 1.6%, respectively, while 39.8% represented shared explained variance. Corresponding dominance shares were 55.5% and 44.5%. For peak power, the unique contributions were 14.2% and 0.1%, respectively, with 41.5% shared variance; dominance shares were 62.6% for trunk and 37.4% for lower-limb lean mass. In secondary adjusted models, the association of trunk segment lean mass with peak power remained statistically significant, whereas its association with maximal strength was attenuated after adjustment for combined club/tier grouping and playing position (p = 0.096). The relative load at peak power was not associated with trunk segment lean mass, lower-limb lean mass, absolute peak power, or maximal strength (all p > 0.19). Log–log allometric sensitivity analyses produced consistent results, with trunk segment lean mass remaining associated with maximal strength and peak power after adjustment for lower-limb lean mass and height. Within the specified two-predictor models, trunk segment lean mass had a larger estimated unique R2 component and received a larger dominance-weight allocation than lower-limb lean mass, particularly for peak power. However, most of the explained variance was shared between the two regional measures. These findings describe statistical associations involving BIA-derived morphological estimates and do not establish a causal, functional, or biomechanical role of trunk musculature.