Morphological and mechanical properties of the knee extensors between strength training and cross-training...

It remains unclear whether different training modalities, such as strength training (ST) and cross-training (CT), induce distinct musculoskeletal adaptations. In this cross-sectional study, thirty-seven males with at least 2 years of experience in the respective modality participated (ST = 20; CT = 17). After anthropometric assessment, vastus lateralis (VL) muscle architecture and stiffness were evaluated, determining fascicle length (FL), muscle thickness (MT), pennation angle (PA), and shear-wave velocity. Knee extensor peak torque was measured in an isokinetic dynamometer at 60°/s, 180°/s, and 300°/s and normalized to the maximum voluntary isometric contraction. One-repetition maximum (1RM) in the barbell back squat was estimated within three trials with knee flexion standardized at 120° (0°= full extension) and normalized to body mass. Specific tension was calculated based on MT and peak torque. Statistical significance was set at α = 0.05, and Cohen's D effect size was calculated. The intraclass correlation coefficient (ICC) was used to assess muscle architecture reliability. An independent sample t-test revealed a higher training experience (ES = 1.02) and weekly training volume (ES = 0.88; p < 0.05) in ST, whereas CT group showed higher age (ES = 1.09) and PA (ES = 0.66). No differences between groups were found for FL, MT, stiffness, and specific tension (p > 0.05). The peak torque in all tested velocities and 1RM was higher for CT compared to ST (ES = 1.03-1.38; p < 0.05). Interrater reliability ranged from good to excellent (ICC = 0.841-0.992; p < 0.05). Although the cross-sectional design adopted, the current study provides important insights into musculoskeletal differences between training modalities, in accordance with the principle of specificity.