Kinematic characteristics associated with right-side cross-step blocking performance in elite youth male volleyball players: a cross-sectional study

Background Effective blocking is an important contributor to match outcomes in volleyball. However, the phase-specific kinematic characteristics associated with approach velocity (AV) and jump height (JH) during cross-step blocking have not been comprehensively examined. This study aimed to identify the kinematic variables associated with AV and JH during right-side cross-step blocking in elite youth male volleyball players. Methods This cross-sectional study included 22 elite youth male volleyball players performing right-side cross-step blocking under standardized conditions, with each participant’s highest-rated eligible trial selected for kinematic analysis based on assessments by two volleyball experts. Kinematic data were recorded using two high-speed video cameras and processed with Fastmove Motion-3D software. Correlation analyses were conducted to identify kinematic variables associated with AV and JH, with p values adjusted using the Benjamini–Hochberg false discovery rate (FDR) procedure. Variables that remained significant after FDR correction were subsequently examined using univariable linear regression, followed by parsimonious multivariable linear regression where appropriate. Results For AV, five kinematic variables remained significantly associated with AV after FDR correction: third-step right hip linear velocity (R-LVH-TS, r = 0.80, FDR q < 0.001), second-step left knee angular velocity (L-AVK-SS, r = 0.71, FDR q = 0.003), second-step left hip linear velocity (L-LVH-SS, r = 0.62, FDR q = 0.015), second-step foot displacement (SFD, r = 0.61, FDR q = 0.015), and third-step right knee linear velocity (R-LVK-TS, ρ = 0.67, FDR q = 0.007). In univariable linear regression models, these variables explained 63.5%, 50.7%, 38.8%, 37.8%, and 24.7% of the variance in AV, respectively. The parsimonious multivariable regression model including third-step right hip linear velocity and second-step left knee angular velocity explained 67.7% of the variance in AV. In this model, only third-step right hip linear velocity remained independently associated with AV. For JH, take-off-phase center-of-mass (CoM) linear velocity was the only variable that remained significantly associated with JH after FDR correction (LVCoM-TO, ρ = 0.65, FDR q = 0.025), explaining 57.9% of the variance in JH in the univariable regression model. Conclusions The findings suggest that AV during right-side cross-step blocking is related to phase-specific lower-limb kinematic coordination during second- and third-step phases, especially right hip linear velocity during the third step. JH is associated with greater CoM linear velocity during take-off. In practice, third-step right hip linear velocity and take-off-phase CoM linear velocity may serve as biomechanical reference points for evaluating approach and jump performance, respectively.