Early Horizontal Deceleration Ability Across Multiple Steps and Approach Speeds in Multidirectional Team Sport Athletes.

Horizontal deceleration ability (HDA) is a critical component of multidirectional team sport performance. This study aimed to identify the interaction between external kinetic and kinematic determinants of HDA across multiple deceleration steps and approach speeds. Nineteen multidirectional team sport athletes completed five maximal horizontal decelerations at 100%, 85%, and 70% of maximal sprint velocity, while three-dimensional ground reaction forces (GRF) and kinematics were captured during the first three deceleration steps. HDA was quantified as the average rate of velocity reduction (i.e., deceleration) within each step and cumulatively across steps 1-3 (early HDA). Greater within-step deceleration significantly correlated with greater mean horizontal GRF (HGRF) and horizontal-to-vertical (H-V) force ratio across all steps and approach speeds (r = 0.56-0.95, p = 0.001-0.013). Mean HGRF in step 1 (β = 0.58-0.83, p = 0.01) and H-V force ratio in step 3 (β = 0.50-0.68, p = 0.01) were the strongest predictors of early HDA. Greater peak hip and knee flexion angles in step 1, and a lower centre-of-mass height, increased anterior foot placement and a more negative shank inclination at touchdown in steps 2 and 3 were associated with greater mean HGRF and H-V force ratio, with stronger associations observed at slower speeds (r = 0.49-0.90, p = 0.001-0.033). These findings indicate that early HDA is underpinned by step-specific kinetic and kinematic strategies. Practitioners should target the attenuation of horizontal force magnitude in step 1 via greater peak hip and knee flexion and enhance horizontal force orientation in later steps by optimising touchdown postures, such as centre-of-mass height, anterior foot placement and shank inclination.