Direction-led temporal control and expertise-based load redistribution in 45° cutting: an SPM-based analysis of ankle mechanics.

Rapid change-of-direction movements are essential in basketball and other multidirectional sports and impose substantial mechanical demands on the ankle. However, how cutting direction and athletic level jointly influence ankle-centered biomechanics across the stance phase remains insufficiently characterized. This study aimed to quantify the direction- and athletic-level-associated differences in lower-limb kinematics and kinetics during 45° cutting and to determine whether between-group effects are expressed primarily in internal joint mechanics rather than external ground reaction forces. Twenty-four healthy males (12 professional basketball athletes and 12 collegiate students) performed 45° lateral cutting (LC) and crossover cutting (CC) at a controlled approach speed (4.0 ± 0.2 m/s). Three-dimensional kinematics (250 Hz) and ground reaction forces (1,000 Hz) were synchronously recorded using motion capture and a force platform. Discrete outcomes were compared using independent-samples t-tests, and time-continuous waveforms were assessed using one-dimensional statistical parametric mapping with a mixed-design ANOVA (group × task). Cutting direction produced significant stance-phase effects across large portions of stance for ground reaction forces, ankle joint forces, and ankle joint moments, whereas ground reaction force waveforms showed no group × task interactions. Athletic-level differences were task-specific and time-localized. Professional athletes exhibited smaller non-sagittal ankle range of motion (adduction/abduction during LC; internal/external rotation during CC) and greater ankle plantarflexion moments. Significant group × task interactions were observed in frontal- and transverse-plane ankle kinematics, and the ankle adduction/abduction moment differed between groups only during CC within restricted stance intervals. These findings indicate that 45° cutting biomechanics are predominantly direction-dependent, whereas athletic level influences phase-specific modulation of ankle motion and joint moments. Athletic-level effects were primarily expressed in internal joint mechanics rather than external ground reaction forces. This information may support more targeted biomechanical assessment and training strategies for multidirectional sports.