Effects of Medial and Lateral Foot Wedge Placement on Lower Limb Biomechanics and Muscle Activation During the Split Squat: A Randomized Crossover Trial

Background and Objectives: Foot wedges are widely used to modulate ankle alignment in clinical and athletic settings, yet the effects of mediolateral wedge placement on multi-planar lower limb biomechanics during functional unilateral exercises remain poorly characterized. This study aimed to quantify the effects of medial and lateral foot wedge placement on lower limb joint kinematics, muscle activation, and ground reaction forces (GRFs) during the split squat. Materials and Methods: Thirty healthy young adults (12 males, 18 females; 24.5 ± 2.7 years) performed split squats under three randomized conditions using a rigid inclined platform rather than a custom foot orthosis: no wedge (NW), medial wedge (MW), and lateral wedge (LW). Three-dimensional kinematics (Qualisys, 100 Hz), bilateral GRFs (Bertec, 1000 Hz), and surface electromyography (sEMG, 1000 Hz) of the peroneus longus (PL), tibialis anterior (TA), vastus medialis (VM), and vastus lateralis (VL) were recorded synchronously. Repeated-measures ANOVA with Bonferroni post hoc tests and partial eta-squared (η2p) were used (α = 0.05). Results: LW significantly increased PL and VM activation, sagittal-plane range of motion (ROM) at the ankle, knee, and pelvis, and vertical GRF, compared with MW and NW (p < 0.05). MW significantly increased TA and VL activation and reduced sagittal hip ROM (p < 0.05). No significant differences were observed for mediolateral or anteroposterior GRF. Conclusions: Mediolateral foot wedge placement acutely reorganizes lower limb neuromuscular recruitment, joint kinematics, and vertical ground reaction force during the split squat in healthy young adults. These preliminary findings indicate that wedge orientation, applied via a rigid inclined platform, can acutely and selectively modulate muscle activation patterns; any therapeutic or performance applications, however, were not evaluated here and should not be generalized to conventional clinical orthoses without further investigation.