Sensory Reweighting and Neuromuscular Decoupling in Athletic Diagnostics: A Multi-Modal Smart Sensing Analysis of Knee Isokinetics and Postural Sway

Background: The diagnostic integration of complementary smart sensing technologies offers significant advantages for functional neuromuscular profiling and athletic screening. This study investigated the biomechanical coupling between unilateral postural stability and multi-speed isokinetic knee strength in thirty physically active males (mean age: 24.9 ± 3.97 years, body mass: 84.8 ± 10.50 kg) using a multi-modal smart-sensing framework. Methods: Postural sway kinematics were captured on an AMTI high-frequency force platform (1000 Hz) during single-leg stance under Eyes Open (EO) and Eyes Closed (EC) conditions. Multi-angular muscular torque, total work, and concentric Hamstrings-to-Quadriceps (H/Q) ratios were evaluated via a computerized Biodex System 4 dynamometer across three angular velocities (60°/s, 180°/s, and 240°/s). Repeated-measures Linear Mixed-Effects Models (LMM) with Torque × Condition interaction terms and False Discovery Rate (FDR) corrections were applied to assess sensory reweighting and torque–sway interactions. Results: Visual deprivation elicited a substantial sensory reweighting response, with Center of Pressure path length nearly tripling from EO to EC across both limbs (left: 1655.4 ± 437.6 mm vs. 4772.3 ± 1929.9 mm, p < 0.001, Cohen’s d = 2.23; right: 1641.4 ± 412.6 mm vs. 4885.9 ± 1968.0 mm, p < 0.001, Cohen’s d = 2.28). Concentric Hamstrings-to-Quadriceps (H/Q) ratios increased progressively with angular velocity, rising for the left limb from 0.49 ± 0.05 (60°/s) to 0.60 ± 0.10 (180°/s) and 0.64 ± 0.10 (240°/s), and for the right limb from 0.51 ± 0.08 (60°/s) to 0.59 ± 0.11 (180°/s) and 0.64 ± 0.11 (240°/s). Under EO, maximal extensor torque (60°/s) showed no correlation with postural sway (r = +0.007, p = 0.969); however, during EC, torque demonstrated a significant positive correlation with sway (r = +0.546, p = 0.0018). LMM confirmed a significant Torque × Condition interaction (β = +21.13 mm/(N·m), p < 0.001), indicating divergence in postural control dynamics under sensory challenge. Bilateral strength asymmetries exceeding 10% were prevalent in 30.0% to 46.7% of participants depending on velocity. Conclusions: These empirical findings confirm a sensory-dependent neuromuscular decoupling: high maximal knee strength does not inherently confer somatosensory stabilization when visual feedback is occluded. The established exploratory four-quadrant screening framework provides an objective screening model to detect functional strength–stability mismatches and guide individualized athletic conditioning.