Wearable sensor assessment of neuromuscular latency: revealing the strength-timing trade-off in female soccer

BACKGROUND: The high incidence of anterior cruciate ligament (ACL) injuries in female soccer players persists despite widespread preventive interventions. Traditional screening relies heavily on isokinetic torque ratios to assess mechanical joint stability; however, this approach often fails to capture the temporal dynamics of sensorimotor control. Wearable wireless electromyography (sEMG) provides a viable modality to assess these neuromuscular latency deficits. METHODS: Twenty-one female soccer players (age: 17.60 ± 0.87 years) underwent reciprocal concentric isokinetic testing at 60°/s, 180°/s, and 240°/s. The hamstring-quadriceps torque ratio was measured via an isokinetic dynamometer and normalized to body weight. Simultaneously, neuromuscular latency was acquired using a wearable wireless sEMG system (BTS FreeEMG) on the vastus lateralis and semitendinosus. Neuromuscular latency was quantified using a computerized threshold algorithm to determine the agonist-antagonist asynchrony. RESULTS: A significant main effect of angular velocity was observed on neuromuscular latency (p < 0.05), which decreased with increasing velocity, reflecting feed-forward adaptation. A positive correlation emerged between the mechanical H/Q torque ratio and neuromuscular latency, most notably at 60°/s (r = 0.792) and 240°/s (r = 0.681). This indicates a paradoxical latency-strength mismatch, in which players with more favourable H/Q torque ratios exhibit significantly delayed neuromuscular reflexive responses. CONCLUSIONS: Static mechanical symmetry does not guarantee dynamic temporal efficiency. The identified latency-strength mismatch suggests that standard dynamometry may mask critical sensorimotor deficits. The integration of wearable wireless sEMG technology into injury risk screening is essential to capture these temporal asymmetries and ensure that mechanical capacity is matched by rapid neural drive.