Postural control and leg muscle activation in athletes who underwent anterior cruciate ligament reconstruction and healthy controls: A preliminary study on acute responses to whole-body vibration

BACKGROUND: Anterior cruciate ligament reconstruction (ACL-R) restores mechanical knee stability, but neuromuscular and balance deficits often persist. Whole-body vibration (WBV) has been widely studied as a method to improve postural control and stimulate the neuromuscular system. However, the acute effects of WBV following ACL-R on postural control and muscle activation remain unclear. METHODS: Twenty-seven competitive athletes (13 ACL-R, 14 healthy athletes) underwent static and dynamic balance assessments using centre of pressure (CoP) measures synchronised with surface electromyography (sEMG) recorded in the vastus lateralis, biceps femoris, tibialis anterior, and lateral gastrocnemius muscles during single- and double-leg, in static and dynamic conditions. All participants completed a single WBV session. FINDINGS: Post-WBV, healthy controls showed reduced CoP sway during static single-leg (p < 0.05), while ACL-R participants exhibited no significant change (p > 0.05). In dynamic double-leg with eyes closed, ACL-R participants showed increased medio-lateral sway (p < 0.05). ACL-R group demonstrated reduced sEMG activity in proximal muscles (particularly biceps femoris) during double-leg (p < 0.05), and controls in distal muscles during single-leg tasks (tibialis anterior, lateral gastrocnemius p < 0.05). INTERPRETATION: WBV acutely influenced postural stability, improving static balance in healthy controls but increasing dynamic sway in ACL-R individuals, suggesting a recalibration of the sensorimotor set. In addition, WBV modulated biceps femoris activation in the operated leg, reducing over-activation, indicating a specific neuromuscular response. These preliminary findings highlight persistent neuromechanical alterations in ACL-R athletes and may support the potential integration of WBV exercise into rehabilitation programs designed to restore balance control.