Effects of Stroboscopic Visual Feedback Disruption on Postural Control during Dynamic Single-Limb Balance Tasks in Female Athletes After Anterior Cruciate Ligament Reconstruction. A Pilot Study.

Purpose: Athletes involved in a primary anterior cruciate ligament (ACL) injury are predisposed to an increased risk of experiencing a second noncontact ACL injury, despite surgical ACL reconstruction (ACLR) and rehabilitation. Females are also at a high risk, with nearly 4 times as likely as their male counterparts to experience an ACL reinjury. Researchers exploring neuroplasticity after ACLR showed different brain-area activation during repeated cycles of knee flexion and extension and inferred a possible visual-motor control alteration after ACL injury. Such hypothesis would be confirmed by previous biomechanical studies showing a greater degradation in postural control in athletes with ACL when visual information was minimized when compared to healthy control group. However, the approach used in these studies to minimize vision (closed eyes condition) permitted to assess movements that lacked generalizability and sport specificity. The development of visual-disruption technology, such as stroboscopic glasses, that obstruct vision without completely obscuring it has enable to the assessment of visual-motor control during dynamic movements more closely mimicking the dynamic demands of athletic activity. This pilot study explores the effect of stroboscopic visual feedback disruption (SVFD) on postural control during single-limb dynamic balance tasks in female athletes with ACLR. Methods: Seven athletes with ACLR and 7 matched healthy control athletes performed the Drop Landing, the Dynamic Postural Stability Index (DPSI) and 90° Jump Cut, under normal and SVFD conditions. The three single-limb dynamic balance tasks were performed on the Kistler force platform. The Senaptec Strobe glasses imposed the SVFD. For drop landing task, peak of vertical ground reaction force (GRF) and loading rate were measured; for DPSI task, DPSI and balance of the Centre of Pressure (COP) were calculated; for 90° Jump Cut, vertical and lateral peaks of GRF and vertical/lateral ratio (Lat/Ver Max) were measured. Peak Vertical of GRF were expressed relative to body weight. Results. Preliminary data show that ACLR may induce alterations on postural control in all the three tasks investigated. In addition, SVFD via stroboscopic glasses alters parameters investigated in the drop landing, DPSI and 90° Jump Cut. Finally, in the drop landing task, peak of GRF and loading rate decremented more under the SVFD condition in participants with ACLR than in controls. Conclusions. SVFD via stroboscopic glasses can influence postural control during single-limb dynamic balance tasks. The fact that, under the SVFD condition, postural control during the drop landing was found to be reduced more in athletes with ACLR than in controls suggest possible sensorimotor adaptations occurring after ACL reconstruction. Finally, the limited and dynamic vision disruption provided by stroboscopic glasses can allow for the investigation of possible visual-motor control alteration following ACL injury, by means of reproducing in clinical setting motor tasks that more closely mimic the cognitive stress of sport.