Do Athletes With a Reconstructed Anterior Cruciate Ligament Respond Differently Than Controls to Visual Challenges When Dynamic Postural Stability is Assessed?

Individuals returning to sport after anterior cruciate ligament reconstruction (ACLR) are at an increased risk of sustaining a subsequent ACL injury. It is suspected that increased reliance on visual information to maintain stability may factor into this increased risk. The connection between visual reliance and ACLR is not well understood during dynamic tasks. Examination of the proposed visual reliance may help improve returning to sport standards and reduce subsequent ACL injury risk. A total of 12 ACLR individuals and 12 age- and sex-matched controls completed several trials of a normalized dynamic hop task on both limbs under 3 different visual conditions (eyes open, low visual disruption, and high visual disruption). Stroboscopic eyewear were worn by each participant to disrupt vision during testing. Ground reaction force data were collected during landing. Dynamic postural stability was assessed using 2 separate calculations: dynamic postural stability index and time to stability. No significant statistical interactions or group differences were observed. The stroboscopic eyewear did increase the medial-lateral stability index from the eyes open to the low visual disruption condition (P < .05). These findings suggest that ACLR individuals do not rely on visual information more than controls during a dynamic hop task.

Acceleration and Jerk After a Jump Stabilization Task in Individuals With and Without Chronic Ankle Instability.

Studies have demonstrated that individuals with chronic ankle instability (CAI) have diminished dynamic stability. Jerk-based measures have been utilized to examine dynamic balance because of their ability to quantify changes in acceleration and may provide an understanding of the postural corrections that occur during stabilizing following a jumping task. The purpose of this study was to compare acceleration and jerk following a jump stabilization task between individuals with CAI and the uninjured controls. Thirty-nine participants volunteered to participate in this case control study. Participants completed a jump stabilization task requiring them to jump off 2 feet, touch a marker set at 50% of their maximal vertical jump height, land on a single limb, and maintain balance for 3 seconds. Acceleration was calculated as the second derivative, and jerk was calculated as the third derivative of the displacement of the resultant vector position. Participants with CAI had greater acceleration (mean difference = 55.6 cm/s2; 95% confidence interval, 10.3 to 100.90; P = .017) and jerk compared with the uninjured controls (mean difference = 1804.5 cm/s3; 95% confidence interval, 98.7 to 3510.3; P = .039). These results suggest that individuals with CAI made faster and more frequent active postural control corrections to regain balance following a jump compared with the uninjured controls.