Date of Award

8-2023

Degree Type

Creative Project

Degree Name

Master of Science (MS)

Department

Kinesiology and Health Science

Committee Chair(s)

David Bolton

Committee

David Bolton

Committee

Anne Beethe

Committee

Breanna Studenka

Committee

Sara Harper

Abstract

The anterior cruciate ligament (ACL) rupture is a common sports injury. ACL reconstruction (ACLR) is a necessary treatment for individuals to return to competitive sports. However, a high rate of secondary injury occurs when individuals return to sport. Past research has shown that ACLR impairs physical performance, including reduction of force generate against the floor under the injured leg, changes in the gait pattern, and a loss of knee stability. While structural changes following ACL injury can leave the knee joint less stable, neurophysiological changes following ACL injury represent one potentially important mechanism underlying the performance deficits. Healthy individuals rely on reliable sensory data from the knee joint; however, given the neural adaptations after injuries, evidence suggests that the sensory feedback is altered, and visual processing is increased to compensate for lack of joint sensation. The purpose of the study was to investigate reaction time of ACLR between injured and uninjured leg under limited vision with cognitive challenge. We predicted that an ACLR deficit would be exposed under limited vision and further amplified under cognitive challenge. A total of 55 participants completed the study, including 36 healthy control (CON) and 19 ACLR. (Note: This thesis focused primarily on the ACLR subset of data, however the CON group data were also explored). A modified version of a lean and release task was used to force participants to make a quick decision and avoid stepping into an obstacle with one leg, while using the other leg to step into an available pathway and recover balance. Access to vision was manipulated in this study by using liquid crystal goggles. The visual preview times were manipulated to control how much time participants had to view leg blocks before cable release. The Proactive condition was the easier task, allowing participants to see leg blocks closed or opened and know which step to take before being blinded, and thus it provides a longer preparation time for participants to respond. The Reactive condition, the harder task, blinded participants until 400ms before release. This was designed to elicit a greater challenge with participants had less time to use vision to prepare their response. In each test section, one leg was required to step more frequently (75% of trials), and was referred as “Common step leg”. The other leg that stepped less frequently (25% of trials) in the same section, was referred as “Uncommon step leg”. Three force plates were embedded into the wooden platform. One force plate for each foot when participants were in the starting lean position, and one in the front for the touchdown step after postural perturbation (i.e., cable release from a supported forward lean). Reaction time was recorded as lift-off from the force plate. Data from the ACLR group were analyzed using a 3-way repeated measures 2 × 2 × 2 ANOVA. The results showed that there was no significant 3-way interaction between Injured × Step Leg × Vision. There was no significant difference between Injured and Uninjured leg in reaction time. The Common leg had significantly slower average reaction time than the Uncommon leg. Proactive and Reactive conditions did not significantly differ in reaction time. Overall, the findings of this study highlight ACLR injured and uninjured leg had no different reaction time. These results demonstrated that the limited vision given did not expose performance deficit in individuals with ACLR utilizing the methods presented.

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