Date of Award

5-2019

Degree Type

Thesis

Degree Name

Master of Science

Major

Kinesiology

Major Professor

Joshua Weinhandl

Committee Members

Songning Zong, Jeffrey T. Fairbrother

Abstract

Approximately 70-80% of ACL injuries occur via a noncontact mechanism. These noncontact ACL injuries most commonly occur during jumping and/or landing movements. Landing is considered a high-risk movement, as poor landing technique has been linked to ACL injuries via an inability to support rapid changes in acceleration or deceleration concomitantly with high vertical ground reaction forces. The foot and ankle form the initial parts of the lower extremity kinetic chain. Thus, positioning of the foot on the ground may influence the transmission of those forces from the ankle to the knee. Foot progression angle (FPA) is considered a modifiable ACL injury risk variable that can affect both hip, knee, and ankle kinematics and kinetics. The purpose of this study was to examine how introducing a verbal instruction effected the success in practicing and repeating a desired FPA modification during a landing movement, while also examining any changes in knee kinematics and kinetics. Participants were tested over two days and performed 40 drop-landings on day 1 practicing the desired FPA modification. While on day 2, participants were tested to determine if the FPA modification was retained during five more drop-landing trials and five transfer test trials. Results indicated that participant who received the verbal instruction to promote the desired FPA modification significantly increased FPA and knee abduction angle at landing during practice and retention; whereas, the control group did not. No differences were found between or within groups during baseline or transfer tests. This suggest that while the verbal instruction cue was effective in promoting an increase in FPA and reducing some ACL injury risk factors during practice and retention, this cue may only be effective to tasks similar to what was practiced. The transfer test, however, was more dynamic and involved other goal orientated parts of the movement which is similar to dynamic movements as seen in typical ACL injury settings.

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