The Effects and Influences of Localized Muscle Vibration of the Hamstring Muscles on Landing Biomechanics Related to Anterior Cruciate Ligament Injury (2023)
Undergraduate: Sam Duggan
Faculty Advisor: Troy Blackburn
Department: Exercise & Sport Science
Anterior Cruciate Ligament Reconstruction (ACLR) utilizing a hamstring tendon autograft causes dysfunction of the hamstring muscles (e.g. asymmetries in explosive strength and decreased knee flexor strength) and poor landing biomechanics which increase the risk of secondary ACL injury. The hamstrings resist anterior tibial translation, the primary loading mechanism of the ACL. Local muscle vibration (LMV) enhances function of the quadriceps following ACLR and may have a similar effect on hamstring function. Landing biomechanics including knee valgus angle, valgus moment, and flexion angle during singe-leg (SL) landings are influenced by hamstring muscles and are strong predictors of secondary ACL injury. The purpose of this study was to determine if LMV applied to the hamstrings improved landing biomechanics linked to ACL injury risk. We failed to enroll a sufficient number of ACLR patients, so healthy controls were evaluated instead. Participants completed a SL jump landing from which knee valgus angle, valgus moment, and flexion angle were assessed before and after a control or LMV intervention during sessions separated by 1-14 days. A one-way repeated measures ANCOVA compared change scores between interventions, controlling for average pre-test scores from both sessions, but revealed no significant effects of LMV on the biomechanical outcomes (P = 0.393-0.740). Healthy controls could have a ceiling effect that prohibits significant improvement post vibration. The use of 1 session of LMV was likely insufficient, prolonged vibration should be used for larger effect sizes. Future research should investigate LMV to improve landing biomechanics in those with deficient hamstring muscles following ACLR.
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