LE3 .A278 2017

2017

Landry, Scott

Acadia University

Bachelor of Kinesiology

Honours

Kinesiology

Kinesiology

The anterior cruciate ligament (ACL) serves as a major stabilizer of the knee, and injury to this ligament is one of the most devastating knee injuries in sport. The rehabilitation of this injury can result in expensive surgery and extensive recovery time. Individuals that sustain ACL injuries may also be more likely to develop secondary complications later in life such as knee osteoarthritis. Non-contact ACL injuries account for 70-80% of all ACL injuries and common non-contact injury mechanisms include quick changes in direction and jump landings. The sex disparity of this injury is of research interest as females are 2-8 times more likely to sustain a non-contact ACL injury compared to males after the onset of puberty. The purpose of this study was to examine the effect of sex (male versus female) and leg dominance (dominant versus non-dominant) on lower body neuromuscular activation patterns, along with hip and knee joint biomechanics during the post-contact phase (200ms) of single leg drop jump landings. Adduction and internal rotation at the hip may jeopardize the stability of the knee resulting in knee valgus, which is a risk factor for ACL injury. Recent research has focused on the role that the hip musculature, specifically the gluteus medius, may have on the stability of the knee during dynamic movement. Asymmetries between limbs have also been noted to increase one’s risk of lower body injury. Understanding biomechanical and neuromuscular differences between the dominant and non-dominant leg and between sex during jump landings could provide insight into preventing ACL injuries. A total of 37 elite level athletes participated in the present study; 19 post-pubescent males (age = 21.26 ±2.21 years, height = 1.82 ±0.06 m, weight = 84.13 ±10.95 kg), and 18 post-pubescent females (age = 19.72 ±1.99 years, height = 1.69 ± 0.08 m, weight = 65.72 ± 9.22 kg). A 12-camera motion capture system, 3 force plates, and 16 wireless electromyography sensors were used to capture gluteus medius, rectus femoris, medial hamstring, and lateral hamstring activation patterns along with kinematic and kinetic data of the hip and knee during a single leg drop jump protocol. This protocol was developed within the comprehensive protocol from the John MacIntyre motion Laboratory of Applied Biomechanics (mLAB), which enables longitudinal data to be collected for the purpose of identifying non-contact ACL injury risk factors. A two-way mixed model ANOVA was used to test for a between group (male versus female), a within group(dominant versus non-dominant leg), and an interaction (sex by leg) effect for the neuromuscular activation magnitudes and hip and knee joint angles and moments. Bonferroni corrected pairwise comparisons were performed on the data when an interaction effect was identified for a particular measure. The results demonstrated that compared to males, females demonstrated increased rectus femoris activation and altered hip and knee biomechanics. The dominant leg produced greater hip adduction angles and internal rotation moments compared to the non-dominant leg which may compromise the stability of the knee. Females also demonstrated greater internal hip abduction moments during the dominant leg single leg drop jump compared to the non-dominant leg drop jump. These findings provide insight into the sex bias of this injury and suggest that leg dominance may have a role as well.

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https://scholar.acadiau.ca/islandora/object/theses:2070