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Date Permissions Signed


Date of Award

Spring 2015

Document Type

Masters Thesis

Degree Name

Master of Science (MS)


Health and Human Development

First Advisor

San Juan, Jun G.

Second Advisor

Brilla, Lorraine R., 1955-

Third Advisor

Suprak, David N. (David Nathan)


This purpose of this study was to investigate the acute effects of abdominal fatigue on lower-extremity risk factors of anterior cruciate ligament (ACL) injury. Kinematic variables associated with ACL injury include, decreased knee flexion, increased knee valgus, increased hip flexion and increased hip internal rotation. Additionally, increased quadriceps activation relative to hamstring activation is a risk factor, since the quadriceps place strain on the anterior knee.

Subjects were instructed to sit on the ground, knees bent to 90°, feet secured and their trunk supported by a wedge at 40°. The 40° posture was sustained for as long and as accurately as possible. Pre- and post-test included 3 consecutive drop landings from 30.5 cm. Kinematic data was analyzed from the second pre-test landing, as well as the first and the second post-test landing. Muscle activation data was analyzed from the second pre-test landing, and the second post-test landing.

Statistical analysis was carried out using a one-way repeated measures analysis of variance (ANOVA) for kinematic variables. After fatigue, there was a significant effect of time on knee flexion (p < 0.05). Post-hoc analysis revealed a significant increase between pre-test and both post-test values (p=0.012 and p=0.006, post-test 1 and post-test 2 respectively). There was a non-significant effect of time on knee valgus, hip flexion and hip internal rotation. A paired sample t-test was performed to analyze significant differences in muscle activation patterns after abdominal fatigue. There was a significant increase in quadriceps activation (p < 0.05), and an associated non-significant increase in quadriceps:hamstring ratio. In conclusion, abdominal fatigue may increase the risk of ACL injury in college aged females by altering biomechanical variables associated with ACL injury.





Western Washington University

OCLC Number


Subject – LCSH

Fatigue--Physiological aspects; Abdominal exercises--Physiological aspects; Anterior cruciate ligament--Wounds and injuries; Jumping--Physiological aspects; Women athletes




masters theses




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