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The Effects of a New ACL-Injury Prevention Device on Knee Kinematics and Hamstring and Quadriceps Co-Contraction: A Pilot Study
Halmstad University, School of Business and Engineering (SET).
2013 (English)Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Background: The incidence of anterior cruciate ligament (ACL) –injury is 3-5 times greater in female athletes compared to male athletes. This may be partially attributed to lower levels of hamstring-quadriceps co-contraction in females with subsequent knee kinematics that increases risk of ACL-injury. Finding training methods that improves co-contraction and increases knee stability is important.

Objectives: To evaluate the effects of a new device on hamstring-quadriceps co-contraction and to investigate if training with the device can alter knee kinematics in female athletes.

Study design: Controlled experimental study design with repeated measures.

Method: Twenty soccer and floor ball athletes were measured with electromyography (EMG) for hamstring-quadriceps co-contraction while performing squats with and without the device. Thirteen athletes also underwent three-dimensional kinematic analyses, measuring knee abduction angles (at initial ground contact and peak angle) during a drop jump, before and after a six week intervention period with the device. Friedman’s test and Wilcoxon signed rank test was used to assess differences and effect sizes (ES) were calculated.

Results: Co-contraction was consistently larger on the device (medial side: p<0.001, ES=0.88; lateral side: p<0.001, ES=0.80) and the ratio of medial-to-lateral co-contraction increased (p=0.001, ES=0.79). In the kinematic analysis low adherence rates amongst our subjects meant that the effects of the device on kinematics could not be measured.

Conclusion: Performing squats with the new training device stimulates increased hamstring-quadriceps co-contraction and increases the ratio of medial-to-lateral co-contraction. The effects of the device on knee kinematics have yet to be determined.


Place, publisher, year, edition, pages
2013. , 25 p.
Keyword [en]
Hamstring-quadriceps co-contraction; dynamic valgus; knee abduction, anterior cruciate ligament (ACL) injury; injury prevention, gender differences
National Category
Sport and Fitness Sciences
URN: urn:nbn:se:hh:diva-20561OAI: diva2:585799
Subject / course
Biomedicine Targeting Physical Education
Life Earth Science
Available from: 2013-01-10 Created: 2013-01-08 Last updated: 2013-01-10Bibliographically approved

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Andersson, Niklas
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