The Effects of a New ACL-Injury Prevention Device on Knee Kinematics and Hamstring and Quadriceps Co- Contraction: A Pilot Study

Degree project in Master in biomedicine athletic training 30p Supervisor: Ann Bremander, Sofia Brorsson Datum för examinationen 2012-08-24 2 Abstract 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 hamstringquadriceps 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. Abstrakt Bakgrund: Frekvensen av korsbands (ACL) -skador är 3-5 gånger högre hos kvinnliga idrottare jämfört med manliga. Detta kan delvis härledas till en nedsatt hamstring-quadriceps co-kontraktion hos kvinnor med påföljden att rörelsemönster som ökar risken för ACL-skador blir mer vanliga. Att utveckla träningsmetoder som kan förbättra hamstring-quadriceps cokontraktionen och öka knästabiliteten hos kvinnliga idrottare är viktigt. Syfte: Att utvärdera effekterna av ett nytt träningsredskap på hamstring-quadriceps cokontraktion samt undersöka om träning med redskapet kan förändra rörelsemöster i de lägre extremiteterna hos kvinnliga idrottare. Slutsats: Att träna med redskapet stimulerar till ökad hamstring-quadriceps co-kontraktion samt ökar ration av medial-till-lateral co-kontraktion. Träningsredskapets faktiska påverkan på rörelsemönster har ännu inte fastställts