Både biomekaniska och neuromuskulära faktorer hos kvinnliga fotbollsspelare har visat sig påverka risken att drabbas av främre korsbandsskador. Obalanserad muskelaktivering kring knäleden har visat sig påverka ledstabiliteten. Syftet med studien var därför att undersöka sambandet mellan muskelaktiveringen i vastus medialis och vastus lateralis i relation till valgusvinkel hos fotbollsspelande kvinnor vid ett drop-landingtest. Studien gjordes i samarbete med det finska företaget Fibrux OY, som har utvecklat en bärbar sEMG-apparatur. I studien deltog 15 kvinnliga fotbollsspelare som under en drop-landing bar sEMG-elektroder på vastus medialis och vastus lateralis samtidigt som rörelsen filmades framifrån för att möjliggöra 2D analys av valgusvinkel. Resultaten visar en tendens till samband mellan muskelaktiveringsgrad och valgusvinkel (r=0,51) (p>0,05) samt ett svagt samband mellan muskelaktiveringsordning och valgusvinkel (r=0,32) (p>0,05). Det svaga sambandet gör att det inte går att utesluta att det är andra muskler kring knäleden som har större inverkan på ledstabiliteten. Framtida forskning bör utföras på en större population och rikta sig på prospektiv epidemiologisk forskning eftersom det är den enda studiedesignen som avslöjar vilka variabler som kan associeras med risken att drabbas av en knäskada. / Both biomechanical and neuromuscular factors affect the risk of suffering an ACL rupture among female soccer players. Unbalanced muscle activation around the knee has been found to affect the joint stability. The aim of this study was therefor to investigate the muscle activation in vastus medialis and vastus lateralis in relation to dynamic valgus among female soccer players. The study was conducted in cooperation with the Finnish company Fibrux OY, who has developed a portable sEMG testing equipment. The participants consisted of 15 female soccer players who were tested with sEMG electrodes on vastus medialis and vastus lateralis during a drop-landingtest that was filmed to enable 2D analysis of valgus angle. The results show a tendency to correlation between the activation ratio and valgus(r=0,51) (p>0,05), and between activation delay in vastus medialis and valgus (r=0,32) (p>0,05). But both correlations lack significance. The results could be explained by that there might be other muscles around the knee at that affects the joint stability even more than vastus lateralis and medialis do. Future studies should be conducted with larger sample size and focus on prospective epidemiological research because that is the only study design that reveals what variables can be associated with the risk of suffering a knee injury.

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.

Anterior cruciate ligament (ACL) injuries are a major problem among female athletes. Screening for the risk of ACL injuries tends to focus on landing tasks, which may be limited in sports where changing direction is the main action involved in noncontact ACL injuries such as soccer. To investigate whether there is a relationship between single-legged landing (SLL), cutting (90° cuts), and pivoting (180° turns) in terms of the characteristics of dynamic valgus. Study Design: Controlled laboratory study. Methods: Twenty female soccer players (mean ± SD: age, 21.0 ± 3.9 years; height, 1.65 ± 0.08 m; mass, 58.4 ± 6.4 kg) performed a minimum of 6 trials of SLL from a 0.3-m drop height and cutting and pivoting all on the right leg. Kinematics and kinetics were calculated from 3-dimensional motion analysis. Results: Strong correlations were found for peak knee abduction angles between tasks (R = 0.63-0.86, P < .01), whereas only moderate correlations between SLL and cutting (R = 0.46, P < .05), cutting and pivoting (R = 0.56, P < .05), and SLL and pivoting (R = 0.43, P > .05) were found between tasks for peak knee abduction moments. Conclusion: The results suggest that female athletes who exhibit poor SLL mechanics perform the same during various changing direction tasks. Clinical Relevance: The results support the use of existing screening tests that involve landing tasks to identify at-risk athletes for noncontact ACL injuries.