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No description available.

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.

The broad aim of this thesis was to progress understanding of the neuromechanics of joint stability and injury mechanisms by investigating the interactions between neuromuscular function and balance perturbations as well as the influence of sex and fatigue on these variables. Knee extensor (KE) and plantar flexor (PF) isometric strength parameters (maximum voluntary torque (MVT), explosive voluntary torque (EVT)) were related in young healthy adults. EVT of KE and PF were correlated at 4/5 time points during the rising torque-time curve for all absolute (r = 0.488-0.755) and relative (to body mass (BM) (r = 0.517-0.669) and MVT (r = 0.353-0.480)) expressions of EVT. These results suggest that KE and PF function is related for both maximum and explosive torque. Males were stronger for KE (+89%) and PF (+55%) than females. Males also displayed greater EVT at all time points in KE (+57-109%) and at 50-150 ms in PF (+33-52%). When MVT and EVT were normalised to BM, males continued to be stronger at all time points in KE (+23-60%) and from 100-150 ms (18-20%) in PF. No sex differences were found when EVT was normalised to MVT. Furthermore, sex differences were discovered in muscle morphology. Females had a smaller knee flexor (KF):KE size ratio, a proportionately small sartorius (SA) and gracilis (GR) and a proportionately larger vastus lateralis (VL), potentially predisposing females to greater risk of ACL injury. Females had a larger biceps femoris long head (BFlh) as a proportion of the KF than males, which may contribute to the higher risk of hamstring strain injury (HSI) in males. Regarding explosive performance and perturbation response, explosive PF torque had a weak to moderate correlation with COM displacement (COMD) from 400-500 ms (r = -0.346 to -0.508) and COM velocity (COMV) from 300-500 ms (r = -0.349 to -0.416), with weaker correlations between explosive KE torque and COMV at 400 ms (r = -0.381 to -0.411) but not with COMD. These findings suggest that greater explosive torque results in better control of the COM in response to unexpected perturbations. The effects of football simulated fatigue on these factors resulted in reduced maximal KF and KE torque. However, football simulated fatigue was not found to reduce EVT of either muscle group, or explosive H/Q ratio. Football simulated fatigue resulted in impaired balance response to unexpected perturbation in the posterior but not the anterior direction.

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Purpose: ACL-injuries are comon in female soccer. Preventative intervention has a positive effect on its prevalence. The purpose of this study is to investigate active leader experience of prophylactic neuromuscular exercise and its effect on ACL-rupture in female soccer between 14-16 years. Design and method: A descriptive, qualitative design using semi-structured interviews with active soccer coaches. Qualitative content analysis was employed for data interpretation.  Results: The results contain six categories and fourteen subcategories showing the leaders all had knowledge of neuromuscular exercise (NMT); but that a variety of factors lead to low implementation. Knowledge of NMT was insufficient to support full implementation coupled to a lack of guidelines describing how NMT should be implemented and why. Knowledge of NMT did not reach key people. Courses should include more detailed information with guidance on the design of training, with more information about prophylactic exercise and NMT. Conclusions: Leaders are aware of NMT but there is a lack of knowledge. It is important to supplement course material to include NMT. More guidelines, education and information needs to reach key people for sustainable implementation. Without necessary education, it will not be possible to achieve sufficient compliance to ensure a significant decrease in ACL-ruptures.

Title: Instrumental Gait Analysis in the ACL Patient Aim: to present an up to date review on the topic of instrumental analysis of straight ahead gait on a plain surface (both over-ground and on a treadmill) in ACL patients (both deficient and reconstructed). A second aim is to introduce the clinician (especially in the field of physiotherapy/rehabilitation) to the topic of gait analysis and its specific use for the ACL patient. Methods: a systematic review on the topic Results The review answers the questions of what instrumentation, phases of gait and variables is best to use/measure for clinical purposes. It also identifies and discusses three main gait strategies used by ACL patients: quadriceps avoidance, knee stiffening, pivot shift avoidance. Keywords: gait, analysis, walking, clinical, instrumental, anterior cruciate ligament, ACL, deficient, reconstruction, injury