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Introduction: Cutting is an important skill in team-sports, but unfortunately is also related to non-contact ACL injuries. The purpose was to examine knee kinetics and kinematics at different cutting angles. Material and methods: 13 males and 16 females performed cuts at different angles (45 , 90 , 135 and 180 ) at maximum speed. 3D kinematics and kinetics were collected. To determine differences across cutting angles (45 , 90 , 135 and 180 ) and sex (female, male), a 4 2 repeated measures ANOVA was conducted followed by post hoc comparisons (Bonferroni) with alpha level set at a 0.05 a priori. Results: At all cutting angles, males showed greater knee flexion angles than females (p < 0.01). Also, where males performed all cutting angles with no differences in the amount of knee flexion 42.53 ± 8.95 , females decreased their knee flexion angle from 40.6 ± 7.2 when cutting at 45 to 36.81 ± 9.10 when cutting at 90 , 135 and 180 (p < 0.01). Knee flexion moment decreased for both sexes when cutting towards sharper angles (p < 0.05). At 90 , 135 and 180 , males showed greater knee valgus moments than females. For both sexes, knee valgus moment increased towards the sharper cut- ting angles and then stabilized compared to the 45 cutting angle (p < 0.01). Both females and males showed smaller vGRF when cutting to sharper angles (p < 0.01). Conclusion: It can be concluded that different cutting angles demand different knee kinematics and kinet- ics. Sharper cutting angles place the knee more at risk. However, females and males handle this differ- ently, which has implications for injury prevention.

Background: Retention of movement technique is crucial in anterior cruciate ligament (ACL) injury pre- vention programs. It is unknown if specific instructions or video instructions result in changes in kine- matic and kinetic measures during a relatively short training session, and in a retention test one week later. Hypothesis/Purpose: The purpose was to determine the effects of verbal external focus (EF), verbal inter- nal focus (IF) and video instructions (VI) on landing technique (i.e. kinematics and kinetics) during train- ing and retention. Study Design: Randomized Controlled Trial. Methods: This study compared verbal EF, verbal IF, VI and CTRL group. Forty healthy athletes were assigned to the IF (n=10), EF (n=10), VI (n=10) or CTRL group (n=10). A jump-landing task was per- formed as a baseline, followed by two training blocks (TR1 and TR2) and a post test. Group specific instruc- tions were offered in TR1 and TR2. In addition, subjects in the IF, EF and VI groups were free to ask for feedback after every jump in TR1 and TR2. One week later, a retention test was conducted without specific instructions or feedback. Kinematics and kinetics were captured using an 8-camera motion analysis system. Results: Males and females in the EF and VI instruction group showed beneficial results during and after the training session, in terms of improved landing technique. Retention was achieved after only a short training session. Conclusion: ACL injury prevention programs should include EF and/or VI instructions to improve kine- matics and kinetics and achieve retention. Level of Evidence: 3b Key words: Injury prevention, motor learning, movement technique, retention

Motor learning in ACL injury prevention Anne Benjaminse The physical and psychosocial consequences of an anterior cruciate ligament (ACL) injury are large, for example limitations in daily life, reduction of sports participation, development of osteoarthritis in the knee and increased risk for re-rupture. The importance of prevention is clear, however we have not been able yet to reduce the ACL injury incidence. The aim of this dissertation was therefore to examine how current ACL injury prevention protocols can be optimized through enhanced motor learning. Motor skills can be learned with attention directed to the movement itself (e.g. “flex your knees”), which is defined as an internal focus. Whereas with an external focus, attention is directed towards the effect of the movement (e.g. “imagine you are going to sit on a chair”). In the current ACL injury prevention programs athletes are mostly encouraged to focus on the quality of their movements in order to improve awareness and knee control during cutting, jumping and landing. However, telling athletes explicitly how to move may be counterproductive and less suitable for the acquisition of the control required for complex motor skills. This dissertation shows that providing athletes with individual feedback with an external focus component and video feedback seems promising when learning movement patterns: safer landing techniques were used. A focus on the movement effect (i.e. external focus) probably promotes the utilization of unconscious or automatic processes. This enhances the transfer to the field and retention of learned movement patterns over time. Finally, performance remained optimal (i.e. running speed and jump height). When training staff realize that injury prevention (enhanced movement technique) and performance enhancement go hand in hand, injury prevention can be viewed as ’part of the game’.

Bij handbal scheurt de voorste kruisband (VKB) vaak bij een éénbenigelanding waarbij er meer wordt vereist van de onderste extremiteitdan bij een twee-benige landing. Landen op twee voeten na een sprongschotwordt daarom geadviseerd. Echter, het is van belang om te onderzoeken hóehet aanleren van een twee-benige landing na een sprongschot verbeterd kanworden. Het doel van huidige studie was om te evalueren of video feedbackmet een overlay methode een effectieve manier is om risico factoren voorVKB blessures te reduceren bij het landen na een sprongschot.

Blessurepreventieve oefenprogramma’s zijn in de sport niet erg populair. Hun effectiviteit staat ter discussie en het feit dat ze doorgaans geen directe bijdrage leveren aan prestatieverbetering komt de motivatie van coaches en sporters niet ten goede. Het toepassen van motorische leerprincipes binnen de blessurepreventie lijkt echter beide doelen te kunnen dienen: minder blessures en betere prestaties.

Preventie van voorste kruisband letsel. Helaas hebben de huidige VKB blessure preventieprogramma’s nog niet tot afname van het aantal VKB blessures geleid. Er is dus ruimte voor verbetering van de huidige preventieprogramma’s. Dit kan bijvoorbeeld door het verbeteren van de manier waarop de sporters veilige bewegingen aan wordt geleerd, zodat dit beter beklijft en een goede transfer heeft naar de training of wedstrijd. Er wordt ingezoomd op het effect van het geven van verschillende vormen van feedback (bijvoorbeeld een internal focus of een external focus, positieve of negatieve feedback, self-controlled of vaststaand schema, verbaal of visueel). Het effect van verschillen in ‘attentional focus’ is al aangetoond in de sport performance (bijvoorbeeld hoger of verder springen), echter is nieuw in het domein van blessure preventie. Onderzoeksresultaten van het effect van verschillende vormen van feedback/instructies komen aan bod en de relatie daarmee met de preventie van VKB blessures zal worden gepresenteerd.

External of focus of attention has been shown to result in superior motor performance compared to an internal focus of attention. Adding external focus of attention may optimize current anterior cruciate ligament (ACL) injury prevention programs. Objective: To determine the effect of internal (IF) and external focus (EF) and video instruction (VI) on drop vertical jump (DVJ) landing strategies assessed with landing error scoring system (LESS). Design; Descriptive cohort study. Setting; Controlled laboratory setting. Patients and Other Participants; Forty recreational athletes performed DVJ’s in five sessions: a pretest (baseline measurements), two training blocks (TR1 and TR2), a posttest directly after the training sessions and a retention test one week later. Subjects were randomly assigned to one of the four groups; IF (n=10, ), EF (n=10, ), VI (n=10, ) or the CTRL group (n=10, ), with 5 females and 5 males in each group. 22.60±1.35 years, 1.80±0.14 m, 72.40±10.38 kg Interventions: After a general instruction before pretest, group specific instruction was offered before TR1 and TR2 started and after every 5 trials in TR1 and TR2. The IF group received an instruction regarding attention to the body, the EF group received an instruction directed to the movement effect and the VI group viewed an expert video. Subjects in the IF, EF and VI groups were free to ask for feedback on their real time LESS during TR1 and TR2. Subjects were only aware that a lower LESS score implied a better landing strategy. A 4x5x2 repeated measures ANOVA was conducted to determine differences between groups (IF, EF, VI and CTRL), time (pretest, TR1, TR2, posttest and retention test) and gender (female and male), followed by post hoc comparisons (Bonferroni) with alpha level set at α≤0.05 a priori. Main Outcome Measures: Mean total LESS scores. Results: Males in the VI group had significant lower LESS scores in the post- (1.92±0.27) and retention test (1.72±0.30) compared to the pretest (2.72±0.83).

Objectives: The strategy for dynamic postural stability might be different for male and female players. Additionally, dynamic and challenging tasks are recommended to measure differences in postural stability between injured and non-injured players. Therefore, the dynamic stability index (DSI) was developed which measures the ability of a player to maintain static balance after a dynamic task. The first aim of this study was to evaluate DSI differences between males and females for different jump directions. The second aim was to examine both preseason DSI differences between players with and without a history of ankle sprain, and between players with and without an ankle sprain during the subsequent season.Design: Prospective cohort design. Setting: Laboratory. Participants: 47 male (22.9 ± 3.9 y, 193.5 ± 7.9 cm, 87.1 ± 10.6) and 19 female (21.5 ± 2.9 y, 175.9 ± 7.3 cm, 69.0 ± 11.7 kg) sub-elite and elite basketball, volleyball and korfball players. Main outcome measures: Ankle sprain history was collected using a general injury history questionnaire. DSI on a single-leg hop-stabilization task measured preseason were calculated by using force plates and a Matlab program. Ankle sprains were reported during subsequent season. Results: Male players demonstrated larger DSI than female players on forward medial/lateral stability index (MLSI) (0.037± 0.007 vs 0.029 ± 0.005) and vertical stability index (VSI) (0.369 ± 0.056 vs 0.319 ± 0.034) (p < 0.001), diagonal VSI (0.363 ± 0.046 vs 0.311 ± 0.033) (p < 0.001), and lateral anterior/posterior stability index (APSI) (0.062 ± 0.015 vs 0.047 ± 0.011) and VSI (0.350 ± 0.054 vs 0.294 ± 0.037) (p < 0.001). Forward (0.384 ± 0.055 vs 0.335 ± 0.033), diagonal (0.379 ± 0.046 vs 0.328 ± 0.032) and lateral (0.368 ± 0.053 vs 0.313 ± 0.035) dynamic postural stability indices (DPSI) were larger for males (p < 0.001). No significant differences were found between players with and without a previous ankle sprain nor between players with and without an ankle sprain during subsequent season.

Knee injuries commonly occur in later stages of competition indicating that fatigue may influence dynamic knee stability. Force sense (FS) is a submodality of proprioception influenced by muscle mechanoreceptors, and, if negatively affected by fatigue, may results in less effective neuromuscular control. OBJECTIVES: To determine the effects of peripheral fatigue on FS of the quadriceps and hamstrings. DESIGN: Quasi-experimental study design. PARTICIPANTS: Twenty healthy and physically active females and males (age: 23.4±2.7 years, mass: 69.5±10.9kg, height: 169.7±9.4cm) participated. INTERVENTIONS: Fatigue was induced during a protocol with two sets of 40 repetitions, and the last set truncated at 90 repetitions or stopped if torque production dropped below 25% of peak torque. MAIN OUTCOME MEASURES: FS of the hamstrings and quadriceps was tested on separate days before and after three sets of isokinetic knee flexion and extension to fatigue by examining the ability to produce a target isometric torque (15% MVIC) with and without visual feedback (FS Error). Electromyographic data of the tested musculature were collected in order to calculate and determine median frequency shift. T-tests and Wilcoxon Signed Rank tests were conducted to examine pre-fatigue and post-fatigue FS Error for flexion and extension. RESULTS: Despite verification of fatigue via torque production decrement and shift in median frequency, no significant differences were observed in FS Error for either knee flexion (pre=0.54±2.28 N·m; post=0.47±1.62 N·m) or extension (pre=-0.28±2.69 N·m; post=-0.21±1.78 N·m) pre-fatigue compared to the post-fatigue condition. CONCLUSIONS: Although previous research has demonstrated that peripheral fatigue negatively affects TTDPM, it did not affect FS as measured in this study. The peripheral fatigue protocol may have a greater effect on the mechanoreceptors responsible for TTDPM than those responsible for FS. Further investigation into the effects of fatigue across various modes of proprioception is warranted.

Background Sport injuries are a major reason for reduced participation and drop-out from sports and PE. Refraining from sport participation has negative bearing effects on mental and physical wellbeing, which tracks into adulthood. It is therefore important for youth to be facilitated into lifelong active participation in physical activity and sport, as the importance of physical activity for the health of youth is undisputed. Participation in physical education (PE) classes and membership of sports clubs and are essential for health enhancing physical activity. Despite the importance of sports injury prevention in youth, no broad scale approaches that work in real-life situations with significant positive effects exist. Main reasons for this are very poor uptake and maintenance of current sports injury prevention exercises. Sports coaches and physical educators experience these exercises as not context specific, time consuming and not contributing to their training goals. Whereas youth perceives these exercises as not attractive, no fun and without any play or game component. These aspects cause lack of maintenance and thus no significant reduction of injuries. Recent scientific and practical insights promote more emphasis on motivation through autonomy and attractive exercise routines based on principles of motor learning which can be integrated in regular training sessions or physical education classes. Purpose Therefore, the Move Healthy project develops ICT based support video material of routines for and with physical educators and sport coaches, which supports them to prevent sports injuries in youth. This material should be easy to integrate in regular training sessions or physical education classes. The current study will focus on the results of the mapping phase as fundamental first step in the Move Healthy project. Purpose of the mapping phase is twofold; 1) to identify the status and specifics of current injury prevention programs and 2) to identify the wishes and needs of the end-users (sport coaches, physical educators and children) regarding injury prevention. Methods In the Move Healthy project, a process of co-creation with sport coaches (basketball & soccer) and physical educators (primary & secondary) from six EU countries will be conducted to integrate the wishes and needs of these end-users. With this, direct involvement and implementation is assured right from the start. For data collection, a thorough mapping procedure was conducted: - A rapid literature review was conducted to explore the status and specifics of sports injury prevention programs (PE & sports) (1); - Structured interviews were held with the national stakeholders/ policymakers and sports injury program owners (1); - Focus groups were held with the sport coaches, physical educators and youth respectively (2). Results The preliminary results from the mapping phase that took place in physical education and sport will be presented. The results consist an overview of: a) rapid review literature results b) focus group results YOUTH c) focus group results SPORT COACHES/PHYSICAL EDUCATORS d) interview results from national STAKEHOLDERS/POLICYMAKERS e) interview results from program OWNERS Conclusions: The results from the mapping phase will lead to guidelines and statements regarding educational concepts, content and design criteria for the ICT based support platform for sports coaches and physical educators.

Background The outcome after ACL reconstruction (ACLR) is in general disappointing with unacceptable number of athletes that do not return to pre-injury level of sports, high re-injury rates, early development of osteoarthritis and shorter careers. Athletes after ACLR have high expectation to return to sports which is in contrast with the current outcomes. The aim of this manuscript is to present an overview of factors that are needed to be incorporated and to personalize the rehabilitation process for an athlete who has undergone an ACLR. Level of evidence 4.