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Motor learning might reduce the likelihood of sports injuries by improving movement patterns. This review aimed to critically evaluate and summarize the effects of implicit (IL) and explicit (EL) motor learning on selected biomechanical variables while executing sport-specific tasks. PubMed, Embase, and Cinahl were searched according to PRISMA guidelines. The protocol was registered in PROSPERO (ID: CRD42023390982). Randomised controlled trials published before February 2024, with healthy participants (≥11 years) performing a sport-specific task were considered. Intervention evaluation, at least one kinematic or kinetic value as dependent variable, needed to be minimally one night post-practice. The changes in biomechanical outcomes were considered regarding the goal of the included study and their effect sizes were assessed. Methodological quality was based on the Revised Cochrane Risk-of-Bias tool. Of 18,639 records identified, 25 studies were included leading to 60 comparisons between IL and control (CTRL), EL and CTRL, or IL and EL. In total, the 1020 (520 male, 20.0 ± 3.7 years, 14–91 per study) participants playedvarious sports, from recreational to elite level. External and internal focus of attention, differential learning, analogy, non-linear and linear pedagogy, and observational learning were included.. An overall small positive effect size of IL compared to CTRL group changes was found (g = 0.45 [0.115 – 0.780], p = 0.01). Although premature, IL shows more potential than EL for improving biomechanics of sport-specific tasks. Therefore, practitioners may consider incorporating IL into injury prevention programs. Lastly, recommendations about strengthening research methodology of motor learning studies using biomechanical outcomes are provided.

In team handball, an anterior cruciate ligament injury often occurs during landing after a jump shot. Many intervention programs try to reduce the injury rate by instructing athletes to land more safely. Video is an effective way to provide feedback, but little is known about its influence on landing technique in sport-specific situations.   To test the effectiveness of a video-overlay feedback method on landing technique in elite handball players.   Controlled laboratory study.   Laboratory.   A total of 16 elite female handball players assigned to a control group (n = 8; age = 17.61 ± 1.34 years, height = 1.73 ± 0.06 m, mass = 69.55 ± 4.29 kg) or video group (n = 8; age = 17.81 ± 0.86 years, height = 1.71 ± 0.03 m, mass = 64.28 ± 6.29 kg).   Both groups performed jump shots in a pretest, 2 training sessions, and a posttest. The video group received video feedback of an expert model with an overlay of their own jump shots in training sessions 1 and 2, whereas the control group did not.   We measured ankle, knee, and hip angles in the sagittal plane at initial contact and peak flexion; range of motion; and Landing Error Scoring System (LESS) scores. One 2 × 4 repeated-measures analysis of variance was conducted to analyze the group, time, and interaction effects of all kinematic outcome measures and the LESS score.   The video group improved knee and hip flexion at initial contact and peak flexion and range of motion. In addition, the group's average peak ankle flexion (12.0° at pretest to 21.8° at posttest) and LESS score (8.1 pretest to 4.0 posttest) improved. When we considered performance variables, no differences between groups were found in shot accuracy or vertical jump height, whereas horizontal jump distance in the video group increased over time.   Overlay visual feedback is an effective method for improving landing kinematics during a sport-specific jump shot. Further research is warranted to determine the long-term effects and transfer to training and game situations.

Purpose It is unknown how movement patterns that are learned carry over to the field. The objective was to determine whether training during a jump-landing task would transfer to lower extremity kinematics and kinetics during sidestep cutting. Methods Forty healthy athletes were assigned to the verbal internal focus (IF, n  = 10), verbal external focus (EF, n  = 10), video (VI, n  = 10) or control (CTRL, n  = 10) group. A jump-landing task was performed as baseline followed by training blocks (TR1 and TR2) and a post-test. Group-specific instructions were given in TR1 and TR2. In addition, participants in the IF, EF and VI groups were free to ask for feedback after every jump during TR1 and TR2. Retention was tested after 1 week. Transfer of learned skill was determined by having participants perform a 45° unanticipated sidestep cutting task. 3D hip, knee and ankle kinematics and kinetics were the main outcome measures. Results During sidestep cutting, the VI group showed greater hip flexion ROM compared to the EF and IF groups ( p  < 0.001). The EF ( p  < 0.036) and VI ( p  < 0.004) groups had greater knee flexion ROM compared to the IF group. Conclusions Improved jump-landing technique carried over to sidestep cutting when stimulating an external attentional focus combined with self-controlled feedback. Transfer to more sport-specific skills may demonstrate potential to reduce injuries on the field. Clinicians and practitioners are encouraged to apply instructions that stimulate an external focus of attention, of which visual instructions seem to be very powerful. Level of evidence II.

The purpose of the current study was to compare the results of a progressive strength training protocol for soccer players after anterior cruciate ligament reconstruction (ACLR) with healthy controls, and to investigate the effects of the strength training protocol on peak quadriceps and hamstring muscle strength. Between subjects design. Outpatient physical therapy facility. Thirty-eight amateur male soccer players after ACLR were included. Thirty age-matched amateur male soccer players served as control group. Quadriceps and hamstring muscle strength was measured at three time points during the rehabilitation. Limb symmetry index (LSI) > 90% was used as cut-off criteria. Soccer players after ACLR had no significant differences in peak quadriceps and hamstring muscle strength in the injured leg at 7 months after ACLR compared to the dominant leg of the control group. Furthermore, 65.8% of soccer players after ACLR passed LSI >90% at 10 months for quadriceps muscle strength. Amateur male soccer players after ACLR can achieve similar quadriceps and hamstring muscle strength at 7 months compared to healthy controls. These findings highlight the potential of progressive strength training in rehabilitation after ACLR that may mitigate commonly reported strength deficits. •Soccer players after ACLR showed similar muscle strength at 7 months compared to controls.•Sixty-five percent of soccer players after ACLR passed LSI >90% for quadriceps muscle strength at 10 months.•Soccer players after ACLR showed good self-reported knee function at 10 months.

Purpose Adding external focus of attention (EF, focus on the movement effect) may optimize current anterior cruciate ligament (ACL) injury prevention programmes. The purpose of the current study was to investigate the effects of an EF, by a visual stimulus and an internal focus, by a verbal stimulus during unexpected sidestep cutting in female and male athletes and how these effects remained over time. Methods Ninety experienced basketball athletes performed sidestep cutting manoeuvres in three sessions (S1, S2 and S3). In this randomized controlled trial, athletes were allocated to three groups: visual (VIS), verbal (VER) and control (CTRL). Kinematics and kinetics were collected at the time of peak knee frontal plane moment. Results Males in the VIS group showed a larger vertical ground reaction force (S1: 25.4 ± 3.1 N/kg, S2: 25.8 ± 2.9 N/kg, S3: 25.2 ± 3.2 N/kg) and knee flexion moments (S1: −3.8 ± 0.9 Nm/kg, S2: −4.0 ± 1.2 Nm/kg, S3: −3.9 ± 1.3 Nm/kg) compared to the males in the VER and CTRL groups and to the females in the VIS group ( p  < 0.05). Additionally, the males in the VIS group reduced knee valgus moment and the females in the VER group reduced knee varus moment over time (n.s.). Conclusion Male subjects clearly benefit from visual feedback. Females may need different feedback modes to learn a correct movement pattern. Sex-specific learning preferences may have to be acknowledged in day by day practice. Adding video instruction or feedback to regular training regimens when teaching athletes safe movement patterns and providing individual feedback might target suboptimal long-term results and optimize ACL injury prevention programmes. Level of evidence I.

Background Injuries to lower extremities are common in team sports such as soccer, basketball, volleyball, football and field hockey. Considering personal grief, disabling consequences and high costs caused by injuries to lower extremities, the importance for the prevention of these injuries is evident. From this point of view it is important to know which screening tools can identify athletes who are at risk of injury to their lower extremities. Objective The aim of this article is to determine the predictive values of anthropometric and/or physical screening tests for injuries to the leg, anterior cruciate ligament (ACL), knee, hamstring, groin and ankle in team sports. Methods A systematic review was conducted in MEDLINE (1966 to September 2011), EMBASE (1989 to September 2011) and CINAHL (1982 to September 2011). Based on inclusion criteria defined a priori, titles, abstracts and full texts were analysed to find relevant studies. Results The analysis showed that different screening tools can be predictive for injuries to the knee, ACL, hamstring, groin and ankle. For injuries in general there is some support in the literature to suggest that general joint laxity is a predictive measure for leg injuries. The anterior right/left reach distance >4cm and the composite reach distance <4.0% of limb length in girls measured with the star excursion balance test (SEBT) may predict leg injuries. Furthermore, an increasing age, a lower hamstring/quadriceps (H:Q) ratio and a decreased range of motion (ROM) of hip abduction may predict the occurrence of leg injuries. Hyperextension of the knee, side-to-side differences in anterior-posterior knee laxity and differences in knee abduction moment between both legs are suggested to be predictive tests for sustaining an ACL injury and height was a predictive screening tool for knee ligament injuries. There is some evidence that when age increases, the probability of sustaining a hamstring injury increases. Debate exists in the analysed literature regarding measurement of the flexibility of the hamstring as a predictive screening tool, as well as using the H:Q ratio. Hip-adduction-to-abduction strength is a predictive test for hip adductor muscle strain. Studies do not agree on whether ROM of the hamstring is a predictive screening tool for groin injury. Body mass index and the age of an athlete could contribute to an ankle sprain. There is support in the literature to suggest that greater strength of the plantar flexors may be a predictive measure for sustaining an ankle injury. Furthermore, there is some agreement that the measurement of postural sway is a predictive test for an ankle injury. Conclusions The screening tools mentioned above can be recommended to medical staff and coaches for screening their athletes. Future research should focus on prospective studies in larger groups and should follow athletes over several seasons.

Although it is advocated that end-users are engaged in developing evidence-based injury prevention training to enhance the implementation, this rarely happens. The ‘Implementing injury Prevention training ROutines in TEams and Clubs in youth Team handball (I-PROTECT)’ uses an ecological participatory design incorporating the perspectives of multiple stakeholders throughout the project. Within the I-PROTECT project, the current study aimed to describe the development of holistic injury prevention training specifically for youth handball players through using knowledge from both end-users (coaches and players) and researchers/handball experts. Employing action evaluation within participatory action research, the cyclical development process included three phases: research team preparation, handball expert-based preparation and end-user evaluation to develop injury prevention training incorporating both physical and psychological perspectives. To grow the knowledge of the interdisciplinary research team, rethinking was conducted within and between phases based on participants’ contributions. Researchers and end-users cocreated examples of handball-specific exercises, including injury prevention physical principles (movement technique for upper and lower extremities, respectively, and muscle strength) combined with psychological aspects (increase end-user motivation, task focus and body awareness) to integrate into warm-up and skills training within handball practice. A cyclical development process that engaged researchers/handball experts and end-users to cocreate evidence-based, theory-informed and context-specific injury prevention training specifically for youth handball players generated a first pilot version of exercises including physical principles combined with psychological aspects to be integrated within handball practice.

Background Anterior cruciate ligament (ACL) injury prevention programs have shown mixed results, which may be in part due to suboptimal training components. Objective Determine effects of a prevention program with external and internal focus of attention on (potential) biomechanical risk factors for ACL injury. Design Pretest-posttest control group. Setting Laboratory and field. Participants 31 elite female soccer players participated. Exclusion criteria included previous ACL injury or current lower extremity injury. Intervention Two teams performed warm-up programs, including strength, agility, balance, plyometric, core and speed exercises twice a week for 12 weeks. One team received instructions to focus attention internally toward movements of the body (INT); another team received instructions to focus attention externally near the body (EXT). The control group (CON) performed their regular warming-up without specific instructions. Main outcome measurements Normalized external knee and ankle joint moments and joint angles on a two-legged jump-landing-rebound task. Results Results of 3x2 repeated measures ANOVA revealed significant group x time interaction for peak knee extension moment (F (2,23)=4.09, P=.03), the EXT group decreased more (–0.90±0.16 to −0.73±0.15 Nm/kg*m) than the CON group (P<.05). Regarding knee flexion angle at peak varus-valgus, a significant interaction was observed (F (2,26)=3.95, P=.03), the INT group increased more (61.58±11.14 to 69.07±1.53°) than the EXT group (P=.08). Differences between groups were found for peak varus-valgus moment (F (2,26)=4.81, P=.02) and ankle flexion-extension moment (F (2,26)=6.40, P<.01). No significant main effects for time were displayed. Conclusions External or internal focused instructions could be beneficial in improving landing technique, which is promising as an external focus of attention requires less time from coaches and has therefore great potential in ACL injury prevention.

Background Neuropsychological capabilities in athletes may be associated with a predisposition to anterior cruciate ligament (ACL) injuries. Objective Assess differences between male and female athletes in jump-landing technique in relation to their neuropsychological capabilities. Design Experimental. Setting Laboratory. Participants 31 recreational athletes, free from lower extremity injuries, participated (females: n=16, age=21.0±1.71 years, mass=65.1±5.6 kg, height=174.2±68.9 cm; males n=15, age=22.3±2.2 years, mass=77.9±8.9 kg, height=185.7±78.7 cm). Assessment of risk factors Reaction time (RT) under stress was measured. Furthermore, participants conducted anticipated (ANT) and unanticipated (UNANT) double-legged drop-jumps, followed by running at 4.5-5.5 m/sec 45° to the left, straight, or 45° to the right, depending on the light indication prior to landing on the force plates. Main outcome measures RT and joint kinematics (trunk flexion-TF, ankle flexion-AF) and kinetics (knee abduction moment-KAM, ankle extension moment-AEM) at peak vertical ground reaction force (vGRF,N/kg). Moments are expressed as external moments (Nm/kg). Pearson product-moment correlation between RT and joint biomechanics. Results During UNANT, KAM became significantly larger (P=.010) in females (–0.37±0.1) than males (–0.16±0.1). TF was greater in the AT (29.7°±3.3°) than UNANT (46.1°±3.1°) regardless of gender (P<001). AEM was smaller in females (2.1±0.1) than males (2.6±0.1), (P=.001). AF was smaller (i.e., increased flexion) when running straight (80.8°±0.8°) compared to the left or right (84.6°±0.7°, P=.002 and 84.2°±0.8°, P=.008). vGRF was smaller when running straight (22.8±1.0) compared to the left or right (31.5±1.0, P<.001 and 28.8±1.0, P<.001). Significant correlations (r 0.5-0.8, P<.05) were seen between faster RT and greater hip and knee flexion angle and smaller KAM and knee abduction angle. Conclusions Females reacted differently to UNANT in the frontal plane, potentially placing them at greater ACL injury risk. In the sagittal plane, females showed stiffer ankle landing. Further, a change in direction increased vGRF. Smaller knee flexion combined with smaller TF angles during UNANT, may increase loads at the knee. Lastly, neuropsychological characteristics seem to affect ACL injury risk.

Background Implicit (IF) and explicit (EF) feedback are two motor learning strategies demonstrated to alter movement patterns. There is conflicting evidence on which strategy produces better outcomes. The purpose of this study was to examine the effects of reduced IF and EF video feedback on lower extremity landing mechanics. Methods Thirty participants (24 ± 2 years, 1.7 ± 0.1 m, 70 ± 11 kg) were randomly assigned to three groups: IF ( n  = 10), EF (n = 10), and control (CG) (n = 10). They performed twelve box-drop jumps three times a week on the training sessions for six weeks. Only IF and EF groups received video feedback on the training sessions. IF was cued to focus their attention on the overall jump, while EF was cued to focus on position of their knees. 3D lower extremity biomechanics were tested on testing sessions with no feedback. All sessions were at least 24 h apart from another. Testing sessions included baseline testing (pretest), testing after 3 training sessions with 100% feedback (pst1), testing after 6 training sessions with 33.3% feedback (pst2), testing after 6 training sessions with 16.6% feedback (Pst3), and testing 1 month after with no feedback (retention – ret). ANOVA compared differences between groups and time at initial contact and peak for hip flexion (HF, ° ) and abduction angle (HA, ° ), hip abduction moment (HAM, Nm/kgm), knee flexion (KF, ° ) and abduction angle (KA, ° ), knee abduction moment (KAM, Nm/kgm) and VGRF (N) ( p  < 0.05). Results A significant main effect for group was found between IF and EF groups for HA (IF = − 6.7 ± 4; EF = − 9.4 ± 4.1) and KAM (IF = 0.05 ± 0.2; EF = − 0.07 ± 0.2) at initial contact, and peaks HA (IF = − 3.5 ± 4.5; EF = − 7.9 ± 4.7) and HAM (IF = 1.1 ± 0.6; EF = 0.9 ± 0.4). A significant main effect for time at initial contact for HF (pre = 32.4 ± 3.2; pst2 = 36.9 ± 3.2; pst3 = 37.9 ± 3.7; ret. = 34.1 ± 3.7), HAM (pre = 0.1 ± 0.1; pst1 = 0.04 ± 0.1; pst3 = 0.1 ± 0.01), KA (pre = 0.7 ± 1.1; pst1 = 0.2 ± 1.2; pst3 = 1.7 ± 1), and KAM (pre = 0.003 ± 0.1; pst3 = 0.01 ± 0.1) was found. Discussion/conclusion We found that implicit feedback produced positive changes in landing mechanics while explicit feedback degraded motor learning. Our results indicate that implicit feedback should be used in programs to lower the ACL injury risk. We suggest that implicit feedback should be frequent in the beginning and not be reduced as much following the acquisition phase.