Neurocognitive demands reduce jump distance and coordination variability of the injured leg in athletes after anterior cruciate ligament reconstruction.

PURPOSE: The study aimed to evaluate the impact of neurocognitive reliance on jump distance and lower extremity kinematics in individuals who had undergone anterior cruciate ligament reconstruction (ACLR). This was achieved by comparing hop performance under standard and neurocognitive conditions. METHODS: Thirty-two patients after ACLR and 32 healthy controls (CTRL) participated. Both groups performed a single-leg hop for distance (SLHD) and two neurocognitive hop tests, each designed to evaluate distinct aspects of neurocognition. The neurocognitive tests included the reaction SLHD (R-SLHD), measuring reaction to a central stimulus and working memory SLHD (WM-SLHD) assessing response to a memorized stimulus amidst distractor stimuli. Distances were assessed for the three-hop tests. In addition, joint kinematics were collected to calculate lower extremity coordination of the lower extremity. SLHD performance was defined as the mean hop distance per condition per leg for each participant and was analyzed using a mixed ANOVA with condition and leg as the within-subjects factors and the group (ACLR or CTRL) as the between-subjects factor. Differences in joint coordination variability were analyzed using two-sample t-test statistical parametric mapping (SPM) with linear regression. RESULTS: The WM-SLHD resulted in a significantly decreased jump distance compared with the standard hop test both for ACLR and CTRL. Furthermore, the leg difference within the ACLR group increased under higher cognitive load as tested with the WM-SLHD, indicating leg-specific adaptations in lower extremity coordination. CONCLUSIONS: Neurocognitive single-leg hop tests resulted in reduced jump distance in CTRL and ACLR. The neurocognitive hop test revealed changes in coordination variability for the CTRL and the uninjured leg of ACLR individuals, whereas the injured leg's coordination variability remained unaltered, suggesting persistent cognitive control of movements post-ACLR. LEVEL OF EVIDENCE: Level III.

Application of Machine Learning Methods to Investigate Joint Load in Agility on the Football Field: Creating the Model, Part I.

Laboratory studies have limitations in screening for anterior cruciate ligament (ACL) injury risk due to their lack of ecological validity. Machine learning (ML) methods coupled with wearable sensors are state-of-art approaches for joint load estimation outside the laboratory in athletic tasks. The aim of this study was to investigate ML approaches in predicting knee joint loading during sport-specific agility tasks. We explored the possibility of predicting high and low knee abduction moments (KAMs) from kinematic data collected in a laboratory setting through wearable sensors and of predicting the actual KAM from kinematics. Xsens MVN Analyze and Vicon motion analysis, together with Bertec force plates, were used. Talented female football (soccer) players (n = 32, age 14.8 ± 1.0 y, height 167.9 ± 5.1 cm, mass 57.5 ± 8.0 kg) performed unanticipated sidestep cutting movements (number of trials analyzed = 1105). According to the findings of this technical note, classification models that aim to identify the players exhibiting high or low KAM are preferable to the ones that aim to predict the actual peak KAM magnitude. The possibility of classifying high versus low KAMs during agility with good approximation (AUC 0.81-0.85) represents a step towards testing in an ecologically valid environment.

Motivation Unraveled: Giving Choice to Football Players to Improve Anterior Cruciate Ligament Injury Prevention.

ABSTRACT: Benjaminse, A, Nijmeijer, EM, Gokeler, A, Broekhaar, DC, and Cortes, N. Motivation unraveled: giving choice to football players to improve anterior cruciate ligament injury prevention. J Strength Cond Res XX(X): 000-000, 2024-Providing athletes some control over a training session facilitates motor skill acquisition. This is a promising concept to use in anterior cruciate ligament (ACL) injury prevention, as the key for risk reduction is to improve quality of movement. The goal of this study was to better understand why improved motor learning occurred when football players had the opportunity to choose when to receive feedback when practicing sidestep cutting (SSC) movements. Healthy male recreational football players (n = 22, 22.9 ± 1.7 years, 185.5 ± 7.2 cm, 79.3 ± 9.2 kg) were included and assigned to the self-control (SC) or the yoked (YK) group. The players performed anticipated and unanticipated SSC. They received video instructions and were instructed to "copy the movement of the model to the best of their ability." During the training blocks, the SC group could ask for feedback, whereas the YK group could not. Cutting movement assessment scores (CMAS) were measured to test quality of movement and the Intrinsic Motivation Inventory was administered to measure constructs of motivation. In the anticipated condition, SC group showed better scores in immediate post and the retention test compared with pretest (p < 0.001), whereas the YK group showed worse scores in the retention test compared with immediate posttest (p = 0.001). Perceived competence (p = 0.017) and self-efficacy (p = 0.032) were consistent factors that correlated with improved CMAS in the SC group. This has given us innovative insights into underlying mechanisms optimizing the quality of movement, necessary to improve current ACL injury prevention approaches.

Definition of High-Risk Motion Patterns for Female ACL Injury Based on Football-Specific Field Data: A Wearable Sensors Plus Data Mining Approach.

The aim of the present study was to investigate if the presence of anterior cruciate ligament (ACL) injury risk factors depicted in the laboratory would reflect at-risk patterns in football-specific field data. Twenty-four female footballers (14.9 ± 0.9 year) performed unanticipated cutting maneuvers in a laboratory setting and on the football pitch during football-specific exercises (F-EX) and games (F-GAME). Knee joint moments were collected in the laboratory and grouped using hierarchical agglomerative clustering. The clusters were used to investigate the kinematics collected on field through wearable sensors. Three clusters emerged: Cluster 1 presented the lowest knee moments; Cluster 2 presented high knee extension but low knee abduction and rotation moments; Cluster 3 presented the highest knee abduction, extension, and external rotation moments. In F-EX, greater knee abduction angles were found in Cluster 2 and 3 compared to Cluster 1 (p = 0.007). Cluster 2 showed the lowest knee and hip flexion angles (p < 0.013). Cluster 3 showed the greatest hip external rotation angles (p = 0.006). In F-GAME, Cluster 3 presented the greatest knee external rotation and lowest knee flexion angles (p = 0.003). Clinically relevant differences towards ACL injury identified in the laboratory reflected at-risk patterns only in part when cutting on the field: in the field, low-risk players exhibited similar kinematic patterns as the high-risk players. Therefore, in-lab injury risk screening may lack ecological validity.

Have We Forgotten Our Patient? An Exploration of Patient Experiences After Anterior Cruciate Ligament Reconstruction.

BACKGROUND: Limited information is available on the experiences of patients during rehabilitation after anterior cruciate ligament reconstruction (ACLR). AIM: The current study aimed to identify factors that differentiated positive and negative patient experiences during rehabilitation after ACLR. METHOD AND DESIGN: A survey-based study with an online platform was used to identify factors that differentiated positive and negative patient experiences during rehabilitation after ACLR. Seventy-two patients (age 27.8 [8.8] y) after ACLR participated. Data were analyzed and themes were identified by comparing categories and subcategories on similarity. MAIN FINDINGS: Positive patient experiences were room for own input, supervision, attention, knowledge, honesty, and professionalism of the physiotherapist. Additionally, a varied and structured rehabilitation program, adequate facilities, and contact with other patients were identified as positive patient experiences. Negative experiences were a lack of attention, lack of professionalism of the physiotherapists, a lack of sport-specific field training, a lack of goal setting, a lack of adequate facilities, and health insurance costs. CONCLUSIONS: The current study identified factors that differentiated positive and negative patient experiences during rehabilitation after ACLR. These findings can help physiotherapists in understanding the patient experiences during rehabilitation after ACLR.

Hamstrings substitution via anteromedial portal with optional anterolateral ligament reconstruction is the preferred surgical technique for anterior cruciate ligament reconstruction: a survey among ESSKA members.

PURPOSE: The objective of this study was to report on a worldwide web-based survey among the ESSKA community developed to investigate current recommendations regarding ACL reconstruction surgical procedures. METHODS: All contacts in the official mailing list of the ESSKA were contacted to investigate preferences regarding graft type, anterolateral ligament reconstruction, femoral tunnel drilling technique, single-bundle vs double-bundle technique, femoral and tibial fixation methods. RESULTS: Eight-hundred and twenty responses were analyzed. Hamstrings autograft was the graft of choice in male patients for 634 (79%) and in female patients for 674 (84%) responders, while its preference for ACL reconstruction in professional athletes was for 401 (50%). 480 (63%) surgeons surveyed would include anterolateral ligament reconstruction only if diagnosed and remaining instability after ACL surgery or revision. 598 (75%) respondents were in favor of anteromedial portal for femoral tunnel drilling. The most popular femoral fixation technique was found to be cortical suspension (500-66%), while a compression system was preferred on the tibial side by 537 (71% of the sample). CONCLUSIONS: This survey study found that HT autograft, single-bundle reconstruction, anteromedial portal for femoral tunnel drilling, cortical suspension systems for femoral fixation and compression systems for tibial fixation represent the current standard of ACLR in a large community of orthopedic surgeons. The present study performed with surgeons who are members of the ESSKA community will help to comprehend the actual ACLR worldwide practice patterns. Due to low response rate, these results should be interpreted with caution and not to be intended to represent the state of the art of ESSKA community. LEVEL OF EVIDENCE: III.

Younger age and hamstring tendon graft are associated with higher IKDC 2000 and KOOS scores during the first year after ACL reconstruction.

PURPOSE: Although reference values in healthy subjects have been published for both the International Knee Documentation Committee 2000 subjective knee form (IKDC 2000) and the Knee injury and Osteoarthritis Outcome Score (KOOS), data obtained during the first year after anterior cruciate ligament reconstruction (ACL-R) are sparse. The aim was to establish patient reference values for both questionnaires at different time points and depending on nine individual patient characteristics during the first year after ACL-R. METHODS: Prospectively recorded data from a hospital-based registry were retrospectively extracted from the database. IKDC 2000 and KOOS questionnaires were self-administered pre-operatively and 6 weeks, 3 months, and 6 and 12 months following primary ACL-R. Score values were compared according to nine individual patient criteria: gender, age, body mass index, level of activity, involvement in competition, previous contralateral knee injury and/or surgery, graft type, meniscal repair and/or cartilage lesions. The feature which had a significant and consistent impact on the outcomes was considered as main reference. RESULTS: Two-hundred and nighty-eight patients met the inclusion criteria. Overall, the score values increased over time after ACL-R. At 12 months, they were significantly greater than at any other time point (p < 0.05). The main individual feature influencing the IKDC 2000 score was age. Patients below 30 years of age had up to 9 points higher IKDC 2000 score values at all time points (p < 0.05). The main individual characteristic influencing the KOOS score was graft type. Patients with hamstring tendon grafts (STGR) had up to 15 points higher KOOS score values than patients with bone-patellar tendon-bone (BPTB) grafts during the first months after ACL-R (p < 0.05). At 12 months, no differences in KOOS score values could be identified anymore. CONCLUSIONS: Younger age (< 30 years) and STGR grafts were related to higher IKDC 2000 and KOOS score values within the first year after primary ACL-R. The patient reference values adjusted to age and graft provided in this study may help to identify patients with lower outcomes within the first year after ACL-R. LEVEL OF EVIDENCE: Level III.

Functional progression milestones following anterior cruciate ligament reconstruction are more appropriate than time-based criteria: a survey among the ESSKA.

PURPOSE: The aim of this study was to report current rehabilitation recommendations after ACL reconstruction in ESSKA community, with a particular focus on the specific criteria utilized to guide activity progression METHODS: A web-based survey was developed to investigate preferences between time-based and functional ACL reconstruction rehabilitation progression milestones of ESSKA community. RESULTS: Eight hundred and twenty completed questionnaires were received. Responders were from 86 different countries worldwide, 63% of them from European countries. Functional criteria were considered more appropriate to decide if a patient can start specific activities/exercises by 67% of the responders. Good core and lower extremity neuromuscular control were the most often used functional criteria for decision-making regarding readiness for sport-specific rehabilitation (66%), sport-specific drills without (65%) and with contact (66%). Strength assessed with an isokinetic dynamometer was considered by about half of the responders a determinant to initiate sport-specific drills without (51%-isokinetic strength, LSI > 80%) and with contact (58%-isokinetic strength, LSI > 85-90%). To determine readiness for sport-specific drills, hop tests were used by 40% of respondents for drills without contact and 48% of respondents for drills with contact. CONCLUSION: The results of this survey involving mainly orthopaedic surgeons indicate that functional measures are considered more appropriate than milestones based on time from surgery to guide progression through the postoperative rehabilitation process after ACLR. The main clinical relevance of this study is that updated information on collective agreement could be useful for clinicians and physiotherapists to delineate their postoperative treatments after ACLR. These results should be interpreted with caution, as this sample represents only a small portion of ESSKA community involved in knee surgery and treating patients following ACLR. LEVEL OF EVIDENCE: III.

The Effects of Instruction Exercises on Performance and Kinetic Factors Associated With Lower-Extremity Injury in Landing After Volleyball Blocks.

CONTEXT: Female volleyball players are more predisposed to anterior cruciate ligament injury in comparison with their male counterparts. Recent research on anterior cruciate ligament injury prevention strategies has shown the positive results of adopting the external focus (EF) of attention in sports. OBJECTIVE: To determine the effect of 6-week EF instruction exercises on performance and kinetic factors associated with lower-extremity injury in landing after the volleyball blocks of female athletes. DESIGN: Pretest and posttest control study. SETTING: University research laboratory. PARTICIPANTS: Thirty-two female volleyball players (18-24 y old) from the same team randomly divided into experimental (n = 16) and control (n = 16) groups. INTERVENTION: The experimental group performed a 6-week exercise program with EF instructions. The control group continued its regular volleyball team schedule. MAIN OUTCOME MEASURES: To assess function, single-leg triple hop test for distance was used. A force plate was used to evaluate kinetic variables including vertical ground reaction forces, the rate of loading, and dynamic postural stability index. All data were assessed at baseline and after the intervention. RESULTS: There was a significant increase in single-leg triple hop test (P < .05) and in the first and second peak ground reaction force, rate of loadings, dynamic postural stability index (P < .05). CONCLUSION: According to the results of this study, anterior cruciate ligament injury prevention programs should incorporate EF instruction exercises to enhance the kinetics and to increase athletes' functional performance.

Cross-education does not improve early and late-phase rehabilitation outcomes after ACL reconstruction: a randomized controlled clinical trial.

PURPOSE: Limited evidence suggests that cross-education affords clinical benefits in the initial 8 weeks after anterior cruciate ligament (ACL) reconstruction, but it is unknown if such cross-education effects are reproducible and still present in later phases of rehabilitation. We examined whether cross-education, as an adjuvant to standard therapy, would accelerate the rehabilitation up to 26 weeks after ACL reconstruction by attenuating quadriceps weakness. METHODS: ACL-reconstructed patients were randomized into experimental (n = 22) and control groups (n = 21). Both groups received standard care after ACL reconstruction. In addition, the experimental group strength trained the quadriceps of the non-operated leg during weeks 1-12 after surgery (i.e., cross-education). Self-reported knee function was assessed with the Hughston Clinic Knee score as the primary outcome. Secondary outcomes were maximal quadriceps and hamstring strength and single leg hop distance. All outcomes were measured 29 ± 23 days prior to surgery, as a reference, and at 5-week, 12-week, and 26-week post-surgery. RESULTS: Both groups scored 12% worse on self-reported knee function 5-week post-surgery (95% CI 7-17) and showed 15% improvement 26-week post-surgery (95% CI - 20 to - 10). No cross-education effect was found. Interestingly, males scored 8-10% worse than females at each time point post-surgery. None of 33 secondary outcomes showed a cross-education effect. At 26-week post-surgery, both legs improved maximal quadriceps (5-14%) and hamstring strength (7-18%), and the non-injured leg improved 2% in hop distance. The ACL recovery was not affected by limb dominance and age. CONCLUSION: 26 weeks of standard care improved self-reported knee function and maximal leg strength relative to pre-surgery and adding cross-education did not further accelerate ACL recovery. LEVEL OF EVIDENCE: I. CLINICAL TRIAL REGISTRY NAME AND REGISTRATION: This randomized controlled clinical trial is registered at the Dutch trial register ( http://www.trialregister.nl ) under NTR4395.

Cross-education does not accelerate the rehabilitation of neuromuscular functions after ACL reconstruction: a randomized controlled clinical trial.

PURPOSE: Cross-education reduces quadriceps weakness 8 weeks after anterior cruciate ligament (ACL) surgery, but the long-term effects are unknown. We investigated whether cross-education, as an adjuvant to the standard rehabilitation, would accelerate recovery of quadriceps strength and neuromuscular function up to 26 weeks post-surgery. METHODS: Group allocation was randomized. The experimental (n = 22) and control (n = 21) group received standard rehabilitation. In addition, the experimental group strength trained the quadriceps of the non-injured leg in weeks 1-12 post-surgery (i.e., cross-education). Primary and secondary outcomes were measured in both legs 29 ± 23 days prior to surgery and at 5, 12, and 26 weeks post-surgery. RESULTS: The primary outcome showed time and cross-education effects. Maximal quadriceps strength in the reconstructed leg decreased 35% and 12% at, respectively, 5 and 12 weeks post-surgery and improved 11% at 26 weeks post-surgery, where strength of the non-injured leg showed a gradual increase post-surgery up to 14% (all p ≤ 0.015). Limb symmetry deteriorated 9-10% more for the experimental than control group at 5 and 12 weeks post-surgery (both p ≤ 0.030). One of 34 secondary outcomes revealed a cross-education effect: Voluntary quadriceps activation of the reconstructed leg was 6% reduced for the experimental vs. control group at 12 weeks post-surgery (p = 0.023). Both legs improved force control (22-34%) and dynamic balance (6-7%) at 26 weeks post-surgery (all p ≤ 0.043). Knee joint proprioception and static balance remained unchanged. CONCLUSION: Standard rehabilitation improved maximal quadriceps strength, force control, and dynamic balance in both legs relative to pre-surgery but adding cross-education did not accelerate recovery following ACL reconstruction.

Transfer of improved movement technique after receiving verbal external focus and video instruction.

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.

Altered movement during single leg hop test after ACL reconstruction: implications to incorporate 2-D video movement analysis for hop tests.

PURPOSE: There is a lack of objective factors which can be used in guiding the return to sport (RTS) decision after an anterior cruciate ligament reconstruction (ACLR). The purpose of the current study was to conduct qualitative analysis of the single leg hop (SLH) in patients after ACLR with a simple and clinical friendly method and to compare the possible difference in movement pattern between male and female patients. METHODS: Sixty-five patients performed the single leg hop (SLH) test at 6.8 ± 1.0 months following isolated ACLR. Digital video camcorders recorded frontal and sagittal plane views of the patient performing the SLH. Knee flexion at initial contact (IC), peak knee flexion, knee flexion range of motion (RoM), and knee valgus RoM were calculated. In addition, limb symmetry index (LSI) scores were calculated. RESULTS: No differences were found in movement pattern between males and females. Movement analysis revealed that males had a decrease in knee flexion at IC (p = 0.018), peak knee flexion (p = 0.002), and knee flexion RoM (p = 0.017) in the injured leg compared to the non-injured leg. Females demonstrated a decrease in peak knee flexion (p = 0.011) and knee flexion RoM (p = 0.023) in the injured leg compared to the non-injured leg. Average LSI scores were 92.4% for males and 94.5% for females. CONCLUSIONS: Although LSI scores were > 90%, clinical relevant altered movement patterns were detected in the injured leg compared to the non-injured leg. Caution is warranted to solely rely on LSI scores to determine RTS readiness. CLINICAL TRIAL REGISTRY NAME AND REGISTRATION: The University of Groningen, ID 2012.362. LEVEL OF EVIDENCE: III.

Low rates of patients meeting return to sport criteria 9 months after anterior cruciate ligament reconstruction: a prospective longitudinal study.

PURPOSE: The purpose of the current prospective study was to assess the changes over time in patients tested at 6 months and 9 months after anterior cruciate ligament reconstruction (ACLR) with a return to sport (RTS) test battery. It was hypothesized that more patients passed RTS criteria at 9 months compared to 6 months. METHODS: Sixty-two ACLR patients performed a test battery at an average of 6.5 ± 0.7 and 9.5 ± 0.9 months after ACLR. All patients underwent a standardized rehabilitation protocol. The test battery consisted of the following tests: a jump-landing task assessed with the Landing Error Scoring System (LESS), three single-leg hop tasks (single-leg hop test, triple-leg hop test, side hop test), isokinetic quadriceps and hamstring strength at 60, 180 and 300°/s and two questionnaires (IKDC and ACL-RSI). Cut off criteria were set as Limb Symmetry Index (LSI) > 90% (for isokinetic strength and for single-leg hop tasks), LESS < 5, IKDC score within 15th percentage of healthy subjects and ACL-RSI > 56 respectively. RESULTS: At 6 months, two patients (3.2%) passed all criteria. At 9 months, seven patients (11.3%) passed all criteria. Patients improved in all RTS criteria over time except for the IKDC score. Twenty-nine patients (46.8%) did not pass the strength criterion at 60°/s at 9 months after ACLR. CONCLUSIONS: The percentages of patients passing all RTS criteria were low at both 6 and 9 months after ACLR. Quadriceps strength revealed persistent deficits and the lack of improvement in the IKDC score questionnaires shows insufficient self-reported knee function for RTS. LEVEL OF EVIDENCE: III.

Innovative Video Feedback on Jump Landing Improves Landing Technique in Males.

Video feedback may be a powerful tool to change biomechanical landing patterns associated with anterior cruciate ligament (ACL) injury risk. This study investigated the effect of video feedback on drop vertical jump (DVJ) landing strategies in team sport athletes. 59 athletes were assigned to a video feedback (VI) or control (CTRL) group. A pretest, 2 training sessions and a posttest were conducted. In both training sessions, video feedback, consisting of a video of the athlete's contour superimposed onto an expert's contour performing the DVJ landing task, was provided to the VI group; the CTRL group did not receive feedback. Outcomes included: kinematics and kinetics at peak knee valgus/varus moment during pre- and posttest and percentage overlap of expert and athlete during the training sessions. At posttest, males in the VI group showed greater hip flexion angles (p=0.001) and range of motion (p<0.001), smaller vertical ground reaction force, and smaller ankle dorsiflexion moment (p<0.001) compared to pretest. At posttest, males in the VI group demonstrated smaller vertical ground reaction force (p=0.031) and ankle dorsiflexion moment (p=0.001) compared to males in the CTRL group. The VI group increased percentage overlap with the expert during training sessions and from start of the first to the end of the second training session (p<0.001). Overall, video feedback was effective to modify landing strategies favorably in males. While females imitated the expert model, their landing strategy did not change significantly. While Females may need additional (verbal) feedback to benefit from video feedback.

Do ground reaction forces during unilateral and bilateral movements exhibit compensation strategies following ACL reconstruction?

PURPOSE: The aims of the study were (1) to evaluate the leg asymmetry assessed with ground reaction forces (GRFs) during unilateral and bilateral movements of different knee loads in anterior cruciate ligament (ACL) reconstructed patients and (2) to investigate differences in leg asymmetry depending on the International Knee Documentation Committee Subjective Form (IKDC) in order to identify potential compensation strategies. METHODS: The knee function of 50 ACL reconstructed (patella tendon) patients was examined at 31 ± 7 months after the surgery. GRFs were quantified during the sit-to-stand and stand-to-sit test, the step-up and step-down test, and the two- and one-leg vertical jump. Further, the IKDC score, the anterior-posterior knee laxity, and the concentric torque of the quadriceps and hamstring muscles were evaluated. RESULTS: Differences between the operated and non-operated leg were found in the knee laxity, the quadriceps torque, and GRFs. The patients with low IKDC scores demonstrated greater leg asymmetries in GRFs compared to the patients with high IKDC scores. CONCLUSIONS: ACL reconstructed patients showed GRF asymmetries during unilateral and bilateral movements of different knee loads. Three compensation strategies were found in patients with low subjective knee function: (1) a reduced eccentric load, (2) an inter-limb compensation during bilateral movements, and (3) the avoidance of high vertical impact forces. These compensation strategies may be indicative of a protective adaptation to avoid excessive ACL strain. GRF measurements are practicable and efficient tools to identify individual compensation strategies during early rehabilitation.

Development of a test battery to enhance safe return to sports after anterior cruciate ligament reconstruction.

PURPOSE: There is a lack of consensus regarding the appropriate criteria for releasing patients to return to sports (RTS) after anterior cruciate ligament reconstruction (ACLR). A test battery was developed to support decision-making. METHODS: Twenty-eight patients (22 males and 6 females) with a mean age of 25.4 ± 8.2 years participated and were 6.5 ± 1.0 months post-ACLR. All patients followed the same rehabilitation protocol. The test battery used consisted of the following: isokinetic test, 3 hop tests and the jump-landing task assessed with the LESS. The isokinetic tests and single-leg hop tests were expressed as a LSI (involved limb/uninvolved limb × 100 %). In addition, patients filled out the IKDC and ACL-Return to Sport after Injury (ACL-RSI) scale. RTS criteria to pass were defined as a LSI > 90 % on isokinetic and hop tests, LESS < 5, ACL-RSI > 56 and a IKDC within 15th percentile of healthy subjects. RESULTS: Two out of 28 patients passed all criteria of the test protocol. The pass criterion for the LESS < 5 was reached by 67.9 % of all patients. For the hop tests, 78.5 % of patients passed LSI > 90 % for SLH, 85.7 % for TLH and 50 % for the SH. For the isokinetic test, 39.3 % of patients passed criteria for LSI peak torque quadriceps at 60°/s, 46.4 % at 180°/s and 42.9 at 300°/s. In total, 35.7 % of the patients passed criterion for the peak torque at 60°/s normalized to BW (>3.0 Nm) for the involved limb. The H/Q ratio at 300°/s > 55 % for females was achieved by 4 out of 6 female patients, and the >62.5 % criterion for males was achieved by 75 %. At 6 months post-ACLR, 85.7 % of the patients passed the IKDC score and 75 % the ACL-RSI score >56 criteria. CONCLUSION: The evidence emerging from this study suggests that the majority of patients who are 6 months after ACLR require additional rehabilitation to pass RTS criteria. The RTS battery described in this study may serve as a framework for future studies to implement multivariate models in order to optimize the decision-making regarding RTS after ACLR with the aim to reduce incidence of second ACL injuries. LEVEL OF EVIDENCE: III.

Motor learning strategies in basketball players and its implications for ACL injury prevention: a randomized controlled trial.

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.

An anterior cruciate ligament injury does not affect the neuromuscular function of the non-injured leg except for dynamic balance and voluntary quadriceps activation.

PURPOSE: The function of the anterior cruciate ligament (ACL) patients' non-injured leg is relevant in light of the high incidence of secondary ACL injuries on the contralateral side. However, the non-injured leg's function has only been examined for a selected number of neuromuscular outcomes and often without appropriate control groups. We measured a broad array of neuromuscular functions between legs of ACL patients and compared outcomes to age, sex, and physical activity matched controls. METHODS: Thirty-two ACL-deficient patients (208 ± 145 days post-injury) and active and less-active controls (N = 20 each) participated in the study. We measured single- and multi-joint neuromuscular function in both legs in each group and expressed the overall neuromuscular function in each leg by calculating a mean z-score across all neuromuscular measures. A group by leg MANOVA and ANOVA were performed to examine group and leg differences for the selected outcomes. RESULTS: After an ACL injury, duration (-4.3 h/week) and level (Tegner activity score of -3.9) of sports activity decreased and was comparable to less-active controls. ACL patients showed bilateral impairments in the star excursion balance test compared to both control groups (P ≤ 0.004) and for central activation ratio compared to active controls (P ≤ 0.002). There were between-leg differences within each group for maximal quadriceps and hamstring strength, voluntary quadriceps activation, star excursion balance test performance, and single-leg hop distance (all P < 0.05), but there were no significant differences in quadriceps force accuracy and variability, knee joint proprioception, and static balance. Overall neuromuscular function (mean z-score) did not differ between groups, but ACL patients' non-injured leg displayed better neuromuscular function than the injured leg (P < 0.05). CONCLUSIONS: Except for poorer dynamic balance and reduced quadriceps activation, ACL patients had no bilateral neuromuscular deficits despite reductions in physical activity after injury. Therapists can use the non-injured leg as a reference to assess the injured leg's function for tasks measured in the present study, excluding dynamic balance and quadriceps activation. Rehabilitation after an ACL injury should be mainly focused on the injured leg. LEVEL OF EVIDENCE: III.

A Novel Mass-Spring-Damper Model Analysis to Identify Landing Deficits in Athletes Returning to Sport After Anterior Cruciate Ligament Reconstruction.

Schneider, DK, Gokeler, A, Otten, E, Ford, KR, Hewett, TE, Divine, JG, Colosimo, AJ, Heidt, RS, and Myer, GD. A Novel mass-spring-damper model analysis to identify landing deficits in athletes returning to sport after anterior cruciate ligament reconstruction. J Strength Cond Res 31(9): 2590-2598, 2017-A mass-spring-damper (MSD) model may serve as an extension of biomechanical data from 3-dimensional motion analysis and epidemiological data which helps to delineate populations at risk for anterior cruciate ligament (ACL) injuries. The purpose of this study was to evaluate such a model. Thirty-six ACL reconstruction (ACLR) group subjects and 67 controls (CTRL) completed single-leg drop landing and single-leg broad jump tasks. Landing ground reaction force data were collected and analyzed with an MSD model. Medians, interquartile ranges, and limb symmetry indices (LSIs) were calculated and comparisons were made within and between groups. During a single-leg drop landing, the ACLR group had a lower spring LSI than the CTRL group (p = 0.015) and landed with decreased stiffness in the involved limb relative to the uninvolved limb (p = 0.021). The ACLR group also had an increased damping LSI relative to the CTRL group (p = 0.045). The ACLR subjects landed with increased stiffness (p = 0.006) and decreased damping (p = 0.003) in their involved limbs compared to CTRL subjects' nondominant limbs. During a single-leg forward broad jump, the ACLR group had a greater spring LSI value than the CTRL group (p = 0.045). The CTRL group also recorded decreased damping values in their nondominant limbs compared with the involved limbs of the ACLR group (p = 0.046). Athletes who have undergone ACLR display different lower-limb dynamics than healthy controls, according to an MSD model. Quadriceps dominance and leg dominance are components of ACLR athletes' landing strategies and may be identified with an MSD model and addressed during rehabilitation.