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Individuals with anterior cruciate ligament reconstruction (ACLR) exhibit less knee kinematic variability while walking than uninjured controls, associated with deleterious changes in cartilage composition linked to an increased risk for early knee osteoarthritis (KOA). It is unknown whether less knee kinematic variability is also associated with worse knee-related patient-reported outcomes (PROs) consistent with KOA development. This study examined associations between kinematic variability during gait and PROs in individuals post-ACLR. Gait kinematics and the Knee Injury and Osteoarthritis Outcome Score (KOOS) were collected from 45 participants 6-months post-ACLR (67% Females; 21.45 ± 4.56 years). Overground gait biomechanics using 3D motion capture were collected, and knee kinematics were extracted for post-processing. Sample entropy (SampEn) was used to calculate knee kinematic variability. Pearson's product-moment correlations were conducted to determine the associations between SampEn and KOOS sub-scores. Additionally, independent samples t-tests were performed to evaluate potential differences in SampEn outcomes between individuals with and without clinically relevant symptoms (defined in the introduction). Less sagittal plane kinematic variability is associated with greater pain ( r  = 0.37, p  = 0.01) and symptoms ( r  = 0.32, p  = 0.03). Symptomatic participants demonstrated less sagittal plane knee kinematic variability compared to asymptomatic participants ( p  = 0.01). The findings suggest less variable gait patterns 6-months post-ACLR may be linked to KOA-related symptoms.

This study explores visuomotor control in athletes for collision avoidance using virtual reality. Thirty-nine athletes navigated dynamic scenarios, pursuing a virtual target while avoiding two to five virtual defenders. Confirmatory Factor Analysis validated a model that captured two features of scanning behavior based on head movements recorded during activity: the overall amount and temporal pattern. Linear mixed models showed that these features significantly differentiated successful from unsuccessful defender avoidance (p < .05), suggesting that efficient environmental scanning is crucial for collision avoidance while highlighting the potential of visuomotor interventions to reduce collision-related sport injuries., Competing Interests: Declaration of interest statement None., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

(1) Background: As digital health technology evolves, the role of accurate medical-gloved hand tracking is becoming more important for the assessment and training of practitioners to reduce procedural errors in clinical settings. (2) Method: This study utilized computer vision for hand pose estimation to model skeletal hand movements during in situ aseptic drug compounding procedures. High-definition video cameras recorded hand movements while practitioners wore medical gloves of different colors. Hand poses were manually annotated, and machine learning models were developed and trained using the DeepLabCut interface via an 80/20 training/testing split. (3) Results: The developed model achieved an average root mean square error (RMSE) of 5.89 pixels across the training data set and 10.06 pixels across the test set. When excluding keypoints with a confidence value below 60%, the test set RMSE improved to 7.48 pixels, reflecting high accuracy in hand pose tracking. (4) Conclusions: The developed hand pose estimation model effectively tracks hand movements across both controlled and in situ drug compounding contexts, offering a first-of-its-kind medical glove hand tracking method. This model holds potential for enhancing clinical training and ensuring procedural safety, particularly in tasks requiring high precision such as drug compounding.

Background: Changes in lower limb joint coordination have been shown to increase localized stress on knee joint soft tissue-a known precursor of osteoarthritis. While 50 % of individuals who undergo anterior cruciate ligament reconstruction (ACLR) develop radiographic osteoarthritis, it is unclear how underlying joint coordination during gait changes post-ACLR. The purpose of this study was twofold: to determine differences in lower limb coordination patterns during gait in ACLR individuals 2, 4, and 6 months post-ACLR and to compare the coordination profiles of the ACLR participants at each timepoint post-ACLR to uninjured matched controls., Methods: We conducted a longitudinal assessment to quantify lower limb coordination at 3 timepoints post-ACLR and compared the ACLR coordination profiles to uninjured controls. Thirty-four ACLR (age = 21.43 ± 4.24 years, mean ± SD; 70.59 % female) and 34 controls (age = 21.42 ± 3.43 years; 70.59 % female) participated. The ACLR group completed 3 overground gait assessments (2,4, and 6 months post-ACLR), and the controls completed 1 assessment, at which lower limb kinematics were collected. Cross-recurrence quantification analysis was used to characterize sagittal and frontal plane ankle-knee, ankle-hip, and knee-hip coordination dynamics. Comprehensive general linear mixed models were constructed to compare between-limb and within-limb coordination outcomes over time post-ACLR and a between-group comparison across timepoints., Results: The ACLR limb demonstrated a more "stuck" sagittal plane knee-hip coordination profile (greater trapping time (TT); p = 0.004) compared bilaterally. Between groups, the ACLR participants exhibited a more predictable ankle-knee coordination pattern (percent determinism (%DET); p < 0.05), stronger coupling between joints (meanline (MNLine)) across all segments (p < 0.05), and greater knee-hip TT (more "stuck"; p < 0.05) compared to the controls at each timepoint in the sagittal plane. Stronger frontal plane knee-hip joint coupling (MNLine) persisted across timepoints within the ACLR group compared to the controls (p < 0.05)., Conclusion: The results indicate ACLR individuals exhibit a distinct and rigid coordination pattern during gait compared to controls within 6-month post-ACLR, which may have long-term implications for knee-joint health., Competing Interests: Declaration of competing interests The authors declare that they have no competing interests., (Copyright © 2024. Production and hosting by Elsevier B.V.)

Quiet eye (QE), the visual fixation on a target before initiation of a critical action, is associated with improved performance. While QE is trainable, it is unclear whether QE can directly predict performance, which has implications for training interventions. This study predicted basketball shot outcome (make or miss) from visuomotor control variables using a decision tree classification approach. Twelve basketball athletes completed 200 shots from six on-court locations while wearing mobile eye-tracking glasses. Training and testing data sets were used for modeling eight predictors (shot location, arm extension time, and absolute and relative QE onset, offset, and duration) via standard and conditional inference decision trees and random forests. On average, the trees predicted over 66% of makes and over 50% of misses. The main predictor, relative QE duration, indicated success for durations over 18.4% (range: 14.5%-22.0%). Training to prolong QE duration beyond 18% may enhance shot success.

Objective: Examine patterns and predictors of skill learning during multisession Enhanced FO rward C oncentration and A ttention L earning (FOCAL+) training., Background: FOCAL+ teaches teens to reduce the duration of off-road glances using real-time error learning. In a randomized controlled trial, teens with ADHD received five sessions of FOCAL+ training and demonstrated significant reductions in extended glances (>2-s) away from the roadway (i.e., long-glances) and a 40% reduced risk of a crash/near-crash event. Teens' improvement in limiting long-glances as assessed after each FOCAL+ training session has not been examined., Method: Licensed teen (ages 16-19) drivers with ADHD ( n = 152) were randomly assigned to five sessions of either FOCAL+ or modified standard driver training. Teens completed driving simulation assessments at baseline, after each training session, and 1 month and 6 months posttraining. Naturalistic driving was monitored for one year., Results: FOCAL+ training produced a 53% maximal reduction in long-glances during postsession simulated driving. The number of sessions needed to achieve maximum performance varied across participants. However, after five FOCAL+ training sessions, number of long-glances was comparable irrespective of when teens achieved their maximum performance. The magnitude of reduction in long-glances predicted levels of long-glances during simulated driving at 1 month and 6 months posttraining but not naturalistic driving outcomes. FOCAL+ training provided the most benefit during training to teens who were younger and had less driving experience., Conclusion: FOCAL+ training significantly reduces long-glances beginning at the 1st training session., Application: Providing five FOCAL+ training sessions early on during teen driving may maximize benefit., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

This introduction to a special issue of Nonlinear Dynamics, Psychology and Life Sciences on the topic of resilience discusses the contributing articles in terms of their flexibility in methods, models, scale, and contexts combined with their integrity in shared theoretical understanding and generative knowledge. The ubiquity of resilience is discussed, a feature of potentially any living or non-living system and substance. This breadth calls for a flexible set of models and methods, along with the quest for integrative theory to make resilience science more resilient. Since resilience involves the ability of a substance or system to persist, to repair or recover, and to evolve, any common theory would consider structural integrity (the ability to hold together), flexibility (the ability to adjust and return), time and timing. Nonlinear dynamical systems theory is proposed as the only scientific perspective capable of building this sort of common knowledge of a ubiquitous process involving these specific features. The synopsis of each article's contribution to the issue includes an analysis of the flexibility the article adds in terms of models, methods, scale, and applied context, along with the theoretical integrity produced with respect to these common features of resilient processes: flexibility, integrity, time, and timing.

Context: Mindfulness interventions (yoga, meditation) in traumatic brain injury populations show promising improvements in injury outcomes. However, most studies include all injury severities and use in-person, general programming lacking accessibility and specificity to the nuance of concussion. Therefore, this study investigated the feasibility and preliminary effectiveness of an online, concussion-focused meditation intervention among young adults with a concussion history., Design: Unblinded, single-arm, pilot intervention., Methods: Fifteen young adults aged 18 to 30 with a concussion history within the past 5 years completed 10 to 20 minutes per day of online, guided meditations for 6 weeks. Feasibility was assessed using the Feasibility of Intervention Measure. Concussion symptoms were measured using the Rivermead Post-Concussion Symptom Questionnaire, perceived stress the Perceived Stress Scale-10, and mindfulness the Five Facet Mindfulness Questionnaire. Descriptive statistics described the study sample and determined intervention adherence and feasibility. Paired sample t tests were used to examine preintervention/postintervention changes in concussion symptoms, perceived stress, and mindfulness, with descriptive statistics further detailing significant t tests., Results: Fifteen participants were enrolled, and 12 completed the intervention. The majority completed 5+ days per week of the meditations, and Feasibility of Intervention Measure (17.4 [1.8]) scores indicated high feasibility. Concussion symptom severity significantly decreased after completing the meditation intervention (11.3 [10.3]) compared with before the intervention (24.5 [17.2]; t[11] = 3.0, P = .01). The number of concussion symptoms reported as worse than before their concussion significantly decreased after completing the meditation intervention (2.7 [3.9]) compared with before the intervention (8.0 [5.7]; t[11] = 3.7, P = .004). Postintervention, 83.33% (n = 10) reported lower concussion symptom severity, and 75.00% (n = 9) reported less concussion symptoms as a mild, moderate, or severe problem (ie, worse than before injury)., Conclusions: Findings suggest positive adherence and feasibility of the meditation intervention, with the majority reporting concussion symptom improvement postintervention. Future research is necessary to expand these pilot findings into a large trial investigating concussion-specific meditation programming.

Knee osteoarthritis is a major cause of global disability and is a major cost for the healthcare system. Lower extremity loading is a determinant of knee osteoarthritis onset and progression; however, technology that assists rehabilitative clinicians in optimizing key metrics of lower extremity loading is significantly limited. The peak vertical component of the ground reaction force (vGRF) in the first 50% of stance is highly associated with biological and patient-reported outcomes linked to knee osteoarthritis symptoms. Monitoring and maintaining typical vGRF profiles may support healthy gait biomechanics and joint tissue loading to prevent the onset and progression of knee osteoarthritis. Yet, the optimal number of sensors and sensor placements for predicting accurate vGRF from accelerometry remains unknown. Our goals were to: 1) determine how many sensors and what sensor locations yielded the most accurate vGRF loading peak estimates during walking; and 2) characterize how prescribing different loading conditions affected vGRF loading peak estimates. We asked 20 young adult participants to wear 5 accelerometers on their waist, shanks, and feet and walk on a force-instrumented treadmill during control and targeted biofeedback conditions prompting 5% underloading and overloading vGRFs. We trained and tested machine learning models to estimate vGRF from the various sensor accelerometer inputs and identified which combinations were most accurate. We found that a neural network using one accelerometer at the waist yielded the most accurate loading peak vGRF estimates during walking, with average errors of 4.4% body weight. The waist-only configuration was able to distinguish between control and overloading conditions prescribed using biofeedback, matching measured vGRF outcomes. Including foot or shank acceleration signals in the model reduced accuracy, particularly for the overloading condition. Our results suggest that a system designed to monitor changes in walking vGRF or to deploy targeted biofeedback may only need a single accelerometer located at the waist for healthy participants., Competing Interests: Jason R. Franz and Brian Pietrosimone are founders and Chief Technology Officer and President, respectively, of VETTA Solutions, Inc, a start-up company with prospective product solutions in the areas of wearable sensor solutions for musculoskeletal health applications. The conceptualization of this study and all data collections and analyses were completed prior to the incorporation date of the company., (Copyright: © 2024 Pimentel et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Objective: The present study examined the association between executive functioning (EF) and risky driving behaviors in teens with ADHD., Method: Teens diagnosed with ADHD ( n  = 179; M age  = 17.4 years) completed two 15-min drives in a fixed-base driving simulator. EF was assessed using parent- and self-report Behavior Rating Inventory of Executive Functioning (BRIEF-2), a temporal reproduction task, and a Go/No-Go task (GNG). Driving outcomes included known predictors of crashes: count of long (>2 s) off-road glances, standard deviation (SD) of lane position (SDLP), mean speed, and SD speed. Generalized linear mixed models, controlling for intelligence and driving experience, were conducted., Results: Higher rates of GNG commission errors predicted higher rates of long off-road glances. Lower parent-rated EF and increased rates of GNG omission errors predicted SDLP. Higher rates of GNG commission errors also predicted faster average driving speed., Conclusion: Heterogeneity in EF is associated with differences in teen ADHD risky driving behaviors., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: Adam Kiefer is a co-inventor of University of North Carolina-owned intellectual property related to eye tracking and performance and is a co-founder of a company (Elipsys LLC).

Human resilience is often considered as static traits using a reductionist approach. More recent work has demonstrated it to be a dynamic and emergent property of complex systems. This narrative review explores human resilience through a self-organizing framework with a specific emphasis on the application of nonlinear modeling approaches. Four classes of approaches are examined: univariate dynamics, bivariate coupling, topological modeling, and network modeling. Univariate dynamics capture the temporal structure and flexibility within a single time series, while bivariate coupling approaches quantify the interaction dynamics and coordination between two time series. Topological modeling identifies bifurcations and attractor dynamics as signals of critical transitions relative to emergence and system stability. Network modeling represents system structure with a focus on connectivity, flexibility, and system integrity. Applying a complex systems framework, this review provides insights into data modeling opportunities for characterizing important features of a system's capacity to bounce back and recover from stress. These characteristics are connected to meta-flexibility, which characterizes a system's adaptive responsiveness to stressors, including post-traumatic growth, and the relation between meta-flexibility and metastability is discussed. Overall, this review provides a foundation of tools for researchers interested in under-standing human resilience through a complex systems framework.

Introduction: Aberrant gait variability has been observed after anterior cruciate ligament reconstruction (ACLR), yet it remains unknown if gait variability is associated with early changes in cartilage composition linked to osteoarthritis development. Our purpose was to determine the association between femoral articular cartilage T1ρ magnetic resonance imaging relaxation times and gait variability., Methods: T1ρ magnetic resonance imaging and gait kinematics were collected in 22 ACLR participants (13 women; 21 ± 4 yr old; 7.52 ± 1.43 months post-ACLR). Femoral articular cartilage from the ACLR and uninjured limbs were segmented into anterior, central, and posterior regions from the weight-bearing portions of the medial and lateral condyles. Mean T1ρ relaxation times were extracted from each region and interlimb ratios (ILR) were calculated (i.e., ACLR/uninjured limb). Greater T1ρ ILR values were interpreted as less proteoglycan density (worse cartilage composition) in the injured limb compared with the uninjured limb. Knee kinematics were collected at a self-selected comfortable walking speed on a treadmill with an eight-camera three-dimensional motion capture system. Frontal and sagittal plane kinematics were extracted, and sample entropy was used to calculate kinematic variability structure (KV structure ). Pearson's product-moment correlations were conducted to determine the associations between T1ρ and KV structure variables., Results: Lesser frontal plane KV structure was associated with greater mean T1ρ ILR in the anterior lateral ( r = - 0.44, P = 0.04) and anterior medial condyles ( r = - 0.47, P = 0 .03). Lesser sagittal plane KV structure was associated with greater mean T1ρ ILR in the anterior lateral condyle ( r = - 0.47, P = 0.03)., Conclusions: The association between less KV structure and worse femoral articular cartilage proteoglycan density suggests a link between less variable knee kinematics and deleterious changes joint tissue changes. The findings suggest that less knee kinematic variability structure is a mechanism linking aberrant gait to early osteoarthritis development., (Copyright © 2023 by the American College of Sports Medicine.)

The practice of early sport specialization, defined as intense year-round training in a single sport at the exclusion of others, is increasing in youth athletics. Despite potential benefits, sport specialization may be detrimental to the health of young athletes, as specialization may increase the risk of musculoskeletal injuries-particularly overuse injuries. However, there remains limited knowledge about how sports specialization uniquely alters underlying sports-related motor behavior. The purpose of this study was to compare the variability of movement patterns exhibited by highly sports specialized youth athletes to that of nonspecialized athletes during performance of a sport-specific, virtual reality based cutting task. It was hypothesized that highly specialized athletes would display different patterns of movement coordination compared to nonspecialized athletes during both the run-up phase and cut-and-decelerate phase. In support of the hypothesis, specialized athletes exhibited both intra- and inter-limb coordination that were significantly different than unspecialized athletes. Overall, the results indicate that the highly specialized athletes tended to exhibit greater degrees of coordination but also the ability to break the coordinated patterns of joint angle changes to execute a cutting maneuver, which requires asymmetric demands on the lower extremities while planting on one leg and changing direction.

Background: Teens with attention deficit-hyperactivity disorder (ADHD) are at increased risk for motor vehicle collisions. A computerized skills-training program to reduce long glances away from the roadway, a contributor to collision risk, may ameliorate driving risks among teens with ADHD., Methods: We evaluated a computerized skills-training program designed to reduce long glances (lasting ≥2 seconds) away from the roadway in drivers 16 to 19 years of age with ADHD. Participants were randomly assigned in a 1:1 ratio to undergo either enhanced Focused Concentration and Attention Learning, a program that targets reduction in the number of long glances (intervention) or enhanced conventional driver's education (control). The primary outcomes were the number of long glances away from the roadway and the standard deviation of lane position, a measure of lateral movements away from the center of the lane, during two 15-minute simulated drives at baseline and at 1 month and 6 months after training. Secondary outcomes were the rates of long glances and collisions or near-collisions involving abrupt changes in vehicle momentum (g-force event), as assessed with in-vehicle recordings over the 1-year period after training., Results: During simulated driving after training, participants in the intervention group had a mean of 16.5 long glances per drive at 1 month and 15.7 long glances per drive at 6 months, as compared with 28.0 and 27.0 long glances, respectively, in the control group (incidence rate ratio at 1 month, 0.64; 95% confidence interval [CI], 0.52 to 0.76; P<0.001; incidence rate ratio at 6 months, 0.64; 95% CI, 0.52 to 0.76; P<0.001). The standard deviation of lane position (in feet) was 0.98 SD at 1 month and 0.98 SD at 6 months in the intervention group, as compared with 1.20 SD and 1.20 SD, respectively, in the control group (difference at 1 month, -0.21 SD; 95% CI, -0.29 to -0.13; difference at 6 months, -0.22 SD; 95% CI, -0.31 to -0.13; P<0.001 for interaction for both comparisons). During real-world driving over the year after training, the rate of long glances per g-force event was 18.3% in the intervention group and 23.9% in the control group (relative risk, 0.76; 95% CI, 0.61 to 0.92); the rate of collision or near-collision per g-force event was 3.4% and 5.6%, respectively (relative risk, 0.60, 95% CI, 0.41 to 0.89)., Conclusions: In teens with ADHD, a specially designed computerized simulated-driving program with feedback to reduce long glances away from the roadway reduced the frequency of long glances and lessened variation in lane position as compared with a control program. During real-world driving in the year after training, the rate of collisions and near-collisions was lower in the intervention group. (Funded by the National Institutes of Health; ClinicalTrials.gov number, NCT02848092.)., (Copyright © 2022 Massachusetts Medical Society.)

Methodologies in applied sport science have predominantly driven a reductionist grounding to component-specific mechanisms to drive athlete training and care. While linear mechanistic approaches provide useful insights, they have impeded progress in the development of more complex network physiology models that consider the temporal and spatial interactions of multiple factors within and across systems and subsystems. For this, a more sophisticated approach is needed and the development of such a methodological framework can be considered a Sport Grand Challenge. Specifically, a transdisciplinary phenomics-based scientific and modeling framework has merit. Phenomics is a relatively new area in human precision medicine, but it is also a developed area of research in the plant and evolutionary biology sciences. The convergence of innovative precision medicine, portable non-destructive measurement technologies, and advancements in modeling complex human behavior are central for the integration of phenomics into sport science. The approach enables application of concepts such as phenotypic fitness, plasticity, dose-response dynamics, critical windows, and multi-dimensional network models of behavior. In addition, profiles are grounded in indices of change, and models consider the athlete's performance or recovery trajectory as a function of their dynamic environment. This new framework is introduced across several example sport science domains for potential integration. Specific factors of emphasis are provided as potential candidate fitness variables and example profiles provide a generalizable modeling approach for precision training and care. Finally, considerations for the future are discussed, including scaling from individual athletes to teams and additional factors necessary for the successful implementation of phenomics., Competing Interests: Author DM was employed by company Apeiron Life. The remaining author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Kiefer and Martin.)

Head impacts and physical exertion are ubiquitous in American football, but the relationship between these factors is poorly understood across a competitive season or even within an individual session. Gameplay characteristics, including player position and session type, may contribute to these relationships but have not been prospectively examined. The current study aimed to determine if an association exists between head impact biomechanics and physical load metrics. We prospectively studied college football players during the 2017-2021 football seasons across representative playing positions (15 offensive and defensive linemen, 11 linebackers and tight ends, and 15 defensive backs, running backs, and receivers). Participants wore halters embedded with Catapult Vector GPS monitoring systems to quantify player load and participant helmets were equipped with the Head Impact Telemetry System to quantify head impact biomechanics and repetitive head impact exposure (RHIE). Generalized linear models and linear regression models were employed to analyze in-session and season-long outcomes, while addressing factors such as player position and session type on our data. Player load was associated with RHIE (p < 0.001). Season-long player load predicted season-long RHIE (R 2  = 0.31; p < 0.001). Position group affected in-session player load (p = 0.025). Both player load and RHIE were greater in games than in practices (p < 0.001), and position group did not affect RHIE (p = 0.343). Physical load burden was associated with RHIE within sessions and across an entire season. Session type affected both RHIE and player load, while position group only affected player load. Our data point to tracking physical load burden as a potential proxy for monitoring anticipated RHIE during the season., (© 2022. The Author(s) under exclusive licence to Biomedical Engineering Society.)

Background: Young athletes who specialize early in a single sport may subsequently be at increased risk of injury. While heightened injury risk has been theorized to be related to volume or length of exposure to a single sport, the development of unhealthy, homogenous movement patterns, and rigid neuromuscular control strategies may also be indicted. Unfortunately, traditional laboratory assessments have limited capability to expose such deficits due to the simplistic and constrained nature of laboratory measurement techniques and analyses., Methods: To overcome limitations of prior studies, the authors proposed a soccer-specific virtual reality header assessment to characterize the generalized movement regularity of 44 young female athletes relative to their degree of sport specialization (high vs low). Participants also completed a traditional drop vertical jump assessment., Results: During the virtual reality header assessment, significant differences in center of gravity sample entropy (a measure of movement regularity) were present between specialized (center of gravity sample entropy: mean = 0.08, SD = 0.02) and nonspecialized center of gravity sample entropy: mean = 0.10, SD = 0.03) groups. Specifically, specialized athletes exhibited more regular movement patterns during the soccer header than the nonspecialized athletes. However, no significant between-group differences were observed when comparing participants' center of gravity time series data from the drop vertical jump assessment., Conclusions: This pattern of altered movement strategy indicates that realistic, sport-specific virtual reality assessments may be uniquely beneficial in exposing overly rigid movement patterns of individuals who engage in repeated sport specialized practice.

Purpose: The present study investigated Special Operations Forces (SOF) combat Servicemember mental health at different SOF career stages in association with resilience., Methods: Fifty-eight SOF combat Service Members either entering SOF (career start; n=38) or multiple years with their SOF organization (mid-career; n=20) self-reported mild traumatic brain injury (TBI) history, resilience, subjective well-being, depression, anxiety, and posttraumatic stress. Poisson regression analyses were employed to test SOF career stage differences in each mental health symptom using resilience, while accounting for other pertinent military factors., Results: There were significant interaction effects of SOF career stage and resilience on mental health symptoms. SOF career start combat Servicemembers endorsed lower depression and posttraumatic stress and higher subjective well-being with higher resilience, but these associations between resilience and mental health symptoms were not seen in SOF mid-career Servicemembers., Conclusions: Although preliminary, the adaptive association between resilience and mental health seemed to be blunted in combat Servicemembers having served multiple years in SOF. This information informs research to provide evaluation tools to support prophylactic performance and long-term health preservation in military populations., (2022.)

Context: Neuromuscular training (NMT) facilitates the acquisition of new movement patterns that reduce the anterior cruciate ligament injury risk. However, the neural mechanisms underlying these changes are unknown., Objective: To determine the relationship between brain activation and biomechanical changes after NMT with biofeedback., Design: Cohort study., Setting: Research laboratory., Patients or Other Participants: Twenty female high school soccer athletes, with 10 in an augmented NMT group and 10 in a control (no training) group., Main Outcome Measure(s): Ten participants completed 6 weeks of NMT augmented with real-time biofeedback to reduce knee injury-risk movements, and 10 participants pursued no training. Augmented neuromuscular training (aNMT) was implemented with visual biofeedback that responded in real time to injury-risk biomechanical variables. A drop vertical jump with 3-dimensional motion capture was used to assess injury-risk neuromuscular changes before and after the 6-week intervention. Brain-activation changes were measured using functional magnetic resonance imaging during unilateral knee and multijoint motor tasks., Results: After aNMT, sensory (precuneus), visual-spatial (lingual gyrus), and motor-planning (premotor) brain activity increased for knee-specific movement; sensorimotor cortex activity for multijoint movement decreased. The knee-abduction moment during landing also decreased (4.66 ± 5.45 newton meters; P = .02; Hedges g = 0.82) in the aNMT group but did not change in the control group (P > .05). The training-induced increased brain activity with isolated knee movement was associated with decreases in knee-abduction moment (r = 0.67; P = .036) and sensorimotor cortex activity for multijoint movement (r = 0.87; P = .001). No change in brain activity was observed in the control group (P > .05)., Conclusions: The relationship between neural changes observed across tasks and reduced knee abduction suggests that aNMT facilitated recruitment of sensory integration centers to support reduced injury-risk mechanics and improve sensorimotor neural efficiency for multijoint control. Further research is warranted to determine if this training-related multimodal neuroplasticity enhances neuromuscular control during more complex sport-specific activities., (© by the National Athletic Trainers' Association, Inc.)

Purpose: Our aim in this study was to psychometrically test resilience assessments (Ego Resiliency Scale [ER89], Connor-Davidson Resilience Scale [CD-RISC 25], Responses to Stressful Experiences Scale [RSES short-form]) and describe resilience levels in a Special Operations Forces (SOF) combat sample., Methods: Fifty-eight SOF combat Servicemembers either entering SOF (career start; n = 38) or having served multiple years with their SOF organization (mid-career; n = 20) self-reported resilience, mild traumatic brain injury (mTBI) history, and total military service., Results: All resilience metrics demonstrated acceptable internal consistency, but ceiling effects were found for CD-RISC and RSES scores. ER89 scores were moderate on average. ER89 scores were higher in SOF career start than mid-career Servicemembers (ηρ2 = 0.07) when accounting for the interaction between SOF career stage and total military service (ηρ2 = 0.07)., Discussion: SOF mid-career Servicemembers had similar ER89 resilience scores with more total military service. The SOF career start combat Servicemembers had higher ER89 measured resilience with less total military service only, potentially showing a protective effect of greater service before entering SOF., Conclusion: The ER89 may be a more optimal military resilience metric than the other metrics studied; longitudinal research on SOF combat Servicemember resilience is warranted.

Military resilience research is increasing due to the growing literature associating resilience with stress adaptation. This study aimed to investigate which physiological stress adaptation components were associated with resilience in Special Operations Forces combat service members. Special Operations Forces combat service members (n = 117) self-reported resilience (ER89) and lifetime clinician-confirmed mild traumatic brain injury history. Participants also underwent transcranial Doppler ultrasonography to measure middle cerebral artery velocity during rest and a breath-holding task. Neither resilience nor mild traumatic brain injury history was significantly associated with middle cerebral artery velocity percent increase following breath-holding; younger Special Operations Forces combat service members had a higher percent increase in middle cerebral artery velocity following a breath-holding task. Resilience was negatively associated with time to return to baseline middle cerebral artery velocity following peak velocity; whereas, mild traumatic brain injury history did not have a significant association. The Special Operations Forces combat service members that scored higher in resilience tended to return to baseline middle cerebral artery velocity following peak velocity faster than their less resilient counterparts. More resilient Special Operations Forces combat service members recovered faster from physiological stress (breath-holding) than less resilient counterparts. This is the first study to investigate resilience and cerebrovascular stress response and recovery in this population. Our initial findings indicated that the Ego Resiliency Scale may be an optimal resilience psychometric and should be used to evaluate effective military resilience trainings, which aim to improve performance and mental health., (© 2021 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.)

Markerless motion capture systems are promising for the assessment of movement in more real world research and clinical settings. While the technology has come a long way in the last 20 years, it is important for researchers and clinicians to understand the capacities and considerations for implementing these types of systems. The current review provides a SWOT (Strengths, Weaknesses, Opportunities, and Threats) analysis related to the successful adoption of markerless motion capture technology for the assessment of lower-limb musculoskeletal kinematics in sport medicine and performance settings. 31 articles met the a priori inclusion criteria of this analysis. Findings from the analysis indicate that the improving accuracy of these systems via the refinement of machine learning algorithms, combined with their cost efficacy and the enhanced ecological validity outweighs the current weaknesses and threats. Further, the analysis makes clear that there is a need for multidisciplinary collaboration between sport scientists and computer vision scientists to develop accurate clinical and research applications that are specific to sport. While work remains to be done for broad application, markerless motion capture technology is currently on a positive trajectory and the data from this analysis provide an efficient roadmap toward widespread adoption., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Armitano-Lago, Willoughby and Kiefer.)

The best predictor of future injury is previous injury and this has not changed in a quarter century despite the introduction of evidence-based medicine and associated revisions to post-injury treatment and care. Nearly nine million sports-related injuries occur annually, and the majority of these require medical intervention prior to clearance for the athlete to return to play (RTP). Regardless of formal care, these athletes remain two to four times more likely to suffer a second injury for several years after RTP. In the case of children and young adults, this sets them up for a lifetime of negative health outcomes. Thus, the initial injury is the tipping point for a post-injury cascade of negative sequelae exposing athletes to more physical and psychological pain, higher medical costs, and greater risk of severe long-term negative health throughout their life. This chapter details the technologies and method that make up the automated Intelligent Phenotypic Plasticity Platform (IP 3 )-a revolutionary new approach to the current standard of post-injury care that identifies and targets deficits that underly second injury risk in sport. IP 3 capitalizes on the biological concept of phenotypic plasticity (PP) to quantify an athlete's functional adaptability across different performance environments, and it is implemented in two distinct steps: (1) phenomic profiling and (2) precision treatment. Phenomic profiling indexes the fitness and subsequent phenotypic plasticity of an individual athlete, which drives the personalization of the precision treatment step. IP 3 leverages mixed-reality technologies to present true-to-life environments that test the athlete's ability to adapt to dynamic stressors. The athlete's phenotypic plasticity profile is then used to drive a precision treatment that systematically stresses the athlete, via a combination of behavioral-based and genetic fuzzy system models, to optimally enhance the athlete's functional adaptability. IP 3 is computationally light-weight and, through the integration with mixed-reality technologies, promotes real-time prediction, responsiveness, and adaptation. It is also the first ever phenotypic plasticity-based precision medicine platform, and the first precision sports medicine platform of any kind., (© 2022. Springer Science+Business Media, LLC, part of Springer Nature.)

AbstractsBiofeedback has been effectively implemented to improve the mediation and distribution of joint loads during gait, however, the inability to effectively coordinate lower limb movement by altering loading patterns may increase pathological stress and risk of injury and deleterious joint changes. This study examined the influence cueing an increase or decrease in lower extremity loading has on inter- and intralimb joint coordination during gait, applied herein for 12 persons following anterior cruciate ligament reconstruction across three loading conditions (control, high, and low). Visual biofeedback was presented on a screen via a force-measuring treadmill with targeted changes prescribed based on stride-to-stride peak vertical ground reaction forces bilaterally. The pattern and stability of coordination dynamics among each of the ankle, hip and knee joint pairs were assessed via discrete relative phase and cross-recurrence quantification analyses for each condition. High and low loading altered the pattern and stability of intralimb coordination; low loading led to decreased coordination stability (20° greater than control condition) and high loading resulted in a more tightly coupled coordination pattern (higher %CDET). With thoughtful consideration for movement control, biofeedback can be used to target mechanisms leading to long-term deleterious joint adaptations.

Athletes commonly make decisions about the passability of closing gaps when navigating sport environments. This study examined whether increased temporal pressure to arrive at a desired location modifies these decisions. Thirty participants navigated toward a waypoint in a virtual, sport-inspired environment. To do so, they had to decide whether they could pass through closing gaps of virtual humans (and take the shortest route) or steer around them (and take a longer route). The decision boundary of participants who were time pressured to arrive at a waypoint was biased toward end gaps of smaller sizes and was less reliably defined, resulting in a higher number of collisions. Effects of temporal pressure were minimized with experience in the experimental task. Results indicate that temporal pressure affects perceptual-motor processes supporting information pickup and shapes the information-action coupling that drives compliance with navigation demands. Theoretical and practical implications are discussed.

(1) Background: Biomechanics during landing tasks, such as the kinematics and kinetics of the knee, are altered following anterior cruciate ligament (ACL) injury and reconstruction. These variables are recommended to assess prior to clearance for return to sport, but clinicians lack access to the current gold-standard laboratory-based assessment. Inertial sensors serve as a potential solution to provide a clinically feasible means to assess biomechanics and augment the return to sport testing. The purposes of this study were to (a) develop multi-sensor machine learning algorithms for predicting biomechanics and (b) quantify the accuracy of each algorithm. (2) Methods: 26 healthy young adults completed 8 trials of a double limb jump landing task. Peak vertical ground reaction force, peak knee flexion angle, peak knee extension moment, and peak sagittal knee power absorption were assessed using 3D motion capture and force plates. Shank- and thigh- mounted inertial sensors were used to collect data concurrently. Inertial data were submitted as inputs to single- and multiple- feature linear regressions to predict biomechanical variables in each limb. (3) Results: Multiple-feature models, particularly when an accelerometer and gyroscope were used together, were valid predictors of biomechanics (R 2 = 0.68-0.94, normalized root mean square error = 4.6-10.2%). Single-feature models had decreased performance (R 2 = 0.16-0.60, normalized root mean square error = 10.0-16.2%). (4) Conclusions: The combination of inertial sensors and machine learning provides a valid prediction of biomechanics during a double limb landing task. This is a feasible solution to assess biomechanics for both clinical and real-world settings outside the traditional biomechanics laboratory.

Background: The development of stable postural control is characterized by changes in sway variability and periods of rapid reorganization of motor system components., Research Question: The current study examined whether changing biomechanical and perceptual demands influences the postural control behavior during development., Method: The center of pressure (COP) was assessed via a cross-sectional design. Data were collected from 48 females in three age groups (late childhood, mid-adolescence, and young adulthood) during four quiet stance conditions: (1) eyes open with feet apart, (2) eyes open with feet together, (3) eyes closed with feet apart, and (4) eyes closed with feet together. Linear measures included total path length of the COP and the mean/standard deviation of the overall COP position and speed. To characterize the sway patterns via nonlinear analyses, the speed and two-dimensional positional time series were submitted to sample entropy and Renyi entropy, respectively., Results: The linear results indicated that the late childhood group displayed longer COP trajectories (p < .001) and faster and more variable COP speed (p's < .001). These results held for both the feet apart and feet together conditions, independent of vision. The nonlinear results indicated that the late childhood group exhibited less regularity, overall, in their COP sway position (i.e., Renyi entropy) compared to the two older groups in the feet apart condition (p's ≤ .041), and to the young adults in the feet together condition, independent of vision (p <  .001). However, the mid-adolescent group demonstrated greater regularity in their COP speed (i.e., sample entropy) when their eyes were closed compared to the other two groups, independent of stance (p's < .05)., Significance: The linear results support previous findings, while the nonlinear measures indicate sway characteristics that may provide a window into the development of underlying control processes that regulate quiet standing., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Biofeedback has recently been explored to target deviant lower extremity loading mechanics following anterior cruciate ligament reconstruction (ACLR) to mitigate the development of post traumatic osteoarthritis. The impact this feedback has on the structure of the stride interval dynamics-a barometer of gait system health-however, have yet to be examined. This study was designed to assess how feedback, used to alter lower-extremity loading during gait, affects the structure of stride interval variability by examining long-range stride-to-stride correlations during gait in those with unilateral ACLR. Twelve participants walked under three separate loading conditions: (1) control (i.e., no cue) (2) high loading, and (3) low loading. Baseline vertical ground reaction force (vGRF) data was used to calculate a target 5% change in vGRF for the appropriate loading condition (i.e., high loading was +5% vGRF, low loading was -5% vGRF). The target for the load condition was displayed on a screen along with real-time vGRF values, prescribing changes in stride-to-stride peak vertical ground reaction forces of each limb. From time-series of stride intervals (i.e., duration), we analyzed the mean and standard deviation of stride-to-stride variability and, via detrended fluctuation analysis (i.e., DFA α), temporal persistence for each feedback condition. Both the high and low loading conditions exhibited a change toward more temporally persistent stride intervals (high loading: α =0.92, low loading: α = 0.98) than walking under the control condition (α = 0.78; high vs. control: p = .026, low vs. control: p = .001). Overall, these results indicate that altering lower extremity load changes the temporal persistence of the stride internal dynamics in ACLR individuals, demonstrating the implications of the design of gait training interventions and the influence feedback has on movement strategies., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Background: Improving the assessment and training of tracheal intubation is hindered by the lack of a sufficiently validated profile of expertise. Although several studies have examined biomechanics of tracheal intubation, there are significant gaps in the literature. We used 3-dimensional motion capture to study pediatric providers performing simulated tracheal intubation to identify candidate kinematic variables for inclusion in an expert movement profile., Methods: Pediatric anesthesiologists (experienced) and pediatric residents (novices) were recruited from a pediatric institution to perform tracheal intubation on airway mannequins in a motion capture laboratory. Subjects performed 21 trials of tracheal intubation, 3 each of 7 combinations of laryngoscopic visualization (direct or indirect), blade type (straight or curved), and mannequin size (adult or pediatric). We used repeated measures analysis of variance to determine whether various kinematic variables (3-trial average for each participant) were associated with experience., Results: Eleven experienced and 15 novice providers performed 567 successful tracheal intubation attempts (9 attempts unsuccessful). For laryngoscopy, experienced providers exhibited shorter path length (total distance traveled by laryngoscope handle; 77.6 ± 26.0 cm versus 113.9 ± 53.7 cm; P = 0.013) and greater angular variability at the left wrist (7.4 degrees versus 5.5 degrees, P = 0.013) and the left elbow (10.1 degrees versus 7.6 degrees, P = 0.03). For intubation, experienced providers exhibited shorter path length of the right hand (mean = 61.1 cm versus 99.9 cm, P < 0.001), lower maximum acceleration of the right hand (0.19 versus 0.14 m/s, P = 0.033), and smaller angular, variability at the right elbow (9.7 degrees versus 7.9 degrees, P = 0.03)., Conclusions: Our study and the available literature suggest specific kinematic variables for inclusion in an expert profile for tracheal intubation. Future studies should include a larger sample of practitioners, actual patients, and measures of the cognitive and affective components of expertise.

Prospective evidence indicates that functional biomechanics and brain connectivity may predispose an athlete to an anterior cruciate ligament injury, revealing novel neural linkages for targeted neuromuscular training interventions. The purpose of this study was to determine the efficacy of a real-time biofeedback system for altering knee biomechanics and brain functional connectivity. Seventeen healthy, young, physically active female athletes completed 6 weeks of augmented neuromuscular training (aNMT) utilizing real-time, interactive visual biofeedback and 13 served as untrained controls. A drop vertical jump and resting state functional magnetic resonance imaging were separately completed at pre- and posttest time points to assess sensorimotor adaptation. The aNMT group had a significant reduction in peak knee abduction moment (pKAM) compared to controls (p = .03, d = 0.71). The aNMT group also exhibited a significant increase in functional connectivity between the right supplementary motor area and the left thalamus (p = .0473 after false discovery rate correction). Greater percent change in pKAM was also related to increased connectivity between the right cerebellum and right thalamus for the aNMT group (p = .0292 after false discovery rate correction, r 2  = .62). No significant changes were observed for the controls (ps > .05). Our data provide preliminary evidence of potential neural mechanisms for aNMT-induced motor adaptations that reduce injury risk. Future research is warranted to understand the role of neuromuscular training alone and how each component of aNMT influences biomechanics and functional connectivity., (© 2020 Society for Psychophysiological Research.)

Anterior cruciate ligament (ACL) injuries are physically and emotionally debilitating for athletes,while motor and biomechanical deficits that contribute to ACL injury have been identified, limited knowledge about the relationship between the central nervous system (CNS) and biomechanical patterns of motion has impeded approaches to optimize ACL injury risk reduction strategies. In the current study it was hypothesized that high-risk athletes would exhibit altered temporal dynamics in their resting state electrocortical activity when compared to low-risk athletes. Thirty-eight female athletes performed a drop vertical jump (DVJ) to assess their biomechanical risk factors related to an ACL injury. The athletes' electrocortical activity was also recorded during resting state in the same visit as the DVJ assessment. Athletes were divided into low- and high-risk groups based on their performance of the DVJ. Recurrence quantification analysis was used to quantify the temporal dynamics of two frequency bands previously shown to relate to sensorimotor and attentional control. Results revealed that high-risk participants showed more deterministic electrocortical behavior than the low-risk group in the frontal theta and central/parietal alpha-2 frequency bands. The more deterministic resting state electrocortical dynamics for the high-risk group may reflect maladaptive neural behavior-excessively stable deterministic patterning that makes transitioning among functional task-specific networks more difficult-related to attentional control and sensorimotor processing neural regions., (© 2020 Society for Psychophysiological Research.)

In the past decades, much research has examined the negative effects of stressors on the performance of athletes. However, according to evolutionary biology, organisms may exhibit growth under stress, a phenomenon called antifragility. For both coaches and their athletes, a key question is how to design training conditions to help athletes develop the kinds of physical, physiological, and behavioral adaptations underlying antifragility. An answer to this important question requires a better understanding of how individual athletes respond to stress or loads in the context of relevant sports tasks. In order to contribute to such understanding, the present study leverages a theoretical and methodological approach to generate individualized load-response profiles in the context of a climbing task. Climbers ( n = 37) were asked to complete different bouldering (climbing) routes with increasing loading (i.e. difficulty). We quantified the behavioral responses of each individual athlete by mathematically combining two measures obtained for each route: (a) maximal performance (i.e. the percentage of the route that was completed) and (b) number of attempts required to achieve maximal performance. We mapped this composite response variable as a function of route difficulty. This procedure resulted in load-response curves that captured each athlete's adaptability to stress, termed phenotypic plasticity (PP), specifically operationalized as the area under the generated curves. The results indicate individual load-response profiles (and by extension PP) for athletes who perform at similar maximum levels. We discuss how these profiles might be used by coaches to systematically select stress loads that may be ideally featured in performance training., (Copyright © 2020 Hill, Kiefer, Silva, Van Yperen, Meijer, Fischer and Den Hartigh.)

Context: Laboratory-based biomechanical analyses of sport-relevant movements such as landing and cutting have classically been used to quantify kinematic and kinetic factors in the context of injury risk, which are then used to inform targeted interventions designed to improve risky movement patterns during sport. However, the noncontextual nature of standard assessments presents challenges for assessing sport-relevant skill transfer., Objective: To examine injury-risk biomechanical differences exhibited by athletes during a jump-landing task performed as part of both a standard biomechanical assessment and a simulated, sport-specific virtual reality (VR)-based assessment., Design: Observational study., Setting: Medical center laboratory., Participants: Twenty-two female adolescent soccer athletes (age = 16.0 [1.4] y, height = 165.6 [4.9] cm, and weight = 60.2 [11.4] kg)., Interventions: The landing performance was analyzed for a drop vertical jump task and a VR-based, soccer-specific corner-kick scenario in which the athletes were required to jump to head a virtual soccer ball and land., Main Outcome Measures: Hip, knee, and ankle joint kinematic differences in the frontal and sagittal planes., Results: Athletes exhibited reduced hip and ankle flexion, hip abduction, and frontal plane ankle excursion during landing in realistic sport scenario compared with the standard drop vertical jump task., Conclusion: VR-based assessments can provide a sport-specific context in which to assess biomechanical deficits that predispose athletes for lower-extremity injury and offer a promising approach to better evaluate skill transfer to sport that can guide future injury prevention efforts.

This technical report describes the design and implementation of a novel biofeedback system to reduce biomechanical risk factors associated with anterior cruciate ligament (ACL) injuries. The system provided objective real-time biofeedback driven by biomechanical variables associated with increased ACL injury risk without the need of a present expert. Eleven adolescent female athletes (age = 16.7 ± 1.34 yrs; height = 1.70 ± 0.05 m; weight = 62.20 ± 5.63 kg) from the same varsity high school volleyball team were enrolled in the experiment. Participants first completed 10 bodyweight squats in the absence of the biofeedback (pretest), 40 bodyweight squats while interacting with the biofeedback, and a final 10 bodyweight squats in the absence of the biofeedback (posttest). Participants also completed three pretest drop vertical jumps and three posttest drop vertical jumps. Results revealed significant improvements in squat performance, as quantified by a novel heat map analysis, from the pretest to the posttest. Additionally, participants displayed improvements in landing mechanics during the drop vertical jump. This study demonstrates that participants were able to interact effectively with the real-time biofeedback and that biomechanical improvements observed during squatting translated to a separate task., (© Journal of Sports Science and Medicine.)

Biomechanical analysis can effectively identify factors associated with task performance and injury risk, but often does not account for the interaction among the components that underlie task execution. Uncontrolled manifold (UCM) analyses were applied to data from 38 female, adolescent athletes performing single-leg drop landings and were used to differentiate successful and unsuccessful task performance by examining the frontal plane joint variance within the UCM (VUCM) that stabilized the horizontal center of mass position (VUCM) and within the orthogonal subspace (VORT). The UCM revealed stronger coordination, indicated by the VUCM/VORT ratio, in the successful condition. This may inform future research examining reduced motor coordination in failed movement tasks and its relation to injury risk and allow for targeted interventions that consider coordination processes rather than joint-specific outcomes.

Context: Existing anterior cruciate ligament (ACL) injury prevention programs have failed to reverse the high rate of ACL injuries in adolescent female athletes., Objective: This investigation attempts to overcome factors that limit efficacy with existing injury prevention programs through the use of a novel, objective, and real-time interactive visual feedback system designed to reduce the biomechanical risk factors associated with ACL injuries., Design: Cross-over study., Setting: Medical center laboratory., Participants: A total of 20 females (age = 19.7 [1.34] y; height = 1.74 [0.09] m; weight = 72.16 [12.45] kg) participated in this study., Methods: Participants performed sets of 10 bodyweight squats in each of 8 training blocks (ie, 4 real-time and 4 control blocks) and 3 testing blocks for a total of 110 squats. Feedback conditions were blocked and counterbalanced with half of participants randomly assigned to receive the real-time feedback block first and half receiving the control (sham) feedback first., Results: Heat map analysis revealed that during interaction with the real-time feedback, squat performance measured in terms of key biomechanical parameters was improved compared with performance when participants squatted with the sham stimulus., Conclusions: This study demonstrates that the interactive feedback system guided participants to significantly improve movement biomechanics during performance of a body weight squat, which is a fundamental exercise for a longer term ACL injury risk reduction intervention. A longer training and testing period is necessary to investigate the efficacy of this feedback approach to effect long-term adaptations in the biomechanical risk profile of athletes.

Objective: To estimate the incidence proportion (IP) and incidence rate (IR) of ACL injury in football players., Design: Systematic review with meta-analysis., Data Sources: PubMed, CINAHL and SPORTDiscus electronic databases were searched from inception to 20 January 2017., Eligibility Criteria for Selecting Study: Studies that reported the total number of participants/population by sex, total number of ACL injuries by sex and total person-time by sex were included., Results: Twenty-eight studies were included. The IP and IR of ACL injury in female football players were 2.0% (95% CI 1.2% to 3.1%) and 2.0/10 000 athlete exposures (AEs) (95% CI 1.6 to 2.6; I 2 =91%) over a period of one season to 4 years. The IP and IR of ACL injury in male players were 3.5% (95% CI 0.7% to 8.2%) and 0.9/10 000 AEs (95% CI 0.7 to 1.1; I 2 =94%). Studies that evaluated matched cohorts of female and male players showed no difference in IP (relative risk=1.2; 95% CI 0.9 to 1.6; P=0.47) over a period of one season to 4 years. Women were at greater risk than men (incidence rate ratio (IRR)=2.2; 95% CI 1.6 to 3.1; I 2 =83%; P<0.001). When accounting for participation level, the difference in IR between women and men was greatest for intermediate players (IRR=2.9; 95% CI 2.4 to 3.6) compared with amateur (IRR=2.6; 95% CI 1.4 to 4.8) and elite (IRR=2.0; 95% CI 1.1 to 3.4) players., Summary/conclusion: Overall, more men sustained ACL injury in football. There was no difference in the relative risk of ACL injury between female and male football players in a window that spanned one season to 4 years. The IR of ACL injury among women was 2.2 times higher than the IR of ACL injury among men. The reported sex disparity in ACL injury was independent of participation level., Competing Interests: Competing interests: None declared., (© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2019. All rights reserved. No commercial use is permitted unless otherwise expressly granted.)

Exposure to explosive blasts places one at risk for traumatic brain injury, especially for special weapons and tactics (SWAT) and military personnel, who may be repeatedly exposed to blasts. In the current study, the effectiveness of a jugular vein compression collar to prevent alterations in resting-state electrocortical activity following a single-SWAT breacher training session was investigated. SWAT team personnel were randomly assigned to wear a compression collar during breacher training and resting state electroencephalography (EEG) was measured within 2 days prior to and two after breacher training. It was hypothesized that significant changes in brain dynamics-indicative of possible underlying neurodegenerative processes-would follow blast exposure for those who did not wear the collar, with ameliorated changes for the collar-wearing group. Using recurrence quantification analysis (RQA) it was found that participants who did not wear the collar displayed longer periods of laminar electrocortical behavior (as indexed by RQA's vertical max line measure) after breacher training. It is proposed that the blast wave exposure for the no-collar group may have reduced the number of pathways, via axonal disruption-for electrical transmission-resulting in the EEG signals becoming trapped in laminar states for longer periods of time. Longer laminar states have been associated with other electrocortical pathologies, such as seizure, and may be important for understanding head trauma and recovery.

Context: A limiting factor for reducing anterior cruciate ligament injury risk is ensuring that the movement adaptions made during the prevention program transfer to sport-specific activity. Virtual reality provides a mechanism to assess transferability, and neuroimaging provides a means to assay the neural processes allowing for such skill transfer., Objective: To determine the neural mechanisms for injury risk-reducing biomechanics transfer to sport after anterior cruciate ligament injury prevention training., Design: Cohort study., Setting: Research laboratory., Participants: Four healthy high school soccer athletes., Interventions: Participants completed augmented neuromuscular training utilizing real-time visual feedback. An unloaded knee extension task and a loaded leg press task were completed with neuroimaging before and after training. A virtual reality soccer-specific landing task was also competed following training to assess transfer of movement mechanics., Main Outcome Measures: Landing mechanics during the virtual reality soccer task and blood oxygen level-dependent signal change during neuroimaging., Results: Increased motor planning, sensory and visual region activity during unloaded knee extension and decreased motor cortex activity during loaded leg press were highly correlated with improvements in landing mechanics (decreased hip adduction and knee rotation)., Conclusion: Changes in brain activity may underlie adaptation and transfer of injury risk-reducing movement mechanics to sport activity. Clinicians may be able to target these specific brain processes with adjunctive therapy to facilitate intervention improvements transferring to sport.

Background: Female athletes are at an increased risk of developing patellofemoral pain (PFP) relative to male athletes. The unique effects of maturation may compound that risk. Hypothesis/Purpose: The purpose was to evaluate the neuromuscular control mechanisms that are adaptive to pubertal maturation and determine their relative contribution to PFP development. It was hypothesized that aberrant landing mechanics (reduced sagittal-plane and increased frontal- and transverse-plane kinematics and kinetics) would be associated with an increased risk for PFP., Study Design: Cohort study; Level of evidence, 2., Methods: There were 506 high school female athletes who completed a detailed medical history, the Anterior Knee Pain Scale, and a knee examination for the diagnosis of PFP and attended follow-up appointments. Athletes performed a drop vertical jump task instrumented with force plates, and biomechanical measures generated from standard 3-dimensional biomechanical analyses were used to classify participants into high- or low-risk knee and hip landing profiles for the development of PFP. The biomechanical measures used in the knee landing profile included sagittal-plane knee range of motion, peak knee abduction angle, peak knee abduction moment, and peak-to-peak transverse-plane knee moment. The biomechanical measures used in the hip landing profile included sagittal-plane hip range of motion, peak hip extensor moment, peak abductor moment, and peak hip rotator moment. Testing was conducted at sport-specific preseason appointments over the course of 2 years, and changes in pubertal status, landing profile, and PFP development were documented., Results: Female athletes with high-risk hip landing profiles experienced increased hip flexion and decreased abductor, rotator, and extensor moments. Participants with high-risk hip landing profiles who transitioned to postpubertal status at follow-up had higher odds (odds ratio, 2.1 [95% CI, 1.1-4.0]; P = .02) of moving to a low-risk hip landing profile compared with those who had not reached postpubertal status at follow-up. Participants with high-risk knee landing profiles experienced decreased knee flexion and increased knee abduction, external abductor, and external rotator moments. Pubertal maturation was not associated with a change in the high-risk knee landing profile at follow-up., Conclusion: The progression from prepubertal to postpubertal status may have a protective effect on high-risk hip mechanics but no similar adaptations in high-risk knee mechanics during maturation. These data indicate that before puberty, maladaptive hip mechanics may contribute to PFP, while aberrant knee mechanics associated with PFP are sustained throughout the maturational process in young female athletes.

Dyslexia, or reading difficulty (RD), is characterized by slow, inaccurate reading and accompanied by deficit in executive functions (EF) and altered functional connectivity (FC) in the related networks (i.e., cingulo-opercular). Individuals with RD also present with altered oculomotor gaze patterns that include longer fixation times. The researchers examined the relationship between fixation times and FC of neural circuits related to EF during rest in children with RD and typical readers. Nineteen children participated in a 10-min resting-state scan. FC analysis was performed with the anterior cingulate cortex (ACC), related to cognitive control, chosen as a seed. Fixation time during word reading was used as a covariate of interest. Results demonstrated that FC between the ACC and the left inferior frontal cortex pars triangularis and left inferior prefrontal cortex during rest were negatively correlated with fixation times during word reading. These exploratory results support the critical role for the cingulo-opercular network, which is related to cognitive control, in the reading process, and likely also in reading impairment.

Objectives: To evaluate associations between pre-season oculomotor performance on visual tracking tasks and in-season head impact incidence during high school boys ice hockey., Design: Prospective observational study design., Methods: Fifteen healthy high school aged male hockey athletes (M=16.50±1.17years) performed two 30s blocks each of a prosaccade and self-paced saccade task, and two trials each of a slow, medium, and fast smooth pursuit task (90°s -1 ; 180°s -1 ; 360°s -1 ) during the pre-season. Regular season in-game collision data were collected via helmet-mounted accelerometers. Simple linear regressions were used to examine relations between oculomotor performance measures and collision incidence at various impact thresholds., Results: The variability of prosaccade latency was positively related to total collisions for the 20g force cutoff (p=0.046, adjusted R 2 =0.28). The average self-paced saccade velocity (p=0.020, adjusted R 2 =0.37) and variability of smooth pursuit gaze velocity (p=0.012, adjusted R 2 =0.47) were also positively associated with total collisions for the 50g force cutoff., Conclusions: These results provide preliminary evidence that less efficient oculomotor performance on three different oculomotor tasks is associated with increased incidence of head impacts during a competitive ice hockey season. The variability of prosaccade latency, the average self-paced saccade velocity and the variability of gaze velocity during predictable smooth pursuit all related to increased head impacts. Future work is needed to further understand player initiated collisions, but this is an important first step toward understanding strategies to reduce incidence of injury risk in ice hockey, and potentially contact sports more generally., (Copyright © 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.)

Lack of adequate physical activity in children is an epidemic that can result in obesity and other poor health outcomes across the lifespan. Physical activity interventions focused on motor skill competence continue to be developed, but some interventions, such as neuromuscular training (NMT), may be limited in how early they can be implemented due to dependence on the child's level of cognitive and perceptual-motor development. Early implementation of motor-rich activities that support motor skill development in children is critical for the development of healthy levels of physical activity that carry through into adulthood. Virtual reality (VR) training may be beneficial in this regard. VR training, when grounded in an information-based theory of perceptual-motor behavior that modifies the visual information in the virtual world, can promote early development of motor skills in youth akin to more natural, real-world development as opposed to strictly formalized training. This approach can be tailored to the individual child and training scenarios can increase in complexity as the child develops. Ultimately, training in VR may help serve as a precursor to "real-world" NMT, and once the child reaches the appropriate training age can also augment more complex NMT regimens performed outside of the virtual environment.

Emerging evidence indicates that repetitive head impacts, even at a sub-concussive level, may result in exacerbated or prolonged neurological deficits in athletes. This study aimed to: 1) quantify the effect of repetitive head impacts on the alteration of neuronal activity based on functional magnetic resonance imaging (fMRI) of working memory after a high school football season; and 2) determine whether a neck collar that applies mild jugular vein compression designed to reduce brain energy absorption in head impact through "slosh" mitigation can ameliorate the altered fMRI activation during a working memory task. Participants were recruited from local high school football teams with 27 and 25 athletes assigned to the non-collar and collar group, respectively. A standard N-Back task was used to engage working memory in the fMRI at both pre- and post-season. The two study groups experienced similar head impact frequency and magnitude during the season (all p > 0.05). fMRI blood oxygen level dependent (BOLD) signal response (a reflection of the neuronal activity level) during the working memory task increased significantly from pre- to post-season in the non-collar group (corrected p < 0.05), but not in the collar group. Areas displaying less activation change in the collar group (corrected p < 0.05) included the precuneus, inferior parietal cortex, and dorsal lateral prefrontal cortex. Additionally, BOLD response in the non-collar group increased significantly in direct association with the total number of impacts and total g-force (p < 0.05). Our data provide initial neuroimaging evidence for the effect of repetitive head impacts on the working memory related brain activity, as well as a potential protective effect that resulted from the use of the purported brain slosh reducing neck collar in contact sports.

Coherent collective behavior emerges from local interactions between individuals that generate group dynamics. An outstanding question is how to quantify group coordination of non-rhythmic behavior, in order to understand the nature of these dynamics at both a local and global level. We investigate this problem in the context of a small group of four pedestrians walking to a goal, treating their speed, and heading as behavioral variables. To measure the local coordination between pairs of pedestrians, we employ cross-correlation to estimate coupling strength and cross-recurrence quantification (CRQ) analysis to estimate dynamic stability. When compared to reshuffled virtual control groups, the results indicate lower-dimensional behavior and a stronger, more stable coupling of walking speed in real groups. There were no differences in heading alignment observed between the real and virtual groups, due to the common goal. By modeling the local speed coupling, we can simulate coordination at the dyad and group levels. The findings demonstrate spontaneous coordination in pedestrian groups that gives rise to coherent global behavior. They also offer a methodological approach for investigating group dynamics in more complex settings.

Successfully meeting a shared goal usually requires co-actors to adopt complementary roles. However, in many cases, who adopts what role is not explicitly predetermined, but instead emerges as a consequence of the differences in the individual abilities and constraints imposed upon each actor. Perhaps the most basic of roles are leader and follower . Here, we investigated the emergence of "leader-follower" dynamics in inter-personal coordination using a joint supra-postural task paradigm (Ramenzoni et al., 2011; Athreya et al., 2014). Pairs of actors were tasked with holding two objects in alignment (each actor manually controlled one of the objects) as they faced different demands for stance (stable vs. difficult) and control (which actor controlled the larger or smaller object). Our results indicate that when actors were in identical stances, neither led the inter-personal (between actors) coordination by any systematic fashion. Alternatively, when asymmetries in postural demands were introduced, the actor with the more difficult stance led the coordination (as determined using cross-recurrence quantification analysis). Moreover, changes in individual stance difficulty resulted in similar changes in the structure of both intra-personal (individual) and inter-personal (dyadic) coordination, suggesting a scale invariance of the task dynamics. Implications for the study of interpersonal coordination are discussed.

Assessment of deficits in oculomotor function may be useful to detect visuomotor impairments due to a closed head injury. Systematic analysis schemes are needed to reliably quantify oculomotor deficits associated with oculomotor impairment via brain trauma. We propose a systematic, automated analysis scheme using various eye-tracking tasks to assess oculomotor function in a cohort of adolescents with acute concussion symptoms and aged-matched healthy controls. From these data we have evidence that these methods reliably detect oculomotor deficits in the concussed group, including reduced spatial accuracy and diminished tracking performance during visually guided prosaccade and self-paced saccade tasks. The accuracy and tracking deficits are consistent with prior studies on oculomotor function, while introducing novel discriminatory measures relative to fixation assessments - methodologically, a less complicated measure of performance - and thus represent a reliable and simple scheme of detection and analysis of oculomotor deficits associated with brain injury.

Background: Historical approaches to protect the brain from outside the skull (eg, helmets and mouthpieces) have been ineffective in reducing internal injury to the brain that arises from energy absorption during sports-related collisions. We aimed to evaluate the effects of a neck collar, which applies gentle bilateral jugular vein compression, resulting in cerebral venous engorgement to reduce head impact energy absorption during collision. Specifically, we investigated the effect of collar wearing during head impact exposure on brain microstructure integrity following a competitive high school American football season., Methods: A prospective longitudinal controlled trial was employed to evaluate the effects of collar wearing (n=32) relative to controls (CTRL; n=30) during one competitive football season (age: 17.04±0.67 years). Impact exposure was collected using helmet sensors and white matter (WM) integrity was quantified based on diffusion tensor imaging (DTI) serving as the primary outcome., Results: With similar overall g-forces and total head impact exposure experienced in the two study groups during the season (p>0.05), significant preseason to postseason changes in mean diffusivity, axial diffusivity and radial diffusivity in the WM integrity were noted in the CTRL group (corrected p<0.05) but not in the collar group (p>0.05). The CTRL group demonstrated significantly larger preseason to postseason DTI change in multiple WM regions compared with the collar group (corrected p<0.05)., Discussion: Reduced WM diffusivity alteration was noted in participants wearing a neck collar after a season of competitive football. Collar wearing may have provided a protective effect against brain microstructural changes after repetitive head impacts., Trial Registration Number: NCT02696200., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.)

Objectives: Utilize a prospective in vivo clinical trial to evaluate the potential for mild neck compression applied during head impact exposure to reduce anatomical and physiological biomarkers of brain injury., Methods: This project utilized a prospective randomized controlled trial to evaluate effects of mild jugular vein (neck) compression (collar) relative to controls (no collar) during a competitive hockey season (males; 16.3 ± 1.2 years). The collar was designed to mildly compress the jugular vein bilaterally with the goal to increase intracranial blood volume to reduce risk of brain slosh injury during head impact exposure. Helmet sensors were used to collect daily impact data in excess of 20 g (games and practices) and the primary outcome measures, which included changes in white matter (WM) microstructure, were assessed by diffusion tensor imaging (DTI). Specifically, four DTI measures: fractional anisotropy, mean diffusivity (MD), axial diffusivity, and radial diffusivity (RD) were used in the study. These metrics were analyzed using the tract-based Spatial Statistics (TBSS) approach - a voxel-based analysis. In addition, electroencephalography-derived event-related potentials were used to assess changes in brain network activation (BNA) between study groups., Results: For athletes not wearing the collar, DTI measures corresponding to a disruption of WM microstructure, including MD and RD, increased significantly from pre-season to mid-season (p < 0.05). Athletes wearing the collar did not show a significant change in either MD or RD despite similar accumulated linear accelerations from head impacts (p > 0.05). In addition to these anatomical findings, electrophysiological network analysis of the degree of congruence in the network electrophysiological activation pattern demonstrated concomitant changes in brain network dynamics in the non-collar group only (p < 0.05). Similar to the DTI findings, the increased change in BNA score in the non-collar relative to the collar group was statistically significant (p < 0.01). Changes in DTI outcomes were also directly correlated with altered brain network dynamics (r = 0.76; p < 0.05) as measured by BNA., Conclusion: Group differences in the longitudinal changes in both neuroanatomical and electrophysiological measures, as well as the correlation between the measures, provide initial evidence indicating that mild jugular vein compression may have reduced alterations in the WM response to head impacts during a competitive hockey season. The data indicate sport-related alterations in WM microstructure were ameliorated by application of jugular compression during head impact exposure. These results may lead to a novel line of research inquiry to evaluate the effects of protecting the brain from sports-related head impacts via optimized intracranial fluid dynamics.

Resistance training often is not an inherent component of current dance training for pediatric female dancers. Reasons for this include concerns surrounding injury to the immature skeleton and diminishing dancer aesthetic appearance, as well as questions related to the effectiveness of such training for increasing dancer strength and muscle endurance. Many forms of dance demand sufficient muscle strength and endurance for prolonged periods of high intensity dance, power generation during leaps and jumps, as well as stabilization of the lower extremity to prevent injury. The benefits of resistance training for the pediatric female dancer are multiple, including improved muscle strength and bone health and decreased risk for stress related injuries to the actively growing skeleton. Understanding the biomechanical changes that occur during growth that may predispose the female dancer to injury is important, as well as initiating individualized resistance training protocols early in training that may serve to improve performance and prevent future injury.