Corticomuscular cross-recurrence analysis reveals between-limb differences in motor control among individuals with ACL reconstruction.

Surgical reconstruction of the anterior cruciate ligament (ACL) and subsequent physical therapy can help athletes return to competition; however, re-injury rates remain disproportionately high due, in part, to lingering biomechanical and neurological factors that are not fully addressed during rehabilitation. Prior reports indicate that individuals exhibit altered electrical activity in both brain and muscle after ACL reconstruction (ACLR). In this investigation, we aimed to extend existing approaches by introducing a novel non-linear analysis of corticomuscular dynamics, which does not assume oscillatory coupling between brain and muscle: Corticomuscular cross-recurrence analysis (CM-cRQA). Our findings indicate that corticomuscular dynamics vary significantly between involved (injured) and uninvolved legs of participants with ACLR during voluntary isometric contractions between the brain and both the vastus medialis and lateralis. This finding points to a potential lingering neural deficit underlying re-injury for athletes after surgical reconstruction, namely the dynamical structure of neuromuscular (brain to quad muscle) coordination, which is significantly asymmetric, between limbs, in those who have ACLR.

Suture Augmentation of a Four-Strand Semitendinosus Graft Improves Time-Zero Biomechanical Properties.

PURPOSE: To compare the time-zero biomechanical properties of hamstring graft preparations with or without suture augmentation for anterior cruciate ligament reconstruction (ACLR) in a full-construct cadaveric model. METHODS: Hamstring grafts were harvested from 24 fresh frozen human cadavers and prepared in 1 of 3 ways: quadrupled SemiTendinosus (SemiT), and quadrupled SemiT with suture augmentation (SemiT+2.0-mm tape or SemiT+1.3-mm tape; n = 8 per group). Adjustable loop suspensory implants and cortical buttons were used for fixation on a porcine tibia and acrylic block. Testing included force-controlled cyclic loading at 250 N and 400 N followed by load to failure. RESULTS: The 2 suture augmentation groups had less total elongation and increased stiffness compared to the nonsuture-augmented group (P = .025). The SemiT+2.0-mm tape group had 36% less total elongation and 34% increased stiffness compared to SemiT+1.3mm tape (P < .001). CONCLUSIONS: Suture augmentation improves construct biomechanics at time zero following hamstring tendon ACLR. Augmentation with 2.0-mm tape suture improves construct biomechanics compared to 1.3-mm tape suture. CLINICAL RELEVANCE: Independent suture augmentation of a quadrupled SemiT graft improves ACLR construct biomechanics. Outcomes were improved with augmentation using 2.0-mm tape suture compared to 1.3-mm tape suture.

Most Publications Regarding Platelet-Rich Plasma Use in the Knee Are From Asia, Investigate Injection for Osteoarthritis, and Show Outcome Improvement: A Scoping Review.

PURPOSE: To evaluate and synthesize the available literature related to platelet-rich plasma (PRP) treatment of knee pathologies and to provide recommendations to inform future research in the field. METHODS: PubMed, CINAHL, and Scopus databases were queried on October 6, 2023. All identified citations were collated and uploaded into Covidence for screening and data extraction. Studies were included if they were human studies published in English with adult cohorts that received PRP as a procedural injection or surgical augmentation for knee pathologies with patient-reported outcome measures (PROMs) and level of evidence Levels I-IV. RESULTS: Our search yielded 2,615 studies, of which 155 studies from 2006 to 2023 met the inclusion criteria. Median follow-up was 9 months (±11.2 months). Most studies (75.5%) characterized the leukocyte content of PRP, although most studies (86%) did not use a comprehensive classification scheme. In addition, most studies were from Asia (50%) and Europe (32%) and were from a single center (96%). In terms of treatment, 74% of studies examined PRP as a procedural injection, whereas 26% examined PRP as an augmentation. Most studies (68%) examined treatment of knee osteoarthritis. Many studies (83%) documented significant improvements in PROMs, including 93% of Level III/IV evidence studies and 72% of Level I/II evidence studies, although most studies (70%) failed to include minimal clinically important difference values. The visual analog scale was the most-used PROM (58% of studies), whereas the Short Form Health Survey 36-item was the least-used PROM (5% of studies). CONCLUSIONS: Most published investigations of knee PRP are performed in Asia, investigate procedural injection for osteoarthritis, and show significant outcome improvements. In addition, this review highlights the need for better classification of PRP formulations. LEVEL OF EVIDENCE: Level IV, scoping Review of level I-IV studies.

Anterior pelvic tilt increases hamstring strain and is a key factor to target for injury prevention and rehabilitation.

PURPOSE: Hamstring muscle strain injury is very common in sports involving high-speed running. Hamstring muscles originate from the ischial tuberosity and thus pelvic position may influence hamstring strain during different sports movements like sprinting, but this has only been evaluated by indirect methods. This study tested the hypothesis that a change in anterior pelvic tilt causes elongation of the overall hamstring complex and disproportionately elongates proximal relative to distal muscle regions. METHODS: Seven fresh-frozen specimens (full lower limb with pelvis and lumbar spine) were used for this in vitro study. Specimens were dissected to enable visualization of the hamstring muscles and then fixed into a custom-made testing bench that allowed controlled movement of the pelvis over a fixed femur and tibia. Nine markers were inserted into the hamstring muscles to allow intra- and intermuscle difference measurements. Then, six different anterior pelvic angles were used to measure the difference in hamstring muscle lengthening through a three-dimensional reconstruction system based on stereoscopic machine vision technology. RESULTS: An increase in anterior pelvic tilt produced a significant non-uniform increase in tissue elongation in all regions of the three hamstring muscles (semitendinosus, semimembranosus [SMB] and biceps femoris long head), which was greater in the proximal (>1 cm every 5°) compared to the distal region (≈0.4 cm every 5°). At the proximal hamstring region, SMB showed significantly greater length changes compared to conjoint tendons with nonstatistically significant elongation differences between muscles at the distal region. CONCLUSION: Considering the results of the study, the pelvis segment will likely play a fundamental role as a strain regulator of hamstring muscles. These results will have an impact on injury rehabilitation and prevention processes of hamstring injuries, as well as optimize future musculoskeletal models and avoid potential underestimation of the hamstring muscle-tendon complex lengthening during high-speed running. LEVEL OF EVIDENCE: N/A.

Lower extremity Interlimb coordination associated brain activity in young female athletes: A biomechanically instrumented neuroimaging study.

Bilateral sensorimotor coordination is required for everyday activities, such as walking and sitting down/standing up from a chair. Sensorimotor coordination functional neuroimaging (fMRI) paradigms (e.g., stepping, cycling) increase activity in the sensorimotor cortex, supplementary motor area, insula, and cerebellum. Although these paradigms are designed to assay coordination, performance measures are rarely collected simultaneously with fMRI. Therefore, we aimed to identify neural correlates of lower extremity coordination using a bilateral, in-phase, multi-joint coordination task with concurrent MRI-compatible 3D motion analysis. Seventeen female athletes (15.0 ± 1.4 years) completed a bilateral, multi-joint lower-extremity coordination task during brain fMRI. Interlimb coordination was quantified from kinematic data as the correlation between peak-to-peak knee flexion cycle time between legs. Standard preprocessing and whole-brain analyses for task-based fMRI were completed in FSL, controlling for total movement cycles and neuroanatomical differences, with interlimb coordination as a covariate of interest. A clusterwise multi-comparison correction was applied at z > 3.1 and p < .05. Less interlimb coordination during the task was associated with greater activation in the posterior cingulate and precuneus (zmax  = 6.41, p < .01) and the lateral occipital cortex (zmax  = 7.55, p = .02). The inability to maintain interlimb coordination alongside greater activity in attention- and sensory-related brain regions may indicate a failed compensatory neural strategy to execute the task. Alternatively, greater activity could be secondary to reduced afferent acuity that may be elevating central demand to maintain in-phase lower extremity motor coordination. Future research aiming to improve sensorimotor coordination should consider interventional approaches uniquely capable of promoting adaptive neuroplasticity to enhance motor control.

The Effects of Attention-Deficit/Hyperactivity Disorder Symptoms on the Association between Head Impacts and Post-Season Neurocognitive and Behavioral Outcomes.

OBJECTIVE: Having attention-deficit/hyperactivity disorder (ADHD) is a risk factor for concussion that impacts concussion diagnosis and recovery. The relationship between ADHD and repetitive subconcussive head impacts on neurocognitive and behavioral outcomes is less well known. This study evaluated the role of ADHD as a moderator of the association between repetitive head impacts on neurocognitive test performance and behavioral concussion symptoms over the course of an athletic season. METHOD: Study participants included 284 male athletes aged 13-18 years who participated in high school football. Parents completed the Strengths and Weaknesses of ADHD Symptoms and Normal Behavior (SWAN) ratings about their teen athlete before the season began. Head impacts were measured using an accelerometer worn during all practices and games. Athletes and parents completed behavioral ratings of concussion symptoms and the Attention Network Task (ANT), Digital Trail Making Task (dTMT), and Cued Task Switching Task at pre- and post-season. RESULTS: Mixed model analyses indicated that neither head impacts nor ADHD symptoms were associated with post-season athlete- or parent-reported concussion symptom ratings or neurocognitive task performance. Moreover, no relationships between head impact exposure and neurocognitive or behavioral outcomes emerged when severity of pre-season ADHD symptoms was included as a moderator. CONCLUSION: Athletes' pre-season ADHD symptoms do not appear to influence behavioral or neurocognitive outcomes following a single season of competitive football competition. Results are interpreted in light of several study limitations (e.g., single season, assessment of constructs) that may have impacted this study's pattern of largely null results.

The effects of joint hypermobility on pain and functional biomechanics in adolescents with juvenile fibromyalgia: secondary baseline analysis from a pilot randomized controlled trial.

BACKGROUND: Joint hypermobility is a common clinical finding amongst hereditary connective tissue disorders that is observed in pediatric rheumatological settings, and often associated with chronic pain. Joint hypermobility may also contribute to deficits in physical functioning and physical activity, but previous findings have been inconsistent. It is possible that physical activity impairment in joint hypermobility may be due to chronic aberrant movement patterns subsequent to increased joint laxity. METHOD: As part of a larger randomized pilot trial of juvenile onset fibromyalgia (JFM), a secondary analysis was conducted to explore whether adolescents with JFM and joint hypermobility differed from non-joint hypermobility peers in terms of pain, daily functioning, and biomechanics (i.e., kinetics and kinematics) during a moderately vigorous functional task. RESULTS: From the larger sample of adolescents with JFM (N = 36), 13 adolescents (36.1%) met criteria for joint hypermobility and 23 did not have joint hypermobility. Those with joint hypermobility exhibited poorer overall functioning (Md = 20, Q1,Q3 [5.8, 7.6] vs. Md = 29, Q1,Q3 [5.1, 7.6]) but there were no differences in pain (Md = 6.9, Q1,Q3 [22, 33], vs. Md = 6.45, Q1,Q3 [15, 29.5]). Inspection of time-series plots suggests those with joint hypermobility exhibited decreased hip flexion and frontal plane hip moment (e.g., resistance to dynamic valgus) during the landing phase (early stance) and greater hip and knee transverse plane moments during the propulsion phase (late stance) of the drop vertical jump task (DVJ). No other differences in lower extremity biomechanics were observed between study groups. CONCLUSIONS: In this exploratory study, there were small but notable differences in biomechanics between patients with JFM who also had joint hypermobility versus those without joint hypermobility during a landing and jumping task (e.g., DVJ). These differences may indicate decreased joint stiffness during landing, associated with increased joint laxity and decreased joint stability, which may put them at greater risk for injury. Further study with a larger sample size is warranted to examine whether these biomechanical differences in patients with JFM and joint hypermobility affect their response to typical physical therapy or exercise recommendations.

Design Considerations for the Attenuation of Translational and Rotational Accelerations in American Football Helmets.

Participants in American football experience repetitive head impacts that induce negative changes in neurocognitive function over the course of a single season. This study aimed to quantify the transfer function connecting the force input to the measured output acceleration of the helmet system to provide a comparison of the impact attenuation of various modern American football helmets. Impact mitigation varied considerably between helmet models and with location for each helmet model. The current data indicate that helmet mass is a key variable driving force attenuation, however flexible helmet shells, helmet shell cutouts, and more compliant padding can improve energy absorption.

Localized Anterior Arthrofibrosis After Soft-Tissue Quadriceps Tendon Anterior Cruciate Ligament Reconstruction Is More Common in Patients Who Are Female, Undergo Meniscal Repair, and Have Grafts of Larger Diameter.

PURPOSE: To determine factors associated with localized anterior arthrofibrosis (cyclops lesion), such as graft size, warranting early reoperation for lysis of adhesions after anterior cruciate ligament reconstruction (ACLR) with all-soft tissue quadriceps tendon (ASTQT) autograft. METHODS: All primary ASTQT autograft ACLRs within a single surgeon's prospectively collected registry with minimum 6-month follow-up were included. Patients who underwent multiligament knee reconstruction or cartilage restoration procedures were excluded. Localized anterior arthrofibrosis was defined as the requirement for a second procedure to achieve debridement and lysis of adhesions owing to the inability to regain terminal extension within 6 months of ACLR. The sex-specific incidence of arthrofibrosis was evaluated relative to age, weight, femoral and tibial tunnel sizes, meniscal repair, and meniscectomy by a binary logistic regression. RESULTS: This study included 721 patients (46% female patients). There were 52 cases of localized anterior arthrofibrosis (7.2%). Female patients had a greater incidence of arthrofibrosis than male patients. Male patients with a femoral tunnel diameter of 9.25 mm or greater had an increased incidence of arthrofibrosis compared with those with a diameter of less than 9.25 mm, whereas a similar cutoff was not found to be statistically significant for female patients. Concomitant meniscal repair was associated with an increased risk of arthrofibrosis. CONCLUSIONS: Female sex and concomitant meniscal repair were associated with an increased localized anterior arthrofibrosis incidence. Furthermore, ASTQT with a femoral tunnel diameter of 9.25 mm or greater in male patients was associated with an increased incidence of arthrofibrosis. LEVEL OF EVIDENCE: Level III, retrospective, comparative prognostic trial.

Do Cutting Kinematics Change as Boys Mature? A Longitudinal Cohort Study of High-School Athletes.

OBJECTIVE: Examine longitudinal changes in trunk, hip, and knee kinematics in maturing boys during an unanticipated cutting task. DESIGN: Prospective cohort study. SETTING: Biomechanical laboratory. PARTICIPANTS: Forty-two high-school male basketball, volleyball, and soccer athletes. ASSESSMENT OF RISK FACTORS: Trunk, hip, and knee range-of-motion (RoM), peak angles, and angles at initial contact during an unanticipated 45 degrees sidestep cutting task were estimated using laboratory-based three-dimensional optoelectronic motion capture. Maturation was classified using a modified Pubertal Maturational Observational Scale (PMOS) into prepubertal, midpubertal, or postpubertal stages. MAIN OUTCOME MEASURES: Trunk total RoM in frontal, sagittal, and transverse planes; peak trunk flexion, right lateral flexion and right rotation angles; hip total RoM in frontal, sagittal, and transverse planes; hip flexion angle at initial contact; peak hip flexion and adduction angles; knee total RoM in frontal, sagittal, and transverse planes; knee flexion angle at initial contact; peak knee flexion and abduction angles. RESULTS: As boys matured, there was a decrease in hip sagittal-plane RoM (49.02 degrees to 43.45 degrees, Benjamini-Hochberg adjusted P = 0.027), hip flexion at initial contact (29.33 degrees to 23.08 degrees, P = 0.018), and peak hip flexion (38.66 degrees to 32.71 degrees, P = 0.046), and an increase in trunk contralateral rotation (17.47 degrees to 25.05 degrees, P = 0.027). CONCLUSIONS: Maturing male athletes adopted a more erect cutting strategy that is associated with greater knee joint loading. Knee kinematic changes that increase knee joint loading were not observed in this cohort.

Movement Regularity Differentiates Specialized and Nonspecialized Athletes in a Virtual Reality Soccer Header Task.

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.

Visual-Spatial Attentional Performance Identifies Lower Extremity Injury Risk in Adolescent Athletes.

OBJECTIVE: Strategies to identify lower extremity musculoskeletal (LEMSK) injury risk have been informed by prospectively identified biomechanical and neuromuscular risk factors. Emergent evidence suggests that cognitive and oculomotor performance may also contribute to LEMSK injury. The purpose of this study was to determine whether prospective cognitive and oculomotor measures identify adolescent athletes who sustain an in-season LEMSK injury. DESIGN: Prospective longitudinal study. SETTINGS: Controlled laboratory and athletic event settings. PARTICIPANTS: Four hundred eighty-eight adolescent male football and female soccer athletes aged 13 to 18 years. ASSESSMENT OF RISK FACTORS: Preseason baseline cognitive and oculomotor performance: Attention Network Task (ANT), cued task switching, King-Devick test, and near point of convergence. MAIN OUTCOME MEASURE: Incidence of LEMSK sprains and strains during a single competitive season. RESULTS: Attention Network Task-orienting network reaction time (RT) was the only cognitive or oculomotor measure significantly associated with LEMSK injury [B = 1.015, 95% confidence interval (CI): 1.01-1.024, P < 0.01]. Every 10 milliseconds increase in orienting network RT was associated with a 15% increased risk for LEMSK injury. Athletes demonstrating an orienting network RT ≥ 32.8 milliseconds had a higher risk for LEMSK injury relative to athletes below the cut-point (relative risk, 2.62; 95% CI, 1.52-4.52; odds ratio, 3.00; 95% CI, 1.63-5.52). CONCLUSIONS: Deficits in visual-spatial components of attention were associated with 2.62 times greater risk for LEMSK injury in adolescent athletes. The present results add evidence to suggest that visual-spatial attentional processing contributes to LEMSK injury and may supplement previously established LEMSK injury risk assessments.

Quantification of Global Myoelectric Spatial Activations to Delineate Normal Hamstring Function at Progressive Running Speeds: A Technical Report.

ABSTRACT: Schlink, BR, Nordin, AD, Diekfuss, JA, and Myer, GD. Quantification of global myoelectric spatial activations to delineate normal hamstring function at progressive running speeds: A technical report. J Strength Cond Res 36(3): 867-870, 2022-Hamstring function is critical to maintain sport performance, and strain injuries to the biceps femoris muscle commonly force an athlete to withdraw from their sport while the muscle heals. Current mechanistic understanding of underlying injury and return-to-play (RTP) guidelines has limited prognostic value because of limitations in technology and nonfunctional assessment strategies to guide clinical care. Integrated structural and functional determinants and dynamic assessment methods are needed to guide advanced rehabilitation strategies for safe and rapid return to sport. A potential solution for assessment of hamstring function is high-density electromyography (EMG), which can noninvasively measure spatial muscle activity in dynamic environments. In this study, we demonstrated the utility of high-density EMG by measuring spatial myoelectric activity from the biceps femoris from a group of recreational athletes running at a range of speeds. The level of significance set for this study was p < 0.05. During the late swing phase of running, we observed increased EMG amplitudes in the central and distal portions of the muscle. There were no changes in this pattern of EMG activation across speed, suggesting that running speed does not affect the general neuromuscular recruitment in the biceps femoris. Applying these methods to athletes with hamstring strains may lead to a more complete understanding of muscle function during rehabilitation and adjunctively support current methods to enhance RTP decision-making.

Muscle Architecture and Maturation Influence Sprint and Jump Ability in Young Boys: A Multistudy Approach.

ABSTRACT: Radnor, JM, Oliver, JL, Waugh, CM, Myer, GD, and Lloyd, RS. Muscle Architecture and Maturation Influence Sprint and Jump Ability in Young Boys: A Multistudy Approach. J Strength Cond Res 36(10): 2741-2751, 2022-This series of experiments examined the influence of medial gastrocnemius (GM) and vastus lateralis (VL) muscle architecture (muscle thickness, pennation angle, and fascicle length) on sprint and jump performance in pre-, circa-, and post-peak height velocity (PHV) boys. In experiment 1, 1-way analysis of variance and Cohen's d effect sizes demonstrated that most muscle architecture measures were significantly greater in post-PHV compared with pre-PHV boys ( d = 0.77-1.41; p < 0.05). For most sprint and jump variables, there were small to moderate differences between pre-PHV to circa-PHV and circa-PHV to post-PHV groups ( d = 0.58-0.93; p < 0.05) and moderate to large differences between pre-PHV and post-PHV groups ( d = 1.01-1.47; p < 0.05). Pearson's correlation analyses in experiment 2 determined that muscle architecture had small to moderate correlations with sprint and jump performance ( r = 0.228-0.707, p < 0.05), with strongest associations within the post-PHV cohort. Chi-squared analyses in experiment 3 identified that, over 18 months, more POST-POST responders than expected made positive changes in GM and VL muscle thickness. Significantly more PRE-POST subjects than expected displayed changes in maximal sprint speed, while significantly more POST-POST individuals than expected showed positive changes in jump height. Muscle architecture seems to be larger in more mature boys compared with their less mature peers and likely underlies their greater performance in sprinting and jumping tasks. Boys experiencing, or having experienced, PHV make the largest increases in muscle architecture and sprinting and jumping performance when tracked over 18 months.

A Novel Method to Categorize Stretch-Shortening Cycle Performance Across Maturity in Youth Soccer Players.

ABSTRACT: Pedley, JS, Lloyd, RS, Read, PJ, Moore, IS, Myer, GD, and Oliver, JL. A novel method to categorize stretch-shortening cycle performance across maturity in youth soccer players. J Strength Cond Res 36(9): 2573-2580, 2022-This study used a novel method to categorize stretch-shortening cycle (SSC) function during a drop jump (DJ) using the force-time curve. This method was then used to determine the effect of maturity status upon SSC function and effect of SSC function on DJ performance. Prepeak, circa-peak, and postpeak height velocity male youth soccer players completed a preseason 30-cm DJ onto a force plate. Stretch-shortening cycle function was categorized as poor (impact peak and not spring-like), moderate (impact peak and spring-like), or good (no impact peak and spring-like). Interactions between SSC function and maturity status, and SSC function and kinetic variables were explored. Youth soccer players displaying good SSC function were older and more mature than those with poor SSC function; however, 9.9% of post peak height velocity still displayed poor SSC function. Players with good SSC function recorded significantly shorter ground contact times, reduced time between peak landing and takeoff force, reduced center of mass displacement, and significantly greater takeoff forces than players with moderate and poor SSC function (all p < 0.05). SSC function during a standardized DJ improves with maturation, but a portion of mature players still demonstrate poor SSC function. Good SSC function was associated with improved DJ outcome measures except jump height. Tailored training interventions based on SSC competency may be required to optimally enhance SSC function.

Kinetics and Stabilization of the Tuck Jump Assessment.

CONTEXT: Kinetic profiles of athletes performing the tuck jump assessment (TJA) are unknown and may provide insight into the risk of anterior cruciate ligament injury. DESIGN: The purpose of this study was to (1) analyze vertical kinetics of the TJA and (2) determine the stabilization of the kinetics across successive jumping cycles. METHODS: Twenty-five healthy female athletes (age = 22.0 [4.6] y; height = 1.69 [0.07] m; body mass = 69.3 [10.3] kg) completed one trial of repeated tuck jumps on a force plate for 10 seconds. RESULTS: Vertical ground reaction force data were used to calculate the following variables across all jump cycles: time of jump cycle (0.65 [0.04] s), ground contact time (0.22 [0.03] s), flight time (0.43 [0.04] s), duty factor (0.34 [0.05]), jump height (0.23 [0.04] m), peak vertical force (5.52 [0.91] body weight [BW]), peak center of mass displacement (0.15 [0.02] m), vertical leg stiffness (27.09 [7.06] BW·m-1), vertical average loading rate (105.94 [28.43] BW·s-1), vertical instantaneous loading rate (140.90 [28.49] BW·s-1), and net impulse (0.43 [0.03] BW·s). A sequential averaging technique indicated a minimum of 11 jumps were required for stabilization of the kinetics. CONCLUSIONS: The TJA exposes athletes to high magnitudes of vertical force. Based on the high variability of performance during early repetitions and the potential to miscategorize high-risk landing in female athletes, practitioners should consider scoring the TJA after 11 successive cycles and using kinetic profiling to support landing assessments.

Immersive Real-Time Biofeedback Optimized With Enhanced Expectancies Improves Motor Learning: A Feasibility Study.

CONTEXT: An Optimizing Performance through Intrinsic Motivation and Attention for Learning theory-based motor learning intervention delivering autonomy support and enhanced expectancies (EE) shows promise for reducing cognitive-motor dual-task costs, or the relative difference in primary task performance when completed with and without a secondary cognitive task, that facilitate adaptive injury-resistant movement response. The current pilot study sought to determine the effectiveness of an autonomy support versus an EE-enhanced virtual reality motor learning intervention to reduce dual-task costs during single-leg balance. DESIGN: Within-subjects 3 × 3 trial. METHODS: Twenty-one male and 24 female participants, between the ages of 18 and 30 years, with no history of concussion, vertigo, lower-extremity surgery, or lower-extremity injuries the previous 6 months, were recruited for training sessions on consecutive days. Training consisted of 5 × 8 single-leg squats on each leg, during which all participants mimicked an avatar through virtual reality goggles. The autonomy support group chose an avatar color, and the EE group received positive kinematic biofeedback. Baseline, immediate, and delayed retention testing consisted of single-leg balancing under single- and dual-task conditions. Mixed-model analysis of variances compared dual-task costs for center of pressure velocity and SD between groups on each limb. RESULTS: On the right side, dual-task costs for anterior-posterior center of pressure mean and SD were reduced in the EE group (mean Δ = -51.40, Cohen d = 0.80 and SD Δ = -66.00%, Cohen d = 0.88) compared with the control group (mean Δ = -22.09, Cohen d = 0.33 and SD Δ = -36.10%, Cohen d = 0.68) from baseline to immediate retention. CONCLUSIONS: These findings indicate that EE strategies that can be easily implemented in a clinic or sport setting may be superior to task-irrelevant AS approaches for influencing injury-resistant movement adaptations.

Brain Activity During Experimental Knee Pain and Its Relationship With Kinesiophobia in Patients With Patellofemoral Pain: A Preliminary Functional Magnetic Resonance Imaging Investigation.

CONTEXT: The etiology of patellofemoral pain has remained elusive, potentially due to an incomplete understanding of how pain, motor control, and kinesiophobia disrupt central nervous system functioning. OBJECTIVE: To directly evaluate brain activity during experimental knee pain and its relationship to kinesiophobia in patients with patellofemoral pain. DESIGN: Cross-sectional. METHODS: Young females clinically diagnosed with patellofemoral pain (n = 14; 14.4 [3.3] y; body mass index = 22.4 [3.8]; height = 1.61 [0.1] m; body mass = 58.4 [12.7] kg). A modified Clarke test (experimental pain condition with noxious induction via patella pressure and quadriceps contraction) was administered to the nondominant knee (to minimize limb dominance confounds) of patients during brain functional magnetic resonance imaging (fMRI) acquisition. Patients also completed a quadriceps contraction without application of external pressure (control contraction). Kinesiophobia was measured using the Tampa Scale of Kinesiophobia. The fMRI analyses assessed brain activation during the modified Clarke test and control contraction and assessed relationships between task-induced brain activity and kinesiophobia. Standard processing for neuroimaging and appropriate cluster-wise statistical thresholds to determine significance were applied to the fMRI data (z > 3.1, P < .05). RESULTS: The fMRI revealed widespread neural activation in the frontal, parietal, and occipital lobes, and cerebellum during the modified Clarke test (all zs > 4.4, all Ps < .04), whereas neural activation was localized primarily to frontal and cerebellar regions during the control contraction test (all zs > 4.4, all Ps < .01). Greater kinesiophobia was positively associated with greater activity in the cerebello-frontal network for the modified Clarke test (all zs > 5.0, all Ps < .01), but no relationships between kinesiophobia and brain activity were observed for the control contraction test (all zs < 3.1, all Ps > .05). CONCLUSIONS: Our novel experimental knee pain condition was associated with alterations in central nociceptive processing. These findings may provide novel complementary pathways for targeted restoration of patient function.

Sex Moderates the Relationship between Perceptual-Motor Function and Single-Leg Squatting Mechanics.

To examine the isolated and combined effects of sex and perceptual-motor function on single-leg squatting mechanics in males and females. We employed a cross-sectional design in a research laboratory. Fifty-eight females (22.2 ± 3.5 yrs, 1.60 ± .07 m, 64.1 ± 13.0 kg) and 35 males (23.5 ± 5.0 yrs, 1.80 ± .06m, 84.7 ± 15.3 kg) free from time-loss injury in the six months prior, vertigo, and vestibular conditions participated in this study. Independent variables were sex, perceptual-motor metrics (reaction time, efficiency index, conflict discrepancy), and interaction effects. Dependent variables were peak frontal plane angles of knee projection, ipsilateral trunk flexion, and contralateral pelvic drop during single-leg squatting. After accounting for the sex-specific variance and perceptual-motor function effects on frontal plane squatting kinematics, female sex amplified the associations of: higher reaction time, lower efficiency index, and higher conflict discrepancy with greater right ipsilateral peak trunk lean (R2 = .13; p = .05); higher reaction time, lower efficiency index, and higher conflict discrepancy with decreased right contralateral pelvic drop (R2 = .22; p < .001); higher reaction time and lower conflict discrepancy with greater right frontal plane knee projection angle (R2 = .12; p = .03); and higher reaction time with greater left frontal plane knee projection angle (R2 = .22; p < .001). Female sex amplified the relationship between perceptual-motor function and two-dimensional frontal plane squatting kinematics. Future work should determine the extent to which perceptual-motor improvements translate to safer movement strategies.

The effects of internal jugular vein compression for modulating and preserving white matter following a season of American tackle football: A prospective longitudinal evaluation of differential head impact exposure.

The purpose of this clinical trial was to examine whether internal jugular vein compression (JVC)-using an externally worn neck collar-modulated the relationships between differential head impact exposure levels and pre- to postseason changes in diffusion tensor imaging (DTI)-derived diffusivity and anisotropy metrics of white matter following a season of American tackle football. Male high-school athletes (n = 284) were prospectively assigned to a non-collar group or a collar group. Magnetic resonance imaging data were collected from participants pre- and postseason and head impact exposure was monitored by accelerometers during every practice and game throughout the competitive season. Athletes' accumulated head impact exposure was systematically thresholded based on the frequency of impacts of progressively higher magnitudes (10 g intervals between 20 to 150 g) and modeled with pre- to postseason changes in DTI measures of white matter as a function of JVC neck collar wear. The findings revealed that the JVC neck collar modulated the relationships between greater high-magnitude head impact exposure (110 to 140 g) and longitudinal changes to white matter, with each group showing associations that varied in directionality. Results also revealed that the JVC neck collar group partially preserved longitudinal changes in DTI metrics. Collectively, these data indicate that a JVC neck collar can provide a mechanistic response to the diffusion and anisotropic properties of brain white matter following the highly diverse exposure to repetitive head impacts in American tackle football. Clinicaltrials.gov: NCT# 04068883.