The non-sagittal knee moment vector identifies 'at risk' individuals that the knee abduction moment alone does not.

Multi-planar forces and moments are known to injure the anterior cruciate ligament (ACL). In ACL injury risk studies, however, the uni-planar frontal plane external knee abduction moment is frequently studied in isolation. This study aimed to determine if the frontal plane knee moment (KM-Y) could classify all individuals crossing a risk threshold compared to those classified by a multi-planar non-sagittal knee moment vector (KM-YZ). Recreationally active females completed three sports tasks-drop vertical jumps, single-leg drop vertical jumps and planned sidesteps. Peak knee abduction moments and peak non-sagittal resultant knee moments were obtained for each task, and a risk threshold of the sample mean plus 1.6 standard deviations was used for classification. A sensitivity analysis of the threshold from 1-2 standard deviations was also conducted. KM-Y did not identify all participants who crossed the risk threshold as the non-sagittal moment identified unique individuals. This result was consistent across tasks and threshold sensitivities. Analysing the peak uni-planar knee abduction moment alone is therefore likely overly reductionist, as this study demonstrates that a KM-YZ threshold identifies 'at risk' individuals that a KM-Y threshold does not. Multi-planar moment metrics such as KM-YZ may help facilitate the development of screening protocols across multiple tasks.

Vascular function in the aging human brain during muscle exertion.

To determine how brain oxygenation is stably maintained during advancing age, cerebral oxygenation and hemoglobin were measured real-time at 10 Hz using near-infrared spectroscopy (NIRS) at rest (30 seconds) and during a 10-repeated handgrip strength test (30 seconds) for 834 adults (M/F = 45/55%) aged 20-88 y. The amplitude of cerebral hemodynamic fluctuation was reflected by converting 300 values of % oxygen saturation and hemoglobin of each 30-second phase to standard deviation as indicatives of brain oxygenation variability (BOV) and brain hemodynamic variability (BHV) for each participant. Both BOV (+21-72%) and BHV (+94-158%) increased during the maximal voluntary muscle exertions for all age levels (α < 0.05), suggesting an increased vascular recruitment to maintain oxygen homeostasis in the brain. Intriguingly, BHV was >100 folds for both resting and challenged conditions (α < 0.001) in >80% of adults aged above 50 y despite similar BOV compared with young age counterparts, indicating a huge cost of amplifying hemodynamic oscillation to maintain a stable oxygenation in the aging brain. Since vascular endothelial cells are short-lived, our results implicate a hemodynamic compensation to emergence of daily deficits in replacing senescent endothelial cells after age 50 y.

The effect of planning time on penultimate and ultimate step kinematics and subsequent knee moments during sidestepping.

Frontal plane postures during the ultimate step of sidestepping are linked to increased anterior cruciate ligament injury risk. However, there is a lack of research detailing the kinematic strategies present in the penultimate step. This study, therefore, investigated penultimate and ultimate step kinematics of planned sidestepping (pSS) and unplanned sidestepping (upSS) to further understand the effect of planning time on known ultimate step kinematic and kinetic differences. Sixty male amateur Australian Rules football players performed three trials of straight-line running (RUN), pSS, and upSS in a randomized order. Mediolateral foot placement and three-dimensional joint kinematics for the knee, pelvis, and trunk were measured at final foot contact of the penultimate step and initial foot contact of the ultimate step. Peak knee moments were measured during the weight acceptance phase of the ultimate step. In pSS, at the penultimate step final foot contact, the support foot was placed across the midline of the center of mass, in the frontal plane, contralateral to the sidestep direction. Greater trunk lateral flexion toward the sidestep direction and greater negative pelvic lateral tilt were observed in pSS compared with upSS and RUN. Differences between pSS and upSS frontal plane kinematics at penultimate step final foot contact suggest preparatory reorientation strategies are likely constrained by the amount of planning time available. As there are clear differences in preparatory kinematics, we recommend that planning time be considered when training and assessing sidestepping maneuvers and planned and unplanned maneuvers not be treated as interchangeable skills.

Simultaneously assessing amplitude and temporal effects in biomechanical trajectories using nonlinear registration and statistical nonparametric mapping.

Biomechanical trajectories generally embody amplitude and temporal effects, but these effects are often analyzed separately. Here we demonstrate how amplitude-phase separation techniques from the statistics literature can be used to simultaneously analyze both. The approach hinges on nonlinear registration, which temporally warps trajectories to minimize timing effects, and the resulting optimal time warps can be combined with the resulting amplitudes in a simultaneous test. We first analyzed two simulated datasets with controlled amplitude and temporal effects to demonstrate how amplitude-timing separation can avoid incorrect conclusions from common amplitude-only hypothesis testing. We then analyzed two experimental datasets, demonstrating how amplitude-phase separation can yield unique perspectives on the relative contributions of amplitude and timing effects embodied in biomechanical trajectories. Last, we show that the proposed approach can be sensitive to procedural and parameter specifics, so we recommend that these sensitivities should be explored and reported.

Electromyographic Evaluation of Early-Stage Shoulder Rehabilitation Exercises Following Rotator Cuff Repair.

BACKGROUND: Electromyography (EMG) is frequently used as a guide for exercise rehabilitation progression following rotator cuff repair. Knowledge of EMG activity during passive and active-assisted exercises may help guide clinicians when considering exercise prescription in the early post-operative period. PURPOSE: The purpose of this study was to investigate EMG activity of the rotator cuff and deltoid musculature during passive and active-assisted shoulder range of motion (ROM) exercises commonly performed in post-operative rehabilitation. STUDY DESIGN: Descriptive cohort laboratory study using healthy subjects. METHODS: In sixteen active healthy volunteers, surface and fine-wire EMG activity was measured in the supraspinatus, infraspinatus, subscapularis, and anterior, middle and posterior deltoid muscles during eight common ROM exercises. Mean %MVIC values and 95% confidence intervals were used to rank exercises from the least to the most amount of muscular activity generated during the exercises. RESULTS: Standard pendulum exercises generated low levels of EMG activity in the supraspinatus and infraspinatus (≤15% MVIC), while active-assisted table slides, and the upright wall slide generated low levels of EMG activity in only the supraspinatus. No exercises were found to generate low levels of muscular activation (≤15% MVIC) in the subscapularis. CONCLUSION: This study found no clear distinctions between the EMG activity of the supraspinatus or the infraspinatus occurring during common passive and active-assisted ROM exercises. Subdividing ROM exercises based on muscle activity, may not be necessary to guide progression of exercises prior to commencing active motion after rotator cuff repair. LEVEL OF EVIDENCE: Level 3b.

Optimizing Whole-Body Kinematics During Single-Leg Jump Landing to Reduce Peak Abduction/Adduction and Internal Rotation Knee Moments: Implications for Anterior Cruciate Ligament Injury Risk.

Knee abduction/adduction moment and knee internal rotation moment are known surrogate measures of anterior cruciate ligament (ACL) load during tasks like sidestepping and single-leg landing. Previous experimental literature has shown that a variety of kinematic strategies are associated or correlated with ACL injury risk; however, the optimal kinematic strategies needed to reduce peak knee moments and ACL injury are not well understood. To understand the complex, multifaceted kinematic factors underpinning ACL injury risk and to optimize kinematics to prevent the ACL injury, a musculoskeletal modeling and simulation experimental design was used. A 14-segment, 37-degree-of-freedom, dynamically consistent skeletal model driven by force/torque actuators was used to simulate whole-body single-leg jump landing kinematics. Using the residual reduction algorithm in OpenSim, whole-body kinematics were optimized to reduce the peak knee abduction/adduction and internal/external rotation moments simultaneously. This optimization was repeated across 30 single-leg jump landing trials from 10 participants. The general optimal kinematic strategy was to bring the knee to a more neutral alignment in the transverse plane and frontal plane (featured by reduced hip adduction angle and increased knee adduction angle). This optimized whole-body kinematic strategy significantly reduced the peak knee abduction/adduction and internal rotation moments, transferring most of the knee load to the hip.

Goal-Oriented Optimization of Dynamic Simulations to Find a Balance between Performance Enhancement and Injury Prevention during Volleyball Spiking.

Performance enhancement and injury prevention are often perceived as opposite sides of a coin, where focusing on improvements of one leads to detriment of the other. In this study, we used physics-based simulations with novel optimization methods to find participant-specific, whole-body mechanics of volleyball spiking that enhances performance (the peak height of the hitting hand and its forward velocity) while minimizing injury risk. For the volleyball spiking motion, the shoulder is the most common injury site because of the high mechanical loads that are most pronounced during the follow-through phase of the movement. We analyzed 104 and 209 spiking trials across 13 participants for the power and follow-through phases, respectively. During the power phase, simulations increased (p < 0.025) the peak height of the hitting wrist by 1% and increased (p < 0.025) the forward wrist velocity by 25%, without increasing peak shoulder joint torques, by increasing the lower-limb forward swing (i.e., hip flexion, knee extension). During the follow-through phase, simulations decreased (p < 0.025) peak shoulder joint torques by 75% elicited by synergistic rotation of the trunk along the pathway of the hitting arm. Our results show that performance enhancement and injury prevention are not mutually exclusive and may both be improved simultaneously, potentially leading to better-performing and injury-free athletes.

The inter-laboratory equivalence for lower limb kinematics and kinetics during unplanned sidestepping.

Much inter-intra-tester kinematic and kinetic repeatability research exists, with a paucity investigating inter-laboratory equivalence. The objective of this research was to evaluate the inter-laboratory equivalence between time varying unplanned kinematics and moments of unplanned sidestepping (UnSS). Eight elite female athletes completed an established UnSS procedure motion capture laboratories in the UK and Australia. Three dimensional time varying unplanned sidestepping joint kinematics and moments were compared. Discrete variables were change of direction angles and velocity. Waveform data were compared using mean differences, 1D 95%CI and RMSE. Discrete variables were compared using 0D 95% CI. The mean differences and 95%CI for UnSS kinematics broadly supported equivalence between laboratories (RMSE≤5.1°). Excluding hip flexion/extension moments (RMSE = 1.04 Nm/kg), equivalence was also supported for time varying joint moments between laboratories (RMSE≤0.40 Nm/kg). Dependent variables typically used to characterise UnSS were also equivalent. When consistent experimental and modelling procedures are employed, consistent time varying UnSS lower limb joint kinematic and moment estimates between laboratories can be obtained. We therefore interpret these results as a support of equivalence, yet highlight the challenges of establishing between-laboratory experiments or data sharing, as well as establishing appropriate ranges of acceptable uncertainty. These findings are important for data sharing and multi-centre trials.

Prescribing joint co-ordinates during model preparation in OpenSim improves lower limb unplanned sidestepping kinematics.

OBJECTIVES: Investigate how prescribing participant-specific joint co-ordinates during model preparation influences the measurement agreement of inverse kinematic (IK) derived unplanned sidestepping (UnSS) lower limb kinematics in OpenSim in comparison to an established direct kinematic (DK) model. DESIGN: Parallel forms repeatability. METHODS: The lower limb UnSS kinematics of 20 elite female athletes were calculated using: 1) an established DK model (criterion) and, 2) two IK models; one with (IKPC) and one without (IK0) participant-specific joint co-ordinates prescribed during the marker registration phase of model preparation in OpenSim. Time-varying kinematic analyses were performed using one dimensional (1D) statistical parametric mapping (α=0.05), where zero dimensional (0D) Root Mean Squared Error (RMSE) estimates were calculated and used as a surrogate effect size estimates. RESULTS: Statistical differences were observed between the IKPC and DK derived kinematics as well as the IK0 and DK derived kinematics. For the IKPC and DK models, mean kinematic differences over stance for the three dimensional (3D) hip joint, 3D knee joint and ankle flexion/extension (F/E) degrees of freedom (DoF) were 46±40% (RMSE=5±5°), 56±31% (RMSE=7±4°) and 3% (RMSE=2°) respectively. For the IK0 and DK models, mean kinematics differences over stance for the 3D hip joint, 3D knee joint and ankle F/E DoF were 70±53% (RMSE=14±11°), 46±48% (RMSE=8±7°) and 100% (RMSE=11°) respectively. CONCLUSIONS: Prescribing participant-specific joint co-ordinates during model preparation improves the agreement of IK derived lower limb UnSS kinematics in OpenSim with an established DK model, as well as previously published in-vivo knee kinematic estimates.

DXA reference values and anthropometric screening for visceral obesity in Western Australian adults.

Limited reference values exist for visceral adipose tissue (VAT) mass measured by DXA. The objectives of this study were to provide reference values for DXA-derived VAT mass and compare the association with anthropometry measures. The study cohort comprised 677 men and 738 women aged 18-65 years from Western Australia. Whole-body scans using a GE Lunar iDXA and anthropometry measures were collected. Reference percentile data were stratified by sex and age. Correlation analysis compared DXA-derived and anthropometry variables. Specificity, sensitivity, and Youden's Index were used to evaluate the ability of anthropometric thresholds to predict individuals with high VAT. In men, waist circumference (WC), waist-hip ratio, and waist-height ratio (WHtR) had 'high' correlations with VAT mass. In women, only WHtR was 'highly' correlated with VAT mass. Overweight thresholds for WC, along with a body mass index of 25.0 kg/m2 in women, had the highest combination of sensitivity and specificity when using anthropometry measures to identify individuals with high VAT mass. We provide the first reference data sets for DXA-derived VAT mass among Western Australians. Excessive VAT mass may be identified in men using the overweight WC threshold and in women using both the overweight BMI and WC thresholds.

Field hockey sport-specific postures during unanticipated sidestepping: Implications for anterior cruciate ligament injury prevention.

Much research has investigated whole-body postures and associated knee joint loading during unanticipated sidestepping (UnSS). However, no research has considered sport-specific postures in field hockey. The purpose of this study was to investigate differences in trunk and lower limb angle and lower extremity joint moment waveforms during UnSS while holding a hockey stick in a flexed posture (HS-UnSS) and traditional UnSS. Additionally, we aimed to determine if differences in posture during HS-UnSS were associated with changes in knee joint moments. Twelve elite female field hockey athletes underwent 3D motion analysis during UnSS and HS-UnSS. Athletes increased trunk (0-100% of stance phase, hip (0-15%), knee (12-29%; 39-59%; 78-100%) and ankle (41-57%) flexion angles, and increased hip flexion (19-24%; 42-45%; 75-84%) and external rotation moments (75-80%) during HS-UnSS compared with UnSS (p < 0.05). Flexed postures observed during HS-UnSS did not influence knee flexion and valgus moments when compared with UnSS (p > 0.05), however knee external rotation moments reduced. Changes in trunk flexion were positively associated with peak knee internal rotation moments from UnSS to HS-UnSS (r = 0.779, p = 0.005). These findings indicate that field hockey players sidestep with significantly different techniques when holding a hockey stick, which should be considered in injury prevention training protocols.

By failing to prepare, you are preparing your anterior cruciate ligament to fail.

There is strong evidence linking an athlete's movement technique during sidestepping with anterior cruciate ligament (ACL) injury risk. However, it is unclear how these injurious postures are influenced by prior movement. We aim to describe preparatory trunk and thigh kinematics at toe-off of the penultimate-step and flight-phase angular momenta, and explore their associations with frontal-plane risk factors during unplanned sidestepping maneuvers. We analyzed kinematic and kinetic data of 33 male Australian Football players performing unplanned sidestepping tasks (103 trials). Linear mixed models tested for reliable associations between ACL injury risk during weight acceptance of the execution-step, with preparatory kinematics and angular momenta of the trunk and thigh during the penultimate-step. Multi-planar flight-phase trunk momenta along with hip abduction angle at penultimate-step toe-off were significantly associated with peak knee valgus moments during the execution-step (R2  = .21, P < .01). Execution-step trunk lateral flexion was significantly predicted by frontal and sagittal-plane preparatory trunk positioning at toe-off of the penultimate-step (R2  = .44, P < .01). Multi-planar flight-phase trunk momenta as well as multi-planar trunk and hip positioning at penultimate-step toe-off were associated with hip abduction during the execution-step (R2  = .53, P < .01). Preparatory positioning of the trunk and hip, along with flight-phase trunk momentum adjusting this positioning are linked to known ACL injury risk factors. We recommend that during the penultimate-step athletes maintain an upright trunk, as well as minimize frontal-plane trunk momentum and transverse-plane trunk momentum toward the sidestep direction to reduce risk of ACL injury during unplanned sidesteps.

Pole Dancing for Fitness: The Physiological and Metabolic Demand of a 60-Minute Class.

Nicholas, JC, McDonald, KA, Peeling, P, Jackson, B, Dimmock, JA, Alderson, JA, and Donnelly, CJ. Pole dancing for fitness: The physiological and metabolic demand of a 60-minute class. J Strength Cond Res 33(10): 2704-2710, 2019-Little is understood about the acute physiological or metabolic demand of pole dancing classes. As such, the aims of this study were to quantify the demands of a standardized recreational pole dancing class, classifying outcomes according to American College of Sports Medicine (ACSM) exercise-intensity guidelines, and to explore differences in physiological and metabolic measures between skill- and routine-based class components. Fourteen advanced-level amateur female pole dancers completed three 60-minute standardized pole dancing classes. In one class, participants were fitted with a portable metabolic analysis unit. Overall, classes were performed at a mean VO2 of 16.0 ml·kg·min, total energy cost (EC) of 281.6 kcal (4.7 kcal·min), metabolic equivalent (METs) of 4.6, heart rate of 131 b·min, rate of perceived exertion (RPE) of 6.3/10, and blood lactate of 3.1 mM. When comparing skill- and routine-based components of the class, EC per minute (4.4 vs. 5.3 kcal·min), peak VO2 (21.5 vs. 29.6 ml·kg·min), METs (4.3 vs. 5.2), and RPE (7.2 vs. 8.4) were all greater in the routine-based component (p < 0.01), indicating that classes with an increased focus on routine-based training, as compared to skill-based training, may benefit those seeking to exercise at a higher intensity level, resulting in greater caloric expenditure. In accordance with ASCM guidelines, an advanced-level 60-minute pole dancing class can be classified as a moderate-intensity cardiorespiratory exercise; when completed for ≥30 minutes, ≥5 days per week (total ≥150 minutes) satisfies the recommended level of exercise for improved health and cardiorespiratory fitness.

The applied impact of 'naïve' statistical modelling of clustered observations of motion data in injury biomechanics research.

OBJECTIVES: Appropriate statistical analysis of clustered data necessitates accounting for within-participant effects to ensure results are repeatable and translatable to real-world applications. This study aimed to compare statistical output and injury risk interpretation differences from two statistical regression models built from a clinical movement sidestepping database. A "naïve" regression model, which does not account for within-participant effects, was compared with an appropriately applied mixed effects model. DESIGN: Comparative study. METHODS: Three-dimensional unplanned sidestepping joint angle data (trunk, hip, and knee) from 35 males (112 observations) were used to model peak knee valgus moments and anterior cruciate ligament injury risk during the impact phase of stance. Both statistical models were cross-validated using a k-fold analysis. RESULTS: The naïve regression returned inflated goodness of fit statistics (R2=0.50), which was evident following cross-validation (predicted R2=0.43). Following cross-validation, the mixed effects model (predicted R2=0.40) explained a similar amount of variance, despite containing three less predictors. The naïve model produced inaccurate parameter estimates, overestimating the effects of certain kinematic parameters by as much as 79 %. CONCLUSIONS: A regression model naïvely applied to clustered observations of sidestepping data resulted in erroneous parameter estimates and goodness of fit statistics which have the potential to mislead future research and real-world applications. It is important for sport and clinical scientists to use statistically appropriate mixed effects models when modelling clustered motion capture data for injury biomechanics research to protect the translatability of the findings.

Empirical Based Modeling for the Assessment of Dynamic Knee Stability: Implications for Anterior Cruciate Ligament Injury Risk.

Anterior cruciate ligament (ACL) injuries are common sports injuries, costing the U.S. roughly $1 billion annually. To better understand the underlying injury mechanism, Nyquist and Bode stability criteria were applied to assess frontal plane dynamic knee stability among male Australian Football players during the weight-acceptance phase of single-leg jump landing. Out of 30 landings, 19 were classified as stable and 11 as unstable. Medial and lateral vasti, hamstring and gastrocnemii muscle activation waveforms were analyzed in parallel to determine if individuals with stable and unstable frontal plane joint biomechanics possessed different lower limb neuromuscular strategies. The total quadriceps muscle activation during the stable landings were significantly higher (p=0.02) than during the unstable landings. Additionally, the vasti exhibited a medial dominance during the stable landings compared to the unstable (p=0.06). These results suggest that individuals with unstable frontal plane knee landing mechanics may have reduced recruitment of the muscles crossing the knee; specifically, the medial muscles, which could limit their ability to compress and support the joint. The stability criteria were able to classify stable and unstable knee mechanics. And the differences in muscle activation during these stable and unstable landings provided new insights towards the ACL injury mechanism and possible injury prevention countermeasures.

Muscle volume alterations after first botulinum neurotoxin A treatment in children with cerebral palsy: a 6-month prospective cohort study.

AIM: This study aimed to track alterations in muscle volume for 6 months in children with cerebral palsy (CP) after the first exposure to botulinum neurotoxin A (BoNT-A), a commonly used focal spasticity treatment. METHOD: Eleven ambulant children (eight males, three females) with spastic CP, mean age 8 years 10 months (SD 3y 1mo) participated. Participants received injections to the affected gastrocnemius. The muscle volume of the gastrocnemius, soleus, tibialis anterior, and hamstrings was measured using magnetic resonance imaging. Muscle volume was normalized to bone length, and changes analysed relative to baseline. Assessments were conducted 1 week before, and 4 weeks, 13 weeks, and 25 weeks after BoNT-A treatment. RESULTS: All children demonstrated positive clinical and functional gains. Muscle volume of the injected gastrocnemius was found to be significantly reduced at 4 weeks (-5.9%), 13 weeks (-9.4%), and 25 weeks (-6.8%). Significant increases in normalized soleus muscle volume were identified at each follow-up, while hamstrings showed significant increase at 4 weeks only. INTERPRETATION: Absolute and normalized muscle volume of the injected muscle reduces after first BoNT-A exposure, and does not return to baseline volume by 25 weeks. Hypertrophy is seen in the soleus up to 25 weeks; the volume of the plantar flexor compartment is stable. WHAT THIS PAPER ADDS: Muscle atrophy after first botulinum neurotoxin A (BoNT-A) exposure in children with cerebral palsy is noted. Mild BoNT-A-induced muscle atrophy is still apparent 6 months after BoNT-A exposure. Hypertrophy is evident in soleus after gastrocnemius BoNT-A exposure. Total plantarflexor volume is unchanged.

Synthesis of Subject-Specific Human Balance Responses Using a Task-Level Neuromuscular Control Platform.

Many activities of daily living require a high level of neuromuscular coordination and balance control to avoid falls. Complex musculoskeletal models paired with detailed neuromuscular simulations complement experimental studies and uncover principles of coordinated and uncoordinated movements. Here, we created a closed-loop forward dynamic simulation framework that utilizes a detailed musculoskeletal model (19 degrees of freedom, and 92 muscles) to synthesize human balance responses after support-surface perturbation. In addition, surrogate response models of task-level experimental kinematics from two healthy subjects were provided as inputs to our closed-loop simulations to inform the design of the task-level controller. The predicted muscle activations and the resulting synthesized subject joint angles showed good conformity with the average of experimental trials. The simulated whole-body center of mass displacements, generated from a single kinematics trial per perturbation direction, were on average, within 7 mm (anterior perturbations) and 13 mm (posterior perturbations) of experimental displacements. Our results confirmed how a complex subject-specific movement can be reconstructed by sequencing and prioritizing multiple task-level commands to achieve desired movements. By combining the multidisciplinary approaches of robotics and biomechanics, the platform demonstrated here offers great potential for studying human movement control and subject-specific outcome prediction.

The inter-tester repeatability of a model for analysing elbow flexion-extension during overhead sporting movements.

This study investigates the inter-tester repeatability of an upper limb direct kinematic (ULDK) model specifically for the reporting of elbow flexion-extension (FE) during overhead sporting movements, such as cricket bowling. The ULDK model consists of an upper arm and a forearm connected with a 6° of freedom elbow joint. The ULDK model was assessed for inter-tester repeatability by calculating elbow FE during cricket bowling in two sessions, with unique testers applying the kinematic marker set in each session. Analysis of both elbow FE time-varying waveforms (statistical parametric mapping = 0% time different) and extracted discrete events (no statistical differences, strong correlations > 0.9) support that this model is inter-tester repeatable at assessing elbow FE within the context of cricket bowling. This model is recommended as a framework in future studies for measuring elbow kinematics during other overhead sporting tasks, with recommendations for further participant-specific considerations. Graphical abstract ᅟ.

Predicting athlete ground reaction forces and moments from motion capture.

An understanding of athlete ground reaction forces and moments (GRF/Ms) facilitates the biomechanist's downstream calculation of net joint forces and moments, and associated injury risk. Historically, force platforms used to collect kinetic data are housed within laboratory settings and are not suitable for field-based installation. Given that Newton's Second Law clearly describes the relationship between a body's mass, acceleration, and resultant force, is it possible that marker-based motion capture can represent these parameters sufficiently enough to estimate GRF/Ms, and thereby minimize our reliance on surface embedded force platforms? Specifically, can we successfully use partial least squares (PLS) regression to learn the relationship between motion capture and GRF/Ms data? In total, we analyzed 11 PLS methods and achieved average correlation coefficients of 0.9804 for GRFs and 0.9143 for GRMs. Our results demonstrate the feasibility of predicting accurate GRF/Ms from raw motion capture trajectories in real-time, overcoming what has been a significant barrier to non-invasive collection of such data. In applied biomechanics research, this outcome has the potential to revolutionize athlete performance enhancement and injury prevention. Graphical Abstract Using data science to model high-fidelity motion and force plate data frees biomechanists from the laboratory.

Targeting associated mechanisms of anterior cruciate ligament injury in female community-level athletes.

This study aims to determine if biomechanically informed injury prevention training can reduce associated factors of anterior cruciate ligament injury risk among a general female athletic population. Female community-level team sport athletes, split into intervention (n = 8) and comparison groups (n = 10), completed a sidestepping movement assessment prior to and following a 9-week training period, in which kinetic, kinematic and neuromuscular data were collected. The intervention group completed a biomechanically informed training protocol, consisting of plyometric, resistance and balance exercises, adjunct to normal training, for 15-20 min twice a week. Following the 9-week intervention, total activation of the muscles crossing the knee (n = 7) decreased for both the training (∆ -15.02%, d = 0.45) and comparison (∆ -9.68%, d = 0.47) groups. This decrease was accompanied by elevated peak knee valgus (∆ +27.78%, d = -0.36) and internal rotation moments (∆ +37.50%, d = -0.56) in the comparison group, suggesting that female community athletes are at an increased risk of injury after a season of play. Peak knee valgus and internal rotation knee moments among athletes who participated in training intervention did not change over the intervention period. Results suggest participation in a biomechanically informed training intervention may mitigate the apparent deleterious effects of community-level sport participation.