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For a century, scientists pondered whether bird flight evolved by animals gliding down from trees or by creatures running and flapping from the ground up. A landmark 1974 paper reset the debate to focus on the evolution of the flight stroke instead. Fiftieth anniversary of an advance in understanding how flight evolved. [ABSTRACT FROM AUTHOR]

Walking is a fundamental aspect of human movement, and understanding how irregular surfaces impact gait is crucial. Existing gait research often relies on laboratory settings with ideal surfaces, limiting the applicability of findings to real-world scenarios. While some irregular surface datasets exist, they are often small or lack biomechanical gait data. In this paper, we introduce a new irregular surface dataset with 134 participants walking on surfaces of varying irregularity, equipped with inertial measurement unit (IMU) sensors on the trunk and lower right limb (foot, shank, and thigh). Collected during the North American Congress on Biomechanics conference in 2022, the dataset aims to provide a valuable resource for studying biomechanical adaptations to irregular surfaces. We provide the detailed experimental protocol, as well as a technical validation in which we developed a machine learning model to predict the walking surface. The resulting model achieved an accuracy score of 95.8%, demonstrating the discriminating biomechanical characteristics of the dataset's irregular surface gait data. [ABSTRACT FROM AUTHOR]

Background: The tethered swimming (TS) is an ergometer where swimming is simulated in an ecological environment, commonly used for assessing force in water. Objective: This systematic review aims at a critical appraise of the literature on the biomechanical and physiological variables obtained from many protocols and tests assessing force–time curve in TS. Methods: We explored the databases of PubMed, EMBASE, SPORTDiscus, Web of Science, and Academic Search Premier (PROSPERO protocol CRD42020204826), and manually searched the reference papers list. Observational studies with swimming protocols and tests were included (with any follow-up and published in the full version). The following exclusion criteria would be used, but they were not necessary, as no case met these criteria. Our search was based on the adapted Downs and Black Quality Assessment Checklist. Results: In total, 55 articles were examined extensively for fitting the established inclusion criteria. Quality of the articles included ranged from 35.7 to 85.7% (65.7 ± 13.3%). Most studies addressing TS were assessed [peak = 41 and average force = 39], whereas only a very few studies referred to measures of [force impulse = 21, fatigue index = 11, force development rate = 5], and physiological variables [oxygen consumption = 10, blood lactate concentration = 8, and heart rate = 6]. The studies were carried out with durations of 10 s, 15 s, 20 s, 25 s, 30 s, 55 s, 1, 2, or 3 min, related to the duration to perform 10 and 20 complete strokes in front crawl swimming technique. Conclusion: Based on the general results of this systematic review, the impulse seems to be the most reliable measure and presented linear correlation with swimming speed. In contrast, the TS physiological responses show compatibility for the aerobic response, critical force, and maximal oxygen uptake determination. [ABSTRACT FROM AUTHOR]

As datasets increase in size and complexity, biomechanists have turned to artificial intelligence (AI) to aid their analyses. This paper explores how explainable AI (XAI) can enhance the interpretability of biomechanics data derived from musculoskeletal simulations. We use machine learning to classify the simulated lateral pinch data as belonging to models with healthy or one of two types of surgically altered wrists. This simulation-based classification task is analogous to using biomechanical movement and force data to clinically diagnose a pathological state. The XAI describes which musculoskeletal features best explain the classifications and, in turn, the pathological states, at both the local (individual decision) level and global (entire algorithm) level. We demonstrate that these descriptions agree with assessments in the literature and additionally identify the blind spots that can be missed with traditional statistical techniques. [ABSTRACT FROM AUTHOR]

The actuation of traditional anthropomorphic hands is relatively complex, and there is little research on humanoid skin. In view of the above problems, this study proposed an anthropomorphic hand with biological and kinematic characteristics of the human hand, including structural skeletal parts and humanoid skin. Firstly, the overall structure and control system of the anthropomorphic hand were designed. Then, the humanoid skin was fabricated and its physical and mechanical properties were tested. Based on the overall structure of the rope-driven anthropomorphic hand, its motion characteristics were simulated and analyzed using multi-body dynamics software ADAMS/Cable. Finally, control experiment verifies the performance of the anthropomorphic hand described in this paper. The results are that the proposed anthropomorphic hand can reproduce the movement characteristics of the human hand well, and can grip objects of different shapes, different sizes and different weights stably, with a maximum grip force of 11.91 N measured. [ABSTRACT FROM AUTHOR]

Background: Large and complex defects requiring reconstruction are challenging for orthopaedic surgeons. The use of human acellular dermal (HAD) matrices to augment large soft tissue defects such as those seen in massive rotator cuff tears, knee extensor mechanism failures and neglected Tendo-Achilles tears has proven to be a valuable tool in surgeons reconstructive armamentarium. Different methods for allograft decellularization and preservation alter the native properties of the scaffold. Traditional processing and preservation methods have shown to have drawbacks that preclude its widespread use. Some of the common issues include inferior biomechanical properties, the risk of rejection, limited customization, difficulty in storing and transporting, the requirement of pre-operative preparation, and last but not the least increased cost. Methods: We describe a novel processing and preservation method utilizing a two-step non-denaturing decellularization method coupled with preservation using a water-sequestering agent (glycerol) to remove immunogenic components while retaining biomechanical properties. The efficiency of this novel process was compared with the traditional freeze-drying method and verified by histological evaluation and biomechanical strength analysis. Results: The absence of cellular components and matrix integrity in hematoxylin and eosin-stained glycerol-preserved HAD (gly-HAD) samples compared to freeze-dried HAD (FD-HAD) demonstrated effective yet gentle decellularization. Biomechanical strength analysis revealed that gly-HADs are stronger with an ultimate tensile load to the failure strength of 210 N compared to FD-HAD (124N). The gly-HADs were found to have an optimal suture–retention strength of 126 N. Finally, sterility testing of the resultant grafts was checked to ensure a sterility assurance level of 10−6 to establish implantability. Conclusion: The novel processing and preservation technique is described in this paper to create a Human Acellular Dermis with higher biomechanical strength and superior histological characteristics. The processing and preservation technique ensured high sterility assurance levels to establish implantability. [ABSTRACT FROM AUTHOR]

The fallopian tube (FT) plays a crucial role in the reproductive process by providing an ideal biomechanical and biochemical environment for fertilization and early embryo development. Despite its importance, the biomechanical functions of the FT that originate from its morphological aspects, and ultrastructural aspects, as well as the mechanical properties of FT, have not been studied nor used sufficiently, which limits the understanding of fertilization, mechanotrasduction, and mechanobiology during embryo development, as well as the replication of the FT in laboratory settings for infertility treatments. This paper reviews and revives valuable information on human FT reported in medical literature in the past five decades relevant to the biomechanical aspects of FT. In this review, we summarized the current state of knowledge concerning the morphological, ultrastructural aspects, and mechanical properties of the human FT. We also investigate the potential arising from a thorough consideration of the biomechanical functions and exploring often neglected mechanical aspects. Our investigation encompasses both macroscopic measurements (such as length, diameter, and thickness) and microscopic measurements (including the height of epithelial cells, the percentage of ciliated cells, cilia structure, and ciliary beat frequency). Our primary focus has been on healthy women of reproductive age. We have examined various measurement techniques, encompassing conventional metrology, 2D histological data as well as new spatial measurement techniques such as micro-CT. [ABSTRACT FROM AUTHOR]

The anterolateral ligament (ALL) was first described in 1879 in the context of Segond fractures, which correlate with a 75–100% chance of an anterior cruciate ligament (ACL) tear or a 66–75% chance of a meniscal tear. The purpose of this paper is to provide an updated comprehensive review on the anterolateral ligament complex of the knee focusing on the: (1) anatomy of the ALL/ALC; (2) associated biomechanics/function; and (3) important surgical considerations in contemporary anterior cruciate ligament (ACL) reconstruction and total knee arthroplasty (TKA). A systematic review of studies on ALL was conducted on Pubmed/MEDLINE and Cochrane databases (May 7th, 2020 to February 1st, 2022), with 20 studies meeting inclusion/exclusion criteria. Studies meeting inclusion criteria were anatomical/biomechanical studies assessing ALL function, cadaveric and computer simulations, and comparative studies on surgical outcomes of ALLR (concomitant with ACL reconstruction). Eight studies were included and graded by MINOR and Newcastle–Ottawa scale to identify potential biases. The anatomy of the ALL is part of the anterolateral ligament complex (ALC), which includes the superficial/deep iliotibial band (including the Kaplan fiber system), iliopatellar band, ALL, and anterolateral capsule. Multiple biomechanical studies have characterized the ALC as a secondary passive stabilizer in resisting tibial internal rotation. Given the role of the ALC in resisting internal tibial rotation, lateral extra-articular procedures including ALL augmentation may be considered for chronic ACL tears, ACL revisions, and a high-grade pivot shift test. In the context of TKA, in the event of injury to the ALC, a more constrained implant or soft-tissue reconstruction may be necessary to restore appropriate knee stability. [ABSTRACT FROM AUTHOR]

At what inclination does climbing begin? In this paper, we investigate the transition from walking to climbing in two species of parrot (Agapornis roseicollis and Nymphicus hollandicus) that are known to incorporate both their tail and their craniocervical system into the gait cycle during vertical climbing. Locomotor behaviors ranging in inclination were observed at angles between 0° and 90° for A. roseicollis, and 45°–85° degrees for N. hollandicus. Use of the tail in both species was observed at 45° inclination, and was joined at higher inclinations (> 65°) by use of the craniocervical system. Additionally, as inclination approached (but remained below) 90°, locomotor speeds were reduced while gaits were characterized by higher duty factors and lower stride frequency. These gait changes are consistent with those thought to increase stability. At 90°, A. roseicollis significantly increased its stride length, resulting in higher overall locomotor speed. Collectively these data demonstrate that the transition between horizontal walking and vertical climbing is gradual, incrementally altering several components of gait as inclinations increase. Such data underscore the need for further investigation into how exactly "climbing" is defined and the specific locomotor characteristics that differentiate this behavior from level walking. [ABSTRACT FROM AUTHOR]

The optimal treatment strategy for proximal humerus fractures (PHFs) is debatable owing to the relatively high failure rate of locking plates. Optimizing implants may enhance the fixation stability of PHFs and reduce the rate of mechanical failures. We developed a finite element (FE) model to simulate the treatment of PHFs with Proximal Humerus Internal Locking System (PHILOS) plates. The model evaluated the average bone strain around the screw tips under vertical loading (as an alternative to the risk of cyclic screw cutout failure verified through biomechanical testing) to minimize this strain and maximize predicted fixation stability. After determining the optimal screw configuration, further FE analysis and in vitro biomechanical testing were conducted on both standard and optimized PHILOS screw orientation to assess whether the optimized plates have biomechanical advantages over the standard plates. The FE-based optimized configuration exhibited significantly lower bone strain around the implant than the standard PHILOS screw orientation (− 17.24%, p < 0.001). In both FE analysis and in vitro biomechanical testing, the optimized PHILOS plates achieved significantly lower average bone strain around the screws (p < 0.05), more uniform stress distribution, and greater structural stiffness (p < 0.05) than the standard PHILOS screw orientation. Our results show that biomechanical performance of the PHILOS plates can be improved by altering the orientation of the locking screws. This approach may be useful for future patient-specific design optimization of implants for other fractures. [ABSTRACT FROM AUTHOR]

In biomechanics, computing muscle forces and joint efforts with mathematical optimisation copes with the muscle-redundancy problem, i.e. an infinity of possible muscle forces for a unique configuration. Achievements have been made to develop cost functions that reflect physiologically more correct muscle strategies and to validate them with experiments. It has also been proposed to use experimental input such as electromyography (EMG) in the model to guide the optimisation computation. In line with that, the present study proposes an EMG-based approach to compute back-muscle forces and the resulting intervertebral efforts in a horizontal static configuration of the trunk. This approach is based on EMG signals of three back muscles, lumbar and thoracic paravertebral muscles and the quadratus lumborum (QL), recorded on 19 healthy male subjects. Results of this approach were compared with those from optimisation computations involving four cost functions, classically used in the literature for the trunk and the spine. Our approach showed that muscle forces and intervertebral efforts were in line with these computed by mathematical optimisation, but muscle forces obtained with our approach were more representative of the measured EMG signals compared to muscle forces computed by optimisation. Indeed, three of the four cost functions completely missed to recruit the QL, while the latter was clearly activated during the experiment. This result highlights that EMG and experimental input should be more considered when using a musculoskeletal model and optimisation tools. Since the EMG-based approach used in this study was based on a pure deterministic distribution of a global equivalent force, future work will focus on involving EMG input in the optimisation process to guide its solution in a more physiological manner. [ABSTRACT FROM AUTHOR]

Background: Biomechanical parameters can distinguish a skilled rower from a less skilled rower and can provide coaches with meaningful feedback and objective evidence to inform coaching practices on rowing technique. Therefore, it is critical to understand which technical characteristics can be related to the fundamental rowing performance indicators. The aim of this systematic scoping review was to describe the current focus and density of rowing biomechanics research specific to on-water rowing and provide a guide for practitioners and researchers on future directions for on-water rowing biomechanics research. Methods: All peer-reviewed publications involving the on-water assessment of rowing biomechanics were reviewed from four databases (SPORTDiscus, PubMed, Sage online journals, and Web of Science). Search results returned 1659 records, of which 27 studies met the inclusion criteria for the review. Results: All reported variables were collated and summarised according to the three main measurements of basic mechanics: time, space and force. Study characteristics were collated to provide a descriptive overview of the literature. The main categorical variables included time, distance, velocity, acceleration, force, power and crew synchrony. Conclusion: Data extraction revealed gate force, horizontal oar angle and boat velocity as the most reported variables with numerous subcategories of metrics within each measure. A framework to help guide and standardise on-water rowing biomechanical assessment and the establishment of standards for environmental data collection could help guide practitioners and researchers in the on-water rowing environment. This scoping review was registered on the Open Science Framework (https://osf.io/8q5vw/). Key Points: While the literature has reported on an extensive range of biomechanical metrics relevant to rowing performance, however, the variability of reported measures across the different boat classes, sex and skill levels makes the collation of data challenging. The rate at which a rower can apply force and the ability to maintain the force into the finish are distinguishing features of elite rowing while prioritizing the measurement and application of power is essential for effectively monitoring and controlling training loads, as well as for refining technique. The development of a standardized framework for on-water rowing biomechanical assessment, coupled with established protocols for environmental data collection, would provide practitioners and researchers with a structured approach for navigating the on-water rowing context. [ABSTRACT FROM AUTHOR]

Background: Stress injuries are often missed secondary to their insidious onset, milder symptoms, and subtle or initially absent findings when imaged. Main Body: This review aims to provide strategies for evaluating and treating upper extremity stress fractures. This article outlines the classic presentation of each fracture, the ages during which these injuries often occur, the relevant anatomy and biomechanics, and the mechanism of each injury. Diagnostic imaging and management principles are also discussed, including the use of conservative versus surgical management techniques. Short Conclusion: Upper extremity stress fractures are often mild injuries that resolve with conservative management but can lead to more serious consequences if ignored. Given their increasing incidence, familiarity with diagnosis and management of these injuries is becoming increasingly pertinent. Key Points: Stress injuries are often missed secondary to their insidious onset, milder symptoms, and subtle or initially absent findings when imaged. This review aims to provide strategies for evaluating and treating upper extremity stress fractures. [ABSTRACT FROM AUTHOR]

To reduce breast motion with a bra, we need to understand what drives the motion of the breasts, and what variables change as support increases. Quantifying breast-torso coordination and movement complexity across the gait cycle may offer deeper insights than previously reported discrete time lag. We aimed to compare breast-torso coordination and mutual influence across breast support conditions during running. Twelve female participants ran on a treadmill at 10 km h−1 with an encapsulation and compression sports bra, and in no bra. Nipple and torso position was recorded. Vector coding, granger causality and transfer entropy were calculated within gait cycles. In both bra conditions, a greater percentage of gait cycles was spent with the breast and torso in-phase (> 90%) compared to no bra running (~ 66%, p < 0.001), with most time spent in-phase in the encapsulation versus compression bra (p = 0.006). There was a main effect of breast support condition on Granger causality (p < 0.001), both from breast to torso and torso to breast. Transfer of information was highest from torso to breast, compared to breast to torso in all conditions. Overall, these results provide novel insight into the mutual and complex interaction between the breast and the torso while running in different bra conditions. The approaches presented allow for a greater understanding of bra support conditions than existing discrete measures, which may relate to comfort and performance. Therefore, measures of coupling, predictability and transfer of complexity should be employed in future work examining these features. [ABSTRACT FROM AUTHOR]

Calcification has significant influence over cardiovascular diseases and interventions. Detailed characterization of calcification is thus desired for predictive modeling, but calcium deposits on cardiovascular structures are still often manually reconstructed for physics-driven simulations. This poses a major bottleneck for large-scale adoption of computational simulations for research or clinical use. To address this, we propose an end-to-end automated image-to-mesh algorithm that enables robust incorporation of patient-specific calcification onto a given cardiovascular tissue mesh. The algorithm provides a substantial speed-up from several hours of manual meshing to ~1 min of automated computation, and it solves an important problem that cannot be addressed with recent template-based meshing techniques. We validated our final calcified tissue meshes with extensive simulations, demonstrating our ability to accurately model patient-specific aortic stenosis and Transcatheter Aortic Valve Replacement. Our method may serve as an important tool for accelerating the development and usage of personalized cardiovascular biomechanics. [ABSTRACT FROM AUTHOR]

Objectives: To report the current elastography methods used to quantify back muscles' biomechanical characteristics in patients with musculoskeletal disorders (MSKd) and inform on their reliability, validity, and responsiveness. Methods: MEDLINE, Embase, CINAHL, Cochrane library and grey literature were consulted. Predefined criteria allowed for study selection and data extraction. The quality of evidence was rated using the COSMIN tool. Data were meta-analyzed in terms of pooled intraclass correlation coefficient (pICC) for reliability and pooled standardized mean difference (pSMD) for validity and responsiveness. Heterogeneity was assessed. Results: Seventy-nine studies were included in the meta-analysis (total number of participants N = 3178). Three elastography methods were identified: strain imaging (SI; number of cohorts M = 26), shear wave imaging (SWI; M = 50), and vibration sonoelastography (VSE; M = 3). Strain imaging and SWI studies reported good reliability measurement properties (pICC > 0.70) and a medium pSMD (0.58 for SI and 0.60 for SWI; p ≤ 0.020) in discriminating MSKd from controls' condition (validity). Strain imaging studies reported a medium pSMD (0.64; p = 0.005) in detecting within-group changes over time, whereas SWI pSMD was very high (1.24; p = 0.005). Only SWI reported significant but small pSMD (0.30; p = 0.003) in detecting between-group changes over time. The small number of VSE studies could not be meta-analyzed. Heterogeneity was high (I-squared > 90%; p < 0.001). Conclusions: Elastography presents good reliability results and a medium pSMD in discriminating MSKd from control conditions. Responsiveness data suggest detectable changes within groups over time using SI and SWI, calling for long-term longitudinal studies. Assessing changes between groups over time using elastography still needs to be proven. Highly significant heterogeneity limits meta-analytic results. Critical relevance statement: While still in its early-stage exploration phase, musculoskeletal ultrasound elastography may reliably quantify back muscles' biomechanics in asymptomatic individuals, moderately discriminate back musculoskeletal disorders and detect biomechanical changes over time in these conditions, calling for long-term longitudinal studies. Key Points: Ultrasound elastography is reviewed for back pain and related musculoskeletal disorder assessments. Growing literature supports good reproducibility, some validity and responsiveness. Back muscle elastography considers assumptions calling for standardized protocols. [ABSTRACT FROM AUTHOR]

Background: Step width is a spatial variable in the frontal plane, defined as the mediolateral distance between the heel (forefoot during sprinting) of bilateral feet at initial contact. Variations in step width may impact the lower limb biomechanics. This systematic review aimed to synthesize the published findings to determine the influence of acute changes in step width on locomotion biomechanics and provide implications for injury prevention and enhanced sports performance. Methods: Literature was identified, selected, and appraised in accordance with the methods of a systematic review. Four electronic databases (Web of Science, MEDLINE via PubMed, Scopus, and ScienceDirect) were searched up until May 2023 with the development of inclusion criteria based on the PICO model. Study quality was assessed using the Downs and Black checklist and the measured parameters were summarized. Results: Twenty-three articles and 399 participants were included in the systematic review. The average quality score of the 23 studies included was 9.39 (out of 14). Step width changed the kinematics and kinetics in the sagittal, frontal, and transverse planes of the lower limb, such as peak rearfoot eversion angle and moment, peak hip adduction angle and moment, knee flexion moment, peak knee internal rotation angle, as well as knee external rotation moment. Alteration of step width has the potential to change the stability and posture during locomotion, and evidence exists for the immediate biomechanical effects of variations in step width to alter proximal kinematics and cues to impact loading variables. Conclusion: Short-term changes in step width during walking, running, and sprinting influenced multiple lower extremity biomechanics. Narrower step width may result in poor balance and higher impact loading on the lower extremities during walking and running and may limit an athlete's sprint performance. Increasing step width may be beneficial for injury rehabilitation, i.e., for patients with patellofemoral pain syndrome, iliotibial band syndrome or tibial bone stress injury. Wider steps increase the supporting base and typically enhance balance control, which in turn could reduce the risks of falling during daily activities. Altering the step width is thus proposed as a simple and non-invasive treatment method in clinical practice. Key Points: Short-term changes in step width during gait could influence multiple lower extremity biomechanics. Increasing step width may be beneficial for specific injury rehabilitation. Wider steps increase the supporting base and typically enhance balance control to reduce the falling risks. [ABSTRACT FROM AUTHOR]

Ankle push-off power plays an important role in healthy walking, contributing to center-of-mass acceleration, swing leg dynamics, and accounting for 45% of total leg power. The majority of existing passive energy storage and return prostheses for people with below-knee (transtibial) amputation are stiffer than the biological ankle, particularly at slower walking speeds. Additionally, passive devices provide insufficient levels of energy return and push-off power, negatively impacting biomechanics of gait. Here, we present a clinical study evaluating the kinematics and kinetics of walking with a microprocessor-controlled, variable-stiffness ankle-foot prosthesis (945 g) compared to a standard low-mass passive prosthesis (Ottobock Taleo, 463 g) with 7 study participants having unilateral transtibial amputation. By modulating prosthesis stiffness under computer control across walking speeds, we demonstrate that there exists a stiffness that increases prosthetic-side energy return, peak power, and center-of-mass push-off work, and decreases contralateral limb peak ground reaction force compared to the standard passive prosthesis across all evaluated walking speeds. We demonstrate a significant increase in center-of-mass push-off work of 26.1%, 26.2%, 29.6% and 29.9% at 0.75 m/s, 1.0 m/s, 1.25 m/s, and 1.5 m/s, respectively, and a significant decrease in contralateral limb ground reaction force of 3.1%, 3.9%, and 3.2% at 1.0 m/s, 1.25 m/s, and 1.5 m/s, respectively. This study demonstrates the potential for a quasi-passive microprocessor-controlled variable-stiffness prosthesis to increase push-off power and energy return during gait at a range of walking speeds compared to a passive device of a fixed stiffness. [ABSTRACT FROM AUTHOR]

To investigate the biomechanical factors associated with patellofemoral pain in children and adolescents. A cross-sectional, population-based study conducted in Brazil from 2019 to 2023, involving students from public schools. Adjusted prevalence ratios and their respective 95% confidence intervals for the outcome in relation to independent variables were calculated for association analysis, adopting a significance level of 5%. Out of the total of 283 students, 152 were female and 182 were aged between 16 and 18 years old. A positive association was observed between the presence of patellofemoral pain and a poor movement quality in both lower limbs (right side: p = 0.04 and left side: p = 0.04) as well as with dynamic valgus of the left lower limb (p < 0.01). Patellofemoral pain in children and adolescents is associated with poor movement quality in the lower limbs and dynamic valgus of the left lower limb. Actions targeting these biomechanical factors may be crucial for early diagnosis and clinical treatment of this disfunction. [ABSTRACT FROM AUTHOR]

Enhancing the mechanical properties and cytocompatibility of decellularized heart valves is the key to promote the application of biological heart valves. In order to further improve the mechanical properties, the electrospinning and non-woven processing methods are combined to prepare the polylactic acid (PLA)/decellularized heart valve nanofiber-reinforced sandwich structure electrospun scaffold. The effect of electrospinning time on the performance of decellularized heart valve is investigated from the aspects of morphology, mechanical properties, softness, and biocompatibility of decellularized heart valve. Results of the mechanical tests show that compared with the pure decellularized heart valve, the mechanical properties of the composite heart valve were significantly improved with the tensile strength increasing by 108% and tensile strain increased by 571% when the electrospinning time exceeded 2 h. In addition, with this electrospinning time, the composite heart valve has a certain promoting effect on the human umbilical vein endothelial cells proliferation behavior. This work provides a promising foundation for tissue heart valve reendothelialization to lay the groundwork for organoid. [ABSTRACT FROM AUTHOR]

The flow of fluid through the porous matrix of a reservoir rock applies a seepage force to the solid rock matrix. Although the seepage force exerted by fluid flow through the porous matrix of a reservoir rock has a notable influence on rock deformation and failure, its effect on hydraulic fracture (HF) propagation remains ambiguous. Therefore, in this study, we improved a traditional fluid–solid coupling method by incorporating the role of seepage force during the fracturing fluid seepage, using the discrete element method. First, we validated the simulation results of the improved method by comparing them with an analytical solution of the seepage force and published experimental results. Next, we conducted numerical simulations in both homogeneous and heterogeneous sandstone formations to investigate the influence of seepage force on HF propagation. Our results indicate that fluid viscosity has a greater impact on the magnitude and extent of seepage force compared to injection rate, and that lower viscosity and injection rate correspond to shorter hydraulic fracture lengths. Furthermore, seepage force influences the direction of HF propagation, causing HFs to deflect towards the side of the reservoir with weaker cementation and higher permeability. [ABSTRACT FROM AUTHOR]

Background: Various physical fitness qualities such as muscle strength, speed and endurance are related to soccer performance. Accordingly, the combination of strength and endurance training (i.e., concurrent training [CT]) is an often-encountered training regimen in soccer. Less is known about the effects of CT sequencing on performance in young soccer players. The aim of this study was to assess the sequencing effects of strength and intermittent endurance training applied within the same training session (intrasession) on measures of physical fitness and soccer performance in young soccer players. Methods: Fifty male adolescent soccer players volunteered to participate in this study which was conducted in the Netherlands in 2019. Players were randomly assigned to a strength-endurance (SE) or an endurance-strength (ES) group in matched pairs based on their countermovement jump (CMJ) performance at baseline. Both groups completed a 12-weeks in-season training program with two weekly CT sessions. Training sessions consisted of 15 min plyometric exercises and 15 min soccer-specific intermittent endurance training. Both groups performed the same training volumes and the only difference between the groups was the CT intrasession sequencing scheme (SE vs. ES). Pre and post intervention, proxies of muscle power (CMJ, squat jump [SJ]), linear sprint speed (30-m sprint test), agility (Illinois test with / without ball), and soccer performance (ball kicking velocity) were tested. Results: Data from 38 players aged 14.8 ± 1.0 years (body height 172.9 ± 8.1 cm, body mass: 57.0 ± 7.2 kg, soccer experience: 8.8 ± 2.8 years, age from peak-height-velocity [PHV]: +1.2 ± 1.0 years) were included. Significant main time effects were found for CMJ (p = 0.002, d = 0.55), SJ (p = 0.004, d = 0.51), the Illinois agility test with ball (p = 0.016, d = 0.51), and ball kicking velocity (p = 0.016, d = 0.51). Significant group-by-time interactions were observed for 30-m linear sprint speed (p < 0.001, d = 0.76) with ES showing greater improvements (p = 0.006, d = 0.85, Δ-5%). Conclusions: Both CT-sequencing types improved performance in the tests administered. The intrasession CT sequencing (SE vs. ES) appears not to have a major impact on physical fitness adaptations, except for linear sprint speed which was in favor of ES. Key points: • This study examined the effects of intrasession concurrent training. Findings showed that strength-endurance and endurance-strength sequencing resulted in similar changes in most measures of physical fitness in adolescent male soccer players. • If the goal is to improve linear sprint speed, endurance-strength sequencing appears to be better suited. • More research is needed to acquire further knowledge on concurrent training and effects of different types of sequencing schemes (e.g., training day, microcycle) as well as the strength training (e.g., power training) and endurance training type (e.g., high intensity interval training). [ABSTRACT FROM AUTHOR]

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Background: Change of direction (COD) movements are associated with non-contact anterior cruciate ligament (ACL) injuries in multidirectional sports. Females appear at increased risk compared to males, which could be attributable to whole body kinematic strategies and greater multiplanar knee joint loads (KJLs) during COD which can increase ACL loading. Objective: The aim of this systematic review and meta-analysis was to examine and quantitatively synthesise the evidence for differences between males and females regarding KJLs and their biomechanical determinants (whole body kinematic strategies determining KJLs) during COD tasks. Methods: Databases including SPORTDiscus, Web of Science, and PubMed were systematically searched (July 2021–June 2023) for studies that compared differences in knee joint loads and biomechanical determinants of KJLs during COD between males and females. Inclusion criteria were: (1) females and males with no prior history of ACL injury (18–40 years); (2) examined biomechanical determinants of KJLs and/ or KJLs during COD tasks > 20°; (3) compared ≥ 1 outcome measure between males and females. Studies published between 2000 and 2023 examining a cutting task > 20° with a preceding approach run that compared KJLs or the whole body multiplanar kinematics associated with them, between sexes, using three-dimensional motion analysis. Results: This meta-analysis included 17 studies with a pooled sample size of 451 participants (227 males, 224 females). Meta-analysis revealed females displayed significantly less peak knee flexion during stance (SMD: 0.374, 95% CI 0.098–0.649, p = 0.008, I2: 0%); greater knee abduction at initial contact (IC) (SMD: 0.687, 95% CI 0.299–1.076, p = 0.001, I2: 55%); less hip internal rotation (SMD: 0.437, 95% CI 0.134–0.741, p = 0.005, I2: 34%) and hip abduction at IC (SMD: −0.454, 95% CI 0.151–0.758, p = 0.003, I2: 33%). No significant differences were observed between males and females for any internal or externally applied KJLs. All retrieved studies failed to control for strength, resistance training or skill history status. Conclusion: No differences were observed in KJLs between males and females despite females displaying greater knee abduction at IC and less peak knee flexion during the stance phase of CODs, which are visual characteristics of non-contact ACL injury. Further research is required to examine if this translates to a similar injury risk, considering morphological differences in strain characteristics of the ACL between males and females. This observation may in part explain the disproportionate ACL injury incidence in female multidirectional athletes. Further higher quality controlled research is required whereby participants are matched by skill training history, resistance training history and strength status to ensure an appropriate comparison between males and females. Key Points: No differences between sexes were found for multiplanar KJLs despite previous research supporting this. Further research is required to identify if this is the case and if it affects injury risk between males and females. Females displayed greater knee abduction at initial contact, less peak knee flexion during stance, and less hip rotation and abduction at IC together with less peak hip flexion during stance during CODs. Previous research has failed to account for confounding factors such as skill training history, resistance training history and strength status together with gendered environmental factors that could contribute to the misinterpretation of COD differences between males and females. [ABSTRACT FROM AUTHOR]

Objective: Cartilage degeneration involves structural, compositional, and biomechanical alterations that may be detected non-invasively using quantitative MRI. The goal of this study was to determine if topographical variation in T1rho values correlates with indentation stiffness and biochemical contents of human patellar cartilage. Design: Cadaveric patellae from unilateral knees of 5 donors with moderate degeneration were imaged at 3-Telsa with spiral chopped magnetization preparation T1rho sequence. Indentation testing was performed, followed by biochemical analyses to determine water and sulfated glycosaminoglycan contents. T1rho values were compared to indentation stiffness, using semi-circular regions of interest (ROIs) of varying sizes at each indentation site. ROIs matching the resected tissues were analyzed, and univariate and multivariate regression analyses were performed to compare T1rho values to biochemical contents. Results: Grossly, superficial degenerative change of the cartilage (i.e., roughened texture and erosion) corresponded with regions of high T1rho values. High T1rho values correlated with low indentation stiffness, and the strength of correlation varied slightly with the ROI size. Spatial variations in T1rho values correlated positively with that of the water content (R2 = 0.10, p < 0.05) and negatively with the variations in the GAG content (R2 = 0.13, p < 0.01). Multivariate correlation (R2 = 0.23, p < 0.01) was stronger than either of the univariate correlations. Conclusion: These results demonstrate the sensitivity of T1rho values to spatially varying function and composition of cartilage and that the strength of correlation depends on the method of data analysis and consideration of multiple variables. [ABSTRACT FROM AUTHOR]

Purpose: Preemptively estimating tissue damage is crucial for a safe surgical procedure. We previously investigated the possibility of estimating the fracture energies of biological tissues based on their elasticities. However, the reason behind the presence of these correlations is poorly understood. In this study, we investigate the effect of a tissue's histology on the correlation between the fracture energy and elasticity. We hypothesize that two tissues with similar fibrous structure will show a similar correlation between the fracture energy and elasticity. Methods: Porcine duodenum were used for this study. Two tensile tests were performed for each porcine duodenum specimen to determine its elasticity and tearing energy. The correlation between fracture energy and elasticity was then investigated using the results from the mechanical tests. Furthermore, duodenum specimens were fixed in 10% formalin while under tension. Microscopic images were then taken to visualize the fibrous structure within the duodenum tissues under tension. Results: The results from the tensile test showed that the fracture energy had an isotropic positive and linear correlation with the elasticity to the negative 0.5th power (R2 = 0.89), which was also previously reported in small intestinal (jejunum) specimens. Furthermore, the tearing patterns of the duodenum were identical to the ones reported in the jejunum. Hematoxylin and eosin staining on tissues fixed under tension showed that the endomysium fibers are involved in providing resistance toward traction. Conclusion: Through mechanical tests, we showed that porcine duodenum tissues also have a correlation between its fracture energy and elasticity. We also discussed that the histological structure of a tissue is an important factor that dictates how the tearing energy of a tissue will correlate to the elasticity. We understood that since the tearing mechanism between the duodenum and jejunum was similar, the correlations between their fracture energies and elasticities were also similar. [ABSTRACT FROM AUTHOR]

Purpose: Performance is the benchmark to assess the level of an athlete: in this respect, a more precise qualitative and quantitative evaluation of the performance represents an important target to be achieved. Methods: The work presents a possible method, based on the biomechanical evaluation of the motor exercise with an optoelectronic system, to characterise single or multiple repetitions of pull-ups of 12 athletes of sport climbing and sportive healthy subjects, monitoring and scoring the performance and the safety of the executions. The analysis includes the time courses of the segmental kinematics and some newly developed synthetic indices in the form of performance and safety scores. Results: The time courses make it possible to analyse the linear and angular kinematics district-by-district and have a direct overview of the ranges of motion, the patterns of task execution, together with the possible strategies adopted to complete the exercise in terms of compensations. The proposed characterisation provides a condensed summary of the global execution quality and offers the possibility to identify which single biomechanical parameters are modified. Conclusion: The method is intended as a practical tool to enrich the training schedule in terms of the qualitative and quantitative evaluation of the performances and to increase the self-awareness while training. [ABSTRACT FROM AUTHOR]

Purpose: Increasing access to marker-less technology has enabled practitioners to obtain kinematic data more quickly. However, the validation of many of these methods is lacking. Therefore, the validity of pre-trained neural networks was explored in this study compared to reflective marker tracking from sagittal plane cycling motion. Methods: Twenty-six cyclists were assessed during stationary cycling at self-selected cadence and moderate intensity exercise. Standard video from their sagittal plane was obtained to extract joint kinematics. Hip, knee, and ankle angles were calculated from marker digitisation and from two deep learning-based approaches (TransPose and MediaPipe). Results: Typical errors ranged between 1 and 10° for TransPose and 3–9° for MediaPipe. Correlations between joint angles calculated from TransPose and marker digitalization were stronger (0.47–0.98) than those from MediaPipe (0.25–0.96). Conclusion: TransPose seemed to perform better than MediaPipe but both methods presented poor performance when tracking the foot and ankle. This seems to be associated with the low frame rate and image resolution when using standard video mode. [ABSTRACT FROM AUTHOR]

The gastrointestinal (GI) organs of the human body are responsible for transporting and extracting nutrients from food and drink, as well as excreting solid waste. Biomechanical experimentation of the GI organs provides insight into the mechanisms involved in their normal physiological functions, as well as understanding of how diseases can cause disruption to these. Additionally, experimental findings form the basis of all finite element (FE) modelling of these organs, which have a wide array of applications within medicine and engineering. This systematic review summarises the experimental studies that are currently in the literature (n = 247) and outlines the areas in which experimentation is lacking, highlighting what is still required in order to more fully understand the mechanical behaviour of the GI organs. These include (i) more human data, allowing for more accurate modelling for applications within medicine, (ii) an increase in time-dependent studies, and (iii) more sophisticated in vivo testing methods which allow for both the layer- and direction-dependent characterisation of the GI organs. The findings of this review can also be used to identify experimental data for the readers' own constitutive or FE modelling as the experimental studies have been grouped in terms of organ (oesophagus, stomach, small intestine, large intestine or rectum), test condition (ex vivo or in vivo), number of directions studied (isotropic or anisotropic), species family (human, porcine, feline etc.), tissue condition (intact wall or layer-dependent) and the type of test performed (biaxial tension, inflation–extension, distension (pressure-diameter), etc.). Furthermore, the studies that investigated the time-dependent (viscoelastic) behaviour of the tissues have been presented. [ABSTRACT FROM AUTHOR]

Multi-cellular biomimetic models often comprise heterogenic geometries. Therefore, quantification of their mechanical properties—which is crucial for various biomedical applications—is a challenge. Due to its simplicity, linear fitting is traditionally used in analyzing force—displacement data of parallel compression measurements of multi-cellular clusters, such as tumor spheroids. However, the linear assumption would be artificial when the contact geometry is not planar. We propose here the integrated elasticity (IE) regression, which is based on extrapolation of established elastic theories for well-defined geometries, and is free, extremely simple to apply, and optimal for analyzing coarsely concave multi-cellular clusters. We studied here the quality of the data analysis in force measurements of tumor spheroids comprising different types of melanoma cells, using either the IE or the traditional linear regressions. The IE regression maintained excellent precision also when the contact geometry deviated from planarity (as shown by our image analysis). While the quality of the linear fittings was relatively satisfying, these predicted smaller elastic moduli as compared to the IE regression. This was in accordance with previous studies, in which the elastic moduli predicted by linear fits were smaller compared to those obtained by well-established methods. This suggests that linear regressions underestimate the elastic constants of bio-samples even in cases where the fitting precision seems satisfying, and highlights the need in alternative methods as the IE scheme. For comparison between different types of spheroids we further recommend to increase the soundness by regarding relative moduli, using universal reference samples. [ABSTRACT FROM AUTHOR]

Background: Climbing is an intricate sport composed of various disciplines, holds, styles, distances between holds, and levels of difficulty. In highly skilled climbers the potential for further strength-specific adaptations to increase performance may be marginal in elite climbers. With an eye on the upcoming 2024 Paris Olympics, more climbers are trying to maximize performance and improve training strategies. The relationships between muscular strength and climbing performance, as well as the role of strength in injury prevention, remain to be fully elucidated. This narrative review seeks to discuss the current literature regarding the effect of resistance training in improving maximal strength, muscle hypertrophy, muscular power, and local muscular endurance on climbing performance, and as a strategy to prevent injuries. Main Body: Since sport climbing requires exerting forces against gravity to maintain grip and move the body along the route, it is generally accepted that a climber's absolute and relative muscular strength are important for climbing performance. Performance characteristics of forearm flexor muscles (hang-time on ledge, force output, rate of force development, and oxidative capacity) discriminate between climbing performance level, climbing styles, and between climbers and non-climbers. Strength of the hand and wrist flexors, shoulders and upper limbs has gained much attention in the scientific literature, and it has been suggested that both general and specific strength training should be part of a climber's training program. Furthermore, the ability to generate sub-maximal force in different work-rest ratios has proved useful, in examining finger flexor endurance capacity while trying to mimic real-world climbing demands. Importantly, fingers and shoulders are the most frequent injury locations in climbing. Due to the high mechanical stress and load on the finger flexors, fingerboard and campus board training should be limited in lower-graded climbers. Coaches should address, acknowledge, and screen for amenorrhea and disordered eating in climbers. Conclusion: Structured low-volume high-resistance training, twice per week hanging from small ledges or a fingerboard, is a feasible approach for climbers. The current injury prevention training aims to increase the level of performance through building tolerance to performance-relevant load exposure and promoting this approach in the climbing field. Key Points: Altering the mechanical and metabolic stress, by using different intensities or varying the number of repetitions and sets, and training frequency per week are the most significant variables in manipulating the overall training volume and the variables requiring emphasis in planning incorporation of resistance training (RT) in climbers. Structured low-volume training at high resistance, twice per week, is a feasible approach to RT in climbers. The following classifications are proposed in climbing: > 15 reps (or hang time > 30 s) strength endurance bias; 8–15 RM (or 3–30 s hang time) hypertrophic bias; 1- 5 RM (or 1–5 s hang time) maximal strength bias. Improving maximal finger and shoulder girdle strength may decrease injury risk; as a result of reducing percentage of maximum strength generated in each move, the overall loading stress in a session is also diminished. Upper body RT programs have proven efficient for improving performance in climbing-specific tests among lower- and intermediate-grade climbers, but whether this training approach may improve climbing performance among advanced or elite climbers remains to be elucidated. [ABSTRACT FROM AUTHOR]

Background: Patellofemoral pain (PFP) is among the most common injuries in runners. While multiple risk factors for patellofemoral pain have been investigated, the interactions of variables contributing to this condition have not been explored. This study aimed to classify runners with patellofemoral pain using a combination of factors including biomechanical, anthropometric, and demographic factors through a Classification and Regression Tree analysis. Results: Thirty-eight runners with PFP and 38 healthy controls (CON) were selected with mean (standard deviation) age 33 (16) years old and body mass index 22.3 (2.6) kg/m2. Each ran at self-selected speed, but no between-group difference was identified (PFP = 2.54 (0.2) m/s x CON = 2.55 (0.1) m/s, P =.660). Runners with patellofemoral pain had different patterns of interactions involving braking ground reaction force impulse, contact time, vertical average loading rate, and age. The classification and regression tree model classified 84.2% of runners with patellofemoral pain, and 78.9% of healthy controls. The prevalence ratios ranged from 0.06 (95% confidence interval: 0.02–0.23) to 9.86 (95% confidence interval: 1.16–83.34). The strongest model identified runners with patellofemoral pain as having higher braking ground reaction force impulse, lower contact times, higher vertical average loading rate, and older age. The receiver operating characteristic curve demonstrated high accuracy at 0.83 (95% confidence interval: 0.74–0.93; standard error: 0.04; P <.001). Conclusions: The classification and regression tree model identified an influence of multiple factors associated with patellofemoral pain in runners. Future studies may clarify whether addressing modifiable biomechanical factors may address this form of injury. Key Points: This study highlights interactions between multiple biomechanical factors associated with patellofemoral pain. Interactions between braking ground reaction force impulse, contact time, vertical average loading rate, and age correctly identified runners with patellofemoral pain and controls. Step rate, sex, and body mass index were not predictors of patellofemoral pain in runners when a classification and regression tree analysis was used [ABSTRACT FROM AUTHOR]

Optical motion capture is an essential tool for the study and analysis of human movement. Currently, most manufacturers of motion-capture systems provide software applications for reconstructing the movement in real time, thus allowing for on-the-fly visualization. The captured kinematics can be later used as input data for a further musculoskeletal analysis. However, in advanced biofeedback applications, the results of said analysis, such as joint torques, ground-reaction forces, muscle efforts, and joint-reaction forces, are also required in real time. In this work, an extended Kalman filter (EKF) previously developed by the authors for real-time, whole-body motion capture and reconstruction is augmented with inverse dynamics and muscle-efforts optimization, enabling the calculation and visualization of the latter, along with joint-reaction forces, while capturing the motion. A modified version of the existing motion-capture algorithm provides the positions, velocities, and accelerations at every time step. Then, the joint torques are calculated by solving the inverse-dynamics problem, using force-plate measurements along with previously estimated body-segment parameters. Once the joint torques are obtained, an optimization problem is solved, in order to obtain the muscle forces that provide said torques while minimizing an objective function. This is achieved by a very efficient quadratic programming algorithm, thoroughly tuned for this specific problem. With this procedure, it is possible to capture and label the optical markers, reconstruct the motion of the model, solve the inverse dynamics, and estimate the individual muscle forces, all while providing real-time visualization of the results. [ABSTRACT FROM AUTHOR]

Evidence-based and person-centred care requires the measurement of treatment outcomes that matter to youth and mental health practitioners. Priorities, however, may vary not just between but also within stakeholder groups. This study used Q-methodology to explore differences in outcome priorities among mental health practitioners from two countries in relation to youth depression. Practitioners from the United Kingdom (UK) (n = 27) and Chile (n = 15) sorted 35 outcome descriptions by importance and completed brief semi-structured interviews about their sorting rationale. By-person principal component analysis (PCA) served to identify distinct priority profiles within each country sample; second-order PCA examined whether these profiles could be further reduced into cross-cultural "super profiles". We identified three UK outcome priority profiles (Reduced symptoms and enhanced well-being; improved individual coping and self-management; improved family coping and support), and two Chilean profiles (Strengthened identity and enhanced insight; symptom reduction and self-management). These could be further reduced into two cross-cultural super profiles: one prioritized outcomes related to reduced depressive symptoms and enhanced well-being; the other prioritized outcomes related to improved resilience resources within youth and families. A practitioner focus on symptom reduction aligns with a long-standing focus on symptomatic change in youth depression treatment studies, and with recent measurement recommendations. Less data and guidance are available to those practitioners who prioritize resilience outcomes. To raise the chances that such practitioners will engage in evidence-based practice and measurement-based care, measurement guidance for a broader set of outcomes may be needed. [ABSTRACT FROM AUTHOR]

Certain air sacs have evolved in multiple lineages of soaring birds, and it emerges that these probably function to reduce the force required from the major flight muscles as they hold the wings in place during gliding and soaring.Inflated air sacs reduce the force needed from wing muscles when gliding. [ABSTRACT FROM AUTHOR]

The hinge enables insects to control their wing movements, but how it works is hard to study. Multidisciplinary research, using imaging and machine-learning methods, now sheds light on the mechanism that underlies its operation.Insights into control of the joints that connect fly wings to their body. [ABSTRACT FROM AUTHOR]