3D Kinematics Research Articles

3D Morphology and Motions of the Canis Major Region from Gaia DR3

The Canis Major (CMa) region is known for its prominent arc-shaped morphology, visible at multiple wavelengths. This study integrates molecular gas data with high-precision astrometric parameters of young stellar objects (YSOs) from Gaia DR3 to provide the first three-dimensional (3D) insights into the dynamical evolution and star formation history of the CMa region. By utilizing the average distances and proper motions of the YSOs as proxies for those of the molecular clouds (MCs), we confirm the presence of a slowly expanding shell-like morphology in the CMa region, with an estimated radius of 47 ± 11 pc and expansion velocity of 1.6 ± 0.7 km s−1. Further, the dynamical evolution of the shell supports its expansion, with an expansion timescale of ∼4.4 Myr obtained by the traceback analysis assuming constant velocities. Finally, a momentum estimate suggests that at least two supernova explosions are needed to power the observed expanding shell, reinforcing the previous hypothesis of multiple supernova events. This study effectively combines CO data with the astrometric data of YSOs from Gaia, offering significant support for future studies of the 3D morphology and kinematics of MCs.

Validity and reliability of trunk and lower-limb kinematics during squatting, hopping, jumping and side-stepping using OpenCap markerless motion capture application

ABSTRACT OpenCap is a web-based markerless motion capture platform that estimates 3D kinematics from videos recorded from at least two iOS devices. This study aimed to determine the concurrent validity and inter-session reliability of OpenCap for measuring trunk and lower-limb kinematics during squatting, hopping, countermovement jumping, and cutting. Nineteen participants (10 males, 9 females; age 27.7 ± 4.1 years) were included. Countermovement jump, single-leg triple vertical hop, single-leg squat, sidestep cutting and side hop tasks were assessed. For validity, OpenCap was compared to a marker-based motion capture system using root-mean-square error. Test–retest reliability of OpenCap was determined using intraclass correlations and minimum detectable change (MDC) from two testing sessions. The squat had the lowest RMSE across joint angles (mean = 7.0°, range = 2.9° to 13.6°). For peak angles, the countermovement jump (jump phase) (ICC = 0.62–0.93) and the squat (ICC = 0.60–0.92) had the best reliability across all joints. For initial contact, the side hop had the best inter-session reliability (ICC = 0.70–0.94) across all joint angles. As such, OpenCap validity and reliability are joint and task specific.

Neural network and layer-wise relevance propagation reveal how ice hockey protective equipment restricts players' motion.

Understanding the athlete's movements and the restrictions incurred by protective equipment is crucial for improving the equipment and subsequently, the athlete's performance. The task of equipment improvement is especially challenging in sports including advanced manoeuvres such as ice hockey and requires a holistic approach guiding the researcher's attention toward the right variables. The purposes of this study were (a) to quantify the effects of protective equipment in ice hockey on player's performance and (b) to identify the restrictions incurred by it. Twenty male hockey players performed four different drills with and without protective equipment while their performance was quantified. A neural network accompanied by layer-wise relevance propagation was applied to the 3D kinematic data to identify variables and time points that were most relevant for the neural network to distinguish between the equipment and no equipment condition, and therefore presumable result from restrictions incurred by the protective equipment. The study indicated that wearing the protective equipment, significantly reduced performance. Further, using the 3D kinematics, an artificial neural network could accurately distinguish between the movements performed with and without the equipment. The variables contributing the most to distinguishing between the equipment conditions were related to the upper extremities and movements in the sagittal plane. The presented methodology consisting of artificial neural networks and layer-wise relevance propagation contributed to insights without prior knowledge of how and to which extent joint angles are affected in complex maneuvers in ice hockey in the presence of protective equipment. It was shown that changes to the equipment should support the flexion movements of the knee and hip and should allow players to keep their upper extremities closer to the torso.

Exploring elbow kinematics in the central bearded dragon (Pogona vitticeps) using XROMM: Implications for the role of forearm long-axis rotation in non-avian reptile posture and mobility.

The functional morphology and kinematics of the elbow joint remain relatively understudied in squamates. Previous investigations of lizard elbow morphology and kinematics suggest long-axis rotation (LAR) of the radius and ulna during stance allows the manus to remain pronated during forelimb retraction. Using XROMM (X-ray Reconstruction of Moving Morphology), we explored the range of 3D movements and kinematics of the humerus, radius, and ulna in three adult male Central bearded dragons (Pogona vitticeps) during trackway walking. Our data indicate that the elbow joint of P. vitticeps experiences significant rotations in all three dimensions and that the radius and ulna adduct and rotate laterally on their long axes relative to the elbow joint and to one another during stance. These movements allow the distal ends of the radius and ulna to remain in a configuration necessary for manus pronation. These data support previous inferences that the radius and ulna of lizards move independently at the wrist joint. We suggest that independent LAR of the radius and ulna relative to the elbow joint and to one another may be an ancestral mechanism in lizards and perhaps more broadly across non-avian reptiles.

Plantar massage or ankle mobilization do not alter gait biomechanics in those with chronic ankle instability: a randomized controlled trial

ABSTRACT Objectives Chronic ankle instability (CAI) is characterized by persistent neuromechanical impairments following an initial lateral ankle sprain. Ankle joint mobilization and plantar massage have improved the range of motion and static postural control in those with CAI. This study aimed to determine the impact of two-week joint mobilization and plantar massage interventions on gait kinematics and kinetics in individuals with CAI. Methods A single-blind randomized trial was conducted with 60 participants with CAI, randomized into three groups: joint mobilization (n = 20), plantar massage (n = 20), and control (n = 20). The two treatment groups received six 5-min sessions manual therapy over a 2-week, while the control group received no intervention. Gait biomechanics were assessed on an instrumented treadmill before and after the intervention using 3D kinematics and kinetics analysis. Analyses compared biomechanical outcomes from each treatment group to the control group individually using a 1-dimensional statistical parametric mapping. The alpha level was set at p < 0.05. Results Eighteen participants per group were part of the final analysis. No significant main or interactions effects were found for ankle sagittal or frontal plane positions following either intervention (p > 0.05 for all comparisons). COP location relative to the lateral border of the foot also did not change (p > 0.05). Conclusion The findings suggest that two-week joint mobilization and plantar massage interventions do not significantly alter gait biomechanics in individuals with CAI. These results support the need for gait-specific interventions to modify biomechanics in this population.

Enhancing Maneuverability in a Variable Wheelbase Wheeled Mobile Robot Through Dynamic Steering Curvature Control

ABSTRACTVariable wheelbase wheeled mobile robot (VW‐WMR) is capable of maneuvering flexibly and traversing on rough and soil terrains within confined spaces. While the steering radius of the robot model can be robustly changed by the variable wheelbase length, a challenge is posed in accurately tracking a predefined trajectory through the alteration of wheelbase length. A dynamic steering curvature (DSC) control method is proposed in this work to overcome this challenge, which is achieved by two different approaches utilizing the variable wheelbase length and manipulating drifting motions. First, to enable flexible trajectory adjustments, a 3D Ackermann kinematics model, incorporating the lifting motion of the robot box, is developed to control steering curvature by the changes in wheelbase length. Second, to achieve flexible movement for the inner and outer curves of the originally planned curvilinear trajectory, Ackermann drift models are presented by the establishment of two sequence instantaneous centers. Furthermore, the control performance of DSC is validated through simulation experiments on the ROSTDyn Vortex platform, using a six‐wheeled VW‐WMR named HIT‐MRII robot. The effectiveness of DSC for strategically altering the robot's motion trajectory is demonstrated by the results, which show the relation between the changed trajectory position and the variation in wheelbase length, and the variation in the radii of the instantaneous centers (ICs) in the Ackermann drift model, respectively. In addition, the high maneuverability of the robot using the Ackermann model is proven by physical experiments during steering motions on soil terrain. A comprehensive advantage is demonstrated by the results via Ackermann models, which include shorter runtimes, moderate travel distances, and moderate variations in force on the wheels, compared to different velocity, crabbing motion, and equivalent bicycle models.

Kinematics of elongate harvestmen chelicerae: Comparative range of motion analyses in extant Ischyropsalis (Dyspnoi, Opiliones)

Chelicerae, the mouthparts of chelicerates, are essential for food processing. Particularly within harvestmen (Opiliones), some species have greatly elongated their tripartite chelicerae and utilize them for mating behavior, defense, and primarily for predation. We investigated two European species, Ischyropsalis muellneri and Ischyropsalis hellwigii, which occupy different niches (caves, forests), exhibit different feeding ecologies (opportunist, specialist), and first and foremost possess different chelicerae morphologies (long and thin, short and robust). We scanned the specimens using state-of-the-art micro-CT, generated surface reconstructions, and equipped one chelicera of each specimen with artificial joints to explore their Range of Motion in a 3D kinematic approach. For a size-corrected comparison of the two species, we analyzed the Range of Motion in addition to three different settings (original body size, body scaled to 5 mm, chelicerae scaled to 5 mm). Ischyropsalis muellneri reached a higher maximum excursion angle (= single Range of Motion) in all three joints, also exhibiting a greater total Range of Motion in the original body length setting, as well as the scaled body length setting. Only in the third setting, the total Range of Motion of Ischyropsalis hellwigii was slightly higher, although Ischyropsalis muellneri still extended further ventrally. Our results suggest that the sturdier, more massive chelicerae of Ischyropsalis hellwigii, attributable to strong specialization on snails as prey, are associated with reduced Range of Motion. The less food-specialized species Ischyropsalis muellneri apparently requires higher flexibility of its chelicerae for prey capture, likely due to its restriction to cave ecosystems, where food availability is relatively scarce. We could show that virtual Range of Motion analyses in harvestmen chelicerae can play a pivotal role in understanding the theoretical feeding ecology and functional morphology of this group. This approach can be verified by in-vivo observations and measurements or extended to other arachnid taxa and other body parts.

AI-smartphone markerless motion capturing of hip, knee, and ankle joint kinematics during countermovement jumps.

Recently, AI-driven skeleton reconstruction tools that use multistage computer vision pipelines were designed to estimate 3D kinematics from 2D video sequences. In the present study, we validated a novel markerless, smartphone video-based artificial intelligence (AI) motion capture system for hip, knee, and ankle angles during countermovement jumps (CMJs). Eleven participants performed six CMJs. We used 2D videos created by a smartphone (Apple iPhone X, 4K, 60 fps) to create 24 different keypoints, which together built a full skeleton including joints and their connections. Body parts and skeletal keypoints were localized by calculating confidence maps using a multilevel convolutional neural network that integrated both spatial and temporal features. We calculated hip, knee, and ankle angles in the sagittal plane and compared it with the angles measured by a VICON system. We calculated the correlation between both method's angular progressions, mean squared error (MSE), mean average error (MAE), and the maximum and minimum angular error and run statistical parametric mapping (SPM) analysis. Pearson correlation coefficients (r) for hip, knee, and ankle angular progressions in the sagittal plane during the entire movement were 0.96, 0.99, and 0.87, respectively. SPM group-analysis revealed some significant differences only for ankle angular progression. MSE was below 5.7°, MAE was below 4.5°, and error for maximum amplitudes was below 3.2°. The smartphone AI motion capture system with the trained multistage computer vision pipeline was able to detect, especially hip and knee angles in the sagittal plane during CMJs with high precision from a frontal view only.

Musculoskeletal Disorder Risk Assessment during the Tennis Serve: Performance and Prevention.

Addressing the risk of musculoskeletal disorders (MSDs) during a tennis serve is a challenge for both protecting athletes and maintaining performance. The aim of this study was to investigate the risk of MSD occurrence using the rapid whole-body assessment (REBA) ergonomic tool at each time step, using 3D kinematic analysis of joint angles for slow and fast serves. Two force platforms (750 Hz) and an optoelectronic system including 10 infrared cameras (150 Hz, 82 markers located on the whole body and on the racket) were used to capture the kinematics of the six REBA joint areas over five services in two young male and two young female ranked players. The mean REBA score was 9.66 ± 1.11 (ranging from 7.75 to 11.85) with the maximum value observed for the loading and cocking stage (REBA score > 11). The intermediate scores for each of the six joint areas ranged between 2 and 3 and the maximum value of their respective scales. The lowest scores were observed for the shoulder. Neck rotation and shoulder flexion are parameters that could be taken into account when analyzing performance in the context of MSD prevention.

Head and pelvis are the key segments recruited by adult spinal deformity patients during daily life activities

Functional assessment is a key element in evaluating adult spinal deformity (ASD) patients. The multitude of 3D kinematic parameters provided by movement analysis can be confusing for spine surgeons. The aim was to investigate movement patterns of ASD based on key kinematic parameters. 115 primary ASD and 36 controls underwent biplanar radiographs and 3D movement analysis during walking, sit-to-stand and stair ascent to calculate joint and segment kinematics. Principal component analysis was applied to identify the most relevant kinematic parameters that define movement strategies adopted by ASD. Pelvis and head relative to pelvis kinematics were the most relevant parameters. ASD patients adopted four different movement strategies. Class 1: normative head and pelvis kinematics. Class 2: persistent pelvic backward tilt. Class 3: persistent forward shift of the head. Class 4: both pelvic backward tilt and forward shift of the head. Patients in class 3 and 4 presented sagittal malalignment on static radiographs with increased pelvic tilt, pelvic incidence-lumbar lordosis mismatch and sagittal vertical axis. Surprisingly, patients in class 3 had normal pelvic kinematics during movement, showing the importance of functional evaluation. In addition to being key segments in maintaining static global posture, head and pelvis were found to define movement patterns.

A 3D view of multiple populations' kinematics in Galactic globular clusters

We present the first 3D kinematic analysis of multiple stellar populations (MPs) in a representative sample of 16 Galactic globular clusters (GCs). For each GC in the sample, we studied the MP line-of-sight, plane-of-the-sky and 3D rotation, and velocity distribution anisotropy. The differences between first-population (FP) and second-population (SP) kinematic patterns were constrained by means of parameters specifically defined to provide a global measure of the relevant physical quantities and to enable a meaningful comparison among different clusters. Our analysis provides the first observational description of the MP kinematic properties and of the path they follow during their long-term dynamical evolution. In particular, we find evidence of differences between the rotation of MPs along all velocity components with the SP preferentially rotating faster than the FP. The difference between the rotation strength of MPs is anticorrelated with the cluster dynamical age. We also observe that FPs are characterized by isotropic velocity distributions at any dynamical age probed by our sample. On the contrary, the velocity distribution of SP stars is found to be radially anisotropic in dynamically young clusters and isotropic at later evolutionary stages. The comparison with a set of numerical simulations shows that these observational results are consistent with the long-term evolution of clusters forming with an initially more centrally concentrated and more rapidly rotating SP subsystem. We discuss the possible implications these findings have on our understanding of MP formation and early evolution.

Acute effects of the short-foot exercise in runners with medial tibial stress syndrome: A quasi-experimental study

ObjectivesAnalyze whether there are immediate changes in peak soleus activation and peak hindfoot eversion after short-foot exercise (SFE) in runners with medial tibial stress syndrome (MTSS). Secondarily, establish differences in peak soleus activation and peak hindfoot eversion between asymptomatic individuals and those presenting MTSS. DesignQuasi-experimental study. SettingUniversity Laboratory. ParticipantsThirty-two runners participated: 16 with MTSS and 16 in the no-pain group (NPG). Main outcome measuresSoleus activation was measured using electromyography, and hindfoot eversion via 3D kinematic analysis. Participants performed SFE, and running data were collected at 9,12 and 15 km/h pre- and post-intervention. ResultsSFE reduced peak soleus activation at 9 (p = 0.017) and 15 km/h (p = 0.019) for the MTSS group and at 15 km/h (p < 0.001) for the NPG, suggesting improved neuromuscular efficiency and potentially reduced tibial stress. SFE did not significantly affect peak hindfoot eversion. Significant correlations were found between ankle dorsiflexion range of motion and muscle activation (r = 0.585 to 0.849, p < 0.05). These findings suggest SFE could improve neuromuscular efficiency and reduce tibial stress, and highlights ankle flexibility's role in muscle activation. ConclusionsSFE significantly reduces soleus activation, potentially improving neuromuscular efficiency and decreasing tibial stress.

Assessing lower extremity stiffness in countermovement jumps: a critical analysis of the differences between calculation methods

ABSTRACT Introduction: Stiffness (k) describes a material’s resistance to deformation and is useful for understanding neuromuscular function, performance, and injury risk. The aim of this study is to compare the lower limb stiffness method (k LLS ), which uses only force plate data, with methods combining force plate and motion capture data to calculate stiffness during the eccentric phase of a countermovement. Material and Methods: Twelve resistance-trained males: age 24.9 (4.4) years, height 1.81 (0.05) m, weight 88.2 (14) kg) performed three maximal effort countermovement jumps (CMJ). Data were collected synchronously using three-dimensional (3D) kinematic and kinetic data (dual force plate setup). Lower limb stiffness (z), joint stiffness (x, y, and z), and leg stiffness (linear, sagittal plane, and 3D) were calculated for the eccentric phase of all CMs. Results: k LLS showed high concurrent validity with strong correlations to kinetic-kinematic methods (r = 0.90-0.97, p < 0.05). A linear mixed model revealed no significant differences in k-values between k LLS and leg stiffness, indicating high concurrent validity. Discussion: k LLS offers valid and valuable information affecting performance, injury risk, and return-to-sport decisions. Conclusion: The findings suggest that k LLS is a valid method for calculating stiffness in CMJs and equal to 3D leg stiffness.

The functional role of the rabbit digastric muscle during mastication.

Muscle spindle abundance is highly variable in vertebrates, but the functional determinants of this variation are unclear. Recent work has shown that human leg muscles with the lowest abundance of muscle spindles primarily function to lengthen and absorb energy, while muscles with a greater spindle abundance perform active-stretch-shorten cycles with no net work, suggesting that muscle spindle abundance may be underpinned by muscle function. Compared with other mammalian muscles, the digastric muscle contains the lowest abundance of muscle spindles and, therefore, might be expected to generate substantial negative work. However, it is widely hypothesised that as a jaw-opener (anatomically) the digastric muscle would primarily function to depress the jaw, and consequently do positive work. Through a combination of X-ray reconstruction of moving morphology (XROMM), electromyography and fluoromicrometry, we characterised the 3D kinematics of the jaw and digastric muscle during feeding in rabbits. Subsequently, the work loop technique was used to simulate in vivo muscle behaviour in situ, enabling muscle force to be quantified in relation to muscle strain and hence determine the muscle's function during mastication. When functioning on either the working or balancing side, the digastric muscle generates a large amount of positive work during jaw opening, and a large amount of negative work during jaw closing, on average producing a relatively small amount of net negative work. Our data therefore further support the hypothesis that muscle spindle abundance is linked to muscle function; specifically, muscles that absorb a relatively large amount of negative work have a low spindle abundance.

422 The use of 3D kinematics for improved gait assessment in broilers

Abstract Genetic selection for high growth rates in broiler chickens has resulted in larger broilers and changes in broiler gait. Traditionally, broiler gait is assessed using visual observation which is subjective and labor intensive. In contrast, newer technologies are available which can be adapted to objectively score changes in broiler gait, thereby, increasing the validity and reliability of gait scoring with less labor required. The objective of this study was to compare the use of 3D kinematics versus visual scoring to assess broiler gait. Second, to determine how strain and age affect 3D kinematic gait metrics in broilers. Four strains of broiler chickens were used; two heritage strains: 1957 (H57; n = 52) and 1977 (H77; n = 51); and two commercially available strains: Cobb (n = 50) and Ross (n = 53). All broilers were weighed weekly throughout the study. Kinematic markers were placed along the spine and bony landmarks of each leg. Commercial strains had kinematic recordings and body weights (BW) recorded every week for 4 wk while Heritage strains had measurements recorded every week for 6 wk. Visual gait scoring was completed using a 5-point scale each week by two trained observers. Data were analyzed using the correlation procedure in SAS to determine the relationship between visual gait score and kinematic metrics as well as the GLIMMIX procedure to determine the effects of strain, age, and strain x age on all gait parameters. There was a weak positive correlation (r &amp;lt; 0.2) between visual gait score and all kinematic metrics. Cobb were the heaviest strain (1,292.6 ± 14.71 g P &amp;lt; 0.001) while H57 broilers were the lightest (326.4 ± 9.99 g P &amp;lt; 0.001). Each week, the BW of all strains increased significantly. Total Stride Time differed significantly by strain (P &amp;lt; 0.001; Cobb: 26.3 ± 0.47 cs, Ross: 23.1 ± 0.39 cs, H77: 23.7 ± 0.28 cs, H57: 21.5 ± 0.26 cs) and Age (P &amp;lt; 0.01; Commercial: wk 3: 21.8 ± 0.54 cs, wk 6: 28.1 ± 0.68 cs and Heritage: wk 3: 19.7 ± 0.42 cs, wk 8: 25.4 ± 0.52 cs). Total stride length (SL) also significantly differed by strain. Cobb had the longest SL of the two commercial strains (P &amp;lt; 0.001; 88.6 ± 1.94 mm) while H77 had the longest stride of the heritage strains (97.9 ± 1.51 mm). Total SL also increased with age resulting in longer stride times. Heavier birds, such as Cobb, had longer stride Times and SL compared with lighter birds such as the H57 strain. In conclusion, visual gait score and kinematic metrics were not found to be measuring the same things. However, kinematics can be a used as an informative and objective tool for assessing gait metrics associated with broiler lameness such as changes in stride length and stride time.

2D Path Following Control of Motor Graders

Optimal ground conditions in mining are crucial for operational efficiency and safety. Motor graders play a crucial role in achieving precise grading of passages; however, unlike many other mining vehicles, they have not yet been commercially automated. The redundant kinematics of motor graders, including articulation, front axle steering, and blade operations, pose significant challenges for automation. This research explores path following with a 2D kinematic model of motor graders and uses simulation to evaluate and compare the performance of these controllers in terms of step response and operational effectiveness. To address kinematic redundancy, two methods are proposed: Rear Offset Control, which defines the articulation angle using a lateral offset between the front and rear axles, and Single Track Control, which utilizes steering redundancy to adapt existing automation approaches to articulated vehicles. Simulation tests were conducted using two controllers: a Feedback Linearized PD controller (FBL+PD) and a Feedback Linearized Model Predictive Controller (FBL+MPC). Both were tuned for optimal performance on a step input path, with performance assessed based on Root Mean Square Error (RMSE) and control effort. This work introduces two methodologies—Rear Offset Control and Single Track Control—for autonomous motor grader operation. These were implemented with FBL+PD and FBL+MPC controllers on a 2D kinematic model. Future research will focus on dynamic modeling, implementing a Non-Linear Model-Predictive Controller, refining tuning methodologies for Feedback Linearized systems, and integrating these approaches with live vehicles.

3D characterization of kinematic fields and poroelastic swelling near the tip of a propagating crack in a hydrogel

AbstractIn fracture mechanics, polyacrylamide hydrogel has been widely used as a model material in experiments due to its optical transparency, the brittle nature of its failure, and low Rayleigh wave velocity. Indeed, linear elastic fracture mechanics has been used successfully to model the fracture of polyacrylamide hydrogels. However, in soft materials such as hydrogels, the crack opening can be extremely large, leading to substantial geometric and material nonlinearity at the crack tip. Furthermore, poroelasticity may also modify the local mechanical state within the polymer network due to solvent migration. Direct characterization of the kinematic fields and the poroelastic response at the crack tip is lacking. Here we use a hybrid digital image correlation—particle tracking technique to retrieve high-resolution 3D particle trajectories near the tip of a slowly propagating crack, and measure the near-tip 3D kinematic fields in-situ. With this method, we charactherize the displacement fields, rotation fields, stretch fields, strain fields, and swelling fields. These measurements confirm the complex multi-axial stretching near the crack tip and the substantial geometric nonlinearity, particularly in the wake of the crack, where material rotation exceeds $$30^{\circ }$$ 30 ∘ . Comparison between the measured fields and the corresponding prediction from linear elastic fracture mechanics highlights an increasing disagreement in the direct vicinity of the crack tip, particularly for displacement component $$u_x$$ u x and the through-thickness strain component $$\varepsilon _{zz}$$ ε zz . Significant swelling occurs due to solvent migration, with a strong correlation to the local stretch.

On the role of wake-capture and resonance in spanwise-flexible flapping wings in tandem

Numerical simulations of the flow around spanwise-flexible flapping wings in tandem are reported, focusing on a thrust-generating configuration. Wings of aspect ratio 2 and 4 in forward flight undergo heaving and pitching motion following optimal 2D kinematics. The Reynolds number of the simulations is Re=1000. The effect of flexibility is explored by varying the effective stiffness of the wings, while the effective inertia is kept constant. The aerodynamic performance of the tandem system results from a combination of unsteady aerodynamics mechanisms, fluid–structure resonance, vortex–wing interactions (denoted wake capture in this study) and aerodynamic tailoring. It is found that the aerodynamic performance and structural behavior of forewings are dominated by a fluid–structural resonance. The maximum mean thrust for the forewings is obtained when the driving frequency approaches the first natural frequency of the structure, ωn,f/ω≈1, similarly to what is observed in isolated wings undergoing the same kinematics. On the other hand, hindwings show optimal performance in a broad region near ωn,f/ω≈2, and their aerodynamic performance seems to be dominated by wake–capture and aerodynamic–tailoring effects. The aerodynamic performance of the hindwings is dependent on the flexibility of the forewing, which impacts the intensity of the vortices shed into the wake and the resulting effective angle of attack (i.e., wake capture). The timing between the effective angle of attack and the pitching motion of the hindwing controls the generation of thrust (or drag) of each spanwise section of the hindwing (i.e., aerodynamic tayloring). A proof of concept study on the aerodynamic performance of systems made of wings with different flexibility suggests that they could outperform tandem systems with equally flexible wings. Thus, the optimal mixed–flexibility tandem system is composed by a resonant forewing, which maximizes the thrust generation of the forewing and the intensity of the vortices shed into the wake, and a hindwing whose flexibility must be tuned to maximize wake capture effects.

Novel comprehensive analysis of skilled reaching and grasping behavior in adult rats

BackgroundReaching and grasping (R&G) in rats is commonly used as an outcome measure to investigate the effectiveness of rehabilitation or treatment strategies to recover forelimb function post spinal cord injury. Kinematic analysis has been limited to the wrist and digit movements. Kinematic profiles of the more proximal body segments that play an equally crucial role in successfully executing the task remain unexplored. Additionally, understanding of different forelimb muscle activity, their interactions, and their correlation with the kinematics of R&G movement is scarce. New methodIn this work, novel methodologies to comprehensively assess and quantify the 3D kinematics of the proximal and distal forelimb joints along with associated muscle activity during R&G movements in adult rats are developed and discussed. ResultsOur data show that different phases of R&G identified using the novel kinematic and EMG-based approach correlate with the well-established descriptors of R&G stages derived from the Whishaw scoring system. Additionally, the developed methodology allows describing the temporal activity of individual muscles and associated mechanical and physiological properties during different phases of the motor task. Comparison with existing method(s)R&G phases and their sub-components are identified and quantified using the developed kinematic and EMG-based approach. Importantly, the identified R&G phases closely match the well-established qualitative descriptors of the R&G task proposed by Whishaw and colleagues. ConclusionsThe present work provides an in-depth objective analysis of kinematics and EMG activity of R&G behavior, paving the way to a standardized approach to assessing this critical rodent motor function in future studies.

Talar and Calcaneal Coordinate Axes Definitions across Foot Pathologies

The understanding of foot and ankle biomechanics is improving as new technology provides more detailed information about the motion of foot and ankle bones with biplane fluoroscopy, as well as the ability to analyze the hindfoot under weightbearing conditions with weightbearing computed tomography. Three-dimensional anatomical coordinate systems are necessary to describe the 3D alignment and kinematics of the foot and ankle. The lack of standard coordinate systems across research study sites can significantly alter experimental data analyses used for pre-surgical evaluation and post-operative outcome assessments. Clinical treatment paradigms are changing based on the expanding knowledge of complex pes planovalgus morphologies or progressive collapsing foot deformity, which is present in both neurologic and non-neurologic populations. Four patient cohorts were created from 10 flexible PCFD, 10 rigid PCFD, 10 adult cerebral palsy, and 10 asymptomatic control patients. Six coordinate systems were tested on both the talus and calcaneus for all groups. The aim of this study was to evaluate axes definitions for the subtalar joint across four different patient populations to determine the influence of morphology on the implementation of previously defined coordinate systems. Different morphologic presentations from various pathologies have a substantial impact on coordinate system definitions, given that numerous axes definitions are defined through geometric fits or manual landmark selection. Automated coordinate systems that align with clinically relevant anatomic planes are preferred. Principal component axes are automatic, but do not align with clinically relevant planes and should not be used for such analysis where anatomic planes are critical.