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Spatiotemporal gait parameters are commonly used to quantify physical functioning including in populations with atypical foot strike patterns. The current gold standard measurement system for gait analysis is marker-based motion capture and floor-mounted force plates, but it can be expensive and cumbersome to set up. Pressure sensitive walkways are more affordable, quicker to set up, and more portable. Currently available walkways have not been compared to marker-based motion capture when measuring atypical foot strike patterns. The recently developed Tekscan® Strideway pressure sensitive walkway system has not been compared to any gold standard. This study compared measurements of step width, step length, and step time from the Strideway™ system against a gold standard marker-based motion capture (Vicon® Vantage™) and floor-mounted force plate (AMTI®) system. Ten typically ambulating adults, free of injury, emulated five different foot strike patterns recording two-hundred footsteps for each. Results indicate that the Strideway™ compares well to the gold standard especially under typical foot strike patterns. The errors were highest for step width and near-zero for step time. However, the user needs to be aware that errors can substantially increase with certain foot strike patterns such as when the heel does not make contact with the walkway. The results of this study will help inform users about potential limitations when using a pressure sensitive walkway like the Strideway™ for testing populations with typical and atypical strike patterns. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate clinical utility of 2D-markerless motion analysis (2DMMA) from a single camera during a reaching-sideways-task in individuals with dyskinetic cerebral palsy (DCP) by determining (1) concurrent validity by correlating 2DMMA against marker-based 3D-motion analysis (3DMA) and (2) construct validity by assessing differences in 2DMMA features between DCP and typically developing (TD) peers. 2DMMA key points were tracked from frontal videos of a single camera by DeepLabCut and accuracy was assessed against human labelling. Shoulder, elbow and wrist angles were calculated from 2DMMA and 3DMA (as gold standard) and correlated to assess concurrent validity. Additionally, execution time and variability features such as mean point-wise standard deviation of the angular trajectories (i.e. shoulder elevation, elbow and wrist flexion/extension) and wrist trajectory deviation by mean overshoot and convex hull were calculated from key points. 2DMMA features were compared between the DCP group and TD peers to assess construct validity. Fifty-one individuals (30 DCP;21 TD; age:5–24 years) participated. An accuracy of approximately 1.5 cm was reached for key point tracking. While significant correlations were found for wrist (ρ = 0.810;p < 0.001) and elbow angles (ρ = 0.483;p < 0.001), 2DMMA shoulder angles were not correlated (ρ = 0.247;p = 0.102) to 3DMA. Wrist and elbow angles, execution time and variability features all differed between groups (Effect sizes 0.35–0.81;p < 0.05). Videos of a reaching-sideways-task processed by 2DMMA to assess upper extremity movements in DCP showed promising validity. The method is especially valuable to assess movement variability. [ABSTRACT FROM AUTHOR]

There is widespread and growing use of inertial measurement technology for human motion analysis in biomechanics and clinical research. Due to advancements in sensor miniaturization, inertial measurement units can be used to obtain a description of human body and joint kinematics both inside and outside the laboratory. While algorithms for data processing continue to improve, a lack of standard reporting guidelines compromises the interpretation and reproducibility of results, which hinders advances in research and development of measurement and intervention tools. To address this need, the International Society of Biomechanics approved our proposal to develop recommendations on the use of inertial measurement units for joint kinematics analysis. A collaborative effort that incorporated feedback from the biomechanics community has produced recommendations in five categories: sensor characteristics and calibration, experimental protocol, definition of a kinematic model and subject-specific calibration, analysis of joint kinematics, and quality assessment. We have avoided an overly prescriptive set of recommendations for algorithms and protocols, and instead offer reporting guidelines to facilitate reproducibility and comparability across studies. In addition to a conceptual framework and reporting guidelines, we provide a checklist to guide the design and review of research using inertial measurement units for joint kinematics. [ABSTRACT FROM AUTHOR]

Complex musculoskeletal complications in children with hypermobility spectrum disorder (HSD) include pain, proprioception deficits, and joint instability, which may result in movement dysfunction during walking. However, no studies have explored the inter-joint coordination deficits in children with HSD. The purpose of this study was to determine the lower extremity inter-joint coupling angles, patterns, and variability during walking in children with HSD compared to children without HSD (non-HSD). Ankle, knee, and hip kinematics during the stance phase of walking in 18 children with HSD and 18 children without HSD were measured using three-dimensional motion analysis. Coupling angles, patterns, and variability of hip-knee, hip-ankle, and knee-ankle were quantified in the sagittal, frontal, and transverse planes using vector coding techniques. Statistical modeling of coupling angles on sine and cosine scales and bootstrapped standard errors were used to compare coupling angles between HSD and non-HSD groups. Permutational multivariate analysis of variance and statistical non-parametric mapping two-sample t-tests were used to compare the coupling patterns and variability between HSD and non-HSD groups, respectively. Our results indicated that coupling angles, patterns, and variability were not significantly different between the groups. These findings suggest that lower extremity inter-joint coordination and its variability during walking might not be a promising area for further research or intervention in children with HSD. Further research could use other biomechanical methods to investigate coordination deficits in pediatric patients with HSD, and how aging and disease progression are associated with coordination deficits in individuals with HSD. [ABSTRACT FROM AUTHOR]

Accurate anatomical coordinate systems for the foot and ankle are critical for interpreting their complex biomechanics. The tibial superior-inferior axis is crucial for analyzing joint kinematics, influencing bone motion analysis during gait using CT imaging and biplane fluoroscopy. However, the lack of consensus on how to define the tibial axis has led to variability in research, hindering generalizability. Even as advanced imaging techniques evolve, including biplane fluoroscopy and weightbearing CT, there exist limitations to imaging the entire foot together with the full length of the tibia. These limitations highlight the need to refine axis definitions. This study investigated various superior-inferior axes using multiple distal tibia lengths to determine the minimal field of view for representing the full tibia long-axis. Twenty human cadaver tibias were imaged and segmented to generate 3D bone models. Axes were calculated based on coordinate definitions that required user manual input, and a gold standard mean superior-inferior axis was calculated based on the population's principal component analysis axis. Four manually calculated superior-inferior tibial axes groups were established based on landmarks and geometric fittings. Statistical analysis revealed that geometrically fitting a cylinder 1.5 times the mediolateral tibial width, starting 5 cm above the tibial plafond, yielded the smallest angular deviation from the gold standard. From these findings, we recommend a minimum field of view that includes 1.5 times the mediolateral tibial width, starting 5 cm above the tibial plafond for tibial long-axis definitions. Implementing these findings will help improve foot and ankle research generalizability and impact clinical decisions. [ABSTRACT FROM AUTHOR]

To investigate the effects of intentionally minimizing spinal motion and abdominal muscle contractions on intervertebral angles during quadruped upper and lower extremity lift (QULEL). Fifteen healthy men performed the QULEL under four conditions: without any special instructions (basic), with the intention to minimize spinal motion (intentional), with abdominal bracing (bracing), and with abdominal hollowing (hollowing). Each intervertebral angle was calculated from the local coordinate system using the marker data obtained from a motion capture system. Shear moduli, as indicators of the activities of the right transversus abdominis (TrA), internal and external oblique, and rectus abdominis muscles, were assessed using shear wave elastography during QULEL. One-way repeated-measures analysis of variance and multiple comparisons among conditions were used to compare each shear modulus of the abdominal muscle and the changes in thoracic kyphosis (Th1-12), lumbar lordosis (L1-5), and lumbar intervertebral angles from the quadruped position to QULEL. The significance level was set at P < 0.05. Changes in lumbar lordosis and L2/L3 and L3/L4 extension angles were significantly lower under hollowing than under other conditions (effect size η G 2 : lumbar lordosis, 0.068; L2/L3, 0.072; L3/L4, 0.043). The change in the L1/L2 extension angle significantly decreased in bracing and hollowing compared with the basic (η G 2 = 0.070). Only the TrA shear modulus significantly increased in bracing and hollowing compared with the basic (η G 2 = 0.146). Abdominal hollowing during the QULEL increased TrA activity and suppressed lumbar extension, except at L4/L5, and may be more effective as a rehabilitation exercise for controlling spinal motion. [ABSTRACT FROM AUTHOR]

Increasing the velocity of the lower-limb movement is crucial for improving underwater undulatory swimming (UUS) velocity. However, the underlying mechanism of how these movements influence swimming velocity have remained unclear. This study aimed to clarify the relationship between changes in swimming movement and the resulting changes in flow field as a result of changes in test flow velocity (U) in a water flume. A male student swimmer was tested with the following three U settings 0.8, 1.0 and 1.2 m/s. The lower-limb movements and wake flow behind the swimmer were compared. A motion capture system was employed for motion analysis, and a stereo PIV for visualizing the flow field. The findings revealed that, as U increased, the velocity vectors of the flow field in all directions (u, v, w) increased, as did the toe velocity. It was also suggested that with increasing U , the outward change in the toe velocity vector down-kick and the inward change in the toe velocity vector up-kick may have a positive effect on the vortices, contributing to an increase in the velocity vectors in the flow field. Furthermore, the high U , vortex re-capturing occurred during the transition from down-kick to up-kick, indicating that this might contribute to increased momentum. This suggests that the transition from the down-kick to the up-kick is necessary for gaining greater momentum. Notably, this study is the first to identify the factors that increase the swimming velocity of the UUS in the context of movement and flow field. [ABSTRACT FROM AUTHOR]

Predictions of vertebra positions from external data are required in many fields like motion analysis or for clinical applications. Existing predictions mainly cover the thoraco-lumbar spine, in one posture. The objective of this study was to develop a method offering robust vertebra position predictions in different postures for the whole spine, in the sagittal plane. EOS radiographs were taken in three postures: slouched, erect, and subject's usual sitting posture, using 21 healthy participants pre-equipped with opaque cutaneous markers. Local curvilinear Frenet frames were built on a spline fitted to spinous processes' cutaneous markers. Vertebra positions were expressed as polar coordinates in these frames, defining an angle (α) and distance (d). Multilinear regressions were fitted to explain α and d from anthropometric predictors and predictors presumed to be linked to spinal posture, the predictors' effects being considered both locally and remotely. Anthropometric predictors were the main predictors for d distances, and postural predictors for α angles, with postural predictors still showing a marked influence on d distances for the cervical spine. Vertebra positions were then predicted by cross-validation. The average RMSE on vertebra positions was 11.0 ± 3.7 mm across the entire spine, 13.4 ± 4.1 mm across the cervical spine and 10.1 ± 3.1 mm across the thoraco-lumbar spine for all participants and postures, performances similar to previous models designed for a single posture. Our simple geometrical and statistical model thus appears promising for predicting vertebra positions from external data in several spinal postures and for the whole spine. [ABSTRACT FROM AUTHOR]

Multiplanar kinematic and kinetic sequencing from different approach angles can highlight how soccer players perform fast and accurate kicks. This study therefore aimed to a) determine multiplanar torso, pelvis and kick leg sequencing during instep kicks and b) highlight the effect of different approach angles on these sequencing patterns. Twenty male soccer players (mass 77.9 ± 6.5 kg, height 1.71 ± 0.09 m, age 23.2 ± 3.7 years) performed kicks from self-selected (∼30−45°), straight (0°) and wide (67.5°) approaches and multiplanar lumbo-pelvic, hip and knee angular velocities, moments and powers were derived from 3D motion analysis. The results suggest tension arc release between the upper and lower body functions as a two-stage mechanism. The first phase of arc release was characterised by increases in concentric hip flexion and transverse lumbo-pelvic velocities towards the ball. The second phase was characterised by increasing concentric lumbo-pelvic flexion and knee extension work to angularly accelerate the kicking knee towards foot-to-ball contact. Further, alterations in kinematic and kinetic sequencing helped maintain performance (ball and foot velocities at ball contact) and accuracy at approach angles other than self-selected. These findings can help coaches and practitioners design effective training practices. [ABSTRACT FROM AUTHOR]

Machine-learning based human posture-prediction tools can potentially be robust alternatives to motion capture measurements. Existing posture-prediction approaches are confined to two-handed load-handling activities performed at heights below 120 cm from the floor and to predicting a limited number of body-joint coordinates/angles. Moreover, the extrapolating power of these tools beyond the range of the input dataset they were trained for (e.g., for underweight, overweight, or left-handed individuals) has not been investigated. In this study, we trained/validated/tested two posture-prediction (for full-body joint coordinates and angles) artificial neural networks (ANNs) using both 70%/15%/15% random-hold-out and leave-one-subject-out methods, based on a comprehensive kinematic dataset of forty-one full-body skin markers collected from twenty right-handed normal-weight (BMI = 18–26 kg/m2) subjects. Subjects performed 204 one- and two-handed unloaded activities at different vertical (0 to 180 cm from the floor) and horizontal (up to 60 cm lateral and/or anterior) destinations. Subsequently, the extrapolation capability of the trained/validated/tested ANNs was evaluated using data collected from fifteen additional subjects (unseen by the ANNs); three individuals in five groups: underweight, overweight, obese, left-handed individuals, and subjects with a hand-load. Results indicated that the ANNs predicted body joint coordinates and angles during various activities with errors of ∼ 25 mm and ∼ 10°, respectively; considerable improvements when compared to previous posture-prediction ANNs. Extrapolation errors of our ANNs generally remained within the error range of existing ANNs with obesity and being left-handed having, respectively, the most and least compromising effects on their accuracy. These easy-to-use ANNs appear, therefore, to be robust alternatives to common posture-measurement approaches. [ABSTRACT FROM AUTHOR]

The hip and lumbosacral joint centre (HJC and LSJC) predictions are required to analyse the lumbo-pelvic-hip dynamics during various human motions. Some HJC and LSJC regression equations based on pelvic dimension have been developed; however, the pre-existing methods need to be re-evaluated, and methodological reconsideration may improve the regression methods. Here we show that pre-existing methods produce biased predictions of the LSJC and HJC in 23 male and 24 female Japanese adults, and that the biases in the LSJC differ between sexes, using magnetic resonance imaging (MRI) around the pelvis. Compared with directly measured locations on MRI, the pre-existing regression equations predict LSJC to be more posterior in males and more inferior and posterior in females, and HJC to be more medial in both sexes. The better pre-existing regression equation for LSJC height differs between sexes, with pelvic-width-base better in males and pelvic-depth-base better in females, respectively. We suggest the unsuitability of pre-existing methods to our dataset consisting of Japanese adults and the importance of considering sex differences in regression methods. We propose regression equations to predict HJC and LSJC, considering soft-tissue thickness, sex differences, and a height-directional measure, using least absolute shrinkage and selection operator regression. We validate them using leave-one-out cross-validation (LOOCV). LOOCV shows that our model produces negligible biases and smaller absolute errors than the pre-existing regressions; in particular, the anteroposterior absolute error for LSJC is less than half that of the pre-existing regression. Our regression equation can be a powerful solution for accurate motion analysis. [ABSTRACT FROM AUTHOR]

Musculoskeletal models are commonly used to estimate in vivo spinal loads under various loading conditions. Typically, participant-specific measured kinematics (PSMK) are coupled with participant-specific models, but obtaining PSMK data can be costly and infeasible in large studies or clinical practice. Thus, we evaluated two alternative methods to estimate spinal loads without PSMK: 1) ensemble average kinematics (EAK) based on kinematics from all participants; and 2) using separately measured individual kinematics (SMIK) from multiple other participants as inputs, then averaging the resulting loads. This study compares the dynamic spine loading patterns and peak loads in older adults performing five lifting tasks using PSMK, EAK and SMIK. Median root mean square errors of EAK and SMIK methods versus PSMK ranged from 18 to 72% body weight for compressive loads and from 2 to 25% body weight for shear loads, with median cross-correlations ranging from 0.931 to 0.991. The root mean square errors and cross-correlations between repeated PSMK trials fell within similar ranges. Compressive peak loads evaluated by EAK and SMIK were not different than PSMK in 12 of 15 cases, while by comparison repeated PSMK trials were not different in 13 of 15 cases. Overall, the resulting spine loading magnitudes and profiles using EAK or SMIK were not notably different than using a PSMK approach, and differences were not greater than between two PSMK trials. Thus, these findings indicate that these approaches may be used to make reasonable estimates of dynamic spinal loading without direct measurement of participant kinematics. [ABSTRACT FROM AUTHOR]

Human undulatory underwater swimming (UUS) is an underwater propelling technique in competitive swimming and its propulsive mechanism is poorly understood. The purpose of this study was to visualize the three-dimensional (3D) flow field in the wake region during human UUS in a water flume. A national level male swimmer performed 41 UUS trials in a water flume. A motion capture system and stereo particle image velocimetry (PIV) equipment were used to investigate the 3D coordinates of the swimmer and 3D flow fields in the wake region. After one kick cycle was divided into eight phases, we conducted coordinate transformations and phase averaging method to construct quasi 3D flow fields. At the end of the downward kick, the lower limbs external rotations of the lower limbs were observed, and the feet approached towards each other. A strong downstream flow, i.e. a jet was observed in the wake region during the downward kick, and the paired vortex structure was accompanied by a jet. In the vortex structure, a cluster of vortices and a jet were generated in the wake during the downward kick, and the vortices were subsequently shed from the feet by the rotated leg motion. This suggested that the swimmer gained a thrust by creating vortices around the foot during the downward kick, which collided to form a jet. This paper describes, illustrates, and explains the propulsive mechanism of human UUS. [ABSTRACT FROM AUTHOR]

Adequate glenoid baseplate fixation in reverse total shoulder arthroplasty (rTSA) is important to achieve, but may prove challenging in the context of glenoid bone loss or osteopenia. Current rTSA testing standards rely upon synthetic bone surrogates, but it is unclear if these models accurately recapitulate the mechanics of osteoporotic bone. Additionally, it also unknown if the use of a central screw effectively provides resistance to micromotion in the milieu of poor quality bone. The purpose of this experiment was to create a novel cyclic load test protocol that elicited clinically relevant failures, so that comparisons of relative motion between baseplates and bones could be made with: (1) synthetic bones and poor quality cadaveric bones, and (2) the use or omission of a central screw. rTSA components were implanted into cadaveric and synthetic bones with and without a central screw. To model a range of loads that may be experienced during abduction, increasing cyclic loads were applied to shoulder joints in 30° of humeral abduction. Cycles and loads prior to permanent deformation exceeding 150 µm, 1 mm, and joint failure were determined using measurements from the test frame and from 3-D motion analysis. Synthetic bones demonstrated significantly more resistance to micromotion in comparison to cadaveric bones. Use of the central screw improved resistance to dislodgement, which was only observed in the cadaveric specimens. This study highlights the need for biomechanical testing with cadaveric specimens, especially when assessing osteopenic or osteoporotic populations. [ABSTRACT FROM AUTHOR]

Camera-based motion capture systems are the current gold standard for motion analysis. However, the use of wireless inertial sensor-based systems is increasing in popularity, largely due to convenient portability. The purpose of this study was to validate the use of wireless inertial sensors for measuring hip joint motion with a functional calibration requiring only one motion (walking) and neutral standing. Data were concurrently collected using a 10-camera motion capture system and a wireless inertial sensor-based system. Hip joint angles were measured for 10 participants during walking, jumping jack, and bilateral squat tasks and for a subset (n = 5) a jump turn task. Camera-based system hip joint angles were calculated from retro-reflective marker positions and sensor-based system angles were calculated in MATLAB using the sensor output quaternions. Most hip joint angles measured with the sensor-based system were within 6° of angles measured with the camera motion capture system. Accurate measurement of motion outside of a laboratory setting has broad implications for diagnosing movement abnormalities, monitoring sports performance, and assessing rehabilitation progress. [ABSTRACT FROM AUTHOR]

The plantarflexor moment arm of the Achilles tendon determines the mechanical advantage of the triceps surae and also indirectly affects muscle force generation by setting the amount of muscle-tendon shortening per unit of ankle joint rotation. The Achilles tendon moment arm may be determined geometrically from an axis (or center) of joint rotation and the line of action of the tendon force, but such moment arms may be sensitive to the location of the joint axis. Using motion analysis to track an ultrasound probe overlying the Achilles tendon along with markers on the shank and foot, we measured Achilles tendon moment arm during loaded and unloaded dynamic plantarflexion motions in 15 healthy subjects. Three representations of the axis or center of rotation of the ankle were considered: (1) a functional axis, defined by motions of the foot and shank; (2) a transmalleolar axis; and (3) a transmalleolar midpoint. Moment arms about the functional axis were larger than those found using the transmalleolar axis and transmalleolar midpoint (all p < 0.001). Moment arms computed with the functional axis increased with plantarflexion angle (all p < 0.001), and increased with loading in the most plantarflexed position (p < 0.001) but these patterns were not observed when either using a transmalleolar axis or transmalleolar midpoint. Functional axis moment arms were similar to those estimated previously using magnetic resonance imaging, suggesting that using a functional axis for ultrasound-based geometric estimates of Achilles tendon moment arm is an improvement over landmark-based methods. [ABSTRACT FROM AUTHOR]

Measuring three-dimensional (3D) forearm rotational motion is difficult. We aimed to develop and validate a new method for analyzing 3D forearm rotational motion. We proposed biplane fluoroscopic intensity-based 2D–3D matching, which employs automatic registration processing using the evolutionary optimization strategy. Biplane fluoroscopy was conducted for forearm rotation at 12.5 frames per second along with computed tomography (CT) at one static position. An arm phantom was embedded with eight stainless steel spheres (diameter, 1.5 mm), and forearm rotational motion measurements using the proposed method were compared with those using radiostereometric analysis, which is considered the ground truth. As for the time resolution analysis, we measured radiohumeral joint motion in a patient with posterolateral rotatory instability and compared the 2D–3D matching method with the simulated multiple CT method, which uses CTs at multiple positions and interpolates between the positions. Rotation errors of the radius and ulna between these two methods were 0.31 ± 0.35° and 0.32 ± 0.33°, respectively, translation errors were 0.43 ± 0.35 mm and 0.29 ± 0.25 mm, respectively. Although the 2D–3D method could detect joint dislocation, the multiple CT method could not detect quick motion during joint dislocation. The proposed method enabled high temporal- and spatial-resolution motion analyses with low radiation exposure. Moreover, it enabled the detection of a sudden motion, such as joint dislocation, and may contribute to 3D motion analysis, including joint dislocation, which currently cannot be analyzed using conventional methods. [ABSTRACT FROM AUTHOR]

Abstract RGB-D cameras provide 3-D body joint data in a low-cost, portable and non-intrusive way, when compared with reference motion capture systems used in laboratory settings. In this contribution, we evaluate the validity of both Microsoft Kinect versions (v1 and v2) for motion analysis against a Qualisys system in a simultaneous protocol. Two different walking directions in relation to the Kinect (towards – WT, and away – WA) were explored. For each gait trial, measures related with all body parts were computed: velocity of all joints, distance between symmetrical joints, and angle at some joints. For each measure, we compared each Kinect version and Qualisys by obtaining the mean true error and mean absolute error, Pearson's correlation coefficient, and optical-to-depth ratio. Although both Kinect v1 and v2 and/or WT and WA data present similar accuracy for some measures, better results were achieved, overall, when using WT data provided by the Kinect v2, especially for velocity measures. Moreover, the velocity and distance presented better results than angle measures. Our results show that both Kinect versions can be an alternative to more expensive systems such as Qualisys, for obtaining distance and velocity measures as well as some angles metrics (namely the knee angles). This conclusion is important towards the off-lab non-intrusive assessment of motor function in different areas, including sports and healthcare. [ABSTRACT FROM AUTHOR]

Abstract Kinematic analysis is often performed with a camera system combined with reflective markers placed over bony landmarks. This method is restrictive (and often expensive), and limits the ability to perform analyses outside of the lab. In the present study, we used a markerless deep learning-based method to perform 2D kinematic analysis of deep water running, a task that poses several challenges to image processing methods. A single GoPro camera recorded sagittal plane lower limb motion. A deep neural network was trained using data from 17 individuals, and then used to predict the locations of markers that approximated joint centres. We found that 300–400 labelled images were sufficient to train the network to be able to position joint markers with an accuracy similar to that of a human labeler (mean difference < 3 pixels, around 1 cm). This level of accuracy is sufficient for many 2D applications, such as sports biomechanics, coaching/training, and rehabilitation. The method was sensitive enough to differentiate between closely-spaced running cadences (45–85 strides per minute in increments of 5). We also found high test–retest reliability of mean stride data, with between-session correlation coefficients of 0.90–0.97. Our approach represents a low-cost, adaptable solution for kinematic analysis, and could easily be modified for use in other movements and settings. Using additional cameras, this approach could also be used to perform 3D analyses. The method presented here may have broad applications in different fields, for example by enabling markerless motion analysis to be performed during rehabilitation, training or even competition environments. [ABSTRACT FROM AUTHOR]

Abstract To examine functional differences in total hip replacement patients (THR) when stratified either by age or by functional ability as defined by self-selected walking speed. THR patients and a control group underwent three-dimensional motion analysis under self-selected normal and fast walking conditions. Patients were stratified into five age groups for comparison with existing literature. The THR cohort was also stratified into three functional groups determined by their self-selected gait speed (low function <1SD of total cohort's mean walking speed; high function >1SD; normal function within 1SD). Hip kinematics, ground reaction forces, joint moments and joint powers in all three planes (x-y-z) were analysed. 137 THR and 27 healthy control patients participated. When stratified by age, during normal walking the youngest two age groups walked quicker than the oldest two groups (p < 0.0001) but between-group differences were not consistent across age strata. The differences were diminished under the fast walking condition. When stratified by function, under normal walking conditions, the low function and normal function THR groups had a reduced extension angle (mean = 1.75°, SD = ±7.75, 1.26° ± 7.42, respectively) compared to the control group (−6.07° ± 6.43; p < 0.0001). The low function group had a reduced sagittal plane hip power (0.75 W/kg ± 0.24), reduced flexor (0.60 Nm/kg ± 0.85) and extensor moment (0.51 Nm/kg ± 0.17) compared to controls (p < 0.0001). These differences persisted under the fast walking condition. There were systematic differences between patients when stratified by function, in both walking conditions. Age-related differences were less systematic. Stratifying by biomechanical factors such as gait speed, rather than age, might be more robust for investigating functional differences. [ABSTRACT FROM AUTHOR]

Abstract This study proposed a method to quantify direct and indirect effects of the joint torque inputs in the speed-generating mechanism of a swinging motion. Linear and angular accelerations of all segments within a multi-linked system can be expressed as the sum of contributions from a joint torque term, gravitational force term and motion-dependent term (MDT), where the MDT is a nonlinear term consisting of centrifugal force, Coriolis force and gyroscopic effect moment components. Direct effects result from angular accelerations induced by a joint torque at a given instant, whereas indirect effects arise through the MDT induced by joint torques exerted in the past. These two effects were quantified for the kicking-side leg during a rugby place kick. The MDT was the largest contributor to the foot centre of gravity (CG)'s speed at ball contact. Of the factors responsible for generating the MDT, the direct and indirect effects of the hip flexion-extension torque during both the flight phase (from the final kicking foot take-off to support foot contact) and the subsequent support phase (from support foot contact to ball contact) were important contributors to the foot CG's speed at ball contact. The indirect effect of the ankle plantar-dorsal flexion torque and the direct effect of the knee flexion-extension torque during the support phase showed the largest positive and negative contributions to the foot CG's speed at ball contact, respectively. The proposed method allows the identification of which individual joint torque axes are crucial and the timings of joint torque exertion that are used to generate a high speed of the distal point of a multi-linked system. [ABSTRACT FROM AUTHOR]

Abstract Magnetic and Inertial measurement units (MIMUs) have become exceedingly popular for ambulatory human motion analysis during the past two decades. However, measuring anatomically meaningful segment and joint kinematics requires virtual alignment of the MIMU frame with the anatomical frame of its corresponding segment. Therefore, this paper presents a simple calibration procedure, based on MIMU readouts, to align the inertial frame of the MIMU with the anatomical frames, as recommended by ISB. The proposed calibration includes five seconds of quiet standing in a neutral posture followed by ten consecutive hip flexions/extensions. This procedure will independently calibrate MIMUs attached to the pelvis, thigh, shank, and foot. The accuracy and repeatability of the calibration procedure and the 3D joint angle estimation were validated against the gold standard motion capture system by an experimental study with ten able-bodied participants. The procedure showed high test-retest repeatability in aligning the MIMU frame with its corresponding anatomical frame, i.e., the helical angle between the MIMU and anatomical frames did not significantly differ between the test and retest sessions (except for thigh MIMU). Compared to previously introduced procedures, this procedure attained the highest inter-participant repeatability (inter-participant coefficient of variations of the helical angle: 20.5–42.2%). Further, the proposed calibration would reduce the offset errors of the 3D joint angle estimation (up to 12.8 degrees on average) compared to joint angle estimation without calibration (up to 26.3 degrees on average). The proposed calibration enables MIMU to measure clinically meaningful gait kinematics. [ABSTRACT FROM AUTHOR]

Abstract Inhibited movement patterns of carpal tunnel structures have been found in carpal tunnel syndrome (CTS) patients. Motion analysis on ultrasound images allows us to non-invasively study the (relative) movement of carpal tunnel structures and recently a speckle tracking method using singular value decomposition (SVD) has been proposed to optimize this tracking. This study aims to assess the reliability of longitudinal speckle tracking with SVD in both healthy volunteers and patients with CTS. Images from sixteen healthy volunteers and twenty-two CTS patients were used. Ultrasound clips of the third superficial flexor tendon and surrounding subsynovial connective tissue (SSCT) were acquired during finger flexion-extension. A custom made tracking algorithm was used for the analysis. Intra-class correlation coefficients (ICCs) were calculated using a single measure, two-way random model with absolute agreement and Bland-Altman plots were added for graphical representation. ICC values varied between 0.73 and 0.95 in the control group and 0.66–0.98 in the CTS patients, with the majority of the results classified as good to excellent. Tendon tracking showed higher reliability values compared to the SSCT, but values between the control and CTS groups were comparable. Speckle tracking with SVD can reliably be used to analyze longitudinal movement of anatomical structures with different sizes and compositions within the context of the carpal tunnel in both a healthy as well as a pathological state. Based on these results, this technique also holds relevant potential for areas where ultrasound based dynamic imaging requires quantification of motion. [ABSTRACT FROM AUTHOR]

Abstract The low cost and ease of use of inertial measurement units (IMUs) make them an attractive option for motion analysis tasks that cannot be easily measured in a laboratory. To date, only a limited amount of research has been conducted comparing commercial IMU systems to optoelectronic systems, the gold standard, for everyday tasks like stair climbing and inclined walking. In this paper, the 3D joint angles of the lower limbs are determined using both an IMU system and an optoelectronic system for twelve participants during stair ascent and descent, and inclined, declined and level walking. Three different datasets based on different hardware and anatomical models were collected for the same movement in an effort to determine the cause and quantify the errors involved with the analysis. Firstly, to calculate software errors, two different anatomical models were compared for one hardware system. Secondly, to calculate hardware errors, results were compared between two different measurement systems using the same anatomical model. Finally, the overall error between both systems with their native anatomical models was calculated. Statistical analysis was performed using statistical parametric mapping. When both systems were evaluated based on the same anatomical model, the number of trials with significant differences decreased markedly. Thus, the differences in joint angle measurement can mainly be attributed to the variability in the anatomical models used for calculations and not to the IMU hardware. [ABSTRACT FROM AUTHOR]

Abstract Due to the increased availability of digital human models, the need for knowing human movement is important in product design process. If the human motion is derived rapidly as design parameters change, a developer could determine the optimal parameters. For example, the optimal design of the door panel of an automobile can be obtained for a human operator to conduct the easiest ingress and egress motion. However, acquiring motion data from existing methods provides only unrealistic motion or requires a great amount of time. This not only leads to an increased time consumption for a product development, but also causes inefficiency of the overall design process. To solve such problems, this research proposes an algorithm to rapidly and accurately predict full-body human motion using an artificial neural network (ANN) and a motion database, as the design parameters are varied. To achieve this goal, this study refers to the processes behind human motor learning procedures. According to the previous research, human generate new motion based on past motion experience when they encounter new environments. Based on this principle, we constructed a motion capture database. To construct the database, motion capture experiments were performed in various environments using an optical motion capture system. To generate full-body human motion using this data, a generalized regression neural network (GRNN) was used. The proposed algorithm not only guarantees rapid and accurate results but also overcomes the ambiguity of the human motion objective function, which has been pointed out as a limitation of optimization-based research. Statistical criteria were utilized to confirm the similarity between the generated motion and actual human motion. Our research provides the basis for a rapid motion prediction algorithm that can include a variety of environmental variables. This research contributes to an increase in the usability of digital human models, and it can be applied to various research fields. [ABSTRACT FROM AUTHOR]

Abstract Despite a vast literature on one-leg hops and cutting maneuvers assessing knee control pre/post-injury of the anterior cruciate ligament (ACL), comprehensive and reliable tests performed under unpredictable conditions are lacking. This study aimed to: (1) assess the feasibility of an innovative, knee-challenging, one-leg double-hop test consisting of a forward hop followed by a diagonal hop (45°) performed medially (UMDH) or laterally (ULDH) in an unanticipated manner; and (2) determine within- and between-session reliability for 3-dimensional hip and knee kinematics and kinetics of these tests. Twenty-two healthy women (22.3 ± 3.3 years) performed three successful UMDH and ULDH, twice 1–4 weeks apart. Hop success rate was 69–84%. Peak hip and knee angles demonstrated moderate to excellent within-session reliability (intraclass correlation coefficient [ICC] 95% confidence interval [CI]: 0.67–0.99, standard error of measurement [SEM] ≤ 3°) and poor to excellent between-session reliability (ICC CI: 0.22–0.94, SEM ≤ 3°) for UMDH and ULDH. The smallest real difference (SRD) was low (≤ 5°) for nearly all peak angles. Peak hip and knee moments demonstrated poor to excellent reliability (ICC CI: 0–0.97) and, in general, moments were more reliable within-session (SEM ≤ 0.14 N.m/kg.m, both directions) than between-session (SRD ≤ 0.43 N.m/kg.m). Our novel test was feasible and, in most but not all cases, provided reliable angle estimates (within-session > between-session, both directions) albeit less reliable moments (within-session > between-session, both directions). The relatively large hip and knee movements in the frontal and transverse planes during the unanticipated hops suggest substantial challenge of dynamic knee control. Thus, the test seems appropriate for evaluating knee function during ACL injury rehabilitation. [ABSTRACT FROM AUTHOR]

Abstract To investigate lower-limb muscle function during sidestep cutting, prior studies have analysed electromyography (EMG) data together with three dimensional motion analysis. Such an approach does not directly quantify the biomechanical role of individual lower-limb muscles during a sidestep cut. This study recorded three dimensional motion analysis, ground reaction force (GRF) and EMG data for eight healthy males executing an unanticipated sidestep cut. Using a musculoskeletal modelling approach, muscle function was determined by computing the muscle contributions to the GRFs and lower-limb joint moments. We found that bodyweight support (vertical GRF) was primarily provided by the vasti, gluteus maximus, soleus and gastrocnemius. These same muscles, along with the hamstrings, were also primarily responsible for modulating braking and propulsion (anteroposterior GRF). The vasti, gluteus maximus and gluteus medius were the key muscles for accelerating the centre-of-mass towards the desired cutting direction by generating a medially-directed GRF. Our findings have implications for designing retraining programs to improve sidestep cutting technique. [ABSTRACT FROM AUTHOR]

Total temporomandibular joint (TMJ) replacement surgery aims to improve mandibular function, reduce pain and enhance quality of life in patients suffering from end-stage TMJ disorders. Traditional post-operative jaw evaluation is carried out using measurement of maximum interincisal opening distance; however, this can correlate poorly to joint function. The present study aimed to evaluate three-dimensional (3D) jaw motion during border movements and chewing in unilateral total TMJ replacement patients and healthy controls. Motion analysis experiments were performed on six unilateral total TMJ replacement patients and ten age-matched healthy controls. Subject-specific motion tracking plates worn by each participant were registered to CT scans of each participant's skull and mandible to enable anatomical mandibular kinematics measurement using an optoelectronic system. Participants performed 15 repetitions of maximal opening, protrusion, lateral excursions, and chewing cycles. Total TMJ replacement patients had significantly smaller incisal displacements at maximum mouth opening relative to the controls (median difference: 7.1 mm, p = 0.002) and decreased anterior translation of the prosthetic condyle (median difference: 10.5 mm, p = 0.002). When TMJ replacement subjects chewed using their contralateral molars, there was a significant increase in inferior condylar translation of the non-working condyle (median difference: 9.7 mm, p = 0.016). This study found that unilateral total TMJ replacement surgery was associated with mouth opening capacity within the range of healthy individuals, but reduced anterior movement of the prosthetic condyle and restricted protrusion and lateral excursions. The results provide future direction for prosthetic TMJ design to enhance postsurgical implant functionality and improve long-term clinical outcomes for prosthesis recipients. [ABSTRACT FROM AUTHOR]

Abstract This study evaluated between-session reliability of opto-electronic motion capture to measure trunk posture and three-dimensional ranges of motion (ROM). Nineteen healthy participants aged 24–74 years underwent spine curvature, pelvic tilt and trunk ROM measurements on two separate occasions. Rigid four-marker clusters were attached to the skin overlying seven spinous processes, plus single markers on pelvis landmarks. Rigid body rotations of spine marker clusters were calculated to determine neutral posture and ROM in flexion, extension, total lateral bending (left-right) and total axial rotation (left-right). Segmental spine ROM values were in line with previous reports using opto-electronic motion capture. Intraclass correlation coefficients (ICC) and standard error of measurement (SEM) were calculated as measures of between-session reliability and measurement error, respectively. Retroreflective markers showed fair to excellent between-session reliability to measure thoracic kyphosis, lumbar lordosis, and pelvic tilt (ICC = 0.82, 0.63, and 0.54, respectively). Thoracic and lumbar segments showed highest reliabilities in total axial rotation (ICC = 0.78) and flexion-extension (ICC = 0.77–0.79) ROM, respectively. Pelvic segment showed highest ICC values in flexion (ICC = 0.78) and total axial rotation (ICC = 0.81) trials. Furthermore, it was estimated that four or fewer repeated trials would provide good reliability for key ROM outcomes, including lumbar flexion, thoracic and lumbar lateral bending, and thoracic axial rotation. This demonstration of reliability is a necessary precursor to quantifying spine kinematics in clinical studies, including assessing changes due to clinical treatment or disease progression. [ABSTRACT FROM AUTHOR]

Defining a subject-specific model of the human body is required for motion analysis in many fields, such as in ergonomics and clinical applications. However, locating internal joint centers from external characteristics of the body still remains a challenging issue, in particular for the spine. Current methods mostly require a set of rarely accessible (3D back or trunk surface) or operator dependent inputs (large number of palpated landmarks and landmarks-based anthropometrics). Therefore, there is a need to provide an alternative way to estimate joint centers only using a limited number of easily palpable landmarks and the external back profile. Two methods were proposed to predict the spinal joint centers: one using only 6 anatomical landmarks (ALs) (2 PSIS, T8, C7, IJ and PX) and one using both 6 ALs and the external back profile. Regressions were established using the X-ray based 3D reconstructions of 80 subjects and evaluated on 13 additional subjects of variable anthropometry. The predicted location of joint centers showed an average error 9.7 mm (±5.0) in the sagittal plane for all joints when using the external back profile. Similar results were obtained without using the external back profile, 9.5 mm (±5.0). Compared to other existing methods, the proposed methods offered a more accurate prediction with a smaller number of palpated points. Additional methods have to be developed for considering postures other than standing, such as a sitting position. [ABSTRACT FROM AUTHOR]

This work proposes a real-time monitoring tool aimed to support clinicians for remote assessing exercise performances during home-based rehabilitation. The study relies on clinician indications to define kinematic features, that describe five motor tasks (i.e., the lateral tilt of the trunk, lifting of the arms, trunk rotation, pelvis rotation, squatting) usually adopted in the rehabilitation program for axial disorders. These features are extracted by the Kinect v2 skeleton tracking system and elaborated to return disaggregated scores, representing a measure of subjects performance. A bell-shaped function is used to rank the patient performances and to provide the scores. The proposed rehabilitation tool has been tested on 28 healthy subjects and on 29 patients suffering from different neurological and orthopedic diseases. The reliability of the study has been performed through a cross-sectional controlled design methodology, comparing algorithm scores with respect to blinded judgment provided by clinicians through filling a specific questionnaire. The use of task-specific features and the comparison between the clinical evaluation and the score provided by the instrumental approach constitute the novelty of the study. The proposed methodology is reliable for measuring subject’s performance and able to discriminate between the pathological and healthy condition. [ABSTRACT FROM AUTHOR]

Sit-to-stand tests are used in geriatrics as a qualitative issue in order to evaluate motor control and stability. In terms of measured indicators, it is traditionally the duration of the task that is reported, however it appears that the use of the kinetic energy as a new quantitative criterion allows getting a better understanding of musculoskeletal deficits of elderly subjects. The aim of this study was to determine the feasibility to obtain the measure of kinetic energy using magneto-inertial measurement units (MIMU) during sit-to-stand movements at various paces. 26 healthy subjects contributed to this investigation. Measured results were compared to a marker-based motion capture using the correlation coefficient and the normalized root mean square error (nRMSE). nRMSE were below 10% and correlation coefficients were over 0.97. In addition, errors on the mean kinetic energy were also investigated using Bland-Altman 95% limits of agreement (0.63 J–0.77 J), RMSE (0.29 J–0.38 J) and correlation coefficient (0.96–0.98). The results obtained highlighted that the method based on MIMU data could be an alternative to optoelectronic data acquisition to assess the kinetic energy of the torso during the sit-to-stand test, suggesting this method as being a promising alternative to determine kinetic energy during the sit-to-stand movement. [ABSTRACT FROM AUTHOR]

Motion analysis is essential for assessing in-vivo human biomechanics. Marker-based motion capture is the standard to analyze human motion, but the inherent inaccuracy and practical challenges limit its utility in large-scale and real-world applications. Markerless motion capture has shown promise to overcome these practical barriers. However, its fidelity in quantifying joint kinematics and kinetics has not been verified across multiple common human movements. In this study, we concurrently captured marker-based and markerless motion data on 10 healthy study participants performing 8 daily living and exercise movements. We calculated the correlation (R xy) and root-mean-square difference (RMSD) between markerless and marker-based estimates of ankle dorsi-plantarflexion, knee flexion, and three-dimensional hip kinematics (angles) and kinetics (moments) during each movement. Estimates from markerless motion capture matched closely with marker-based in ankle and knee joint angles (R xy ≥ 0.877, RMSD ≤ 5.9°) and moments (R xy ≥ 0.934, RMSD ≤ 2.66 % height × weight). High outcome comparability means the practical benefits of markerless motion capture can simplify experiments and facilitate large-scale analyses. Hip angles and moments demonstrated more differences between the two systems (RMSD: 6.7–15.9° and up to 7.15 % height × weight), especially during rapid movements such as running. Markerless motion capture appears to improve the accuracy of hip-related measures, yet more research is needed for validation. We encourage the biomechanics community to continue verifying, validating, and establishing best practices for markerless motion capture, which holds exciting potential to advance collaborative biomechanical research and expand real-world assessments needed for clinical translation. [ABSTRACT FROM AUTHOR]

Motion analysis, as applied to evolutionary biomechanics, has experienced its own evolution over the last 50 years. Here we review how an ever-increasing fossil record, together with continuing advancements in biomechanics techniques, have shaped our understanding of the origin of upright bipedal walking. The original, and long-established hypothesis held by Lamarck (1809), Darwin (1859) and Keith (1934), amongst others, maintained that bipedality originated in an arboreal context. However, the first field studies of gorilla and chimpanzees from the 1960's, highlighted their so-called 'knucklewalking' quadrupedalism, leading scientists to assume, semi-automatically, that knucklewalking must have been the precursor to bipedality. It would not be until the discovery of skeletons of early human relatives Australopithecus afarensis and Australopithecus prometheus , and the inclusion of methods of analysis from computer science, biomechanics, sports science and medicine, that the knucklewalking hypothesis would be most robustly challenged. Their short, but human-like lower limbs and human-like hand indicated that knucklewalking was not part of our ancestral locomotor repertoire. Rather, most current research in evolutionary biomechanics agrees it was a combination of climbing and bipedalism, both in an arboreal context, which facilitated upright, terrestrial, bipedal walking over short distances. [ABSTRACT FROM AUTHOR]

Continuous monitoring of spine movement function could enhance our understanding of low back pain development. Wearable technologies have gained popularity as promising alternative to laboratory systems in allowing ambulatory movement analysis. This paper aims to review the state of art of current use of wearable technology to assess spine kinematics and kinetics. Four electronic databases and reference lists of relevant articles were searched to find studies employing wearable technologies to assess the spine in adults performing dynamic movements. Two reviewers independently identified relevant papers. Customised data extraction and quality appraisal form were developed to extrapolate key details and identify risk of biases of each study. Twenty-two articles were retrieved that met the inclusion criteria: 12 were deemed of medium quality (score 33.4–66.7%), and 10 of high quality (score >66.8%). The majority of articles (19/22) reported validation type studies. Only 6 reported data collection in real-life environments. Multiple sensors type were used: electrogoniometers (3/22), strain gauges based sensors (3/22), textile piezoresistive sensor (1/22) and accelerometers often used with gyroscopes and magnetometers (15/22). Two sensors units were mainly used and placing was commonly reported on the spine lumbar and sacral regions. The sensors were often wired to data transmitter/logger resulting in cumbersome systems. Outcomes were mostly reported relative to the lumbar segment and in the sagittal plane, including angles, range of motion, angular velocity, joint moments and forces. This review demonstrates the applicability of wearable technology to assess the spine, although this technique is still at an early stage of development. [ABSTRACT FROM AUTHOR]

Kinematic models of lower limb joints have several potential applications in musculoskeletal modelling of the locomotion apparatus, including the reproduction of the natural joint motion. These models have recently revealed their value also for in vivo motion analysis experiments, where the soft-tissue artefact is a critical known problem. This arises at the interface between the skin markers and the underlying bone, and can be reduced by defining multibody kinematic models of the lower limb and by running optimization processes aimed at obtaining estimates of position and orientation of relevant bones. With respect to standard methods based on the separate optimization of each single body segment, this technique makes it also possible to respect joint kinematic constraints. Whereas the hip joint is traditionally assumed as a 3 degrees of freedom ball and socket articulation, many previous studies have proposed a number of different kinematic models for the knee and ankle joints. Some of these are rigid, while others have compliant elements. Some models have clear anatomical correspondences and include real joint constraints; other models are more kinematically oriented, these being mainly aimed at reproducing joint kinematics. This paper provides a critical review of the kinematic models reported in literature for the major lower limb joints and used for the reduction of soft-tissue artefact. Advantages and disadvantages of these models are discussed, considering their anatomical significance, accuracy of predictions, computational costs, feasibility of personalization, and other features. Their use in the optimization process is also addressed, both in normal and pathological subjects. [ABSTRACT FROM AUTHOR]

Optoelectronic motion capture systems are widely employed to measure the movement of human joints. However, there can be a significant discrepancy between the data obtained by a motion capture system (MCS) and the actual movement of underlying bony structures, which is attributed to soft tissue artefact. In this paper, a computer-aided tracking and motion analysis with ultrasound (CAT & MAUS) system with an augmented globally optimal registration algorithm is presented to dynamically track the underlying bony structure during movement. The augmented registration part of CAT & MAUS was validated with a high system accuracy of 80%. The Euclidean distance between the marker-based bony landmark and the bony landmark tracked by CAT & MAUS was calculated to quantify the measurement error of an MCS caused by soft tissue artefact during movement. The average Euclidean distance between the target bony landmark measured by each of the CAT & MAUS system and the MCS alone varied from 8.32 mm to 16.87 mm in gait. This indicates the discrepancy between the MCS measured bony landmark and the actual underlying bony landmark. Moreover, Procrustes analysis was applied to demonstrate that CAT & MAUS reduces the deformation of the body segment shape modeled by markers during motion. The augmented CAT & MAUS system shows its potential to dynamically detect and locate actual underlying bony landmarks, which reduces the MCS measurement error caused by soft tissue artefact during movement. [ABSTRACT FROM AUTHOR]

We present a supervised machine learning approach for markerless estimation of human full-body kinematics for a cyclist from an unconstrained colour image. This approach is motivated by the limitations of existing marker-based approaches restricted by infrastructure, environmental conditions, and obtrusive markers. By using a discriminatively learned mixture-of-parts model, we construct a probabilistic tree representation to model the configuration and appearance of human body joints. During the learning stage, a Structured Support Vector Machine (SSVM) learns body parts appearance and spatial relations. In the testing stage, the learned models are employed to recover body pose via searching in a test image over a pyramid structure. We focus on the movement modality of cycling to demonstrate the efficacy of our approach. In natura estimation of cycling kinematics using images is challenging because of human interaction with a bicycle causing frequent occlusions. We make no assumptions in relation to the kinematic constraints of the model, nor the appearance of the scene. Our technique finds multiple quality hypotheses for the pose. We evaluate the precision of our method on two new datasets using loss functions. Our method achieves a score of 91.1 and 69.3 on mean Probability of Correct Keypoint (PCK) measure and 88.7 and 66.1 on the Average Precision of Keypoints (APK) measure for the frontal and sagittal datasets respectively. We conclude that our method opens new vistas to robust user-interaction free estimation of full body kinematics, a prerequisite to motion analysis. [ABSTRACT FROM AUTHOR]

Instrumented-pointers are often used to calibrate anatomical landmarks in biomechanical analyses. However, little is known about the effect of altering the orientation of the pointer during calibration on the co-ordinates recorded. Incorrect positioning of a landmark influences the axes created, and thus the kinematic data recorded. This study aimed to investigate the reliability of the pointer method for anatomical calibration. Two points were drawn onto a fixed box to resemble knee joint epicondyles, then a custom-made pointer was used to define the positions of these landmarks in three-dimensions. Twenty different pointer-orientations were chosen, and the position of the pointer in each of these orientations was recorded 8 times. Euclidean distances between single points were calculated for both landmarks and compared statistically ( α = 0.05). Average Euclidean distances between all reconstructed points were 3.2±1.4 mm (range: 0.3–7.1 mm) for one landmark and 3.3±1.5 mm (range: 0.3–7.9mm) for the other. The x - and y -co-ordinates recorded differed statistically when the pointer was moved about the X and Y axes (anterior/posterior and superior/inferior to landmark) ( p < 0.05). No statistical differences were found between co-ordinates recorded when the pointer was moved around the Z axes ( p > 0.05). ICC values for all co-ordinates were excellent, highlighting the reliability of the method (ICC > 0.90). These results support this method of anatomical calibration; however, we recommend that pointers be consistently held in a neutral oriented position (where the handle is not anterior, posterior, superior or inferior to the landmark) during calibration, to reduce the likelihood of calibration errors. [ABSTRACT FROM AUTHOR]

Postural control strategies can be investigated by kinematic analysis of joint movements. However, current research is focussing mainly on the analysis of centre of pressure excursion and lacks consensus on how to assess joint movement during postural control tasks. This study introduces a new signal processing technique to comprehensively quantify joint sway during standing and evaluates its reproducibility. Fifteen patients with non-specific low back pain and ten asymptomatic participants performed three repetitions of a 60-second standing task on foam surface. This procedure was repeated on a second day. Lumbar spine movement was recorded using an inertial measurement system. The signal was temporally divided into six sections. Two outcome variables (mean absolute sway and sways per second) were calculated for each section. The reproducibility of single and averaged measurements was quantified with linear mixed-effects models and the generalizability theory. A single measurement of ten seconds duration revealed reliability coefficients of .75 for mean absolute sway and .76 for sways per second. Averaging a measurement of 40 seconds duration on two different days revealed reliability coefficients higher than .90 for both outcome variables. The outcome variables’ reliability compares favourably to previously published results using different signal processing techniques or centre of pressure excursion. The introduced signal processing technique with two outcome variables to quantify joint sway during standing proved to be a highly reliable method. Since different populations, tasks or measurement tools could influence reproducibility, further investigation in other settings is still necessary. Nevertheless, the presented method has been shown to be highly promising. [ABSTRACT FROM AUTHOR]

Inertial Measurement Units (IMUs) provides embedded and accessible (financially and technically speaking) motion analysis for sports or clinical applications (rehabilitation, therapy...). Despite being advertised for it ease of use, the very nature of IMU sensor makes it prone to errors which are usually corrected through calibration processes thus adding extra complexity for the users. The main goal of this study is to estimate the effect of sensor positioning on the thigh for a simple assessment of squat motion range of motion (ROM) as could be done in a pragmatic clinical approach (i.e., without prior calibration). Kinematics, squat counts and timing of three IMU sensors along the thigh were recorded during squat motion and compared to an optoelectronic reference system. Results showed concordance coefficients of the IMU system over 0.944 without the need for calibration with a preference for placement on the distal part of the segment regarding kinematics data. [ABSTRACT FROM AUTHOR]

Soft tissue artefact (STA) remains a major source of error in human movement analysis. The multibody kinematics optimisation (MKO) approach is widely stated as a solution to reduce the effects of STA. This study aimed at assessing the influence of the MKO STA-compensation on the errors of estimation of the knee intersegment moments. Experimental data were issued from the CAMS-Knee dataset where six participants with instrumented total knee arthroplasty performed five activities of daily living: gait, downhill walking, stair descent, squat, and sit-to-stand. Kinematics was measured both on the basis of skin markers and a mobile mono-plane fluoroscope, used to obtain the STA-free bone movement. For four different lower limb models and one corresponding to a single-body kinematics optimization (SKO), knee intersegmental moments (estimated using model-derived kinematics and ground reaction force) were compared with an estimate based on the fluoroscope. Considering all participants and activities, mean root mean square differences were the largest along the adduction/abduction axis: of 3.22 Nm with a SKO approach, 3.49 Nm with the three-DoF knee model, and 7.66 Nm, 8.52 Nm, and 8.54 Nm with the one-DoF knee models. Results showed that adding joint kinematics constraints can increase the estimation errors of the intersegmental moment. These errors came directly from the errors in the estimation of the position of the knee joint centre induced by the constraints. When using a MKO approach, we recommend to analyse carefully joint centre position estimates that do not remain close to the one obtained with a SKO approach. [ABSTRACT FROM AUTHOR]

Tandem gait is widely used during clinical exams to evaluate dynamic balance in chronic diseases, such as multiple sclerosis (MS). The early detection of balance impairments in MS is challenging to improve the understanding of patients' complaints. The objective was to propose two indexes to quantify the contributions and inefficiency of limb and trunk movements during tandem gait in early-stage MS patients. Fifteen patients with remitting-relapsed MS, with a median Expanded Disability Status Scale of 2.5 [0–4] were compared to 15 matched healthy participants. Three-dimensional motion analysis was performed during tandem gait to calculate spatiotemporal parameters, contribution and inefficiency indexes, based on the linear momentum of body segments. Compared to healthy participants, MS patients at the early stage of disease executed tandem gait with higher speed (p = 0.03) and increased step length (p = 0.03). The contribution indexes of upper limbs were significantly decreased during swing phase in MS patients. The inefficiency index for the upper limbs were around twice higher for MS patients compared to healthy participants. Since the additional movements concerned only light body segments and not contribute to the whole-body forward progression during tandem gait, they could reflected more both upper limb movements alterations and restoring movements to avoid loss of balance during tandem gait around swing phase in MS. These quantified indexes could be used as physical markers to quantify both the balance deterioration and the efficiency of rehabilitation program during the follow up of MS from the early stage of their disease. [ABSTRACT FROM AUTHOR]

Amputation imposes significant challenges in locomotion to millions of people with limb loss worldwide. The decline in the use of the residual limb results in muscle atrophy that affects musculoskeletal dynamics in daily activities. The aim of this study was to quantify the lower limb muscle volume discrepancy based on magnetic resonance (MR) imaging and to combine this with motion analysis and musculoskeletal modelling to quantify the effects in the dynamics of key activities of daily living. Eight male participants with traumatic unilateral transtibial amputation were recruited who were at least six months after receiving their definitive prostheses. The muscle volume discrepancies were found to be largest at the knee extensors (35 %, p = 0.008), followed by the hip abductors (17 %, p = 0.008). Daily activities (level walking, standing up from a chair and ascending one step) were measured in a motion analysis laboratory and muscle and joint forces quantified using a detailed musculoskeletal model for people with unilateral transtibial amputation which was calibrated in terms of the muscle volume discrepancies post-amputation at a subject-specific level. Knee extensor muscle forces were lower at the residual limb than the intact limb for all activities (p ≤ 0.008); residual limb muscle forces of the hip abductors (p ≤ 0.031) and adductors (p ≤ 0.031) were lower for standing-up and ascending one step. While the reduced knee extensor force has been reported by other studies, our results suggest a new biomechanically-based mitigation strategy to improve functional mobility, which could be achieved through strengthening of the hip abd/adductor muscles. [ABSTRACT FROM AUTHOR]

The robustness of movement patterns is an essential factor for characterizing the adaptability of our daily motions; however, details of the mechanism underlying adaptive motion patterns are not well understood. Here, we utilized complex principal component analysis (CPCA) to examine the spatiotemporal structure of dynamic muscle torques during sit-to-stand (STS) movements. The motion of a three-link rigid body model in the sagittal plane was captured by a Vicon motion analysis system to compute the kinematics of the center of mass (COM), angular displacement, and joint torques. Using CPCA, dynamic muscle torques were decomposed into three components: a control signal, the phase lags of the joint torques, and weighting coefficients. Two kinetic modules were identified in STS, indicating spatiotemporal modular control of the COM in the horizontal and vertical directions. Simulation results suggested that fine-tuning of these two modules according to environmental conditions contributes to adaptive changes in motion pattern. Taken together, our findings suggest that the sources of behavioral adaptations to the environment include the use of fixed modules to reduce computational load on the central nervous system, fine-tuning of these modules, and control of the temporal signals that activate them. [ABSTRACT FROM AUTHOR]

In this study, we describe a method to predict 6-axis ground reaction forces based solely on plantar pressure (PP) data obtained from insole type measurement devices free of space limitations. Because only vertical force is calculable from PP data, a wavelet neural network derived from a non-linear mapping function was used to obtain 3-axis ground reaction force in medial-lateral (GRF ML ), anterior-posterior (GRF AP ) and vertical (GRF V ) and 3-axis ground reaction moment in sagittal (GRF S ), frontal (GRF F ) and transverse (GRF T ) data for the remaining axes and planes. As the prediction performance of nonlinear models depends strongly on input variables, in this study, three input variables – accumulated PP with respect to time, center of pressure (COP) pattern, and measurements of the opposite foot, which are calculable only with a PP device – were considered in order to improve prediction performance. To conduct this study, the golf swing motions of 80 subjects were characterized as unilateral movement and GRF patterns as functions of individual characteristics. The prediction model was verified with 5-fold cross-validation utilizing the measured values of two force plates. As a result, prediction model (correlation coefficient, r= 0.73–0.97) utilized accumulated PP and PP data of the opposite foot and showed the highest prediction accuracy in left-foot GRF V , GRM F , GRM T and right-foot GRF AP , GRF ML , GRM F , GRM T . Likewise, another prediction model ( r =0.83–0.98) utilized accumulated PP and COP patterns as input and showed the best accuracy in left-foot GRF AP , GRF ML , GRM S and right-foot GRF V , GRM S . New methods based on the findings of the present study are expected to help resolve problems such as spatial limitation and limited analyzable motions in existing GRF measurement processes. [ABSTRACT FROM AUTHOR]

This study tested the hypothesis that men and women have different preoperative and postoperative gait impairment relative to sex-matched healthy controls, and that the extent of gait improvement after total hip arthroplasty (THA) is different between men and women. A group of 124 THA subjects was identified from a motion analysis data repository; age and BMI-matched male and female control groups were then identified from the same repository. Dynamic sagittal plane hip range of motion (HROM) and peak 3D external moments at subjects’ normal walking speeds were analyzed. Each hypotheses was tested using linear regression models, to adjust for potential confounding effects of walking speed. Preoperatively, the THA vs. control group differences in the HROM and peak adduction moments were larger in women than they were in men ( p =0.007). The THA group vs. control group difference in the peak external rotation moment was larger in men ( p =0.004). After surgery, HROM increased more in women than in men ( p =0.020). However, peak adduction moment decreased in men but increased in women (−0.11±0.93 vs. 0.28±1.3%BWH, p =0.045). Accordingly, postoperatively the THA group vs. control group differences in the peak external rotation moment remained larger in men than in women ( p =0.016). There were no other sex-specific differences ( p =0.072–0.876). This study suggests that men and women have slightly different patterns of gait recovery after THA and may benefit from sex-specific rehabilitation strategies. These differences also underscore the importance of accounting for sex in biomechanical studies. [ABSTRACT FROM AUTHOR]

The Leap Motion Controller (LMC) is a low-cost, markerless motion capture device that tracks hand, wrist and forearm position. Integration of this technology into healthcare applications has begun to occur rapidly, making validation of the LMC׳s data output an important research goal. Here, we perform a detailed evaluation of the kinematic data output from the LMC, and validate this output against gold-standard, markered motion capture technology. We instructed subjects to perform three clinically-relevant wrist (flexion/extension, radial/ulnar deviation) and forearm (pronation/supination) movements. The movements were simultaneously tracked using both the LMC and a marker-based motion capture system from Motion Analysis Corporation (MAC). Adjusting for known inconsistencies in the LMC sampling frequency, we compared simultaneously acquired LMC and MAC data by performing Pearson׳s correlation ( r ) and root mean square error ( RMSE ). Wrist flexion/extension and radial/ulnar deviation showed good overall agreement ( r =0.95; RMSE =11.6°, and r =0.92; RMSE =12.4°, respectively) with the MAC system. However, when tracking forearm pronation/supination, there were serious inconsistencies in reported joint angles ( r =0.79; RMSE =38.4°). Hand posture significantly influenced the quality of wrist deviation ( P <0.005) and forearm supination/pronation ( P <0.001), but not wrist flexion/extension ( P =0.29). We conclude that the LMC is capable of providing data that are clinically meaningful for wrist flexion/extension, and perhaps wrist deviation. It cannot yet return clinically meaningful data for measuring forearm pronation/supination. Future studies should continue to validate the LMC as updated versions of their software are developed. [ABSTRACT FROM AUTHOR]