Segment Kinematics Research Articles

Research on the Construction Method of Driving Conditions with Optimal Deviation Based on Fuzzy C-Means Clustering

To construct a driving condition that conforms to the actual situation, this paper firstly removes, interpolates, and smooths the original data, and obtains several kinematic segments according to the division standard of kinematic segments. Then, extract the feature parameters and analyze the principal components of the kinematic segments obtained by division, and retain the principal components that can describe most of the features. Finally, the FCM clustering method is used to analyze the retained principal components, and the congestion, relative congestion, and relative unblocked and unblocked conditions are obtained. Finally, the comprehensive driving conditions are synthesized by the deviation optimization method, and their rationality and scientificity are verified by simulation analysis.

Generation of forward angular impulse with different initial conditions

Generation of angular impulse during foot contact is regulated by controlling the relative orientation between the total body center of mass (CoM) and the reaction force (RF) applied to the feet. Between-task differences in initial CoM horizontal momentum were hypothesized to alter how forward angular impulse was generated during two forward translating tasks. Five skilled athletes performed standing (SFS) and running (RFS) forward somersaulting dives. Sagittal plane kinematics and RFs were obtained during the take-off phase of both tasks. The initial CoM momentum differences resulted in significant differences in control of the CoM relative to the RF, RF generation mechanisms, and knee and hip net joint moments (NJMs). During the RFS, angular impulse was generated by positioning the feet anterior to the CoM at initial contact so that the RF passed posterior to the CoM throughout the take-off phase. During the SFS, angular impulse was generated by positioning the CoM anterior to the feet prior to the push interval so that the RF passed posterior to the CoM. Task-specific differences in segment kinematics and RF direction contributed to the redistribution of knee and hip NJMs. These results suggest that initial conditions influence strategies the nervous system uses to satisfy task objectives.

Using Sensors for Player Development: Assessing Biomechanical Factors Related to Pitch Command and Velocity.

Pitching biomechanical research is highly focused on injury prevention with little attention to how biomechanical data can facilitate skill development. The overall purpose of this study was to explore how sensor-derived segment kinematics and timing relate to command and ball velocity during baseball pitching. We used a cross-sectional design to analyze a series of pitches thrown from 10 collegiate baseball pitchers. We collected biomechanical data from six inertial sensors, subjective command from the pitchers, and ball velocity from a radar device. Stepwise regression analyses were used to explore biomechanical variables associated with command for all pitches and ball velocity for fastballs only. We found that only peak forearm linear acceleration was significantly associated with command, whereas several segment kinematic measures were significantly associated with ball velocity. Our results suggest that different biomechanical variables are linked to specific pithing skills. Our findings suggest that end-effector (forearm) movement is more important for pitch command, whereas proximal-to-distal (pelvis, trunk, upper arm, forearm) segmental movement is important for ball velocity.

Effects of rod diameter on kinematics of posterior cervical spine instrumented constructs: an ex vivo study.

Posterior cervical spine fixation is a robust strategy for stabilizing the spine for a wide range of spinal disorders. With the evolution of spinal implant technology, posterior fixation with lateral mass screws in the subaxial spine is now common. Despite interest in variable rod diameters to meet a wide range of clinical needs such as trauma, revision, and deformity surgery, indications for use of posterior cervical spine fixation are not clear. This laboratory investigation evaluates the mechanical stability and kinematic properties of lateral mass fixation with various commercially available rod diameters. The authors conducted an ex vivo experiment using 13 fresh-frozen human cervical spine specimens, instrumented from C3 to C6 with lateral mass screws, to evaluate the effects of titanium rod diameter on kinematic stability. Each intact spine was tested using a kinematic profiling machine with an optoelectrical camera and infrared sensors applying 1.5-Nm bending moments to the cranial vertebra (C2) simulating flexion-extension, lateral bending, and axial rotation anatomical motions. A compressive follower preload of 150 N was applied in flexion-extension prior to application of a bending moment. Instrumented spines were then tested with rod diameters of 3.5, 4.0, and 4.5 mm. The kinematic data between intact and surgical cases were studied using a nonparametric Wilcoxon signed-rank test. A multivariable, multilevel linear regression model was built to identify the relationship between segmental motion and rod diameter. Instrumentation resulted in significant reduction in range of motion in all three rod constructs versus intact specimens in flexion-extension, lateral bending, and axial rotation (p < 0.05). The maximum reductions in segmental ROM versus intact spines in 3.5-, 4.0-, and 4.5-mm rod constructs were 61%, 71%, and 81% in flexion-extension; 70%, 76%, and 81% in lateral bending; and 50%, 60%, and 75% in axial rotation, respectively. Segmental motion at the adjacent segments (C2-3 and C6-7) increased significantly (p < 0.05) with increasing rod diameter. The 4.5-mm rod construct had the greatest increase in motion compared to the intact spine. With increasing rod diameters from 3.5 to 4.0 mm, flexion-extension, lateral bending, and axial rotation across C3-6 were significantly reduced (p < 0.05). Similar trends were observed with a statistically significant reduction in motion in all anatomical planes when the rod diameter was increased to 4.5 mm. Although the increase in rod diameter resulted in a more rigid construct, it also created an increase (p < 0.05) in the kinematics of the adjacent segments (C2-3 and C6-7). Whether this increase translates into adverse long-term clinical effects in vivo requires further investigation and clinical assessment.

Impairments in the mechanical effectiveness of reactive balance control strategies during walking in people post-stroke.

People post-stroke have an increased risk of falls compared to neurotypical individuals, partly resulting from an inability to generate appropriate reactions to restore balance. However, few studies investigated the effect of paretic deficits on the mechanics of reactive control strategies following forward losses of balance during walking. Here, we characterized the biomechanical consequences of reactive control strategies following perturbations induced by the treadmill belt accelerations. Thirty-eight post-stroke participants and thirteen age-matched and speed-matched neurotypical participants walked on a dual-belt treadmill while receiving perturbations that induced a forward loss of balance. We computed whole-body angular momentum and angular impulse using segment kinematics and reaction forces to quantify the effect of impulse generation by both the leading and trailing limbs in response to perturbations in the sagittal plane. We found that perturbations to the paretic limb led to larger increases in forward angular momentum during the perturbation step than perturbations to the non-paretic limb or to neurotypical individuals. To recover from the forward loss of balance, neurotypical individuals coordinated reaction forces generated by both legs to decrease the forward angular impulse relative to the pre-perturbation step. They first decreased the forward pitch angular impulse during the perturbation step. Then, during the first recovery step, they increased the backward angular impulse by the leading limb and decreased the forward angular impulse by the trailing limb. In contrast to neurotypical participants, people post-stroke did not reduce the forward angular impulse generated by the stance limb during the perturbed step. They also did not increase leading limb angular impulse or decrease the forward trailing limb angular impulse using their paretic limb during the first recovery step. Lastly, post-stroke individuals who scored poorer on clinical assessments of balance and had greater motor impairment made less use of the paretic limb to reduce forward momentum. Overall, these results suggest that paretic deficits limit the ability to recover from forward loss of balance. Future perturbation-based balance training targeting reactive stepping response in stroke populations may benefit from improving the ability to modulate paretic ground reaction forces to better control whole-body dynamics.

Do individuals with knee osteoarthritis walk with distinct knee biomechanics and muscle activation characteristics? An investigation of knee osteoarthritis, hip osteoarthritis, and asymptomatic groups

BackgroundBiomechanical markers including reductions in sagittal plane kinematics and moments, increases in knee adduction moments (KAM), and altered muscle activations have been identified as hallmark indicators of knee osteoarthritis (OA). However, it remains unknown whether these features of knee OA gait are exclusive to the diseased joint. Research questionTo determine whether specific gait outcomes previously linked to symptomatic medial compartment knee OA are unique to knee OA by concurrently investigating a group of asymptomatic individuals and those with hip OA. Methods16 individuals with moderate medial compartment knee OA, 16 individuals with moderate hip OA, and 16 asymptomatic controls were recruited. Participants walked on a treadmill while segment kinematics and ground reaction forces were recorded. Sagittal plane kinematics and sagittal and frontal plane moments were calculated. Surface electromyograms were recorded from lateral and medial hamstrings and gastrocnemius and vastus lateralis and medialis. Discrete variable analysis was used to investigate knee joint mechanics and muscle activation ratios. Analysis of Variance models using Bonferroni corrections determined between group differences (α = 0.0167). ResultsSagittal plane knee kinematics and moments were statistically similar among all groups (p > 0.0167). No differences were found for peak KAM and impulse between knee OA and asymptomatic groups (p > 0.0167) but peak KAM (p = 0.006 and impulse (p = 0.001) were greater in the knee OA group compared to hip OA. The hip OA group had a lower KAM impulse (p < 0.0167) compared to the knee OA and asymptomatic groups. A greater LH:MH activation ratio (p < 0.0167) was found in the knee OA group compared to hip OA and asymptomatic groups. No other activation ratio differences were found (p > 0.0167). SignificanceMedial and lateral hamstring muscle activation levels may provide utility as a knee OA gait biomarker compared to biomechanical outcomes, quadriceps and gastrocnemius activation, when differentiating knee OA from asymptomatic and hip OA cohorts.

Effects of Shoe Midfoot Bending Stiffness on Multi-Segment Foot Kinematics and Ground Reaction Force during Heel-Toe Running.

We investigated how midfoot stiffness of running shoes influences foot segment kinematics and ground reaction force (GRF) during heel-toe running. Nineteen male rearfoot strike runners performed overground heel-toe running at 3.3 m/s when wearing shoes with different midfoot bending stiffnesses (low, medium, and high) in a randomized order. A synchronized motion capture system (200 Hz) and force plate (1000 Hz) were used to collect the foot-marker trajectories and GRF data. Foot kinematics, including rearfoot-lab, midfoot-rearfoot, forefoot-rearfoot, and forefoot-midfoot interactions, and kinetics, including GRF characteristics, were analyzed. Our results indicated that high midfoot stiffness shoes reduced the forefoot-rearfoot range of motion (mean ± SD; high stiffness, 7.8 ± 2.0°, low stiffness, 8.7 ± 2.1°; p < 0.05) and forefoot-midfoot range of motion (mean ± SD; high stiffness, 4.2 ± 1.1°, medium stiffness, 4.6 ± 0.9°; p < 0.05) in the frontal plane. No differences were found in the GRF characteristics among the shoe conditions. These findings suggest that an increase in midsole stiffness only in the midfoot region can reduce intersegmental foot medial-lateral movements during the stance phase of running. This may further decrease the tension of the foot muscles and tendons during prolonged exercises.

A Clustering-Based Optimization Method for the Driving Cycle Construction: A Case Study in Fuzhou and Putian, China

Driving cycle is a crucial topic for the auto industry. It is developed to provide a quantitative measure on the fuel consumption and emission of a vehicle. In recent years, massive amount of driving data has been collected but has not yet been commonly used for the evaluation of driving cycle. We believe the collection of such data and the advancement in analytics models may provide a fresh perspective for the construction of driving cycle. Therefore, we propose a novel clustering-based optimization method for the construction of driving cycles. We employ the principal component analysis and spectral clustering algorithms to eliminate redundant features and analyze data structure. We further develop an adaptive optimization algorithm to select the appropriate kinematic segments to form a representative driving cycle. To demonstrate the effectiveness of our method, we compare our performance against the baselines including the New European Driving Cycle (NEDC), Federal Test Procedure (FTP), and Markov chain-based methods. The model performance is evaluated with real driving data from two cities in Fujian, China. Our proposed method is shown to be superior to all baselines. In addition, based on our optimized driving cycle, we can also estimate the fuel consumption to evaluate its energy economy. To sum up, this study offers a novel methodology to establish the driving cycle based on real and localized traffic data, where the constructed driving cycle can further be used for the development of energy economy and emission control.

Kinematic Analysis of the Underwater Undulatory Swimming Cycle: A Systematic and Synthetic Review.

The increase of low-cost technology for underwater filming has made quantitative analysis an affordable resource for swimming coaches on a frequent basis. In this context, a synthesis of the kinematic determinants of underwater undulatory swimming (UUS) seems to be lacking. The aim of the present study was to synthesise the scientific evidence on the kinematic characteristics of competitive swimmers during UUS and the main kinematic determinants of UUS performance, as well as to summarise the main methodological considerations for UUS kinematic analysis. A systematic literature search was performed through four electronic databases following the PRISMA guidelines and STROBE for evaluating the quality of the included studies. Twenty-three research studies from the first search and two from the second search were finally considered. In total, 412 competitive swimmers (321 males and 91 females) with a performance standard of international B (11%), national (51%), or regional (35%) level were analysed. Most studies focused on a two-dimensional analysis of the ventral UUS performed from a push start and filmed 6–12 m from the starting wall. Kinematic analysis of UUS included kicking parameters (kicking length, frequency, and amplitude) as well as selected segmental kinematics in 76% of studies and the analysis of UUS performance determinants in 36%. Information about the determinants of UUS performance was inconsistent due in part to inconsistencies in the definition of kinematic parameters. Further research studies where automatic motion capture systems are applied to the analysis of UUS on the aforementioned conditions should be conducted.

Evaluating the Energy Consumption of an Electric Vehicle Under Real-World Driving Conditions

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;This investigation evaluates the energy consumption of an electric vehicle (EV) and identifies key factors that affect its energy efficiency, based on real-world operation for a range of driving characteristics and climate conditions over nearly four years in the streets of the second-largest UK city. The driving modes investigated were acceleration, deceleration, idling and cruise, determined by dividing each individual trip into kinematic segments based on vehicle speed and acceleration calculated second by second. From the results obtained, the EV energy consumption is directly influenced by changes in ambient temperature outside, largely due to the corresponding loads required from the use of auxiliary systems, mainly heating and air conditioning. An increase in trip idling events directly translates to a rise in EV energy consumption, while opposite outcomes were produced during cruising state with decreasing energy consumption. During the periods of high traffic on weekdays, the energy consumption is increased by nearly 15% as a direct impact of the increase in the number of stops, as the auxiliaries still require energy while the vehicle is at idle. The difference in energy consumption between weekday and weekend driving occurs mainly during heavy traffic periods, increasing by 20% on weekdays, primarily due to the rise in the number of stops for weekday driving. The results also show that the EV specific energy consumption varies each month, reaching a 55% increase from summer of least energy consumption to winter with the most requires energy, mainly due to large average ambient temperature changes.&lt;/div&gt;&lt;/div&gt;

33. Comparison of the biomechanics of lumbar spine instrumented with standalone interbody fixation constructs vs interbody with supplemental fixation: a finite element investigation

<h3>BACKGROUND CONTEXT</h3> Low fusion rates and cage subsidence have been reported as the main drawbacks of lumbar fixation with static interbody cages. Although several clinical and biomechanical studies have evaluated the efficacy of 360 interbody fixation constructs (anterior cage plus posterior fixation), no study has reported the biomechanical comparison between such constructs and more novel techniques which use standalone fixation implants. A cadaver validated computational model of lumbar spine was used to compare the biomechanics of spine instrumented with 360 fixations vs standalone cage and screw and cage with lateral plate systems. <h3>PURPOSE</h3> To compare the mechanical stability of different interbody fixation techniques in lumbar spinal segments with standalone interbody vs static cage with posterior fixation or lateral plate system. <h3>STUDY DESIGN/SETTING</h3> Finite element modeling. <h3>OUTCOME MEASURES</h3> Range of motion across instrument segments and load sharing on vertebral endplate. <h3>METHODS</h3> An experimentally validated finite element (FE) model of L1-pelvic segment was used to simulate ALIF and LIF lumbar fixation techniques including: ALIF cage at L5-S1 plus posterior screw-rod fixation (360 construct) vs ALIF standalone (screw through the cage). LIF cage at L4-L5 vs LIF cage with integrated two-hole lateral plate system. 4WEB Medical's Truss ALIF (27mm x 25mm), Lateral Truss (22mm X 5mm) cages and 2-hole integrated plate systems were used for simulation of the surgical procedure. For 360 constructs, a generic posterior rod and screw system was used. All models were subjected to a 400N compressive pre-load followed by an 8Nm moment to simulation flexion-extension, left and right bending and axial rotation motions. The segmental kinematics and the load sharing at the inferior endplate were compared among cases. <h3>RESULTS</h3> The segmental motion in standalone ALIF construct was 1.1°(Flex-Ext), 0.9° (LB) and 0.4° vs 0.8°, 0.8° and 0.6° in 360 ALIF in the same planes of motion. When comparing lateral cases, the motions were 1.2° (Flex-Ext), 1.4° (LB) and 0.5° (AR) in lateral cage with plate vs 0.9°, 1.0° and 0.8° in the 360 lateral construct for the same loads. The peak stresses in extension for the LIF stand-alone cage were somewhat higher than the posterior instrumented cases, but not significant. When comparing the mechanical stress on the inferior endplate of the index segment, the standalone ALIF had almost 20% higher peak stress compared to the 360 ALIF. In the lateral construct, the cage-plate segment experienced 15% lower stresses on the endplate compared to the 360 lateral construct. <h3>CONCLUSIONS</h3> Our data suggest that standalone ALIF cage with screw through the cage is able to provide kinematic stability in the fixation construct comparable to the cage plus posterior fixation, although the 360 construct is able to provide slightly more stability in the sagittal plane. Also, the standalone cage results in higher stresses applied to the endplate compared the cage in 360 constructs. The lateral cage with integrated plate had superior stability in axial rotation compared to the 360 lateral construct. The loads on the endplate were also slightly lower compared to the 360-fixation case. Standalone ALIF and LIF with lateral plate are biomechanically effecient alternatives to 360-fixation constructs at least under the controlled conditions analyzed in the present study. Clinical data are required to support the findings and define the further role and application of standalone cages. <h3>FDA DEVICE/DRUG STATUS</h3> 4WEB ALIF Truss System (Approved for this indication), 4WEB Lateral Plate System (Approved for this indication), 4WEB Lateral Truss System (Approved for this indication)

In Vivo Evidence of Early Instability and Late Stabilization in Motion Segments Immediately Superior to Anterior Cervical Arthrodesis.

Prospective cohort study. The aim was to identify patient factors that affect adjacent segment kinematics after anterior cervical discectomy and fusion (ACDF) as measured by biplane radiography. The etiology of adjacent segment disease (ASD) may be multifactorial. Previous studies have investigated associations between patient factors and ASD, although few attempted to link patient factors with mechanical changes in the spine that may explain ASD development. Previous studies manually measured intervertebral motion from static flexion/extension radiographs, however, manual measurements are unreliable, and those studies failed to measure intervertebral motion during rotation. Patients had continuous cervical spine flexion/extension and axial rotation movements captured at 30 images per second in a dynamic biplane radiography system preoperatively and 1 year after ACDF. Digitally reconstructed radiographs generated from subject-specific computed tomography scans were matched to the biplane radiographs using a validated tracking process. Dynamic kinematics and preoperative disc height were calculated from this tracking process. Preoperative magnetic resonance imagings were evaluated for disc bulge. Patient age, sex, body mass index, smoking status, diabetes, psychiatric history, presence of an inciting event, and length of symptoms were collected. Multivariate linear regression was performed to identify patient factors associated with 1-year postoperative changes in adjacent segment kinematics. Sixty-three patients completed preoperative and postoperative testing. Superior adjacent segment disc height and disc bulge predicted the change in superior adjacent segment range of motion after surgery. Inferior adjacent segment disc bulge, smoking history, and the use of psychiatric medications predicted the change in inferior adjacent segment flexion/extension range of motion after surgery. Preexisting adjacent segment disc degeneration, as indicated by disc height and disc bulge, was associated with reduced adjacent segment motion after ACDF, while lack of preexisting adjacent disc degeneration was associated with increased adjacent segment motion after ACDF. These findings provide in vivo evidence supporting early instability and late stabilization in the pathophysiology of disc degeneration.

Applications of Biomechanical Foot Models to Evaluate Dance Movements Using Three-Dimensional Motion Capture: A Review of the Literature.

Dance movement requires excessive, repetitive range of motion (ROM) at the foot-ankle complex, possibly contributing to the high rate of injury among dancers. However, we know little about foot biomechanics during dance movements. Researchers are using three-dimensional (3D) motion capture systems to study the in vivo kinematics of joint segments more frequently in dance-medicine research, warranting a literature review and quality assessment evaluation. The purpose of this literature review was to identify and evaluate studies that used 3D motion capture to analyze in vivo biomechanics of the foot and ankle for a cohort of dancers during dance-specific movement. Three databases (PubMed, Ovid MEDLINE, CINAHL) were accessed along with hand searches of dance-specific journals to identify relevant articles through March 2020. Using specific selection criteria, 25 studies were identified. Fifteen studies used single-segment biomechanical foot models originally created to study gait, four used a novel two-segment model, and six utilized a multi-seg- ment foot model. Nine of the studies referenced common and frequently published gait marker sets and four used a dance-specific biomechanical model with purposefully designed foot segments to analyze the dancers' foot and ankle. Description of the biomechanical models varied, reducing the reproducibility of the models and protocols. Investigators concluded that there is little evidence that the extreme total, segmental, and inter-segmental foot and ankle ROM exerted by dancers are being evaluated during dance-specific movements using 3D motion capture. Findings suggest that 3D motion capture is a robust measurement tool that has the capability to assist researchers in evaluating the in vivo, inter-segmental motion of the foot and ankle to potentially discover many of the remaining significant factors predisposing dancers to injury. The literature review synthesis is presented with recommendations for consideration when evaluating results from studies that utilized a 3D biomechanical foot model to evaluate dance-specific movement.

Biomechanical analysis of stand-alone lumbar interbody cages versus 360° constructs: an in vitro and finite element investigation.

Low fusion rates and cage subsidence are limitations of lumbar fixation with stand-alone interbody cages. Various approaches to interbody cage placement exist, yet the need for supplemental posterior fixation is not clear from clinical studies. Therefore, as prospective clinical studies are lacking, a comparison of segmental kinematics, cage properties, and load sharing on vertebral endplates is needed. This laboratory investigation evaluates the mechanical stability and biomechanical properties of various interbody fixation techniques by performing cadaveric and finite element (FE) modeling studies. An in vitro experiment using 7 fresh-frozen human cadavers was designed to test intact spines with 1) stand-alone lateral interbody cage constructs (lateral interbody fusion, LIF) and 2) LIF supplemented with posterior pedicle screw-rod fixation (360° constructs). FE and kinematic data were used to validate a ligamentous FE model of the lumbopelvic spine. The validated model was then used to evaluate the stability of stand-alone LIF, transforaminal lumbar interbody fusion (TLIF), and anterior lumbar interbody fusion (ALIF) cages with and without supplemental posterior fixation at the L4-5 level. The FE models of intact and instrumented cases were subjected to a 400-N compressive preload followed by an 8-Nm bending moment to simulate physiological flexion, extension, bending, and axial rotation. Segmental kinematics and load sharing at the inferior endplate were compared. The FE kinematic predictions were consistent with cadaveric data. The range of motion (ROM) in LIF was significantly lower than intact spines for both stand-alone and 360° constructs. The calculated reduction in motion with respect to intact spines for stand-alone constructs ranged from 43% to 66% for TLIF, 67%-82% for LIF, and 69%-86% for ALIF in flexion, extension, lateral bending, and axial rotation. In flexion and extension, the maximum reduction in motion was 70% for ALIF versus 81% in LIF for stand-alone cases. When supplemented with posterior fixation, the corresponding reduction in ROM was 76%-87% for TLIF, 86%-91% for LIF, and 90%-92% for ALIF. The addition of posterior instrumentation resulted in a significant reduction in peak stress at the superior endplate of the inferior segment in all scenarios. Stand-alone ALIF and LIF cages are most effective in providing stability in lateral bending and axial rotation and less so in flexion and extension. Supplemental posterior instrumentation improves stability for all interbody techniques. Comparative clinical data are needed to further define the indications for stand-alone cages in lumbar fusion surgery.

Predicting the Internal Knee Abduction Impulse During Walking Using Deep Learning.

Knee joint moments are commonly calculated to provide an indirect measure of knee joint loads. A shortcoming of inverse dynamics approaches is that the process of collecting and processing human motion data can be time-consuming. This study aimed to benchmark five different deep learning methods in using walking segment kinematics for predicting internal knee abduction impulse during walking. Three-dimensional kinematic and kinetic data used for the present analyses came from a publicly available dataset on walking (participants n = 33). The outcome for prediction was the internal knee abduction impulse over the stance phase. Three-dimensional (3D) angular and linear displacement, velocity, and acceleration of the seven lower body segment’s center of mass (COM), relative to a fixed global coordinate system were derived and formed the predictor space (126 time-series predictors). The total number of observations in the dataset was 6,737. The datasets were split into training (75%, n = 5,052) and testing (25%, n = 1685) datasets. Five deep learning models were benchmarked against inverse dynamics in quantifying knee abduction impulse. A baseline 2D convolutional network model achieved a mean absolute percentage error (MAPE) of 10.80%. Transfer learning with InceptionTime was the best performing model, achieving the best MAPE of 8.28%. Encoding the time-series as images then using a 2D convolutional model performed worse than the baseline model with a MAPE of 16.17%. Time-series based deep learning models were superior to an image-based method when predicting knee abduction moment impulse during walking. Future studies looking to develop wearable technologies will benefit from knowing the optimal network architecture, and the benefit of transfer learning for predicting joint moments.

Age-related changes in three-dimensional foot motion during barefoot walking in children aged between 7 and 11 years old

BackgroundThe biomechanical complexity of children’s feet changes throughout childhood, yet kinematic development of the feet is poorly understood. Further work exploring the kinematic profile of children’s feet would be beneficial to help inform our understanding of the typical development of children’s feet. Research QuestionDo three-dimensional segmental kinematics of the feet during gait relate to age in a sample of children age 7–11 years? MethodsThis study was a secondary analysis of an existing database representing one hundred and twenty-one children age 7 – 11 years (90 male, 31 female; mean ± SD: age 9.57 ± , 1.17 years, height 1.37 ± 0.08 m, body mass 35.61 ± 9.33 kg). Fifteen, 9 mm retroreflective markers were attached to the right shank and foot of each participant in, line with the 3DFoot model. Multi-segmental joint kinematics were collected during barefoot walking. Sagittal, frontal, and transverse planar motion was described for the shank-calcaneus, calcaneus-midfoot, and midfoot-metatarsals segment of the right foot. Principal component analysis (PCA) was used to reduce the major modes of variation in the data to fully explore foot segment motion over the entire gait cycle. Correlations and multiple regression between PCA outputs with age, and potential confounding factors are presented. ResultsSignificant positive correlations were found between age and greater calcaneus, dorsiflexion, midfoot inversion and adduction, and metatarsal dorsiflexion, plantarflexion and abduction. There were no significant confounding effects of height, body mass, walking speed or gender on the relationships between age and PCA outputs. SignificanceThe findings from this study demonstrated a relationship between foot kinematics and age suggesting that the development of foot kinematics is ongoing until at least the age of 11 years. This work offers a comprehensive data set of inter-segmental kinematics which helps to advance understanding of the development of the pediatric foot.

Concurrent validity of an easy-to-use inertial measurement unit-system to evaluate sagittal plane segment kinematics during overground sprinting at different speeds

ABSTRACT This study investigated concurrent validity of inertial measurement units (IMUs) and high-speed video for sagittal plane kinematics during overground sprinting. The practical relevance is demonstrated by reporting the changes in thigh kinematics in relation to toe-off and touch-down of the feet at near maximal to maximal (80–100%) speeds. Sixteen athletes ran multiple 60 m sprints with IMUs on their feet, shanks, thighs, pelvis and trunk. High-speed video data were captured of the start strides and of one complete stride at full speed. Coefficients of multiple correlation with video were >0.99 for angles and angular velocities of the thigh and shank but low for the pelvis and trunk (0.13–0.66). For the limb segment angles (minimum, maximum, at toe-off and at touch-down) absolute biases (limits of agreement) were ≤2.9°(≤7.7°) and for angular velocities the values were ≤57°.s−1(≤93°.s−1). Many of the expected speed-related changes in thigh kinematics were significant (linear mixed effect regression; p < 0.05). In conclusion, an easy-to-use IMU system has good concurrent validity with video, especially for the thigh. It registers the kinematics of all strides in multiple sprints and can detect relatively small changes thereof, including those at key moments of foot-touch-down and toe-off.

Quantitative Characterization of Motor Control during Gait in Dravet Syndrome Using Wearable Sensors: A Preliminary Study.

Dravet syndrome (DS) is a rare and severe form of genetic epilepsy characterized by cognitive and behavioural impairments and progressive gait deterioration. The characterization of gait parameters in DS needs efficient, non-invasive quantification. The aim of the present study is to apply nonlinear indexes calculated from inertial measurements to describe the dynamics of DS gait. Twenty participants (7 M, age 9–33 years) diagnosed with DS were enrolled. Three wearable inertial measurement units (OPAL, Apdm, Portland, OR, USA; Miniwave, Cometa s.r.l., Italy) were attached to the lower back and ankles and 3D acceleration and angular velocity were acquired while participants walked back and forth along a straight path. Segmental kinematics were acquired by means of stereophotogrammetry (SMART, BTS). Community functioning data were collected using the functional independence measure (FIM). Mean velocity and step width were calculated from stereophotogrammetric data; fundamental frequency, harmonic ratio, recurrence quantification analysis, and multiscale entropy (τ = 1...6) indexes along anteroposterior (AP), mediolateral (ML), and vertical (V) axes were calculated from trunk acceleration. Results were compared to a reference age-matched control group (112 subjects, 6–25 years old). All nonlinear indexes show a disruption of the cyclic pattern of the centre of mass in the sagittal plane, quantitatively supporting the clinical observation of ataxic gait. Indexes in the ML direction were less altered, suggesting the efficacy of the compensatory strategy (widening the base of support). Nonlinear indexes correlated significantly with functional scores (i.e., FIM and speed), confirming their effectiveness in capturing clinically meaningful biomarkers of gait.

The effects of pathology and one-level versus two-level arthrodesis on cervical spine intervertebral helical axis of motion

The etiology of adjacent segment disease after anterior cervical discectomy and fusion (ACDF) remains controversial. Range of motion (ROM) is typically used to infer the effects of arthrodesis on adjacent segment motion following ACDF, however, ROM only measures the total amount of motion. In contrast, the helical axis of motion (HAM) quantifies how the motion occurs and may provide additional insight into the etiology of adjacent segment pathology. Synchronized biplane radiographs of the cervical spine were acquired at 30 images per second while 62 ACDF patients and 38 control participants performed dynamic neck flexion/extension. A validated tracking process matched digitally reconstructed radiographs created from subject-specific bone models to the radiographs with sub-millimeter accuracy. The intervertebral HAM was then calculated and compared between pre and 1 year post surgery in patients, and between patients and controls at corresponding motion segments using linear mixed-effects analysis. Small differences in the anterior/posterior location of the HAM were found between the symptomatic motion segments before surgery and corresponding motion segments in controls. No changes in the HAM of motion segments adjacent to the arthrodesis were observed from pre to 1-year post-surgery. No differences in adjacent segment HAM were found between patients with one- versus two-level arthrodesis. Neither symptomatic pathology nor arthrodesis appear to change the way motion occurs in the cervical spine during flexion/extension one year after one or two-level arthrodesis. These results suggest ACDF does not alter short-term adjacent segment kinematics in a way that would contribute to the development of adjacent segment disease.

Difference in the foot intersegmental coordination pattern between female lacrosse players with and without a history of medial Tibial stress syndrome; a cross-sectional study

BackgroundMedial tibial stress syndrome is a common sports related injury. Altered foot kinematics can be a risk factor for the injury. Since foot segments can move independently, intersegment coordination is important for proper foot function. This study aimed to compare the foot intersegmental coordination pattern and single segment kinematics between female lacrosse players with and without a history of medial tibial stress syndrome during drop jump.MethodsTwelve players with a medial tibial stress syndrome history and 12 players with no history were enrolled. Foot kinematics, including angle at landing and peak angle and excursion at the rearfoot, midfoot, and forefoot during single-leg drop jumps were analysed. Each segment motion data from landing to leaping was time-scaled to 100% to analyse the intersegmental coordination with a modified vector coding technique. Instant intersegmental coordination of every 1% was classified into four patterns (in-phase, two segments rotate in the same direction with similar amplitudes; anti-phase, two segments rotate in opposite directions; proximal phase, proximal segment dominantly rotates in the same direction compared to the distal segment; and distal phase, distal segment dominantly rotates in the same direction compared to the proximal segment). The percentage of intersegmental coordination pattern and kinematics in each segment were compared between the groups using the Student’s t test.ResultsGroups with a history of medial stress syndrome showed a significantly higher percentage of proximal phase between the rearfoot and midfoot in the sagittal (Mean ± SD; history, 52.2 ± 17.9%, no history, 29.3 ± 16.7%; p = 0.004) and coronal planes (history, 40.3 ± 22.0%, no history, 15.9 ± 9.1%; p = 0.004). Dorsiflexion excursion (history, 34.5 ± 4.5°, no history, 29.6 ± 2.1°; p = 0.003) were significantly larger in a history of medial tibial stress syndrome group compared to no history group.ConclusionsRearfoot dominant motion pattern relative to the midfoot may be related to medial tibial stress syndrome. Intersegmental coordination analysis may be useful for detecting abnormal foot coordination patterns. Also, stabilization for the rearfoot may be required rather than the midfoot for intervention.