Comparison of Concurrent and Asynchronous Running Kinematics and Kinetics From Marker-Based and Markerless Motion Capture Under Varying Clothing Conditions.

As markerless motion capture is increasingly used to measure 3-dimensional human pose, it is important to understand how markerless results can be interpreted alongside historical marker-based data and how they are impacted by clothing. We compared concurrent running kinematics and kinetics between marker-based and markerless motion capture, and between 2 markerless clothing conditions. Thirty adults ran on an instrumented treadmill wearing motion capture clothing while concurrent marker-based and markerless data were recorded, and ran a second time wearing athletic clothing (shorts and t-shirt) while markerless data were recorded. Differences calculated between the concurrent signals from both systems, and also between each participant's mean signals from both asynchronous clothing conditions were summarized across all participants using root mean square differences. Most kinematic and kinetic signals were visually consistent between systems and markerless clothing conditions. Between systems, joint center positions differed by 3 cm or less, sagittal plane joint angles differed by 5° or less, and frontal and transverse plane angles differed by 5° to 10°. Joint moments differed by 0.3 N·m/kg or less between systems. Differences were sensitive to segment coordinate system definitions, highlighting the effects of these definitions when comparing against historical data or other motion capture modalities.

Concurrent assessment of gait kinematics using marker-based and markerless motion capture.

Kinematic analysis is a useful and widespread tool used in research and clinical biomechanics for the quantification of human movement. Common marker-based optical motion capture systems are time intensive and require highly trained operators to obtain kinematic data. Markerless motion capture systems offer an alternative method for the measurement of kinematic data with several practical benefits. This work compared the kinematics of human gait measured using a deep learning algorithm-based markerless motion capture system to those from a standard marker-based motion capture system. Thirty healthy adult participants walked on a treadmill while data were simultaneously recorded using eight video cameras and seven infrared optical motion capture cameras, providing synchronized markerless and marker-based data for comparison. The average root mean square distance (RMSD) between corresponding joint centers was less than 2.5 cm for all joints except the hip, which was 3.6 cm. Lower limb segment angles relative to the global coordinate system indicated the global segment pose estimates from both systems were very similar, with RMSD of less than 5.5° for all segment angles except those that represent rotations about the long axis of the segment. Lower limb joint angles captured similar patterns for flexion/extension at all joints, ab/adduction at the knee and hip, and toe-in/toe-out at the ankle. These findings indicate that the markerless system would be a suitable alternative technology in cases where the practical benefits of markerless data collection are preferred.

Assessment of spatiotemporal gait parameters using a deep learning algorithm-based markerless motion capture system.

Spatiotemporal parameters can characterize the gait patterns of individuals, allowing assessment of their health status and detection of clinically meaningful changes in their gait. Video-based markerless motion capture is a user-friendly, inexpensive, and widely applicable technology that could reduce the barriers to measuring spatiotemporal gait parameters in clinical and more diverse settings. Two studies were performed to determine whether gait parameters measured using markerless motion capture demonstrate concurrent validity with those measured using marker-based motion capture and a pressure-sensitive gait mat. For the first study, thirty healthy young adults performed treadmill gait at self-selected speeds while marker-based motion capture and synchronized video data were recorded simultaneously. For the second study, twenty-five healthy young adults performed over-ground gait at self-selected speeds while footfalls were recorded using a gait mat and synchronized video data were recorded simultaneously. Kinematic heel-strike and toe-off gait events were used to identify the same gait cycles between systems. Nine spatiotemporal gait parameters were measured by each system and directly compared between systems. Measurements were compared using Bland-Altman methods, mean differences, Pearson correlation coefficients, and intraclass correlation coefficients. The results indicate that markerless measurements of spatiotemporal gait parameters have good to excellent agreement with marker-based motion capture and gait mat systems, except for stance time and double limb support time relative to both systems and stride width relative to the gait mat. These findings indicate that markerless motion capture can adequately measure spatiotemporal gait parameters of healthy young adults during treadmill and over-ground gait.

Inter-session repeatability of markerless motion capture gait kinematics.

The clinical uptake and influence of gait analysis has been hindered by inherent limitations of marker-based motion capture systems, which have long been the standard method for the collection of gait data including kinematics. Markerless motion capture offers an alternative method for the collection of gait kinematics that presents several practical benefits over marker-based systems. This work aimed to determine the reliability of lower limb gait kinematics from video based markerless motion capture using an established experimental protocol for testing reliability. Eight healthy adult participants performed three sessions of five over-ground walking trials in their own self-selected clothing, separated by an average of 8.5 days, while eight synchronized and calibrated cameras recorded video. Three-dimensional pose estimates from the video data were used to compute lower limb joint angles. Inter-session variability, inter-trial variability, and the variability ratio were used to assess the reliability of the gait kinematics. Compared to repeatability studies based on marker-based motion capture, inter-trial variability was slightly greater than previously reported for some angles, with an average across all joint angles of 2.5°. Inter-session variability was smaller on average than all previously reported values, with an average across all joint angles of 2.8°. Variability ratios were all smaller than those previously reported with an average of 1.1, indicating that the multi-session protocol increased the total variability of joint angles by 10% of the inter-trial variability. These results indicate that gait kinematics can be reliably measured using markerless motion capture.

Inter-session agreement and reliability of the Global Gait Asymmetry index in healthy adults.

There has been a growing effort in restoring gait symmetry in clinical conditions associated with pronounced gait asymmetry. A prerequisite to achieve this is that the chosen approach can accurately assess symmetry and detect/impose changes that exceed the natural day to day variability. Global symmetry indices are superior to local and discrete indices because they capture the patient's overall gait symmetry. However, their repeatability is unknown. This study assessed the inter-session agreement and reliability of the Global Gait Asymmetry index. Twenty-three healthy individuals participated in two 3D gait analyses, performed approximately one week apart. The 95% limits of agreement, standard error of measurement, smallest detectable change, and intraclass correlation coefficient were analysed. The obtained values showed this index has poor agreement and reliability between sessions. Therefore, it cannot be used to assess the patient's progress overtime nor to compare symmetry levels among groups.

A Global Gait Asymmetry Index.

High levels of gait asymmetry are associated with many pathologies. Our long-term goal is to improve gait symmetry through real-time biofeedback of a symmetry index. Symmetry is often reported as a single metric or a collective signature of multiple discrete measures. While this is useful for assessment, incorporating multiple feedback metrics presents too much information for most subjects to use as visual feedback for gait retraining. The aim of this article was to develop a global gait asymmetry (GGA) score that could be used as a biofeedback metric for gait retraining and to test the effectiveness of the GGA for classifying artificially-induced asymmetry. Eighteen participants (11 males; age 26.9 y [SD = 7.7]; height 1.8 m [SD = 0.1]; body mass 72.7 kg [SD = 8.9]) walked on a treadmill in 3 symmetry conditions, induced by wearing custom-made sandals: a symmetric condition (identical sandals) and 2 asymmetric conditions (different sandals). The GGA score was calculated, based on several joint angles, and compared between conditions. Significant differences were found among all conditions (P < .001), meaning that the GGA score is sensitive to different levels of asymmetry, and may be useful for rehabilitation and assessment.

The X-Factor: an evaluation of common methods used to analyse major inter-segment kinematics during the golf swing.

A common biomechanical feature of a golf swing, described in various ways in the literature, is the interaction between the thorax and pelvis, often termed the X-Factor. There is no consistent method used within golf biomechanics literature however to calculate these segment interactions. The purpose of this study was to examine X-factor data calculated using three reported methods in order to determine the similarity or otherwise of the data calculated using each method. A twelve-camera three-dimensional motion capture system was used to capture the driver swings of 19 participants and a subject specific three-dimensional biomechanical model was created with the position and orientation of each model estimated using a global optimisation algorithm. Comparison of the X-Factor methods showed significant differences for events during the swing (P < 0.05). Data for each kinematic measure were derived as a times series for all three methods and regression analysis of these data showed that whilst one method could be successfully mapped to another, the mappings between methods are subject dependent (P <0.05). Findings suggest that a consistent methodology considering the X-Factor from a joint angle approach is most insightful in describing a golf swing.

Determination of the swing technique characteristics and performance outcome relationship in golf driving for low handicap female golfers.

Previous studies on the kinematics of the golf swing have mainly focused on group analysis of male golfers of a wide ability range. In the present study, we investigated gross body kinematics using a novel method of analysis for golf research for a group of low handicap female golfers to provide an understanding of their swing mechanics in relation to performance. Data were collected for the drive swings of 16 golfers using a 12-camera three-dimensional motion capture system and a stereoscopic launch monitor. Analysis of covariance identified three covariates (increased pelvis-thorax differential at the top of the backswing, increased pelvis translation during the backswing, and a decrease in absolute backswing time) as determinants of the variance in clubhead speed (adjusted r (2) = 0.965, P < 0.05). A significant correlation was found between left-hand grip strength and clubhead speed (r = 0.54, P < 0.05) and between handicap and clubhead speed (r = -0.612, P < 0.05). Flexibility measures showed some correlation with clubhead speed; both sitting flexibility tests gave positive correlations (clockwise: r = 0.522, P < 0.05; counterclockwise: r = 0.711, P < 0.01). The results suggest that there is no common driver swing technique for optimal performance in low handicap female golfers, and therefore consideration should be given to individual swing characteristics in future studies.

In vivo lumbo-sacral forces and moments during constant speed running at different stride lengths.

The aim of this study was to introduce a Newton-Euler inverse dynamics model that included reaction force and moment estimation at the lumbo-sacral (L5-S1) and thoraco-lumbar (T12-L1) joints. Data were collected while participants ran over ground at 3.8 m x s(-1) at three different stride lengths: preferred stride length, 20% greater than preferred, and 20% less than preferred. Inputs to the model were ground reaction forces, bilateral lower extremity and pelvis kinematics and inertial parameters, kinematics of the lumbar spine and thorax and inertial parameters of the lumbar segment. Repeated measures ANOVA were performed on the lower extremity sagittal kinematics and kinetics, including L5-S1 and T12-L1 three-dimensional joint angles, reaction forces and moments at touchdown and peak values during impact phase across the three stride conditions. Results indicated that L5-S1 and T12-L1 vertical reaction forces at touchdown and during the impact portion of the support phase increased significantly as stride length increased (P < 0.001), as did peak sagittal L5-S1 moments during impact (P = 0.018). Additionally, the transverse T12-L1 joint moment increased as running speed increased (P = 0.006). We concluded from our findings that our model was sensitive to our perturbations in healthy runners, and may prove useful in future mechanistic studies of L5-S1 mechanics.

Neuronal activation in the medulla oblongata during selective elicitation of the laryngeal adductor response.

Swallow and cough are complex motor patterns elicited by rapid and intense electrical stimulation of the internal branch of the superior laryngeal nerve (ISLN). The laryngeal adductor response (LAR) includes only a laryngeal response, is elicited by single stimuli to the ISLN, and is thought to represent the brain stem pathway involved in laryngospasm. To identify which regions in the medulla are activated during elicitation of the LAR alone, single electrical stimuli were presented once every 2 s to the ISLN. Two groups of five cats each were studied; an experimental group with unilateral ISLN stimulation at 0.5 Hz and a surgical control group. Three additional cats were studied to evaluate whether other oral, pharyngeal, or respiratory muscles were activated during ISLN stimulation eliciting LAR. We quantified < or = 22 sections for each of 14 structures in the medulla to determine if regions had increased Fos-like immunoreactive neurons in the experimental group. Significant increases (P < 0.0033) occurred with unilateral ISLN stimulation in the interstitial subnucleus, the ventrolateral subnucleus, the commissural subnucleus of the nucleus tractus solitarius, the lateral tegmental field of the reticular formation, the area postrema, and the nucleus ambiguus. Neither the dorsal motor nucleus of the vagus, usually active for swallow, nor the nucleus retroambiguus, retrofacial nucleus, and the lateral reticular nucleus, usually active for cough, were active with elicitation of the laryngeal adductor response alone. The results demonstrate that the laryngeal adductor pathway is contained within the broader pathways for cough and swallow in the medulla.

A proposed test to support the clinical movement analysis laboratory accreditation process.

This paper describes a testing methodology and resultant set of four variables that can be used to quickly and easily document the correct installation, configuration, and combined working status of force platform (FP) and three-dimensional (3D) motion capture components of a clinical movement analysis (CMA) laboratory. Using a rigid, rod-shaped testing device, CMA laboratory data are collected simultaneously from the FP and motion capture components (typically, video-based kinematic measurements) as the device is manually loaded while being pivoted broadly about a point on the FP. Using a computational method based on static equilibrium, it is possible to independently measure the rod's orientation and tip position during the moving trial, using FP derived data exclusively, and to compare these estimates to rod orientation and tip position estimates derived exclusively from the motion capture component. The motion laboratory accreditation test (MLAT) variables include: the difference (angle) between the orientation of the long axis of the testing device as independently determined from kinematic measures (motion capture component) and the FP derived data; and the difference (x, y, z) between the center of pressure position (FP derived) and the position of the testing device tip (motion capture derived) that loads the FP. A numerical dynamics model was explored to evaluate the appropriateness of the static equilibrium-based FP data model and to determine guidelines for testing device movement frequency and FP loading. The MLAT technique provides a simple means of detecting the combined presence of errors from many sources, several of which are explored in this paper. The MLAT has been developed to help meet one criteria of the CMA laboratory accreditation process, and to serve as a routine quality assessment tool.

Developing an anatomical model of the human laryngeal cartilages from magnetic resonance imaging.

The purpose of this work was to construct a three-dimensional anatomical framework of the cartilages of the human larynx. The framework included representative surface models of the four laryngeal cartilages and estimated attachment points for the intrinsic laryngeal muscles. High-resolution magnetic resonance imaging (MRI) was used to scan one female and four male human cadaveric larynges. The cartilages were segmented manually from the MRI volume for analysis. Two of these larynges were subsequently dissected and the landmark distances on the cartilages measured for comparison with the MRI measures and previous studies. The MRI measures were 8% smaller than the anatomical measures and 12% smaller than data reported in the literature. A laryngeal coordinate system was defined using the plane of symmetry of the cricoid cartilage. Measures of cricoid cartilage symmetry had less than 3% difference between the two sides for a series of measures. An algorithm for registering larynges that minimized the root-mean-square distance between the surface of a reference cricoid cartilage and the surfaces of nonisotropically scaled candidate cricoid cartilages was evaluated. This study provided an anatomical framework for registering different larynges to the same coordinate space.