- A novel device for improving marker placement accuracy "Background: Repeatability of marker placement has been acknowledged as a major factor affecting the reliability of multi-segment foot models. A novel device is proposed that is intended to reduce marker placement error and its effect on the reliability of inter-segmental foot kinematic data is investigated."
- Analysis of accuracy in optical motion capture – A protocol for laboratory setup evaluation "Validity and reliability as scientific quality criteria have to be considered when using optical motion capture (OMC) for research purposes. Literature and standards recommend individual laboratory setup evaluation. However, system characteristics such as trueness, precision and uncertainty are often not addressed in scientific reports on 3D human movement analysis. One reason may be the lack of simple and practical methods for evaluating accuracy parameters of OMC. A protocol was developed for investigating the accuracy of an OMC system (Vicon, volume 5.5!1.2!2.0 m3) with standard laboratory equipment and by means of trueness and uncertainty of marker distances. The study investigated the effects of number of cameras (6, 8 and 10), measurement height (foot, knee and hip) and movement condition (static and dynamic) on accuracy."
- Analysis of measurement performance in optical motion capturing - (extended abstracts) Analysis of accuracy in optical motion capture – A protocol for laboratory setup evaluation
- Cane-Assisted Gait Biomechanics and Electromyography After Total Hip Arthroplasty "OBJECTIVE: To quantify the effects of cane use during walking on hip joint kinematics, kinetics, and muscle activity patterns after unilateral total hip arthroplasty (THA). DESIGN: Nonrandomized experimental design."
- Design and evaluation of a new three-dimensional motion capture system based on video SOMCAM3D "This technical note describes the development and evaluation of a low-cost motion capture and analysis system (SOMCAM3D). From diverse video sequences obtained by commercial cameras, synchronized by a certain event, and calibrated from a calibration process, the system is able to reconstruct three-dimensional positions in a reference system defined by the calibration process. From these positions, a wide variety of kinematic variables could be calculated. This system aims to analyze movement in applications of gait analysis, sports, animals, ergonomics, robotics, etc."
- Fish-eye lens Calibration Intrinsic parameter calibration procedure for a (high-distortion) fish-eye lens camera with distortion model and accuracy estimation
- GaitRite walkway system Reliability of the GAITRite walkway system for the quantification of temporo-spatial parameters of gait in young and older people
- Reducing the number of cameras and increasing the calibrated volume - (open access) "Despite advances in motion capture systems, camera placement is still a challenging task, requiring expertise and experience, especially when the scene to acquire is complex and encumbered. In order to assist experimenters in this task, Aissaoui et al. (2014) proposed to develop an algorithm-based optimization, which aims to find the optimal position of the cameras. In continuity, 2 questions arise: (1) Can we reduce the number of cameras, despite the presence of an obstacle, without reducing the calibrated volume? (2) Can we increase the volume calibrated with the same number of cameras, which would be better positioned? The objective of this paper is to shed light on these questions through the application of the developed algorithm."
"Validity and reliability as scientific quality criteria have to be considered when using motion capture systems for research purposes. System characteristics such as accuracy and precision are often not addressed in scientific reports of human motion analysis studies, even though literature and standards recommend individual laboratory setup evaluation. One reason could be due to the lack of a simple and practical method to evaluate system performance. We developed a protocol for practical laboratory setup evaluation in context of usability in human movement analysis."
"This paper presents a calibration procedure for a fish-eye lens (a high-distortion lens) mounted on a CCD TV camera. The method is designed to account for the differences in images acquired via a distortion-free lens camera setup and the images obtained by a fish-eye lens camera. The calibration procedure essentially defines a mapping between points in the world coordinate system and their corresponding point locations in the image plane. This step is important for applications in computer vision which involve quantitative measurements. The objective of this mapping is to estimate the internal parameters of the camera, including the effective focal length, one-pixel width on the image plane, image distortion center, and distortion coefficients."
"The purpose of this study was to evaluate the test-retest reliability of an instrumented walkway system (the GAITRite mat) for the measurement of temporal and spatial parameters of gait in young and older people. Thirty young subjects (12 males, 18 females) aged between 22 and 40 years (mean 28.5, S.D. 4.8) and 31 older subjects (13 males, 18 females) aged between 76 and 87 years (mean 80.8, S.D. 3.1) walked at a self-selected comfortable walking speed across the pressure-sensor mat three times and repeated the process approximately 2 weeks later."
Depth Camera Motion Assessment and Markerless MoCap System
- A Kinect-Based Movement Assessment System: Marker Position Comparison to Vicon "Accurate movement analysis systems are prohibitive in cost and size to be accessible to the general population while commercially available, affordable systems lack the accuracy needed for clinical relevance. To address these limitations, we have developed a Depth Camera Movement Assessment System (DCMAS) that features an affordable, widely available depth camera, such as the Microsoft Kinect. After examining position data for markers adhered to participants and a flat surface captured both with the DCMAS and the industry standard Vicon system, we then demonstrate that the DCMAS can be used to obtain 3D marker position measurements that are comparable, within soft tissue artifact, to the Vicon system. Our results pave the way for a breakthrough technology in preventative medicine."
- Accuracy and repeatability of joint angles Accuracy and repeatability of joint angles measured using a single camera markerless motion capture system "Markerless motion capture systems have developed in an effort to evaluate human movement in a natural setting. However, the accuracy and reliability of these systems remain understudied. Therefore, the goals of this study were to quantify the accuracy and repeatability of joint angles using a single camera markerless motion capture system and to compare the markerless system performance with that of a marker-based system."
- Comparative abilities of Microsoft Kinect and Vicon 3D motion capture for gait analysis "Biomechanical analysis is a powerful tool in the evaluation of movement dysfunction in orthopaedic and neurologic populations. Three-dimensional (3D) motion capture systems are widely used, accurate systems, but are costly and not available in many clinical settings. The Microsoft Kinect has the potential to be used as an alternative low-cost motion analysis tool. The purpose of this study was to assess concurrent validity of the Kinect with Brekel Kinect software in comparison to Vicon Nexus during sagittal plane gait kinematics."
- Estimating Sit-to-Stand Dynamics using a Single Depth Camera "Abstract—Kinetic and dynamic motion analysis provides quantitative, functional assessments of human ability that are unobtainable through static imaging methods or subjective surveys. While biomechanics facilities are equipped to perform this measurement and analysis, the clinical translation of these methods is limited by the specialised skills and equipment needed. This paper presents and validates a method for estimating dynamic effects such as joint torques and body momenta using a single depth camera."
- Evaluation of Calibrated Kinect Gait Kinematics Using a Vicon Motion Capture System - (open access) "Several studies have been conducted in evaluating the Kinect sensor using another gold standard device (Springer & Seligmann 2016)(Pfister et al. 2014). For these works, gait kinematic parameters were obtained independently from each system. In the negative, we performed a calibration procedure between the Kinect and the Vicon gold standard device. Thereby, kinematics data can be written in the same reference frame, and hence, joint centers can be defined as same for both systems. The aim of this work is to evaluate the validity of the Kinect for gait kinematics analysis in comparison to the Vicon system where a Cartesian calibration is made for both motion capture devices."
- Gait analysis using a single depth camera "Gait analysis is often used as part of the rehabilitation program for post-stoke recovery assessment. Since current optical diagnostic and patient assessment tools tend to be expensive and not portable, this paper proposes a novel marker-based tracking system using a single depth camera which provides a cost-effective solution suitable for home and clinic use. The proposed system can simultaneously generate motion patterns even within a complex background using the proposed geometric model-based algorithm and autonomously provide gait analysis results."
- Kinect as a Tool for Gait Analysis - (open access) Kinect as a Tool for Gait Analysis: Validation of a Real-Time Joint Extraction Algorithm Working in Side View "The Microsoft Kinect sensor has gained attention as a tool for gait analysis for several years. Despite the many advantages the sensor provides, however, the lack of a native capability to extract joints from the side view of a human body still limits the adoption of the device to a number of relevant applications. This paper presents an algorithm to locate and estimate the trajectories of up to six joints extracted from the side depth view of a human body captured by the Kinect device."
- Kinematic and Kinetic Validation Kinematic and Kinetic Validation of an Improved Depth Camera Motion Assessment System Using Rigid Bodies "The study of joint kinematics and dynamics has broad clinical applications, including the identification of pathological motions or compensation strategies and the analysis of dynamic stability. High-end motion capture systems, however, are expensive and require dedicated camera spaces with lengthy setup and data processing commitments. Depth cameras, such as the Microsoft Kinect, provide an inexpensive, marker-free alternative at the sacrifice of joint-position accuracy. In this work, we present a fast framework for adding biomechanical constraints to the joint estimates provided by a depth camera system. We also present a new model for the lower lumbar joint angle. We validate key joint position, angle, and velocity measurements against a gold standard active motion-capture system on ten healthy subjects performing sit to stand (STS)."
- Markerless Human Motion Tracking Using Microsoft Kinect SDK and Inverse Kinematics "Motion capture systems are used to gauge the kinematic features of the motion in numerous fields of research. Despite superb accuracy performance, the commercial systems are costly and difficult to use. To solve these issues, Kinect has been proposed as a low-priced markerless motion capture sensor, and its accuracy has been assessed using previous motion capture systems. However, in many of these studies, the anatomical joint angles captured using the Kinect are compared to the 3D rotation angles reported by the gold standard motion capture systems. These incompatibilities in the determination of the human joint angles can lead to higher error estimation. To accomplish a valid accuracy evaluation of the Kinect, we applied the inverse kinematics techniques in both Vicon and Kinect version 2 skeleton models to estimate lower body joint angles. The proposed method enabled us to capture the pelvic, hip, and knee joint angles using a single Kinect camera during gait."
- Towards a marker-less human gait analysis system International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B5. Amsterdam 2000 "A non–invasive system is described which is capable of extracting and describing the three–dimensional nature of humangait thereby extending the use of gait as a biometric. Of current three–dimensional systems, those using multiple viewsappear to be the most suitable. Reformulating the three–dimensional analysis algorithm known as Volume Intersectionas an evidence gathering process for moving object extraction gives means to overcome concavities and to handle noiseand occlusion. Results on synthetic imagery show that the technique does indeed process a multi-view image sequence toderive the parameters of interest thereby providing a suitable basis for future development as a marker-less gait analysissystem."
Massachusetts General Hospital, Biomotion Laboratory
Gait Analysis Using a Wireless Shoe-Integrated Sensor System
- Wireless Shoe-Integrated Sensor System: GaitShoe "This paper describes a wireless wearable system capable of measuring many parameters relevant to gait analysis, and developed to provide quantitative analysis of gait outside of the confines of the traditional motion laboratory. The extensive sensor suite includes three orthogonal accelerometers, and three orthogonal gyroscopes, four force sensors, two bi-directional bend sensors, two dynamic pressure sensors, as well as electric field height sensors. The "GaitShoe" was built to be worn on any athletic shoe, without interfering with gait, and was designed to collect data unobtrusively, in any environment, and over long periods of time. The calibrated sensor outputs were analyzed and validated with results obtained simultaneously from The Massachusetts General Hospital Biomotion Lab during subject testing. The GaitShoe proved highly capable of detecting heel strike and toe off, as well as estimating orientation and position of the subject."