Camera-based Motion Analysis System Research Articles

Digital Motor Biomarkers of Cerebellar Ataxia Using an RGB-Depth Camera-Based Motion Analysis System.

This study aimed to identify quantitative biomarkers of motor function for cerebellar ataxia by evaluating gait and postural control using an RGB-depth camera-based motion analysis system. In 28 patients with degenerative cerebellar ataxia and 33 age- and sex-matched healthy controls, motor tasks (short-distance walk, closed feet stance, and stepping in place) were selected from a previously reported protocol, and scanned using Kinect V2 and customized software. The Clinical Assessment Scale for the Assessment and Rating of Ataxia (SARA) was also evaluated. Compared with the normal control group, the cerebellar ataxia group had slower gait speed and shorter step lengths, increased step width, and mediolateral trunk sway in the walk test (all P < 0.001). Lateral sway increased in the stance test in the ataxia group (P < 0.001). When stepping in place, the ataxia group showed higher arrhythmicity of stepping and increased stance time (P < 0.001). In the correlation analyses, the ataxia group showed a positive correlation between the total SARA score and arrhythmicity of stepping in place (r = 0.587, P = 0.001). SARA total score (r = 0.561, P = 0.002) and gait subscore (ρ = 0.556, P = 0.002) correlated with mediolateral truncal sway during walking. These results suggest that the RGB-depth camera-based motion analyses on mediolateral truncal sway during walking and arrhythmicity of stepping in place are useful digital motor biomarkers for the assessment of cerebellar ataxia, and could be utilized in future clinical trials.

Effect of Aging on the Trunk and Lower Limb Kinematics during Gait on a Compliant Surface in Healthy Individuals

Older adults have a smaller effective living space and reduced physical activity. Although walking ability in various living spaces is necessary to maintain a healthy life and a high level of physical activity, it is unclear how older adults adapt to compliant surfaces when walking. The purpose of this study was to determine the differences in the trunk and lower limb kinematics while walking on a level versus compliant surface, and the effect of aging on these kinematic changes. Twenty-two healthy individuals (aged from 20–80 years) were asked to walk along a 7-m walkway at a comfortable speed on a level and compliant surface. Gait kinematics were measured using a three-dimensional camera-based motion analysis system. We found that knee and hip flexion and ankle plantarflexion angles in the early stance phase and thoracic flexion angle throughout the gait cycle were significantly increased when walking on a compliant surface versus a level surface. The change in the thoracic flexion angle, ankle plantarflexion angle, and cadence between level and compliant surfaces was significantly correlated with age. Therefore, older adults use increased thoracic flexion and ankle plantarflexion angles along with a higher cadence to navigate compliant surfaces.

Kinect-based objective evaluation of bradykinesia in patients with Parkinson's disease.

To quantify bradykinesia in Parkinson's disease (PD) with a Kinect depth camera-based motion analysis system and to compare PD and healthy control (HC) subjects. Fifty PD patients and twenty-five HCs were recruited. The Movement Disorder Society-Sponsored Revision of the Unified Parkinson's Disease Rating Scale part III (MDS-UPDRS III) was used to evaluate the motor symptoms of PD. Kinematic features of five bradykinesia-related motor tasks were collected using Kinect depth camera. Then, kinematic features were correlated with the clinical scales and compared between groups. Significant correlations were found between kinematic features and clinical scales (P < 0.05). Compared with HCs, PD patients exhibited a significant decrease in the frequency of finger tapping (P < 0.001), hand movement (P < 0.001), hand pronation-supination movements (P = 0.005), and leg agility (P = 0.003). Meanwhile, PD patients had a significant decrease in the speed of hand movements (P = 0.003) and toe tapping (P < 0.001) compared with HCs. Several kinematic features exhibited potential diagnostic value in distinguishing PD from HCs with area under the curve (AUC) ranging from 0.684-0.894 (P < 0.05). Furthermore, the combination of motor tasks exhibited the best diagnostic value with the highest AUC of 0.955 (95% CI = 0.913-0.997, P < 0.001). The Kinect-based motion analysis system can be applied to evaluate bradykinesia in PD. Kinematic features can be used to differentiate PD patients from HCs and combining kinematic features from different motor tasks can significantly improve the diagnostic value.

RGB-Depth Camera-Based Assessment of Motor Capacity: Normative Data for Six Standardized Motor Tasks.

Instrumental motion analysis constitutes a promising development in the assessment of motor function in clinical populations affected by movement disorders. To foster implementation and facilitate interpretation of respective outcomes, we aimed to establish normative data of healthy subjects for a markerless RGB-Depth camera-based motion analysis system and to illustrate their use. We recorded 133 healthy adults (56% female) aged 20 to 60 years with an RGB-Depth camera-based motion analysis system. Forty-three spatiotemporal parameters were extracted from six short, standardized motor tasks-including three gait tasks, stepping in place, standing-up and sitting down, and a postural control task. Associations with confounding factors, height, weight, age, and sex were modelled using a predictive linear regression approach. A z-score normalization approach was provided to improve usability of the data. We reported descriptive statistics for each spatiotemporal parameter (mean, standard deviation, coefficient of variation, quartiles). Robust confounding associations emerged for step length and step width in comfortable speed gait only. Accessible normative data usage was lastly exemplified with recordings from one randomly selected individual with multiple sclerosis. We provided normative data for an RGB depth camera-based motion analysis system covering broad aspects of motor capacity.

Functional movement assessment by means of inertial sensor technology to discriminate between movement behaviour of healthy controls and persons with knee osteoarthritis

BackgroundApart from biomechanical alterations in movement patterns, it is known that movement limitations in persons with knee osteoarthritis (PwKOA) are related to an individual’s perception and belief regarding pain and disability. To gain more insights into the functional movement behaviour of PwKOA in a clinical setting, inertial sensor technology can be applied. This study first aims to evaluate the ability of inertial sensors to discriminate between healthy controls (HC) and PwKOA. Secondly, this study aims to determine the relationship between movement behaviour, pain-related factors and disability scores.MethodsTwelve HC and 19 PwKOA were included. Five repetitions of six functional movement tasks (walking, forward lunge, sideward lunge, ascent and descent stairs, single leg squat and sit-to-stand) were simultaneously recorded by the inertial sensor system and a camera-based motion analysis system. Statistically significant differences in angular waveforms of the trunk, pelvis and lower limb joints between HC and PwKOA were determined using one-dimensional statistical parametric mapping (SPM1D). The Knee injury and Osteoarthritis Outcome Score and TAMPA scale for Kinesiophobia were used to evaluate the relationship between discriminating joint motion, pain-related factors and disability using spearman’s correlation coefficients.ResultsPwKOA had significantly less trunk rotation, internal pelvis rotation and knee flexion ROM during walking. Additionally, the reduced knee flexion (i.e. at the end of the stance phase and swing phase) was related to increased level of perceived pain. During the sideward lunge, PwKOA had significantly less knee flexion, ankle plantarflexion and hip abduction. This decreased hip abduction (i.e. during stance) was related to higher fear of movement. Finally, PwKOA had significantly less knee flexion during the forward lunge, single leg squat and during ascent and descent stairs. No significant correlations were observed with disability.ConclusionsInertial sensors were able to discriminate between movement characteristics of PwKOA and HC. Additionally, significant relationships were found between joint motion, perceived pain and fear of movement. Since inertial sensors can be used outside the laboratory setting, these results are promising as they indicate the ability to evaluate movement deviations. Further research is required to enable measurements of small movement deviations in clinically relevant tasks.

Bit type exerts an influence on self-controlled rein tension in unridden horses

Bit configuration and acting rein forces play a crucial role in oral health and comfort of ridden horses. Although it is a big animal welfare issue, dynamic response of horses to different bits has yet not been thoroughly investigated. This convenience sample experimental study describes a model to overcome the almost uncontrollable influence of riders on rein tension and evaluates self-controlled maximum side rein tension of ten sound horses randomly bitted with a double-jointed (DJS) and a version of a Mullen mouth snaffle-bit under unridden conditions. Horses were exercised at walk and trot on a horizontal treadmill wearing custom made force-sensing resistors (FSR) equipped to side reins. FSR were synchronized with a camera-based motion analysis system providing information on amplitudes and temporal occurrence of self-controlled maximum side rein tensile forces during different phases of separated motion cycles. The DJS exhibited larger side rein tension, indicating higher bit contact. Constant temporal occurrence of monophasic maxima at walk and biphasic maxima at trot could be observed in both bits. Within the limitations of this study, application of FSR linked to side reins in unridden horses may provide a promising tool when studying subjective response of horses to different bits.

Detection and Quantification of Screw-Home Movement Using Nine-Axis Inertial Sensors

Purpose: Although previous studies on the screw-home movement (SHM) for autopsy specimen and walking of living persons conduc­t ed, the possibility of acquiring SHM based on inertial measurement units received little attention. This study aimed to investigate the possibility of measuring SHM for the non-weighted bearing using a micro-electro-mechanical system-based wearable motion capture system (MEMSS). Methods: MEMSS and camera-based motion analysis systems were used to obtain kinematic data of the knee joint. The knee joint moved from the flexion position to a fully extended position and then back to the start point. The coefficient of multiple correlation and the difference in the range of motion were used to assess the waveform similarity in the movement measured by two measurement sys­ tems. Results: The waveform similarity in the sagittal plane was excellent and the in the transverse plane was good. Significant differences were found in the sagittal plane between the two systems (p 0.05). Conclusion: The SHM during the passive motion without muscle contraction in the non-weighted bearing appeared in the entire range. We thought that the MEMSS could be easily applied to the acquisition of biomechanical data on the knee related to physical therapy.

Experimental Validation of the Tyndall Portable Lower-limb Analysis System with Wearable Inertial Sensors

Biomechanical analysis of movement during sport practice is extremely useful to assess and, subsequently, optimise movement performance during sport which can also assist athletes during rehabilitation following injury (such as Anterior Cruciate Ligament reconstruction). It is mostly performed using camera-based motion analysis systems, which provide good results but present serious drawbacks (for instance, consistent size, high cost, and lack of portability). Thus, small-size low-cost wearable sensors are an emerging tool for biomechanics monitoring. Aim of the present work is to implement a novel wireless portable easy-to-use system, consisting of two Tyndall Wireless Inertial Measurement Units (WIMUs) per leg, suitable for free-living environments and able to provide a complete biomechanics assessment (generated on a report) without the constraints of a laboratory. Validation for the lower-limbs using state-of-the-art camera-based motion capture is presented here. Algorithms are implemented in Matlab, and the scenarios considered simulate a free-living environment and exercises performed in a rehabilitation procedure. The system has been validated with healthy and impaired subjects. This novel system shows high accuracy values for all considered scenarios. Moreover, it is able to detect atypical movement characteristics. The results of this feasibility study support the next phase which will be to assess the external and ecological validity of athletes’ on-field movement performance, which will help to inform individualised training protocols or enhance targeted rehabilitation programmes.

Impact of Ulnar Collateral Ligament Tear on Posteromedial Elbow Biomechanics.

Ulnar collateral ligament insufficiency has been shown to result in changes in contact pressure and contact area in the posteromedial elbow. This study used new digital technology to assess the effect of a complete ulnar collateral ligament tear on ulnohumeral contact area, contact pressure, and valgus laxity throughout the throwing motion. Nine elbow cadaveric specimens were tested at 90° and 30° of elbow flexion to simulate the late cocking/early acceleration and deceleration phases of throwing, respectively. A digital sensor was placed in the posteromedial elbow. Each specimen was tested with valgus torque of 2.5 Nm with the anterior band of the ulnar collateral ligament intact and transected. A camera-based motion analysis system was used to measure valgus inclination of the forearm with the applied torque. At 90° of elbow flexion, mean contact area decreased significantly (107.9 mm(2) intact vs 84.9 mm(2) transected, P=.05) and average maximum contact pressure increased significantly (457.6 kPa intact vs 548.6 kPa transected, P<.001). At 30° of elbow flexion, mean contact area decreased significantly (83.9 mm(2) intact vs 65.8 mm(2) transected, P=.01) and average maximum contact pressure increased nonsignificantly (365.9 kPa intact vs 450.7 kPa transected, P=.08). Valgus laxity increased significantly at elbow flexion of 90° (1.1° intact vs 3.3° transected, P=.01) and 30° (1.0° intact vs 1.7° transected, P=.05). Ulnar collateral ligament insufficiency was associated with significant changes in contact area, contact pressure, and valgus laxity during both relative flexion (late cocking/early acceleration phase) and relative extension (deceleration phase) moments during the throwing motion arc.

Triaxial joint moment estimation using a wearable three-dimensional gait analysis system

We developed a wireless sensor system composed of a mobile force plate system, three-dimensional (3D) motion sensor units and a wireless data logger. Triaxial joint moments of the ankle, knee and hip joints were calculated using measurements of the sensor system. The accuracy of the joint moment estimation is validated against results obtained from the reference measurement system composed of a camera based motion analysis system and force plates. Triaxial joint moments measured by the sensor system showed normalized root mean square error (NRMSE) and correlation coefficient (R) of less than 22% and more than 0.80 in comparison with the stationary system.

Three Dimensional Gait Analysis Using Wearable Acceleration and Gyro Sensors Based on Quaternion Calculations

This paper proposes a method for three dimensional gait analysis using wearable sensors and quaternion calculations. Seven sensor units consisting of a tri-axial acceleration and gyro sensors, were fixed to the lower limbs. The acceleration and angular velocity data of each sensor unit were measured during level walking. The initial orientations of the sensor units were estimated using acceleration data during upright standing position and the angular displacements were estimated afterwards using angular velocity data during gait. Here, an algorithm based on quaternion calculation was implemented for orientation estimation of the sensor units. The orientations of the sensor units were converted to the orientations of the body segments by a rotation matrix obtained from a calibration trial. Body segment orientations were then used for constructing a three dimensional wire frame animation of the volunteers during the gait. Gait analysis was conducted on five volunteers, and results were compared with those from a camera-based motion analysis system. Comparisons were made for the joint trajectory in the horizontal and sagittal plane. The average RMSE and correlation coefficient (CC) were 10.14 deg and 0.98, 7.88 deg and 0.97, 9.75 deg and 0.78 for the hip, knee and ankle flexion angles, respectively.

A Preliminary Assessment of a Novel Pneumatic Unloading Knee Brace on the Gait Mechanics of Patients With Knee Osteoarthritis

To determine whether a knee brace incorporating inflatable air bladders can alter the net peak external knee adduction moment in persons with medial compartment knee osteoarthritis. Prospective cohort study. Motion analysis laboratory. Subjects (n= 18) diagnosed with knee osteoarthritis as defined by the Diagnostic and Therapeutic Criteria Committee of the American Rheumatism Association. Instrumented gait analysis was performed while subjects walked with and without the knee brace. When subjects wore the knee brace, the air bladders were either uninflated or inflated to 7 psi. The net external knee adduction moment was obtained by subtracting the abduction moment produced by the knee brace (estimated using a finite element analysis model) from the external knee adduction moment (estimated using a camera-based motion analysis system). The net external knee adduction moment was compared across all testing conditions. A 7.6% decrease in net peak external knee adduction moment was observed when subjects wore the knee brace uninflated compared with when they did not wear the brace. Inflation of the bladders to 7 psi led to a 26.0% decrease in net peak external knee adduction moment. The results of the study suggest that the effects of an unloading knee brace may be enhanced by incorporating inflatable air bladders into the design of the brace, thus leading to an improved correction of the excessive peak external knee adduction moment observed in patients with medial compartment knee osteoarthritis.

3-D Localization of Human Based on an Inertial Capture System

This paper introduces a method to track the spatial location and movement of a human using wearable inertia sensors without additional external global positioning devices. Starting from the lower limb kinematics of a human, the method uses multiple wearable inertia sensors to determine the orientation of the body segments and lower limb joint motions. At the same time, based on human kinematics and locomotion phase detection, the spatial position and the trajectory of a reference point on the body can be determined. An experimental study has shown that the position error can be controlled within 1-2% of the total distance in both indoor and outdoor environments. The system is capable of localization on irregular terrains (like uphill/downhill). From the localization results, the ground shape and the height information that can be recovered after localization experiments are conducted. A benchmark study on the accuracy of this method was carried out using the camera-based motion analysis system to study the validity of the system. The localization data that are obtained from the proposed method match well with those from the commercial system. Since the sensors can be worn on the human at any time and any place, this method has no restriction to indoor and outdoor applications.

Vibration Measurement and Data Analysis of a Spinning Shaft Using a Camera-Based Motion Analysis System

This paper presents the use of a camera-based 3D motion analysis system for non-contact dynamic testing of a highly flexible spinning vertical shaft. The camera system uses high-resolution CMOS cameras to measure instant geometry of the shaft when visible red digital LED strobes are synchronized to work at a speed between 0.1 to 2000 frames per second. Dynamically deformed geometries are obtained by tracing the three-dimensional instantaneous coordinates of markers adhered to the shaft’s outside surface and triangulation techniques for identifying markers’ coordinates. Numerical simulation and experimental results show that the use of camera-based motion analysis systems is feasible and accurate enough for dynamic experiments. For dynamics characterization, we present the use of the Hilbert-Huang transform (HHT) for time frequency analysis of measured dynamic responses. The results show that the third-mode vibration has a cubic nonlinearity.

Camera-based noncontact metrology for static/dynamic testing of flexible multibody systems

Presented here is a camera-based noncontact measurement theory for static/dynamic testing of flexible multibody systems that undergo large rigid, elastic and/or plastic deformations. The procedure and equations for accurate estimation of system parameters (i.e. the location and focal length of each camera and the transformation matrix relating its image and object coordinate systems) using an L-frame with four retroreflective markers are described in detail. Moreover, a method for refinement of estimated system parameters and establishment of a lens distortion model for correcting optical distortions using a T-wand with three markers is described. Dynamically deformed geometries of a multibody system are assumed to be obtained by tracing the three-dimensional instantaneous coordinates of markers adhered to the system's outside surfaces, and cameras and triangulation techniques are used for capturing marker images and identifying markers' coordinates. Furthermore, an EAGLE-500 motion analysis system is used to demonstrate measurements of static/dynamic deformations of six different flexible multibody systems. All numerical simulations and experimental results show that the use of camera-based motion analysis systems is feasible and accurate enough for static/dynamic experiments on flexible multibody systems, especially those that cannot be measured using conventional contact sensors.