3D Motion Capture Research Articles

Validity and reliability of running gait measurement with the ViMove2 system.

Running biomechanics have traditionally been analysed in laboratory settings, but this may not reflect natural running gait. Wearable technology has the potential to enable precise monitoring of running gait beyond the laboratory. This study aimed to evaluate the analytical validity and intra-session reliability of temporal running gait outcomes measured by the ViMove2 wearable system in healthy adults. Seventy-four healthy adults (43 males, 31 females, aged 18-55 years) wore the inertial device, ViMove2 on the tibia. Participants ran on a treadmill for one minute at various speeds (8, 10, 12, 14km/hr), completed in a standardised shoe (Saucony Guide Runner). Running gait was measured with the ViMove2 wearable and 3D motion capture (Vicon). Temporal running gait outcomes included ground contact time (GCT) and cadence (steps/min). GCT and cadence from the ViMove2 had face validity with expected changes in outcome with different running speeds, but ViMove2 tended to over-estimate GCT, and under-estimate cadence compared to the reference, especially at slower speeds. GCT demonstrated moderate to good agreement to the reference at speeds >10km/hr, but poor agreement at 8km/hr and within female runners. Cadence had moderate to excellent agreement across speeds compared to the reference. GCT and cadence had excellent reliability across speeds, but at 8km/hr GCT had good agreement between trials. Overall, temporal gait outcomes of GCT and cadence can be measured with the ViMove2, but accuracy and reliability are impacted at slow running speeds and within female runners. Future work is needed to clarify sex or speed-dependent corrections to algorithms / outcomes to aid interpretation and application.

Advances in Markerless Motion Capture Systems: A Review of OpenCap and Its Applications

Motion capture technology has long been a cornerstone of biomechanical research and analysis, traditionally relying on marker-based systems. However, these systems have inherent limitations, including high costs, time-consuming setup, and constraints on natural movement. Recent advancements in computer vision and machine learning have paved the way for markerless motion capture systems, such as OpenCap, which offer a more accessible and natural approach to biomechanical analysis. This review focuses on OpenCap, exploring its accuracy, challenges, and future potential, while comparing it with traditional motion capture technologies and discussing its applications in sports, clinical rehabilitation, and everyday use. Areas in need of refinement, such as improving pose estimation algorithms and addressing inter-trial variability, are identified as key future research directions. Other markerless systems are also compared in terms of advantages, limitations, and application. The findings suggest that while OpenCap and similar systems hold significant promise, further research and refinement are necessary to fully realize their potential and integrate them seamlessly into various biomechanical applications.

The Kinetic and Kinematic Efficacy of Posterior Leaf Spring Ankle-foot Orthosis in Patients with Drop foot

Background: Dorsi flexor weakness is one of the common consequences of stroke with a negative impact on normal walking. Posterior leaf spring (PLS) Ankle Foot Orthosis (AFO) is the most frequent prescription to assist foot clearance and leg propulsion in these patients. However, the real efficacy of this AFO needs more attention. This study aimed to investigate the efficacy of PLS AFO on gait outcomes as the most common AFO in drop foot post-stroke patients. Methods: The study design was a pre–post-test experiments in which twenty drop foot patients with a mean age of 65 years with a mean age of 58.45 (±5.23) years who were 4/5 years post-stroke. They walked at self-selected walking speed on a 10 meters walk away in two conditions of with their own shoes and PLS AFO. The 3D motion capture gait analysis system including 6 vicon cameras and a Kistler force plate were used in order to measure gait kinetic and kinematic variables. For each trial, each joints (ankle, knee and hip) angle, moment and power were averaged over one-minute walking. Results: Walking with PLS showed a statistically significant improve kinetic and kinematic variables in hip, knee and ankle joints included power, moments and angles at entire gait cycle. P<0.05. Conclusions: In our study of stroke patients who were fitted with a PLS AFO, immediate significant improvements occurred in most kinetic and kinematic than shoes only in sacrifice some others.

Body of Mine, Yours, and Everyone in Between: Communicating Gender Dysphoria Through Immersive Storytelling

<div><span>This article explores the potential of new, immersive realities to convey the complex experiences of gender dysphoria and body dissatisfaction, using the innovative and multi-award-winning experience <em>Body of Mine</em> as a case study. Recognizing a gap in understanding and empathy towards gender-queer communities, <em>Body of Mine</em> employs an innovative full-body tracking solution to place users into the body of someone else, combined with first-person documentary interviews and interactive elements aimed at fostering a deeper connection and insight into the transgender experience. Initial feedback from users indicates a heightened awareness and emotional connection to the challenges faced by individuals with gender dysphoria, as well as an increase in self-body positivity, based on a study conducted in collaboration with the University of Tübingen’s Department of Psychology. This project underscores the power of immersive storytelling in fostering embodied understanding, while also acknowledging the ethical complexities and voyeuristic risks when sharing narratives from vulnerable communities, and explores innovative methods for tackling social issues through emerging technology. It concludes by contemplating the implications of immersive technologies for the concept of identity in a world that increasingly transcends the physical body, suggesting a future where the notion of self is not confined to physical form but is fluid, multifaceted, and continually redefined within boundless digital horizons.</span></div>

Baby’s first jets: a kinematic and hydrodynamic analysis of turning in cuttlefish hatchlings

AbstractTurning is an important aspect of life underwater, playing integral roles in predator avoidance, prey capture, and communication. While turning abilities have been explored in a diversity of adult nekton, little is currently known about turning in early ontogeny, especially for cephalopods. In this study, we investigated the turning abilities of hatchling common cuttlefish (Sepia officinalis, n = 49) and dwarf cuttlefish (Sepia bandensis, n = 30), using both kinematic and wake-based analyses. Using body tracking software and particle image velocimetry (PIV), we found that S. officinalis turned faster than S. bandensis, but both species completed equally tight turns. Orientation (arms-first or tail-first) did not have a significant effect on turning performance for either species. Cuttlefish hatchlings used multiple short jets for more controlled turning, with jet mode I (isolated vortex rings) being 3–4 times more common than jet mode II (elongated jets with leading ring structures) for both species. While both hatchlings turned more broadly than adult squid and cuttlefish, S. officinalis hatchlings turned faster than adult cuttlefish, and both hatchlings turned more tightly than other jet-propelled animals and some non-jet-propelled swimmers.

Comparison of gait deviation index (GDI) and gait variability index (GVI) measured by marker-based and markerless motion capture systems in children with cerebral palsy (CP)

BackgroundThe Gait Deviation Index (GDI) is a metric clinicians use to assess overall gait pathology in children with cerebral palsy (CP) by comparing kinematic data to a normative sample. The Gait Variability Index (GVI) is a related metric that quantifies the variability in spatio-temporal variables during gait. The GDI and GVI have been verified using marker-based motion capture approaches, but video-based markerless motion capture has not been compared using these tools in children with CP. Research questionDo GDI and GVI scores differ when measured using markerlessTheia3D and a marker-based approach between the more and less affected legs in children with CP? MethodsFifteen children with CP (GMFCS levels I-IV) and 24 typically developing children aged 6–18 years were recruited for this study. Overground walking was performed at a self-selected pace while the pelvis and lower limb kinematics were simultaneously recorded using both motion capture systems. Differences in GDI and GVI scores when considering the effect of system and limb impairment were analyzed using two-way repeated-measures ANOVAs. ResultsGDI scores were 6.9 points lower (p < 0.05) when measured using Theia3D compared to the marker-based approach and 6.8 points lower (p < 0.05) in the more affected limbs than in the less affected limbs. These GDI score differences are considered clinically significant. No differences were identified in GVI scores between systems or limb impairment. Differences in kinematic measurements were found in children with CP, including pelvic tilt, hip flexion/extension, hip rotation, and foot progression angle, where root mean square differences between systems exceeded 10°. SignificanceTheia3D can adequately measure variability in spatio-temporal gait parameters for quantifying GVI scores in children with CP compared to the marker-based approach. However, caution is needed when quantifying lower limb kinematics and interpreting GDI and GVI scores using Theia3D in children with CP.

Validity and reliability of trunk and lower-limb kinematics during squatting, hopping, jumping and side-stepping using OpenCap markerless motion capture application

ABSTRACT OpenCap is a web-based markerless motion capture platform that estimates 3D kinematics from videos recorded from at least two iOS devices. This study aimed to determine the concurrent validity and inter-session reliability of OpenCap for measuring trunk and lower-limb kinematics during squatting, hopping, countermovement jumping, and cutting. Nineteen participants (10 males, 9 females; age 27.7 ± 4.1 years) were included. Countermovement jump, single-leg triple vertical hop, single-leg squat, sidestep cutting and side hop tasks were assessed. For validity, OpenCap was compared to a marker-based motion capture system using root-mean-square error. Test–retest reliability of OpenCap was determined using intraclass correlations and minimum detectable change (MDC) from two testing sessions. The squat had the lowest RMSE across joint angles (mean = 7.0°, range = 2.9° to 13.6°). For peak angles, the countermovement jump (jump phase) (ICC = 0.62–0.93) and the squat (ICC = 0.60–0.92) had the best reliability across all joints. For initial contact, the side hop had the best inter-session reliability (ICC = 0.70–0.94) across all joint angles. As such, OpenCap validity and reliability are joint and task specific.

Investigating Creation Perspectives and Icon Placement Preferences for On-Body Menus in Virtual Reality

On-body menus present a novel interaction paradigm within Virtual Reality (VR) environments by embedding virtual interfaces directly onto the user’s body. Unlike traditional screen-based interfaces, on-body menus enable users to interact with virtual options or icons visually attached to their physical form. In this paper, We investigated the impact of the creation process on the effectiveness of on-body menus, comparing first-person, third-person, and mirror perspectives. Our first study ( N = 12) revealed that the mirror perspective led to faster creation times and more accurate recall compared to the other two perspectives. To further explore user preferences, we conducted a second study ( N = 18) utilizing a VR system with integrated body tracking. By combining distributions of icons from both studies ( N = 30), we confirmed significant preferences in on-body menu placement based on icon category ( e.g. , Social Media icons were consistently placed on forearms). We also discovered associations between categories, such as Leisure and Social Media icons frequently co-occurring. Our findings highlight the importance of the creation process, uncover user preferences for on-body menu organization, and provide insights to guide the development of intuitive and effective on-body interactions within virtual environments.

The Validity and Usability of Markerless Motion Capture and Inertial Measurement Units for Quantifying Dynamic Movements

ABSTRACT Purpose Motion capture technology is quickly evolving providing researchers, clinicians, and coaches with more access to biomechanics data. Markerless motion capture and inertial measurement units (IMUs) are continually developing biomechanics tools that need validation for dynamic movements before widespread use in applied settings. This study evaluated the validity of a markerless motion capture, IMU, and red, green, blue, and depth (RGBD) camera system as compared to marker-based motion capture during countermovement jumps, overhead squats, lunges, and runs with cuts. Methods Thirty adults were recruited for this study (sex: 18 females, 12 males; age: 25.4 ± 8.6 years; height: 1.71 ± 0.08 m; weight: 71.6 ± 11.5 kg). Data were collected simultaneously with four motion capture technologies (i.e., Vicon – marker-based, Theia/Optitrack – markerless, APDM Opals – IMUs, and Vald HumanTrak – RGBD camera). System validity for lower and upper body joint angles was evaluated using bias, root mean squared error (RMSE), precision, maximum absolute error, and intraclass correlation coefficients. System usability was descriptively analyzed. Results Overall, markerless motion capture had the highest validity (sagittal plane RMSE: 3.20-15.66°; frontal plane RMSE: 2.12-9.14°; transverse plane RMSE: 3.160-56.61°), followed by the IMU system (sagittal plane RMSE: 8.11-28.37°; frontal plane RMSE: 3.26-16.98°; transverse plane RMSE: 5.08-116.75°), and lastly the RGBD system (sagittal plane bias: 0.55-129.48°; frontal plane bias: 1.35-52.06°). Conclusions Markerless motion capture and IMUs have moderate validity for joint kinematics, while the RGBD system did not have adequate validity. Markerless systems have lower data processing time, require moderate technical expertise, but have high data storage size. IMUs are easier to use, can collect data in any location, but require participant set-up. Overall, individuals using motion capture should consider the specific movements, testing locations, and technical expertise available prior to selecting a system.

Correlation between the biomechanical characteristics and stability of the 143D movement during the balance phase in competitive Tai Chi.

To explore the biomechanical factors affecting the stability of athletes in the 143D balance phase of competitive Tai Chi. The Vicon 3D motion capture system, Kistler 3D force platform, and Noraxon surface electromyography (sEMG) system were used to measure the joint angle, joint moment, center of gravity, ground reaction force, and sEMG data of athletes. The stability index was then calculated according to the formula. Pearson's or Spearman's correlation tests were used to analyze the associations between the biomechanical factors and stability index. (1) Medial lateral stability index (MLSI): A significant negative correlation was found between the ankle inversion angle of the supporting leg (SL) and MLSI (p < 0.05). (2) Anterior posterior stability index (APSI): Significant negative correlations were observed between the ankle intorsion angle, integrated electromyography (iEMG) of the gastrocnemius, and muscle contribution rates of the tibialis anterior, external oblique, and gastrocnemius of the non-supporting leg (NL) with the APSI (p < 0.05). The ankle dorsiflexion moment, iEMG of the rectus femoris and tibialis anterior, muscle contribution rate of the biceps femoris, and root mean-squared (RMS) amplitude of the gluteus maximus of the SL also showed significant negative correlations with the APSI (p < 0.05). Strong and significant negative correlations were also identified between the hip intorsion angle, iEMG of the tibialis anterior, and RMS amplitude of the rectus femoris of the NL with the APSI (p < 0.01). Further strong and significant negative correlation was also found between the RMS amplitude of the biceps femoris of the SL and APSI (p < 0.01). The knee extorsion angle of the NL was positively correlated with the APSI (p < 0.05). (3) Dynamic postural stability index (DPSI): The knee adduction angle, iEMG of the tibialis anterior, and RMS amplitude of the erector spinae of the NL were significantly positively correlated with the DPSI (p < 0.05). The knee abduction and hip extension moments of the SL were also significantly positively correlated with the DPSI (p < 0.05). The ankle inversion angle of the SL impacts left-right stability, while the NL's hip and ankle intorsion angles, knee extorsion angle, and exertion on the core muscle and SL's main muscles, as well as exertion of specific muscles of the NL affect anterior-posterior stability. The hip extension and knee abduction moments of the SL, knee adduction angle, exertion on the tibialis anterior, and activation of the erector spinae of the NL significantly affect the overall stability of an athlete.

Movement Outcomes Acquired via Markerless Motion Capture Systems Compared with Marker-Based Systems for Adult Patient Populations: A Scoping Review

Mobile motion capture is a promising technology for assessing physical movement; markerless motion capture systems (MLSs) offer great potential in rehabilitation settings, given their accessibility compared to marker-based motion capture systems (MBSs). This review explores the current literature on rehabilitation, for direct comparison of movement-related outcomes captured by MLSs to MBSs and for application of MLSs in movement measurements. Following a scoping review methodology, nine databases were searched (May to August 2023). Eligible articles had to present at least one estimate of the mean difference between a measure of a physical movement assessed by MLS and by MBS. Sixteen studies met the selection criteria and were included. For comparison of MLSs with MBSs, measures of mean joint range of motion (ROM) displacement were found to be similar, while peak joint angle outcomes were significantly different. Upper body movement outcomes were found to be comparable, while lower body movement outcomes were very different. Overall, nearly two-thirds of measurements identified statistical differences between MLS and MBS outcomes. Regarding application, no studies assessed the technology with patient populations. Further MLS-specific research with consideration of patient populations (e.g., intentional error testing, testing in less-than-ideal settings) would be beneficial for utilization of motion capture in rehabilitation contexts.

Validation of Markerless Motion Capture for Soldier Movement Patterns Assessment Under Varying Body-Borne Loads.

Field performance of modern soldiers is affected by an increase in body-borne load due to technological advancements related to their armour and equipment. In this project, the Theia3D markerless motion capture system was compared to the marker-based gold standard for capturing movement patterns of participants wearing various body-borne loads. The aim was to estimate lower body joint kinematics, gastrocnemius lateralis and medialis muscle activation patterns, and lower body joint reaction forces from the two motion capture systems. Data were collected on 16 participants performing three repetitions of walking and running under four body-borne load conditions by both motion capture systems simultaneously. A complete musculoskeletal analysis was completed in OpenSim. Strong correlations ( ) and acceptable differences were observed between the kinematics of the marker-based and markerless systems. Timing of muscle activations of the gastrocnemius lateralis and medialis, as estimated through OpenSim from both systems, agreed with the ones measured using electromyography. Joint reaction force results showed a very strong correlation ( ) between the systems; however, the markerless model estimated greater joint reaction forces when compared the marker-based model due to differences in muscle recruitment strategy. Overall, this research highlights the potential of markerless motion capture to track participants wearing body-borne loads.

Reliability Of Vertical Oscillation During Running Using Marker-less Motion Capture

Reliability Of Vertical Oscillation During Running Using Marker-less Motion Capture

Validity of IMU sensors for assessing features of walking in laboratory and outdoor environments among older adults

IntroductionIMU sensors (three-dimensional accelerometer, gyroscope and magnetometer) enable assessment of walking in older adults outside the laboratory. We studied whether IMUs are valid for detecting walking parameters (step events, time, length, and cadence) in a laboratory and outdoors on a level surface in older adults. MethodsThis validation study is part of a larger cross-sectional study. Twenty-six participants (mean age 76 years, 65 % female) walked on a treadmill indoors and on a sport track outdoors at self-selected speed. IMUs were attached laterally on the shanks and on the lower back at the level of L3-L4. Initial contact (IC) and step lengths were also estimated using acceleration signals (vertical, antero-posterior) from the pelvic IMU. Terminal contact (TC) was determined from the shank IMU sagittal angular velocity. For step length, inverted pendulum model and participant’s leg length (0.53 x height) was used. Step duration was calculated from IC to the opposite leg IC and stride duration from IC to next ipsilateral IC. Cadence was calculated as steps/min. As reference data, 3D motion capture was used in the laboratory and a high-speed video camera outdoors. Intraclass correlation coefficients (ICC), root mean squared errors (RMSE), typical errors and Bland-Altman plots were calculated and drawn. ResultsWhen comparing IC timing between IMU and reference data, mean bias was 0.031 s in the laboratory and −0.004 s outdoors, and for TC −0.057 s and −0.070 s respectively. Step and stride duration and cadence showed ICC values >0.80 and mean bias was <0.005 s for step and stride durations and <0.05 steps/min for cadence in both environments. Step length ICC values were <0.40 in the laboratory and outdoors. SignificanceIMUs can be used to monitor temporal walking variables in older adults and may be useful for rehabilitation interventions and functional capacity assessment.

Safe Iterative Learning for Attitude Tracking of Rigid Bodies Under Nonconvex Constraints

Safe Iterative Learning for Attitude Tracking of Rigid Bodies Under Nonconvex Constraints

Within-subject time series angular velocity differences between in-game high and low velocity fastballs in college baseball pitchers

PurposeThe purpose of the current study is to investigate the within-pitcher differences in time series angular velocities of the pelvis, trunk, shoulder, and elbow for high and low velocity fastballs in college baseball pitchers. MethodsIn-game data were retrospectively analyzed from 82 NCAA Division 1 pitchers ([1.89 ​± ​0.06] m, [92.8 ​± ​9.5] kg). Kinematic data were collected using an in-game markerless motion capture system. Time series data of pelvis, trunk, shoulder, and elbow angular velocities for each pitcher's fastest and slowest fastball were extracted for the pitch cycle (foot contact to ball release) and used for analysis. Within-subject time series comparisons were conducted using statistical parametric mapping (SPM) paired samples t-tests (α ​= ​0.012 5). ResultsEach of the tested segments were significantly faster in the fastest fastball trial compared to the slowest fastball trial. The duration of significance in reference to the pitch cycle, test statistic, and p-value, for each segment are as follows: Pelvis: 0%–4%, t ​= ​3.54, p ​= ​0.012; Trunk: 30%–67%, t ​= ​5.62, p ​< ​0.001; Shoulder External Rotation: 3%–50%, t ​= ​−6.03, p ​< ​0.001; Shoulder Internal Rotation: 96%–100%, t ​= ​4.11, p ​= ​0.008; Elbow: 75%–86%, t ​= ​4.13, p ​< ​0.001. DiscussionWithin-subjects differences exist in time series angular velocities when comparing the fastest and slowest fastball. These time series differences provide additional information to distinguish fastball velocity beyond what discrete metrics can provide. Pitchers should look to rotate each segment faster, and optimize the sequencing of these movements, to increase pitch velocity.

Joint Moments And Powers Variability Estimated By Markerless Motion Capture System May Affect Clinical Interpretations

Joint Moments And Powers Variability Estimated By Markerless Motion Capture System May Affect Clinical Interpretations

In-process part tracking and shape measurement using vision-based motion capture for automated English wheeling

An English wheel is an exceedingly adaptable instrument in traditional metalworking. It is a manual manufacturing technique, enabling skilled craftsmen and blacksmiths to shape complex compound curves in sheet metal panels. Accurate measurements and precise adjustments are essential when operating an English wheel to ensure that the metal is shaped with the desired curvature. An automated method to form English wheeled panels through robot forming has recently been proposed. For such a method to be successful, accurate tracking of sheet information including positions, orientations, and deformation is important for error compensation and the design of the subsequent tool paths. In this study, a Vicon motion capture system is employed to monitor the position and shape of the sheet metal during the English wheeling process. The initial experimental results demonstrate the potential of such an in-process metrology system, along with possible avenues for future work.

Dynamic three-dimensional facial topography in pediatric facial palsy: Understanding asymmetrical facial contours

BackgroundObjective assessment of facial movements remains pivotal for diagnosis, treatment, and long-term monitoring of patients with facial palsy (FP). This study aims to utilize curvature analysis in pediatric patients with and without FP to define facial contours and to quantify three-dimensional (3D) excursion during smile. MethodsPediatric patients with and without FP had 3D motion capture acquired from rest to maximum smile positions. 3D curvature analysis was performed with a custom MATLAB algorithm. A 40-vertex “smile curve” along the nasolabial fold-cheek-orbit contour was extracted from each patient-specific 3D mesh hemiface. This allowed quantification of excursion and asymmetry for affected vs. unaffected sides in FP patients, and comparison with controls. ResultsTwelve FP (mean 12.5yr., range 5-18) and 12 control (mean 12.1yr., range 5-18) patients were analyzed. Differences in facial contour are intensified during animation, especially in the nasolabial fold, cheek, and periorbital regions of interest and the smile curve which links them. Mean excursion differed significantly between the FP and control groups in all regions of interest (p < 0.0001). ConclusionsCurvature analysis provides insight into the unexplored relationship of the 3D morphological dynamics of the concavity and convexity of the face, to add to the understanding of this complex condition. The magnitude of asymmetry between a FP patient’s affected vs. unaffected smile curve excursion, and comparison to the control group, could allow surgical treatment to be tailored to an individual patient’s dynamic anatomy by identifying and quantifying facial region-specific asymmetry.

Multi-sensor fusion for biomechanical analysis: evaluation of dynamic interactions between self-contained breathing apparatus and firefighter using computational methods

Understanding the complex three-dimensional (3D) dynamic interactions between self-contained breathing apparatus (SCBA) and the human torso is critical to assessing potential impacts on firefighter health and informing equipment design. This study employed a multi-inertial sensor fusion technology to quantify these interactions. Six volunteer firefighters performed walking and running experiments on a treadmill while wearing the SCBA. Calculations of interaction forces and moments from the multi-inertial sensor technology were validated against a 3D motion capture system. The predicted interaction forces and moments showed good agreement with the measured data, especially for the forces (normal and lateral) and moments (x- and z-direction components) with relative root mean square errors (RMSEs) below 9.4%, 7.7%, 7.7%, and 7.8%, respectively. Peak pack force reached up to 150 N, significantly exceeding the SCBA’s intrinsic weight during SCBA carriage. The proposed multi-inertial sensor fusion technique can effectively evaluate the 3D dynamic interactions and provide a scientific basis for health monitoring and ergonomic optimization of SCBA systems for firefighters.