1,721,075 research outputs found
Is a portable pressure plate an alternative to force plates for measuring postural stability and interlimb coordination of quiet standing balance control?
No full textIntroduction: Center-of-pressure (COP) synchronization and symmetry can inform adaptations in balance control following one-sided sensorimotor impairments (e.g., stroke). As established force plates are impossible to transport, we aimed to criterion validate a portable pressure plate for obtaining reliable COP synchronization and symmetry measures, next to conventional postural stability measures. Methods: Twenty healthy adults participated. In a single session, three 40-s eyes-open and eyes-closed quiet stance trials were performed per plate-type, randomly ordered. Individual-limb COPs were measured to calculate between-limb synchronization (BLS) and dynamic control asymmetry (DCA). Net COP (i.e., limbs combined) area, amplitude, and velocity were used to describe anteroposterior (AP) and mediolateral (ML) postural stability. Criterion validity was evaluated using Spearman correlations (r) and Bland-Altman plots. Test-retest reliability was tested using intraclass correlation coefficients (ICC). Results: Strong correlations (r > 0.75) and acceptable reliability (ICC > 0.80) were found regarding individual-limb COP velocity and DCA, net COP ML amplitude and AP and ML velocities. Bland-Altman plots yielded possible proportional bias; the pressure plate systematically underestimated COP scores by force plates and a larger error associated with a larger measurement. Conclusions: Despite correlations between instruments and sufficient reliability for measuring postural stability and DCA, this technical note strongly suggests, due to a systematic deviation, using the same plate-type to accurately assess performance change within subjects longitudinally over time.Funding
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The authors would like to acknowledge funding by the Research Foundation Flanders (FWO), Belgium who provided JS a doctoral (PhD) grant for strategic basic research (application number 1S64819N) to conduct this research.
Acknowledgments
The authors would like to thank Charlotte Johnson for writing assistance, and the following M.Sc. students for aiding data collection and subject recruitment: Heleen Leurs, Carolien Van de Perck, Silke Van Goubergen, Gabriela Wimberska, Denice Kliebisch, and Sofia Lopez-Cotarelo Flemons
Are standing balance and walking ability deficits poststroke related to the integrity of the corticospinal and non-corticospinal tracts? A meta-analysis
No full textBackground: The importance of corticospinal tract (CST) integrity in upper limb recovery poststroke is well established, but its association with standing balance and walking remains unclear. This meta-analysis aimed to establish the relationship between CST and non-CST motor tract integrity, and clinical scores of standing balance and walking poststroke. Methods: In July 2024, five databases were searched for studies, focusing on diffusion MRI metrics and clinical scores of standing balance and/or walking independence poststroke. Meta-analyses were conducted to pool correlation coefficients (r) and group differences (d) based on CST integrity. Results: Twenty-two studies were included. Cross-sectional analysis showed no correlation (r < .25) between CST metrics and the functional ambulation category (FAC) in the sub-acute phase. Weak prognostic associations were found for CST-FA and CST-FN with FAC. Significant FAC score differences were found between preserved- and disrupted CST groups in the sub-acute (d = .79) and chronic (d = 1.07) phase and for prognostic analysis (d = 1.40). Non-CST metrics showed no cross-sectional associations and mixed prognostic associations. Conclusions: CST integrity was not significantly associated with standing balance or walking independence in the sub-acute phase. Early CST integrity showed weak prognostic value for walking at 6 months. Multimodal longitudinal research is needed to improve lower limb recovery prognostics.This work was supported by the BOF (bijzonder onderzoeksfond) of the University of Antwerp, and was funded by the Flemish Government under Grant ID: [44607]. The authors would like to thank the University of Antwerp and the research groups of MovAnt and Translational Neuroscience for their contributions
Computationally Efficient Human Body Modelling for Real Time Motion Comfort Assessment
No full textDue to the complexity of the human body and its neuromuscular stabilization, it has been challenging to efficiently and accurately predict human motion and capture posture while being driven. Existing simple models of the seated human body are mostly two-dimensional and developed in the mid-sagittal plane exposed to in-plane excitation. Such models capture fore-aft and vertical motion but not the more complex 3D motions due to lateral loading. Advanced 3D full body active human models (AHMs), such as in MADYMO, can be used for comfort analysis and to investigate how vibrations influence the human body while being driven. However, such AHMs are very time-consuming due to their complexity. To effectively analyze motion comfort, a computationally efficient and accurate three dimensional (3D) human model, which runs faster than real time, is presented. The model's postural stabilization parameters are tuned using available 3D vibration data for head, trunk and pelvis translation and rotation. A comparison between AHM and EHM is conducted regarding human body kinematics. According to the results, the EHM model configuration with two neck joints, two torso bending joints, and a spinal compression joint accurately predicts body kinematics.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Intelligent Vehicle
Modelling Neck Postural Stabilization Using Optimal Control Techniques for Dynamic Driving
No full textThe goal of this paper is to contribute to the accurate prediction of human body motion by proposing a novel head-neck model for dynamic driving scenarios with complex vehicle motions. While automated vehicles are considered a potential solution to several transportation issues, there are still significant challenges that need to be addressed, including fundamental questions regarding motion comfort and postural stability. Existing standards fail to accurately describe motion comfort, and current head-neck models have limitations, such as their inability to accurately capture human head responses to dynamic perturbations and lack of adaptability to different perturbations, amplitudes, and individual characteristics. To address these challenges, the authors propose a 3D double inverted pendulum model (DIPM) with a total of 6 degrees of freedom (DoF) as an approximation of head-neck system. The proposed model uses Model Predictive Control (MPC) to derive optimal control inputs for head-neck stabilization. The study validates the proposed model against experimental data of anterior-posterior seat translation and rotation from the literature. The results indicate that the model fitted the experimental data with a variance accounted for 82.80 % in translation and 73.15 % in rotation (pitch). The proposed model paves the path for the accurate assessment of occupants’ postural stability in automated vehicles.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Intelligent Vehicle
Time-dependency of test-retest reliability and measurement error of center-of-pressure synchronization and symmetry during quiet standing within specific frequencies in early sub-acute stroke
No full textBackground: People with unilateral sensorimotor impairments after a stroke exhibit poor between-limb synchronization and asymmetries in balance control by relying on their less-affected side to maintain stability during standing. Therefore, there is a growing consensus to include center-of-pressure metrics as between-limb synchronization and dynamic control asymmetry when investigating balance improvements poststroke. However, the test-retest reliability of these metrics remains under-investigated, hindering uptake of these assessments in future stroke rehabilitation and recovery studies. Research question: First, are three immediate test-repetitions necessary for obtaining reliable synchronization and asymmetry scores in individuals with sub-acute stroke, or can fewer repetitions suffice? Second, does timing of assessments at 3-, 5-, 8-, and 12-weeks poststroke affect these estimates' test-retest reliability and measurement error? Methods: Thirty stroke survivors with moderate-to-severe motor impairments were tested at 3-, 5-, 8-, and 12weeks poststroke. At each timepoint, they completed three 40-second quiet standing trials on a dual force plate which measured center-of-pressure signals separately on each side. We calculated between-limb synchronization (i.e., cross-correlation) and dynamic control asymmetry (i.e., symmetry index) using the original centerof-pressure signal, and after decomposition into high and low (cut-off 0.4 Hz) frequency bands. Intraclass correlation coefficients (ICC) and Bland-Altman plots were used to assess test-retest reliability and measurement error. A cut-off was used to determine acceptable reliability (ICC>0.75). Results: Between-limb synchronization and dynamic control asymmetry showed good-to-excellent reliability (ICCs=0.80-0.97) across three repetitions at all timepoints. Reducing to two repetitions yielded acceptable reliability (ICC=0.77-0.95) for dynamic control asymmetry and high-frequency measures, yet insufficient reliability for between-limb synchronization. At the 3-weeks timepoint, ICCs were generally lower, with more error, compared to later timepoints. Conclusion: Novel performance metrics quantifying synchronization and asymmetry of balance control can be reliably obtained during the early sub-acute phase if three test-repetitions are administered per assessment.JS received a strategic basic research doctoral (PhD) fellowship by the Research Foundation Flanders (FWO), Belgium (application no.1S64819N) for conducting the TARGEt studies; AvH received a doctoral (PhD) fellowship from the special reserach fund DOCPRO, University of Antwerp, Belgium (application no.44607) for the analyses set forth here
Trunk and gait performance after stroke : a biomechanical approach
No full textAbstract: Approximately 80 percent of all stroke survivors show mobility deficits after their diagnosis and select gait recovery as the primary therapy goal. However, gait is not merely the ability to walk up and down a corridor. People living with stroke need to walk independently, on unstable surfaces, in crowded environments while performing dual tasks. To optimize their walking pattern, we need to understand the underlying impairments. The importance of the trunk during walking is often neglected and still misconceived. The aim of this thesis was to enhance our understanding about the trunk\u2019s involvement during walking after stroke and how the walking pattern recovers by resolving truncal deficits. Detailed analysis of the literature provided knowledge concerning the state of the art on trunk motion and trunk rehabilitation, whereby gaps were identified and further investigated. First, an instrumented gait analysis was performed on 57 stroke survivors and 105 healthy individuals during a cross-sectional study. The use of the Full Body Plug-In Gait model (Vicon), together with a specified trunk model and electromyography, made comparison of trunk and lower limb kinematics, spatiotemporal step parameters and muscle activity between healthy adults and stroke survivors possible. Second, of the participants with stroke, 39 were included in a randomized controlled trial receiving either trunk or cognitive training. Findings suggest that important deviations in trunk kinematics during walking were present after stroke. Stroke survivors walked with increased mediolateral/anteroposterior trunk movements, increased thoracic flexion, a neutral position of the pelvis during stance, a pelvic hike during swing, and a backward rotation of the hemiplegic thorax and pelvis resulting in more in-phase coordination. In addition, patients with more severe lower limb impairments had more pronounced deficits in truncal motion, especially in the frontal plane. Second, trunk training was able to improve balance and mobility. These improvements in gait performance were not secondary to changes in lower limb kinematics but due to decreased anteroposterior movements of the thorax and an increase in the fatigue-resistance of trunk muscles. The results of this thesis showed that trunk impairments are clearly present during walking after a stroke. By giving patients trunk exercises, their walking pattern was optimized which ensures us that trunk exercises should be incorporated in treatment strategies for gait recovery. Results suggest that stroke survivors adopted a more energy efficient walking pattern after trunk training. However, this was not directly investigated in the current trial and necessitates further study
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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