1,721,077 research outputs found
Estimation of stride length in level walking using an inertial measurement unit attached to the foot: A validation of the zero velocity assumption during stance
No full textIn a variety of applications, inertial sensors are used to estimate spatial parameters by double integrating over time their coordinate acceleration components. In human movement applications, the drift inherent to the accelerometer signals is often reduced by exploiting the cyclical nature of gait and under the hypothesis that the velocity of the sensor is zero at some point in stance. In this study, the validity of the latter hypothesis was investigated by determining the minimum velocity of progression of selected points of the foot and shank during the stance phase of the gait cycle while walking at three different speeds on level ground. The errors affecting the accuracy of the stride length estimation resulting from assuming a zero velocity at the beginning of the integration interval were evaluated on twenty healthy subjects. Results showed that the minimum velocity of the selected points on the foot and shank increased as gait speed increased. Whereas the average minimum velocity of the foot locations was lower than 0.011. m/s, the velocity of the shank locations were up to 0.049. m/s corresponding to a percent error of the stride length equal to 3.3%. The preferable foot locations for an inertial sensor resulted to be the calcaneus and the lateral aspect of the rearfoot. In estimating the stride length, the hypothesis that the velocity of the sensor can be set to zero sometimes during stance is acceptable only if the sensor is attached to the foot. © 2011 Elsevier Ltd
Accuracy, sensitivity and robustness of five different methods for the estimation of gait temporal parameters using a single inertial sensor mounted on the lower trunk
No full textLa valutazione e l’intervento riabilitativo del cammino mediante l’uso di sensori a basso costo
No full textPerformance of a remote eye-tracker in measuring gaze during walking
No full textCombining virtual environments and eyetracking can provide insights about the relationship between gaze and gait in people at high risk of fall. Remote eye-trackers can estimate gaze while the head moves within a limited workspace, but several factors can influence accuracy and precision. This study aimed at assessing the performance of a remote eyetracker both during controlled head movements and walking on a treadmill, while the visual stimulus moved on the screen. The head range of motion during gaze estimation was determined. The distance from the eye-tracker influenced data accuracy and precision of gaze estimation, while the target location was not a critical factor. The best accuracy was achieved at 650 mm from the eye-tracker (11±3 mm) and, during walking. Gaze fixations hitting static and moving objects were counted during standing (87 to 93 %) and walking (85 to 98 %), providing promising results for applications in virtual environments
An improved technique for the extraction of stochastic parameters from stabilograms
No full textAn improved characterization of the dynamics of postural sway can provide a better understanding about the functional organization of the postural control system as well as a more robust tool for postural pattern recognition. To this aim, a novel parameterization was applied to the stabilogram diffusion analysis formerly proposed by Collins and De Luca [Collins JJ, De Luca CJ. Open-loop and closed-loop control of posture: a random-walk analysis of center-of-pressure trajectories. Exp Brain Res 1993;95:308-18] that considered the act of maintaining posture as a stochastic process. The main purpose of the present technique was to overcome some drawbacks of the model presented by Collins and De Luca that may restrain its potential application in clinical practice. The approach uses a unique non-linear model to describe the center of pressure (COP) dynamics that reduces the number of parameters and decreases their intra-subject variability; consequently, fewer trials are required to perform reliable estimates of stochastic parameters and this is of particular importance for subjects that cannot afford many repeated measurements because of age or pathology. Four new statistical mechanics parameters (NSMP) were computed on the log-log stabilogram diffusion plots and their estimates were compared in terms of reliability and sensitivity to the visual conditions with: (1) a minimal set of four summary statistic scores (SSS); and (2) the six statistical mechanics parameters (SMP) proposed by Collins and De Luca. All four NSMP showed at least a fair-to-good reliability (intraclass correlation coefficient, ICC=0.49) while SMP (ICC=0.20) showed some poor reliability. A better overall reliability was also observed with respect to SSS. Moreover, only NSMP had a similar score for eyes open and eyes closed conditions. Three out of four NSMP were also significantly sensitive to eyes open or closed conditions (P<0.001) while only three out of six SMP were sensitive to operating conditions (P<0.01). © 2001 Elsevier Science Inc
Objective measures to investigate turning impairments and freezing of gait in people with Parkinson's disease
No full textBackground: Turning is impaired in people with Parkinson's Disease (PD) and it is a common trigger for freezing of gait (FoG). Recent evidence suggests that people with PD who freeze (PD+FoG) have worse turning performance than those who don't have freezing (non-freezers, PD-FoG), and the freezing episodes are exacerbated by increasing the turn angular amplitude. Research question: We investigated the difference between turning 180° while walking versus turning 360° in place, in both single- and dual-task conditions, by means of objective measures in people with PD with and without FoG. Methods: Twenty-four PD+FoG and eighteen PD-FoG performed 180° turns while walking and 360° turns in place during single- and dual-task conditions. Quantitative measures of turning and the dual-task cost were computed. Differences were investigated between groups and within turning types using ANOVA. Associations between turn measures and clinical scales were examined with Spearman correlations. Results: Turn duration and the number of steps were greater, and peak angular velocity slower, in PD+FoG compared to PD-FoG (p < 0.001). Dual-task costs were similar across groups, but turn duration showed significant interaction (p = 0.03). Posture Instability and Gait Disability (PIGD) subscore was associated with all turn measures in PD-FoG; whereas PIGD was mainly associated with turning while walking in PD+FoG. Significance: Objective measures of turning revealed differences between people with and without FoG, specifically, people with FoG showed more impairments in 360° turning in place compared to 180° turning while walking. However, as the turning challenges were increased by adding a dual-task, results from PD+FoG were similar to those from PD-FoG
Gait phases determination using Markov models applied to the recordings of a shank-worn gyroscope
No full textFeasibility and Acceptance of a Virtual Reality System for Gait Training of Individuals with Multiple Sclerosis
Full text link"The goals of motor rehabilitation are the improvement of mobility and the achievement of greater independence in everyday life, which requires specific multi-factorial improvements in sensory, motor, and cognitive functions. These can be addressed through multi-sensory interventions delivering stimuli, while engaging the participant in dual task activities, typical of daily living, using customized virtual reality (VR) rehabilitation tools. A prerequisite of a successful VR-based rehabilitation intervention is the patient’s engagement, motivation and satisfaction. In this study, a newly developed VR-based gait training approach for patients affected by multiple sclerosis is described and the technology required for its implementation is evaluated in terms of acceptance and feasibility. The results have shown that the use of this technology was well accepted by the participants, the system was durable and demonstrated high adaptability to patient's motor and cognitive status. This pilot study has demonstrated the usability of such a system for the training of patients with MS and suggests that VR-treadmill training could be useful to improve gait and cognitive function in such a cohort
2D video-based human gait analysis: A novel markerless approach
No full textA 2-D markerless technique for the analysis of the lower limbs kinematics during gait is presented and preliminarily validated. Data were recorded using a single video camera placed laterally to the walkway. The preliminary validation was performed using a optoelectronic marker based system as gold standard. The lower limb facing the camera was modelled with four body segments: foot, shank, thigh and pelvis. Ankle socks and underwear garments were used as segmental markers to track the foot and the pelvis, respectively. The shank and thigh were tracked using multiple reference points defined in a calibration reference image. The comparison between the estimated segment angular kinematics and that obtained with the gold standard revealed a high correlation index and limited Root Mean Square Deviation (RMSD) values. The proposed technique can be considered as an easy-to-configure and affordable alternative to marker-based systems, for 2D human lower limb motion tracking during gait
Comparative evaluation of scapular and humeral coordinate systems based on biomedical images of the glenohumeral joint
No full textBio-imaging techniques represent a powerful tool for shoulder joint biomechanical analysis. However,
the restricted field of view may prevent the acquisition of complete scapula and humerus bone models
and hence limiting the applicability of standardized anatomical coordinate system (ACS) definitions.
The aim of this study was to propose ACS definitions for both scapula and humerus which can be
implemented when limited portions of the relevant bones are available. Magnetic resonance (MR)
images of twenty right humeri and scapulae were acquired. The proposed ACSs were assessed in terms of
(1) sensitivity to bone morphological variation, (2) intra – and inter – operator repeatability and (3)
consistency with the anatomical cardinal directions. A comparison with alternative ACS definitions was
also performed. Overall, our ACS scapular proposal and that presented in Kedgley and Dunning (2010)
were found to be the least sensitive to the morphometric variability (mean angular absolute deviation
lower than 8.3 deg) and they were characterized by a high intra – and inter – operator repeatability
(mean angular absolute deviation lower than 1.5 deg). The humeral ACS proposal showed a morphometric
variability similar to Amadi et al. (2009b) (mean angular absolute deviation lower than 8.3 deg)
but a higher reproducibility. The scapular and humeral ACS mean angular deviation from
the reference anatomical cardinal directions were smaller than 15 deg and 8.6 deg, respectively. The
proposed scapular and humeral ACS definitions are therefore suitable to be applied when a limited
portion of the glenohumeral joint is available as it may occur in standard shoulder clinical exams
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