Publications by authors named "Rachid Aissaoui"

Background: Inertial systems are increasingly used to analyze human motion, especially for gait analyses and in clinical settings. Calibration methods for these systems are designed for ease of implementation, and previous studies have shown that they can provide accurate knee kinematics in the sagittal plane. However, the reason of their lack of accuracy in the other planes (i.

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Manual wheelchair propulsion represents a repetitive and constraining task, which leads mainly to the development of joint injury in spinal cord-injured people. One of the main reasons is the load sustained by the shoulder joint during the propulsion cycle. Moreover, the load at the shoulder joint is highly correlated with the force and moment acting at the handrim level.

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Several studies have shown that users of immersive virtual reality can feel high levels of embodiment in self-avatars that have different morphological proportions than those of their actual bodies. Deformed and unrealistic morphological modifications are accepted by embodied users, underlying the adaptability of one's mental map of their body (body schema) in response to incoming sensory feedback. Before initiating a motor action, the brain uses the body schema to plan and sequence the necessary movements.

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Background: Asymmetric weight distribution in sitting has been reported in people after stroke. However, postural strategies used during bilateral symmetric and asymmetric movements performed while seated require more evidence to inform rehabilitation strategies.

Research Questions: How do symmetric and asymmetric effort levels exerted during upper limb (UL) pushing movements affect seated postural organization parameters (weight bearing (WB) between hands and hemibody sides, and forward trunk displacement) of stroke compared to healthy individuals? How are these parameters associated?

Methods: Using an instrumented exerciser, 19 post-stroke individuals were compared to 17 healthy individuals when executing four bilateral UL pushing movements in a seated position: symmetrical pushing at 30 % and 15 % of their maximal force (MF) and asymmetrical pushing with 15 % of their MF for one UL vs.

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Tibiofemoral contact loads are crucial parameters in the onset and progression of osteoarthrosis. While contact loads are frequently estimated from musculoskeletal models, their customization is often limited to scaling musculoskeletal geometry or adapting muscle lines. Moreover, studies have usually focused on superior-inferior contact force without investigating three-dimensional contact loads.

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Background: Manual wheelchair propulsion remains a very ineffective means of locomotion in terms of energy cost and mechanical efficiency, as more than half of the forces applied to the pushrim do not contribute to move the wheelchair forward. Manual wheelchair propulsion training using the haptic biofeedback has shown an increase in mechanical efficiency at the handrim level. However, no information is available about the impact of this training on the load at the shoulders.

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Modeling the interface between the lower limb segments and a socket, orthosis or exoskeleton is crucial to the design, control, and assessment of such devices. The present study aimed to estimate translational and rotational soft tissue stiffness at the thigh and shank during daily living activities performed by six subjects. Smooth orthogonal decomposition (SOD) was used on skin marker trajectories and fluoroscopy-based knee joint kinematics to compute stiffness coefficients during squatting, sitting and rising from a chair, level walking, and stair descending.

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Background: Impairments of the upper limb (UL) are common after a stroke and may affect bilateral coordination. A better understanding of UL bilateral coordination is required for designing innovative rehabilitation strategies.

Objective: To assess bilateral coordination after stroke using time-distance, velocity and force parameters during an UL bilateral task performed by simultaneously pushing handles on a bilateral exerciser at two levels of force.

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Background: Postural strategies of the trunk and the lower limbs are linked to upper limb motor activities. The objective was to analyze the postural organization at the lower limbs as well as the inter-limb coordination during isometric maximal bilateral pushing of upper limbs.

Methods: Fifteen individuals after stroke and 17 healthy participants were assessed with an instrumented exerciser paired with an instrumented sitting surface while they executed isometric bilateral pushes with the upper limbs.

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This study evaluated the association of contact point locations with the knee medial and lateral contact force (F, F) alterations in OA and healthy subjects. A musculoskeletal model of the lower limb with subject-specific tibiofemoral contact point trajectories was used to estimate the F and F in ten healthy and twelve OA subjects during treadmill gait. Regression analyses were performed to evaluate the correlation of the contact point locations, knee adduction moment (KAM), knee flexion moment (KFM), frontal plane alignment, and gait speed with the F and F.

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Knee orthoses are designed to reestablish the normal kinematics of the knee joint. However, the data on the effectiveness of them on modifying the internal joint kinematics are scarce. The aim of this study was to develop a method to allow accurate comparison of the knee contact kinematics in osteoarthritic (OA) subjects with and without wearing a valgus knee orthosis using imaging techniques.

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Background: Inertial motion capture (IMC) is rapidly gaining in popularity to evaluate gait in clinical settings. Previous examinations of IMC knee kinematics were often limited to the sagittal plane and IMC calibration has not been thoroughly investigated.

Research Question: The objective was to validate IMC 3D knee kinematics calibrated with a double-pose during gait with reference to optical motion capture (OMC).

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Musculoskeletal models generally solve the muscular redundancy by numerical optimisation. They have been extensively validated using instrumented implants. Conversely, a reduction approach considers only one flexor or extensor muscle group at the time to equilibrate the inter-segmental joint moment.

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Background: Total knee arthroplasty (TKA) is the treatment of choice for end-stage knee osteoarthritis. Postoperative static knee alignment has been recognized as a key component of successful surgery. A correction toward the kinematics of a native knee is expected after TKA, with an aim for neutral mechanical alignment.

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Background: Different environmental factors may affect the accuracy of step-count activity monitors (AM). However, the validation conditions for AM accuracy largely differ from ecological environments.

Objectives: To assess and compare the accuracy of AM in counting steps among poststroke individuals: during different locomotor tasks, with AM placed at the nonparetic ankle or hip, and when walking in a laboratory or inside a mall.

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The estimation of joint kinematics from skin markers is hindered by the soft tissue artefact (STA), a well-known phenomenon although not fully characterized. While most assessments of the STA have been performed based on the individual skin markers displacements, recent assessments were based on the marker-cluster geometrical transformations using, e.g.

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The commercially available SmartWheel is largely used in research and increasingly used in clinical practice to measure the forces and moments applied on the wheelchair pushrims by the user. However, in some situations (i.e.

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Objective: To determine if the level of effort in paretic plantar flexors during gait could be a factor in explaining locomotor asymmetry.

Design: Cross-sectional study.

Subjects: Twenty individuals with chronic stroke (mean age 49.

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Background: Some studies in post-stroke individuals hypothesized that asymmetrical gait might be a strategy to symmetrize the effort in lower limb muscles. This study analyzed the asymmetry in the levels of effort, net joint moment during gait (walking moment) and maximal potential moment in the plantarflexors, hip flexors and extensors during gait.

Methods: Twenty post-stroke and 10 healthy individuals were assessed when walking at a comfortable speed on a treadmill.

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The main objective was to quantify the effects of five different slopes on trunk and shoulder kinematics as well as shoulder kinetic and muscular demands during manual wheelchair (MWC) propulsion on a motorized treadmill. Eighteen participants with spinal cord injury propelled their MWC at a self-selected constant speed on a motorized treadmill set at different slopes (0°, 2.7°, 3.

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The purpose of this study was to quantify the effects of five distinct slopes on spatiotemporal and pushrim kinetic measures at the nondominant upper limb during manual wheelchair (MWC) propulsion on a motorized treadmill in individuals with spinal cord injury (SCI). Eighteen participants with SCI propelled their MWC at a self-selected natural speed on a treadmill at different slopes (0, 2.7, 3.

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Wheelchair propulsion exposes the user to a high risk of shoulder injury and to whole-body vibration that exceeds recommendations of ISO 2631-1:1997. Reducing the mechanical work required to travel a given distance (WN-WPM, weight-normalized work-per-meter) can help reduce the risk of shoulder injury, while reducing the vibration transmissibility (VT) of the wheelchair frame can reduce whole-body vibration. New materials such as titanium and carbon are used in today's wheelchairs and are advertised to improve both parameters, but current knowledge on this matter is limited.

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Objective: To assess plantarflexion moment and hip joint moment after-effects following walking on a split-belt treadmill in healthy individuals and individuals post-stroke.

Design: Cross-sectional study.

Subjects: Ten healthy individuals (mean age 57.

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Eighteen manual wheelchair users (MWUs) with spinal cord injury participated in a training session on a new manual wheelchair simulator with haptic biofeedback (HB). The training aimed to modify participants' mechanical effective force (MEF) along the push phase to achieve a target MEF pattern slightly more effective than their pre-training pattern. More HB was provided if the participants' achieved MEF pattern deviated from the target.

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Some hemiparetic patients walk asymmetrically. To better understand the mechanisms of this deficiency, the perception of locomotor symmetry was investigated in healthy elderly individuals. 16 participants (6 women, 10 men; M age = 70.

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