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Leboeuf F.,Laboratoire dAnalyse du Mouvement | Seguin P.,University of Poitiers | Lacouture P.,University of Poitiers
Movement and Sports Sciences - Science et Motricite | Year: 2012

A predictive method: The optimal synthesis, based on an optimal dynamic problem, was solved for generating the aerial phase of a backward somersault. Optimal joint torques were compared with those resulting from inverse dynamics. A gymnast was modeled as a planar seven-segment multibody system with six internal degrees of freedom. The aerial motion was generated using a parametric optimization technique. The performance criterion minimized the time integral of quadratic joint torques. Optimal synthesis has produced a somersault closely mimicking the experimental one. Optimal joint torques revealed the motor control at the knee after takeoff unattainable by inverse dynamics analysis because of the measurement uncertainty propagation. Moreover, our study suggests that minimization of joint torques might be the primary control objective of a backward somersault. © ACAPS, EDP Sciences, 2012. Source

Desroches G.,University Claude Bernard Lyon 1 | Desroches G.,INRETS | Desroches G.,Laboratoire Of Biomecanique Et Mecanique Des Chocs | Dumas R.,University Claude Bernard Lyon 1 | And 9 more authors.
Clinical Biomechanics | Year: 2010

Background: Inverse dynamic methods have been widely used to estimate joint loads during manual wheelchair propulsion. However, the interpretation of 3D net joint moments and powers is not always straightforward. It has been suggested to use joint coordinate systems (expression of joint moment on anatomical axes) and the 3D angle between joint moment and angular velocity vectors (propulsion, resistance or stabilization joint configuration) for a better understanding of joint dynamics. Methods: Nine spinal cord injured subjects equipped with reflective markers propelled in a wheelchair with an instrumented wheel. Inverse dynamic results were interpreted using joint coordinate systems, 3D joint power and the 3D angle between the joint moment and joint angular velocity vectors at the three upper limb joints. The 3D angle was used to determine if the joints were predominantly driven (angle close to 0 or 180 degrees) or stabilized (angle close to 90°). Findings: The wrist and elbow joints are mainly in a stabilization configuration (angle close to 90°) with a combination of extension and ulnar deviation moments and an adduction moment respectively. The shoulder is in a propulsion configuration, but close to stabilization (angle hardly below 60°) with a combination of flexion and internal rotation moments. Interpretation: Stabilization configuration at the joints could partly explain the low mechanical efficiency of manual wheelchair propulsion and could give insight about injury risk at the wrist, elbow and shoulder joints. © 2009 Elsevier Ltd. All rights reserved. Source

Pradon D.,Laboratoire dAnalyse du Mouvement | Hutin E.,Laboratoire dAnalyse du Mouvement | Hutin E.,University of Valenciennes and HainautCambresis | Khadir S.,Laboratoire dAnalyse du Mouvement | And 3 more authors.
Clinical Biomechanics | Year: 2011

Background: Botulinum toxin is commonly used to treat spastic equinus foot. This treatment seems to improve gait in hemiplegic patients when used alone or combined with an ankle-foot orthosis. However, the nature and effects of this improvement have until now rarely been studied. The aim of this study was to quantify the impact of a Botulinum toxin injection in the triceps surae of hemiplegic patients with equinus foot, used either alone or in combination with an ankle-foot orthosis, on the kinematics and dynamics of the paretic lower limb, and to determine the advantage of combining an ankle-foot orthosis with this pharmacological treatment. Methods: Patients were assessed using gait analysis to measure spatio-temporal, kinematic and dynamic parameters of the gait cycle before Botulinum toxin injection and then 3 and 6 weeks after injection. Eight chronic hemiplegics following central nervous system lesion were included. Findings: Botulinum toxin injection led to an increase in velocity, peak ankle dorsiflexion during stance phase, and peak knee flexion during swing phase. It also resulted in an increased peak plantarflexion moment. Use of ankle-foot orthosis led to a specific increase in peak ankle dorsiflexion during swing phase and also increased peak plantarflexion moment. Interpretation: The results indicate that combined Botulinum toxin injection of the triceps surae and wearing an ankle-foot orthosis is more effective than the use of Botulinum toxin only. Use of an ankle-foot orthosis increases ankle dorsiflexion during the swing phase and does not reduce the benefits gained by the use of Botulinum toxin in stance phase. © 2011 Elsevier Ltd. All rights reserved. Source

Hutin E.,Laboratoire dAnalyse du Mouvement | Hutin E.,University of Lille Nord de France | Hutin E.,University of Valenciennes and HainautCambresis | Hutin E.,French National Center for Scientific Research | And 6 more authors.
Clinical Biomechanics | Year: 2011

Background: The mechanisms altering knee flexion in hemiparetic gait may be neurological (muscle overactivity) or orthopedic (soft tissue contracture) in nature, a distinction which is difficult to ascertain clinically during gait. This study aimed to distinguish the 2 mechanisms in evaluating thigh-shank coordination, which may show instability across the gait cycle in the case of bursting rectus femoris overactivity. Methods: We measured thigh-shank coordination in the sagittal plane using the continuous relative phase during gait in 15 healthy subjects without and with an orthotic knee constraint (control and constrained) and 14 subjects with hemiparesis and rectus femoris overactivity before (pre) and after botulinum toxin injection. Findings: Compared with the control group, both orthopedic and neurological knee flexion limitations were associated with decreased root-mean square of continuous relative phase over swing (control, 72.9; constrained, 26.0, P < 0.001; pre, 31.3, P < 0.001). However, only the neurological limitation was characterized by a higher number of continuous relative phase reversals over swing (control, 2.3; pre, 4.0; P = 0.001) and late stance (control, 0.6; pre, 1.7; P < 0.001). Botulinum toxin injection was associated with a 40% increase in root-mean square of continuous relative phase during swing and a 41% decrease in number of continuous relative phase reversals during late stance, while peak knee flexion was increased by 31%. Interpretation: In hemiparesis, rectus femoris overactivity at swing phase is associated with alternating thigh-shank coordination in swing and late stance, which improves after botulinum toxin injection. Coordination analysis may help to distinguish neurological from orthopedic factors in knee flexion impairment. © 2010 Elsevier Ltd. Source

Hutin E.,Biomecanique and Systeme Nerveux | Hutin E.,University of Lille Nord de France | Hutin E.,University of Valenciennes and HainautCambresis | Hutin E.,Laboratoire dAnalyse du Mouvement | And 6 more authors.
Neurorehabilitation and Neural Repair | Year: 2010

Background. Botulinum toxin (BTX) injection into rectus femoris (RF) is a therapeutic modality used to improve knee flexion during the swing phase of gait in hemiparesis. The impact of this treatment on lower limb coordination is unknown. The authors evaluated whether BTX injection into RF is associated with modifications of intersegmental coordination in hemiparesis. Methods. The authors evaluated gait in 10 control and 14 hemiparetic subjects with low peak knee flexion associated with inappropriate RF activity in mid-swing, using 3-dimensional analysis before and 1 month after BTX injection into RF (Botox, 200 units). Thighg-shank coordination was measured in the sagittal plane by averaging the continuous relative phase (CRPThighg-Shank) during each phase of the gait cycle in both lower limbs. The CRP is a validated metric that integrates angle positions and velocities of 2 limb segments to quantify their temporalg-spatial coordination. Results. Before treatment, the low peak knee flexion in hemiparetic subjects (paretic limb 29 ± 9°) was associated with a decreased CRPThighg-Shank in the paretic limb in swing (paretic limb 26.0 ± 16.6° vs controls 73.5± 7.4°, P <.001) and with a trend of an increased CRPThigh g-Shank in the nonparetic limb over the full gait cycle (nonparetic limb 77.9 ± 14.1° vs controls 66.2 ± 19.8°, P =.083). After treatment, the CRPThighg- Shank increased by 11.9° in the swing phase of the paretic limb (P =.002) and decreased by 8.0° over the full gait cycle ( P =.002) in the nonparetic limb. Conclusions. BTX injection into RF was associated with improved thighg-shank coordination in parts of the gait cycle, in both injected paretic and noninjected nonparetic limbs. © 2010 The Author(s). Source

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