Effets de la majoration du déficit moteur du quadriceps, induite expérimentalement, sur la locomotion des patients hémiparétiques

The main objective of this thesis was to study the effects of experimentally increasing quadriceps motor impairment on the locomotor capacity of hemiparetic stroke patients, with stiff-knee gait. The second objective was to investigate the relationship between fatigue and overactivity of the quadriceps muscle in these patients. Four studies were carried out. Study 1 was carried out to verify our methodology, and it evaluated spatiotemporal and kinematic changes which occur, in hemiparetic patients, during a gait analysis session (GA). The results suggest that at the beginning of the GA session, stroke patients exhibited phase of adaptation, characterized by a ''cautious gait'', but no fatigue was observed at the end. Thus, evaluation of the effects of experimentally increasing quadriceps motor impairment, following a fatigue protocol, on the biomechanical gait parameters of hemiparetic stroke patients can be carried out with GA. In studies 2 and 3, patients' gait was assessed before and after an experimental increase in the motor impairment of the quadriceps using two methods: pharmacological, using botulinum toxin type-A injection (BoNT -A) in the hyperactive rectus femoris (RF) (study 2) and following a fatigue protocol involving repeated contractions of the knee extensors, with an isokinetic dynamometer (study 3). Finally, in study 4, the effect of quadriceps fatigue on the characteristics of muscle spasticity was evaluated using an isokinetic dynamometer. Surprisingly, the results showed that increasing the motor impairment of one part of, or the whole quadriceps muscle, induced the same improvements in biomechanical gait parameters (spatiotemporal, kinematic and EMG), whatever the method used (after injection of BoNT-A or after fatigue). Gait velocity increased, along with peak hip and knee flexion during the swing phase, and inappropriate activity of the RF during the pre-swing and swing phases decreased. The reduction of the mechanical restriction, due to the decrease in inappropriate muscle activity appeared to be associated with a compensatory reorganization of the gait pattern in order to counteract the negative effects of the increased motor impairment of the quadriceps. In addition, although muscle fatigue reduced inappropriate activity of the RF muscle during the semi-automatic task of walking, the characteristics of the stretch reflex were not altered during passive stretching, evaluated with an isokinetic dynamometer. Disruption of the fusimotor system during the fatigue protocols may only have changed the excitability of muscle spindles in dynamic conditions (during walking). In view of all these results, it seems likely that patients' complaints of feeling more spastic and vulnerable in situations in which their quadriceps motor impairment is increased, is the result of greater neural activity of central origin and/or a "real" increase in spasticity, but which occurs in other muscles such as the ankle plantarflexors.L'objectif principal de ce travail de thèse était d'étudier les effets de la majoration du déficit moteur focal du quadriceps, sur les capacités locomotrices de patients hémiparétiques, présentant un genou raide à la marche, communément appelé stiff-knee gait. L'objectif secondaire était d'investiguer les relations entre la fatigue et l'hyperactivité musculaire du quadriceps, chez ces patients. Quatre études ont été menées. La première étude de ce travail a permis de mettre en évidence qu'au début d'une session d'AQM, le pattern de marche des patients hémiparétiques est influencé par une phase d'adaptation, caracterisée par une " marche prudente ", mais que le phénomène de fatigue n'est pas présent en fin d'examen. L'évaluation des effets de la majoration du déficit moteur du quadriceps, suite à un protocole de fatigue, sur les paramètres biomécaniques de la marche des patients hémiparétiques, peut donc être réalisée au moyen de l'AQM sans biais méthodologique. Ainsi, dans les études 2 et 3, la locomotion des patients a été évaluée avant et après une majoration du déficit moteur du quadriceps, induite expérimentalement par deux méthodes: soit pharmaco-induite par l'injection de toxine botulique de type-A (BoNT-A) dans le rectus femoris (RF) hyperactif (étude 2), soit résultante de la contraction répétée des extenseurs de genou, jusqu'à l'apparition de fatigue, par le biais d'un dynamomètre isocinétique (étude 3). Enfin dans l'étude 4, l'effet de la fatigue du quadriceps sur les caractéristiques de la spasticité a été évalué par le biais d'un dynamomètre isocinétique. De manière surprenante, les résultats montrent que la majoration du déficit moteur, d'une partie ou de toute partie du muscle quadriceps, induit des améliorations identiques sur les paramètres biomécaniques de la marche (spatiotemporels, cinématiques et EMG), quelle que soit la méthode utilisée (après injection de BoNT-A ou après fatigue). Une augmentation de la vitesse de marche, une augmentation de la flexion maximale de la hanche et du genou lors de la phase oscillante, ainsi qu'une réduction de l'activité inappropriée du RF, lors des phases pré-oscillante et oscillantes sont conjointement reportées. La réduction des freins mécaniques, liée à la baisse de l'activité musculaire inappropriée, semble être associée à une réorganisation compensatrice du pattern de marche, mise en place afin de contrer les effets néfastes de la majoration du déficit moteur du quadriceps et à l'origine de ces améliorations. De plus, alors que la fatigue musculaire réduit l'activité inappropriée du muscle RF, au cours d'une tache semi-automatique représentée par la marche, ses caractéristiques ne sont pas modifiées, au cours d'un étirement passif, évaluées par le biais d'un dynamomètre isocinétique. Au cours des protocoles de fatigue, la perturbation du système fusimoteur peut avoir modifiée l'excitabilité des fuseaux neuromusculaires, uniquement lors de sa sollicitation en condition dynamique (à la marche). Au regard de l'ensemble de ces résultats, il semble probable que, dans le contexte clinique, la plainte des patients de se sentir plus spastiques et plus vulnérables, en situation de majoration de leur déficit moteur du quadriceps, soit attribuée à une plus grande activité nerveuse d'origine centrale et/ou à une augmentation " effective " de la spasticité, mais présente au niveau d'autres muscles, comme les fléchisseurs plantaires de cheville

Variations in Kinematics during Clinical Gait Analysis in Stroke Patients

International audienceIn addition to changes in spatio-temporal and kinematic parameters, patients with stroke exhibit fear of falling as well as fatigability during gait. These changes could compromise interpretation of data from gait analysis. The aim of this study was to determine if the gait of hemiplegic patients changes significantly over successive gait trials. Forty two stroke patients and twenty healthy subjects performed 9 gait trials during a gait analysis session. The mean and variability of spatio-temporal and kinematic joint parameters were analyzed during 3 groups of consecutive gait trials (1-3, 4-6 and 7-9). Principal component analysis was used to reduce the number of variables from the joint kinematic waveforms and to identify the parts of the gait cycle which changed during the gait analysis session. The results showed that i) spontaneous gait velocity and the other spatio-temporal parameters significantly increased, and ii) gait variability decreased, over the last 6 gait trials compared to the first 3, for hemiplegic patients but not healthy subjects. Principal component analysis revealed changes in the sagittal waveforms of the hip, knee and ankle for hemiplegic patients after the first 3 gait trials. These results suggest that at the beginning of the gait analysis session, stroke patients exhibited phase of adaptation,characterized by a ''cautious gait'' but no fatigue was observed

Effects of Quadriceps Muscle Fatigue on Stiff-Knee Gait in Patients with Hemiparesis

International audienceThe relationship between neuromuscular fatigue and locomotion has never been investigated in hemiparetic patients despite the fact that, in the clinical context, patients report to be more spastic or stiffer after walking a long distance or after a rehabilitation session. The aim of this study was to evaluate the effects of quadriceps muscle fatigue on the biomechanical gait parameters of patients with a stiff-knee gait (SKG). Thirteen patients and eleven healthy controls performed one gait analysis before a protocol of isokinetic quadriceps fatigue and two after (immediately after and after 10 minutes of rest). Spatiotemporal parameters, sagittal knee and hip kinematics, rectus femoris (RF) and vastus lateralis (VL) kinematics and electromyographic (EMG) activity were analyzed. The results showed that quadriceps muscle weakness, produced by repetitive concentric contractions of the knee extensors, induced an improvement of spatiotemporal parameters for patients and healthy subjects. For the patient group, the increase in gait velocity and step length was associated with i) an increase of sagittal hip and knee flexion during the swing phase, ii) an increase of the maximal normalized length of the RF and VL and of the maximal VL lengthening velocity during the pre-swing and swing phases, and iii) a decrease in EMG activity of the RF muscle during the initial pre-swing phase and during the latter 2/3 of the initial swing phase. These results suggest that quadriceps fatigue did not alter the gait of patients with hemiparesis walking with a SKG and that neuromuscular fatigue may play the same functional role as an anti-spastic treatment such as botulinum toxin-A injection. Strength training of knee extensors, although commonly performed in rehabilitation, does not seem to be a priority to improve gait of these patients

Coactivation of Lower Limb Muscles during Gait in Patients with Multiple Sclerosis

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Faster speed at the expense of arm-trunk coordination during reaching in chronic spastic stroke patients

International audienceBackground. The velocity of reaching movements is often reduced in patients with stroke-related hemiparesis; however,they are able to voluntarily increase paretic hand velocity. Previous studies have proposed that faster speed improvesmovement quality. Objective. To investigate the combined effects of reaching distance and speed instruction on trunk andparetic upper-limb coordination. The hypothesis was that increased speed would reduce elbow extension and increasecompensatory trunk movement. Methods. A single session study in which reaching kinematics were recorded in a groupof 14 patients with spastic hemiparesis. A 3-dimensional motion analysis system was used to track the trajectories of 5reflective markers fixed on the finger, wrist, elbow, acromion, and sternum. The reaching movements were performedto 2 targets at 60% and 90% arm length, respectively, at preferred and maximum velocity. The experiment was repeatedwith the trunk restrained by a strap. Results. All the patients were able to voluntarily increase reaching velocity. In thetrunk free, faster speed condition, elbow extension velocity increased but elbow extension amplitude decreased and trunkmovement increased. In the trunk restraint condition, elbow extension amplitude did not decrease with faster speed.Seven patients scaled elbow extension and elbow extension velocity as a function of reach distance, the other 7 mainlyincreased trunk compensation with increased task constraints. There were no clear clinical characteristics that couldexplain this difference. Conclusions. Faster speed may encourage some patients to use compensation. Individual indicationsfor therapy could be based on a quantitative analysis of reaching coordination

Relationship between neuromuscular fatigue and spasticity in chronic stroke patients: A pilot study

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Muscle force strategies for poststroke hemiparetic patients during gait

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Demographic characteristics of subjects.

<p>For the demographic characteristics of hemiparetic patients and healthy subjects, mean (SD) values are presented. For the clinical examination, median values [1^st; 3^rd quartiles] are presented. M = male, F = female, R = right, L = left, MAS = Modified Ashworth Scale, MRC = Medical Research Council.</p

Mean sagittal-plan knee joint angle for the hemiparetic group and the healthy group.

<p>The solid black line indicates the PRE condition for the hemiparetic group walking at a mean spontaneous gait velocity of 0.68/s, the dotted black line indicates the POST_0 condition for the hemiparetic group walking at a mean spontaneous gait velocity of 0.75 m/s and the dashed black line indicates the POST_10 condition for the hemiparetic group waking at a mean spontaneous gait velocity of 0.78 m/s. The solid gray line indicates the PRE condition for the healthy group walking at a mean spontaneous gait velocity of 1.32 m/s. The vertical solid line represents the beginning of the swing phase of gait.</p