- Email: [email protected]
20.8 Postural disturbances in multiple sclerosis
Chapter 20. Rehabilitation and training
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References [1] Williams CL, Barnett AM, Meck WH. Organisational effects of early gonadal secretions on sexual differentiation in spatial memory. Behavioural Neuroscience. 1990; 104(1): 84 97. [2] Saucier DM, Green SM, Leason J, MacFadden A, Bell S, Ellias LJ. Are sex differences in navigation caused by sexually dimorphic strategies or by differences in the ability to use the strategies? Behavioural Neuroscience. 2002; 116(3): 403 410.
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Differences in the coordination of sit-to-stand in teachers of the Alexander technique
T.W. Cacciatore, EB. Horak, V.S. Gurfinkel. Neurological Sciences Institute, Oregon Health & Sciences University, USA Introduction: The coordination of the sit-to-stand motion may affect
the ability to stand up in the elderly; however, features affecting the efficiency of sit-to-stand are not understood. The Alexander Technique (AT) is a methodology that aims to improve the efficiency of coordination through consciously influencing tonic muscle activity. The AT uses sit-to-stand during instruction, evaluating specific features thought to relate to the efficiency of coordination, such as coordination of the spine during weight transfer. Investigation into the AT could suggest features important to the efficiency of coordination. Methods: Fourteen AT instructors and matched controls were asked to stand up as smoothly as possible from a standardized position while measuring surface forces and spinal kinematics. Results: AT and control subjects differed significantly in the relative durations of sit-to-stand phases, the smoothness of weight transfer, and spinal kinematics. AT subjects had a longer weight transfer duration from seat to feet (19.4±5.5% vs. 11.3±2.5%) that occurred earlier relative to trunk inclination, reduced force transients, and reduced alterations in spinal angles during weight transfer in cervical (2.1 ± 1.1 vs. 11.7±5.4°), thoracic (3.4±1.3 vs. 11.9±4.5 o) and lumbar regions (16.8±6.2 vs. 27.1±9.2°). Discussion: Differences between AT instructors and control subjects may reflect an altered kinetic strategy for sit-to-stand. The altered coordination of the spine may relate to the observed smoothness and phasing of weight transfer. Implications of this strategy are not clear and may relate to increased adaptability of tonic muscle activity observed in AT instructors (Cacciatore et al, in preparation).
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Development and clinical assessment of a copfeedback control fes balance training system for the hemiplegics
S.C. Chen 1, C.H. Lai 1, W.S. Chen 1, Y.L. Chen 2. 1Department of
Physical Medicine and Rehabilitation, Taipei Medical University and Hospital, TaipeL 2Department of Electronic Engineering, Hwa-Hsai College of Technology and Commerce, Taipei, Taiwan
Discussion: Comparing with traditional approaches, this FES system facilitated balance improvement by stimulating hemiplegic lower limbs. Results showed a clinical usefulness of this system. Conclusion: The using of prototype CoP-feedback control FES balance training system can improve standing balance of the hemiplegics effectively.
References [1] Tyler AE, Karst GM. Timing of muscle activity during reaching while standing: systematic changes with target distance. Gait & Posture 2004; 20(2): 126 33. [2] Lee MY. Using Biofeedback for Standing Steadiness, Weight Bearing Training. IEEE Engineering in Medicine and Biology 1996; 15(6): 112 116.
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synchronisation of lower limb responses with a variable metronome: the effect of biomechanical constraints on timing
H.Y. Chen, A.M. Wing. Behavioural Brain Sciences Centre, UK Introduction: Stepping in time with a metronome has been reported to
improve pathological gait [1]. Although there have been many studies of finger tapping synchronisation with a metronome [2], the specific details of the metronome's influence on walking remain unknown. We designed an experiment with four synchronisation tasks, unilateral heel tapping in sitting, bilateral heel tapping in sitting, bilateral heel tapping in standing, and stepping on the spot, which allow study of the effects of bilateral co-ordination and maintenance of balance on timing. Methods: Eight healthy participants made heel tapping and stepping responses in synchrony with a metronome producing 500 ms interpulse intervals. In each trial one interval was lengthened or shortened at a random point resulting in a shift in phase of subsequent pulses. We modelled the compensation function2 following the phase shift, in terms of the temporal difference between response and metronome pulse. Results: There was a reliable task effect [F(3,21)=7.2, P<0.05] due to decreased speed of compensation in going from bilateral heel tapping in sitting through standing to stepping. Discussion: Stepping with a variable metronome offers a new method for study of control of timing in stepping. We propose future studies of synchronisation in normal and pathological gait. Conclusion: Increasing the demand of maintaining balance causes deterioration in synchronisation performance.
References [1] Thaut MH, McIntosh GC, Rice RR. Rhythmic facilitation of gait training in hemiparetic stroke rehabilitation. J Neurol Sci 1997; 151(2): 207 12. [2] Repp BH. Compensation for subliminal timing perturbations in perceptual-motor synchronization. Psychol Res 2000; 63(2): 106 28.
Introduction: The purposes of this study are to develop a CoP-
feedback control FES balance training system for the hemiplegics and to assess the system by performing a clinical trial. By using this system, we expect an improvement of standing balance training effects. Methods: Based on analyzing the EMG of lower extremities during standing [1], we developed a CoP-feedback control FES balance training system. Quadriceps, hamstrings, anterior tibialis and gastrocnemius are stimulated individually according to feedback signals by using a fuzzy controller. Twelve subjects with hemiplegia were divided into 2 groups randomly. Six subjects received training by using this FES system (group A) for 2 weeks. Another 6 subjects received traditional rehabilitation (group B). Standing steadiness index (SSI) [2] and CoP tracks were measured before and after training. Results: Results demonstrated that improvements of standing balance are significantly better in group A than in group B (p < 0.05) in SSI and CoP tracks analyses.
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Postural disturbances in multiple sclerosis
L.A. Chernikova 1, A.V. Peressedova2, I.A. Zavalishin2. 1Department
of neurorehabilitation, Institute of neurology RAMS, Volokolamskoyo shosse, 80, Moscow 125367, Russia," 2 Department of neurology, Institute of neurology RAMS, Volokolamskoyo shosse, 80, Moscow 125367, Russia Introduction: The destabilization of the posture is one of the main
clinical features of multiple sclerosis (MS). The aim of our study was the clinico-stabilometric correlations in MS. Method: Stabilometric analysis of postural disturbances has been performed in 45 MS patients, which were divided into subgroups according to stage and course of disease. The parameters have been analyzed according to the dominant neurological syndrome.
Chapter 20. Rehabilitation and training Results: The increase of area of sway and amplitude of deviation in the sagittal and frontal planes has been revealed in the whole MS patients group and also in relapse and secondary progressive MS as compared with control. The hyperstability type of spectral changes has been shown in remission of disease. Patients with dominant paresis were more unstable than healthy subjects in the sagittal plane. The changes of all parameters (area of sway, amplitude of deviation in both planes, spectral characteristics) have been found at the Romberg test (with closed eyes). Vestibulo-cerebellar disorders were accompanied by increase of area of sway and amplitude of deviation in the sagittal and frontal planes and the changes of spectral analysis. Discussion and conclusion: Results reflect the presence of different patterns of postural ataxias in MS. The presence of compensative reorganization of the postural control system in remission and the presence of tremor in patients with vestibulo-cerebellar disorders have been revealed by spectral analysis. Thus, MS may be used as the model for posturograthic study of the role of vision, vestibular and pyramidal systems in the maintenance of standing balance.
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Correlation between the speed of exercise and joint loading during a close-chain exercise of the upper extremity
RH. Chou 1, Y.L. Chou 2, C.K. Chen 1, C.M. Kuo 2. 1Department of Orthopedic Surgery, Kaohsiung Medical University, Kaohsiung, Taiwan," 2 Institute of Biomedical Engineering, National Cheng-Kung University, Tainan, Taiwan Introduction: Push-up is a commonly used close-chain exercise to strengthen the upper extremity. Nonetheless, there is very little research regarding the kinematics of the close-chain exercise of the upper extremity. The purpose of this study is to investigate the correlation between the speed of exercise and joint loading during a close-chain exercise of the upper extremity. Methods: Fourteen male subjects volunteered in this study. The subjects were asked to perform push-up exercises in various speed (fast, regular, and slow). The Expert Vision motion system was used to measure relative joint positions and ground reaction forces. The kinematics and kinetics of the upper extremity were calculated by inverse dynamics and Newton-Eulerian's equation. Additionally, muscle activities of the shoulder were measured with surface EMG during the push-up exercise. Results: Results showed that the loading biomechanics of the upper extremity differed with various exercise speed (Table 1). Performing push-up exercise in a faster speed resulted in the greatest joint loading upon the upper extremity. Furthermore, performing the exercise in slower speed resulted in more muscle activities in pectorals, triceps, biceps, and deltoid (p < 0.05). Discussion and Conclusion: Greatest medial and lateral shear stress was produced during faster speed of push-up exercise. Performing push-up exercise in a slower speed resulted in smaller joint loading and more muscle activation upon the upper extremity. Therefore, performing close-chain exercise under slower speed may be a better strategy for strengthening of the upper extremity.
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Analysis of locomotor parameter programming in a neuromuscular disease
A. Couillandre 1'2, Y. Breni~re 3, J.Y. Hogrel 1, B. Eymard 4, R Portero 1. llnstitut de Myologie, GH Piti~ SalpOtri~re, Paris',
2Laboratoire Sport et Culture, EA 2931, UniversitO Paris' X, France; SlSERM U-483, Laboratoire de Physiologie du Mouvement, Orsay, France; 4 Unit~ clinique de pathologic neuromusculaire, Institut de Myologie, GH Piti~ SalpOtri~re, Paris', France Introduction: The nervous system has to combine step length (L) and frequency (f) in order to adjust the velocity of the centre of foot pressure (CP), expressed as v Lf, to the one of the centre of gravity (CG) at the end of gait initiation, expressed as V, resulting from the integration of propulsives forces acting on the body. Locomotor parameter programming is considered through: a) its objective, i.e., the
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adjustment of both velocities which is a necessary condition for normal walking and b) the strategy used in order to achieve this objective, i.e., the contributions of L and f to CP velocity [1]. Here, we wanted to know if a neuromuscular disease could change this programming. Methods: Gait initiation was performed by a control group and by a patient group presenting Becket Myopathy on a force plate, which allowed the computing of CG accelerations and CP positions from the ground reaction forces. We analysed the adjustment of both velocities through the slopes (s) of the linear regressions established between V and v L f a n d used the differential method [1] to analyse the strategy. Results: For both groups, V and v were adjusted at the end of the first step (sc 1.09 and sp 1.016). Step length and frequency had different contributions to CP velocity from one group to another, step frequency being the parameter contributing the most to CP velocity in the patient group. Discussion and Conclusion: These results suggest that the nervous system, by taking into account the motor deficit induced by the pathology, introduces specific changes on step length and frequency, in order to preserve the adjustment of CP to CG velocity. The differential method could be very useful in the follow up of a disease, where one could see modifications of the strategy.
References [1] Couillandre A, Breni~re Y. J Mot Behav. 2003 Sep; 35 (3): 221 7.
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Change in standing posture of lower limb amputees after muscle vibration: a potential tool for rehabilitation
C. Duclos 1'2, R. Roll 2, A. Kavounoudias 2, J.R Roll 2, R. Forget 1.
1Centre de recherche interdisciplinaire en rdadaptation du MontrEal mdtropolitain (CRIR), Institut de Rdadaptation de Montrdal, 6300 avenue Darlington, Montreal (QC), H3S 2J4, Canada; 2 UMR 6149, Laboratoire de Neurobiologie Humaine, Universitd de Provence/CNRS, 3 place Victor Hugo, case B, 13331 Marseille cedex 03, France The application of a 30s proprioceptive stimulation, such as an isometric voluntary contraction or mechanical vibration to the neck muscles leads to long-lasting body leanings [1,2]. Both types of stimulation produce postural post-effects of similar duration with a direction of response that is specific to the stimulated muscle. In this study, muscle vibration was used in lower-leg amputees to increase weight bearing on their prosthetic leg. A 30 s vibration (80 Hz) was applied to the trapezius and medial gluteus muscles ipsilaterally to the amputation (14 patients) or to the left body side (18 healthy subjects). The centre of pressure (COP) displacements were recorded for 15 minutes after the vibration to evaluate postural changes while standing with closed eyes. Asymmetrical weight bearing was observed before vibration in the amputees. Vibration of either one of the muscles produced changes of CoP position in the frontal plane that were of similar amplitudes in both groups of individuals. Although larger in the first minute after vibration, the changes remained significant for the duration of the recording. The direction of the changes was variable in both groups, but less in the amputees where overall reduced asymmetrical weight bearing was observed, particularly following a medial gluteus muscle vibration. Amputees are therefore likely to experience vibration-induced posteffects that help to correct their standing posture. However, vibration application procedures need further exploration to induce stronger oriented post-effects.
References [1] Duclos C, Roll R, Kavounoudias A, Roll J-P. Long-lasting body leanings following neck muscle isometric contractions. Exp Brain Res 2004; 158:58 66. [2] Wierzbicka MM, Gilhodes J-C, Roll J-R Vibration-induced postural posteffects. J Neurophysiol 1998; 79:143 150.
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References [1] Williams CL, Barnett AM, Meck WH. Organisational effects of early gonadal secretions on sexual differentiation in spatial memory. Behavioural Neuroscience. 1990; 104(1): 84 97. [2] Saucier DM, Green SM, Leason J, MacFadden A, Bell S, Ellias LJ. Are sex differences in navigation caused by sexually dimorphic strategies or by differences in the ability to use the strategies? Behavioural Neuroscience. 2002; 116(3): 403 410.
I•
Differences in the coordination of sit-to-stand in teachers of the Alexander technique
T.W. Cacciatore, EB. Horak, V.S. Gurfinkel. Neurological Sciences Institute, Oregon Health & Sciences University, USA Introduction: The coordination of the sit-to-stand motion may affect
the ability to stand up in the elderly; however, features affecting the efficiency of sit-to-stand are not understood. The Alexander Technique (AT) is a methodology that aims to improve the efficiency of coordination through consciously influencing tonic muscle activity. The AT uses sit-to-stand during instruction, evaluating specific features thought to relate to the efficiency of coordination, such as coordination of the spine during weight transfer. Investigation into the AT could suggest features important to the efficiency of coordination. Methods: Fourteen AT instructors and matched controls were asked to stand up as smoothly as possible from a standardized position while measuring surface forces and spinal kinematics. Results: AT and control subjects differed significantly in the relative durations of sit-to-stand phases, the smoothness of weight transfer, and spinal kinematics. AT subjects had a longer weight transfer duration from seat to feet (19.4±5.5% vs. 11.3±2.5%) that occurred earlier relative to trunk inclination, reduced force transients, and reduced alterations in spinal angles during weight transfer in cervical (2.1 ± 1.1 vs. 11.7±5.4°), thoracic (3.4±1.3 vs. 11.9±4.5 o) and lumbar regions (16.8±6.2 vs. 27.1±9.2°). Discussion: Differences between AT instructors and control subjects may reflect an altered kinetic strategy for sit-to-stand. The altered coordination of the spine may relate to the observed smoothness and phasing of weight transfer. Implications of this strategy are not clear and may relate to increased adaptability of tonic muscle activity observed in AT instructors (Cacciatore et al, in preparation).
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Development and clinical assessment of a copfeedback control fes balance training system for the hemiplegics
S.C. Chen 1, C.H. Lai 1, W.S. Chen 1, Y.L. Chen 2. 1Department of
Physical Medicine and Rehabilitation, Taipei Medical University and Hospital, TaipeL 2Department of Electronic Engineering, Hwa-Hsai College of Technology and Commerce, Taipei, Taiwan
Discussion: Comparing with traditional approaches, this FES system facilitated balance improvement by stimulating hemiplegic lower limbs. Results showed a clinical usefulness of this system. Conclusion: The using of prototype CoP-feedback control FES balance training system can improve standing balance of the hemiplegics effectively.
References [1] Tyler AE, Karst GM. Timing of muscle activity during reaching while standing: systematic changes with target distance. Gait & Posture 2004; 20(2): 126 33. [2] Lee MY. Using Biofeedback for Standing Steadiness, Weight Bearing Training. IEEE Engineering in Medicine and Biology 1996; 15(6): 112 116.
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h
e
synchronisation of lower limb responses with a variable metronome: the effect of biomechanical constraints on timing
H.Y. Chen, A.M. Wing. Behavioural Brain Sciences Centre, UK Introduction: Stepping in time with a metronome has been reported to
improve pathological gait [1]. Although there have been many studies of finger tapping synchronisation with a metronome [2], the specific details of the metronome's influence on walking remain unknown. We designed an experiment with four synchronisation tasks, unilateral heel tapping in sitting, bilateral heel tapping in sitting, bilateral heel tapping in standing, and stepping on the spot, which allow study of the effects of bilateral co-ordination and maintenance of balance on timing. Methods: Eight healthy participants made heel tapping and stepping responses in synchrony with a metronome producing 500 ms interpulse intervals. In each trial one interval was lengthened or shortened at a random point resulting in a shift in phase of subsequent pulses. We modelled the compensation function2 following the phase shift, in terms of the temporal difference between response and metronome pulse. Results: There was a reliable task effect [F(3,21)=7.2, P<0.05] due to decreased speed of compensation in going from bilateral heel tapping in sitting through standing to stepping. Discussion: Stepping with a variable metronome offers a new method for study of control of timing in stepping. We propose future studies of synchronisation in normal and pathological gait. Conclusion: Increasing the demand of maintaining balance causes deterioration in synchronisation performance.
References [1] Thaut MH, McIntosh GC, Rice RR. Rhythmic facilitation of gait training in hemiparetic stroke rehabilitation. J Neurol Sci 1997; 151(2): 207 12. [2] Repp BH. Compensation for subliminal timing perturbations in perceptual-motor synchronization. Psychol Res 2000; 63(2): 106 28.
Introduction: The purposes of this study are to develop a CoP-
feedback control FES balance training system for the hemiplegics and to assess the system by performing a clinical trial. By using this system, we expect an improvement of standing balance training effects. Methods: Based on analyzing the EMG of lower extremities during standing [1], we developed a CoP-feedback control FES balance training system. Quadriceps, hamstrings, anterior tibialis and gastrocnemius are stimulated individually according to feedback signals by using a fuzzy controller. Twelve subjects with hemiplegia were divided into 2 groups randomly. Six subjects received training by using this FES system (group A) for 2 weeks. Another 6 subjects received traditional rehabilitation (group B). Standing steadiness index (SSI) [2] and CoP tracks were measured before and after training. Results: Results demonstrated that improvements of standing balance are significantly better in group A than in group B (p < 0.05) in SSI and CoP tracks analyses.
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Postural disturbances in multiple sclerosis
L.A. Chernikova 1, A.V. Peressedova2, I.A. Zavalishin2. 1Department
of neurorehabilitation, Institute of neurology RAMS, Volokolamskoyo shosse, 80, Moscow 125367, Russia," 2 Department of neurology, Institute of neurology RAMS, Volokolamskoyo shosse, 80, Moscow 125367, Russia Introduction: The destabilization of the posture is one of the main
clinical features of multiple sclerosis (MS). The aim of our study was the clinico-stabilometric correlations in MS. Method: Stabilometric analysis of postural disturbances has been performed in 45 MS patients, which were divided into subgroups according to stage and course of disease. The parameters have been analyzed according to the dominant neurological syndrome.
Chapter 20. Rehabilitation and training Results: The increase of area of sway and amplitude of deviation in the sagittal and frontal planes has been revealed in the whole MS patients group and also in relapse and secondary progressive MS as compared with control. The hyperstability type of spectral changes has been shown in remission of disease. Patients with dominant paresis were more unstable than healthy subjects in the sagittal plane. The changes of all parameters (area of sway, amplitude of deviation in both planes, spectral characteristics) have been found at the Romberg test (with closed eyes). Vestibulo-cerebellar disorders were accompanied by increase of area of sway and amplitude of deviation in the sagittal and frontal planes and the changes of spectral analysis. Discussion and conclusion: Results reflect the presence of different patterns of postural ataxias in MS. The presence of compensative reorganization of the postural control system in remission and the presence of tremor in patients with vestibulo-cerebellar disorders have been revealed by spectral analysis. Thus, MS may be used as the model for posturograthic study of the role of vision, vestibular and pyramidal systems in the maintenance of standing balance.
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Correlation between the speed of exercise and joint loading during a close-chain exercise of the upper extremity
RH. Chou 1, Y.L. Chou 2, C.K. Chen 1, C.M. Kuo 2. 1Department of Orthopedic Surgery, Kaohsiung Medical University, Kaohsiung, Taiwan," 2 Institute of Biomedical Engineering, National Cheng-Kung University, Tainan, Taiwan Introduction: Push-up is a commonly used close-chain exercise to strengthen the upper extremity. Nonetheless, there is very little research regarding the kinematics of the close-chain exercise of the upper extremity. The purpose of this study is to investigate the correlation between the speed of exercise and joint loading during a close-chain exercise of the upper extremity. Methods: Fourteen male subjects volunteered in this study. The subjects were asked to perform push-up exercises in various speed (fast, regular, and slow). The Expert Vision motion system was used to measure relative joint positions and ground reaction forces. The kinematics and kinetics of the upper extremity were calculated by inverse dynamics and Newton-Eulerian's equation. Additionally, muscle activities of the shoulder were measured with surface EMG during the push-up exercise. Results: Results showed that the loading biomechanics of the upper extremity differed with various exercise speed (Table 1). Performing push-up exercise in a faster speed resulted in the greatest joint loading upon the upper extremity. Furthermore, performing the exercise in slower speed resulted in more muscle activities in pectorals, triceps, biceps, and deltoid (p < 0.05). Discussion and Conclusion: Greatest medial and lateral shear stress was produced during faster speed of push-up exercise. Performing push-up exercise in a slower speed resulted in smaller joint loading and more muscle activation upon the upper extremity. Therefore, performing close-chain exercise under slower speed may be a better strategy for strengthening of the upper extremity.
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Analysis of locomotor parameter programming in a neuromuscular disease
A. Couillandre 1'2, Y. Breni~re 3, J.Y. Hogrel 1, B. Eymard 4, R Portero 1. llnstitut de Myologie, GH Piti~ SalpOtri~re, Paris',
2Laboratoire Sport et Culture, EA 2931, UniversitO Paris' X, France; SlSERM U-483, Laboratoire de Physiologie du Mouvement, Orsay, France; 4 Unit~ clinique de pathologic neuromusculaire, Institut de Myologie, GH Piti~ SalpOtri~re, Paris', France Introduction: The nervous system has to combine step length (L) and frequency (f) in order to adjust the velocity of the centre of foot pressure (CP), expressed as v Lf, to the one of the centre of gravity (CG) at the end of gait initiation, expressed as V, resulting from the integration of propulsives forces acting on the body. Locomotor parameter programming is considered through: a) its objective, i.e., the
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adjustment of both velocities which is a necessary condition for normal walking and b) the strategy used in order to achieve this objective, i.e., the contributions of L and f to CP velocity [1]. Here, we wanted to know if a neuromuscular disease could change this programming. Methods: Gait initiation was performed by a control group and by a patient group presenting Becket Myopathy on a force plate, which allowed the computing of CG accelerations and CP positions from the ground reaction forces. We analysed the adjustment of both velocities through the slopes (s) of the linear regressions established between V and v L f a n d used the differential method [1] to analyse the strategy. Results: For both groups, V and v were adjusted at the end of the first step (sc 1.09 and sp 1.016). Step length and frequency had different contributions to CP velocity from one group to another, step frequency being the parameter contributing the most to CP velocity in the patient group. Discussion and Conclusion: These results suggest that the nervous system, by taking into account the motor deficit induced by the pathology, introduces specific changes on step length and frequency, in order to preserve the adjustment of CP to CG velocity. The differential method could be very useful in the follow up of a disease, where one could see modifications of the strategy.
References [1] Couillandre A, Breni~re Y. J Mot Behav. 2003 Sep; 35 (3): 221 7.
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Change in standing posture of lower limb amputees after muscle vibration: a potential tool for rehabilitation
C. Duclos 1'2, R. Roll 2, A. Kavounoudias 2, J.R Roll 2, R. Forget 1.
1Centre de recherche interdisciplinaire en rdadaptation du MontrEal mdtropolitain (CRIR), Institut de Rdadaptation de Montrdal, 6300 avenue Darlington, Montreal (QC), H3S 2J4, Canada; 2 UMR 6149, Laboratoire de Neurobiologie Humaine, Universitd de Provence/CNRS, 3 place Victor Hugo, case B, 13331 Marseille cedex 03, France The application of a 30s proprioceptive stimulation, such as an isometric voluntary contraction or mechanical vibration to the neck muscles leads to long-lasting body leanings [1,2]. Both types of stimulation produce postural post-effects of similar duration with a direction of response that is specific to the stimulated muscle. In this study, muscle vibration was used in lower-leg amputees to increase weight bearing on their prosthetic leg. A 30 s vibration (80 Hz) was applied to the trapezius and medial gluteus muscles ipsilaterally to the amputation (14 patients) or to the left body side (18 healthy subjects). The centre of pressure (COP) displacements were recorded for 15 minutes after the vibration to evaluate postural changes while standing with closed eyes. Asymmetrical weight bearing was observed before vibration in the amputees. Vibration of either one of the muscles produced changes of CoP position in the frontal plane that were of similar amplitudes in both groups of individuals. Although larger in the first minute after vibration, the changes remained significant for the duration of the recording. The direction of the changes was variable in both groups, but less in the amputees where overall reduced asymmetrical weight bearing was observed, particularly following a medial gluteus muscle vibration. Amputees are therefore likely to experience vibration-induced posteffects that help to correct their standing posture. However, vibration application procedures need further exploration to induce stronger oriented post-effects.
References [1] Duclos C, Roll R, Kavounoudias A, Roll J-P. Long-lasting body leanings following neck muscle isometric contractions. Exp Brain Res 2004; 158:58 66. [2] Wierzbicka MM, Gilhodes J-C, Roll J-R Vibration-induced postural posteffects. J Neurophysiol 1998; 79:143 150.