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1.
Hum Mov Sci ; 97: 103258, 2024 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-39116509

RESUMEN

PURPOSE: To determine whether the application of continuous lateral trunk support forces during walking would improve trunk postural control and improve gait performance in children with CP. MATERIALS AND METHODS: Nineteen children with spastic CP participated in this study (8 boys; mean age 10.6 ± 3.4 years old). Fourteen of them were tested in the following sessions: 1) walking on a treadmill without force for 1-min (baseline), 2) with lateral trunk support force for 7-min (adaptation), and 3) without force for 1-min (post-adaptation). Overground walking pre/post treadmill walking. Five of them were tested using a similar protocol but without trunk support force (i.e., control). RESULTS: Participants from the experimental group showed enhancement in gait phase dependent muscle activation of rectus abdominis in late adaptation period compared to baseline (P = 0.005), which was retained during the post-adaptation period (P = 0.036), reduced variability of the peak trunk oblique angle during the late post-adaptation period (P = 0.023), and increased overground walking speed after treadmill walking (P = 0.032). Participants from the control group showed modest changes in kinematics and EMG during treadmill and overground walking performance. These results suggest that applying continuous lateral trunk support during walking is likely to induce learning of improved trunk postural control in children with CP, which may partially transfer to overground walking, although we do not have a firm conclusion due to the small sample size in the control group.


Asunto(s)
Parálisis Cerebral , Electromiografía , Equilibrio Postural , Torso , Caminata , Humanos , Masculino , Niño , Parálisis Cerebral/fisiopatología , Proyectos Piloto , Femenino , Caminata/fisiología , Equilibrio Postural/fisiología , Fenómenos Biomecánicos/fisiología , Torso/fisiopatología , Torso/fisiología , Adolescente , Adaptación Fisiológica/fisiología , Marcha/fisiología , Postura/fisiología , Prueba de Esfuerzo , Músculo Esquelético/fisiopatología
2.
Artículo en Inglés | MEDLINE | ID: mdl-38969255

RESUMEN

OBJECTIVES: To evaluate if acute intermittent hypoxia (AIH) coupled with transcutaneous spinal cord stimulation (tSCS) enhances task-specific training and leads to superior and more sustained gait improvements as compared with each of these strategies used in isolation in persons with chronic, incomplete spinal cord injury. DESIGN: Proof of concept, randomized crossover trial. SETTING: Outpatient, rehabilitation hospital. INTERVENTIONS: Ten participants completed 3 intervention arms: (1) AIH, tSCS, and gait training (AIH + tSCS); (2) tSCS plus gait training (SHAM AIH + tSCS); and (3) gait training alone (SHAM + SHAM). Each arm consisted of 5 consecutive days of intervention with a minimum of a 4-week washout between arms. The order of arms was randomized. The study took place from December 3, 2020, to January 4, 2023. MAIN OUTCOME MEASURES: 10-meter walk test at self-selected velocity (SSV) and fast velocity, 6-minute walk test, timed Up and Go (TUG) and secondary outcome measures included isometric ankle plantarflexion and dorsiflexion torque RESULTS: TUG improvements were 3.44 seconds (95% CI: 1.24-5.65) significantly greater in the AIH + tSCS arm than the SHAM AIH + tSCS arm at post-intervention (POST), and 3.31 seconds (95% CI: 1.03-5.58) greater than the SHAM + SHAM arm at 1-week follow up (1WK). SSV was 0.08 m/s (95% CI: 0.02-0.14) significantly greater following the AIH + tSCS arm than the SHAM AIH + tSCS at POST. Although not significant, the AIH + tSCS arm also demonstrated the greatest average improvements compared with the other 2 arms at POST and 1WK for the 6-minute walk test, fast velocity, and ankle plantarflexion torque. CONCLUSIONS: This pilot study is the first to demonstrate that combining these 3 neuromodulation strategies leads to superior improvements in the TUG and SSV for individuals with chronic incomplete spinal cord injury and warrants further investigation.

3.
Biomed Eng Lett ; 14(3): 523-535, 2024 May.
Artículo en Inglés | MEDLINE | ID: mdl-38645583

RESUMEN

Despite recent studies indicating a significant correlation between somatosensory deficits and rehabilitation outcomes, how prevailing somatosensory deficits affect stroke survivors' ability to correct their movements and recover overall remains unclear. To explore how major deficits in somatosensory systems impede stroke survivors' motor correction to various external loads, we conducted a study with 13 chronic stroke survivors who had hemiparesis. An inertial, elastic, or viscous load, which was designed to impose perturbing forces with various force profiles, was introduced unexpectedly during the reaching task using a programmable haptic robot. Participants' proprioception and cutaneous sensation were also assessed using passive movement detection, finger-to-nose, mirror, repositioning, and Weinstein pressure tests. These measures were then analyzed to determine whether the somatosensory measures significantly correlated with the estimated reaching performance parameters, such as initial directional error, positional deviation, velocity deviations, and speed of motor correction were measured. Of 13 participants, 5 had impaired proprioception, as they could not recognize the passive movement of their elbow joint, and they kept showing larger initial directional errors even after the familiarization block. Such continuously found inaccurate initial movement direction might be correlated with the inability to develop the spatial body map especially for calculating the initial joint torques when starting the reaching movement. Regardless of whether proprioception was impaired or not, all participants could show the stabilized, constant reaching movement trajectories. This highlights the role of proprioception especially in the execution of a planned movement at the early stage of reaching movement.

4.
Exp Brain Res ; 242(1): 275-293, 2024 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-38015245

RESUMEN

The purpose of this study was to examine kinematic and neuromuscular responses of the head and body to pelvis perturbations with different intensities and frequencies during sitting astride in children with CP. Sixteen children with spastic CP (mean age 7.4 ± 2.4 years old) were recruited in this study. A custom designed cable-driven robotic horse was used to apply controlled force perturbations to the pelvis during sitting astride. Each participant was tested in four force intensity conditions (i.e., 10%, 15%, 20%, and 25% of body weight (BW), frequency = 1 Hz), and six force frequency conditions (i.e., 0.5 Hz, 1 Hz, 1.5 Hz, 2 Hz, 2.5 Hz, and 3 Hz, intensity = 20% of BW). Each testing session lasted for one minute with a one-minute rest break inserted between two sessions. Kinematic data of the head, trunk, and legs were recorded using wearable sensors, and EMG signals of neck, trunk, and leg muscles were recorded. Children with CP showed direction-specific trunk and neck muscle activity in response to the pelvis perturbations during sitting astride. Greater EMG activities of trunk and neck muscles were observed for the greater intensities of force perturbations (P < .05). Participants also showed enhanced activation of antagonistic muscles rather than direction-specific trunk and neck muscle activities for the conditions of higher frequency perturbations (P < .05). Children with CP may modulate trunk and neck muscle activities in response to greater changes in intensity of pelvis perturbation during sitting astride. Perturbations with too high frequency may be less effective in inducing direction-specific trunk and neck muscle activities.


Asunto(s)
Parálisis Cerebral , Postura , Sedestación , Niño , Preescolar , Humanos , Electromiografía , Músculo Esquelético/fisiología , Postura/fisiología
5.
Neurorehabil Neural Repair ; 37(2-3): 83-93, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-36987396

RESUMEN

BACKGROUND: The Graded Redefined Assessment of Strength, Sensation, and Prehension (GRASSP V1.0) was developed in 2010 as a 3-domain assessment for upper extremity function after tetraplegia (domains: Strength, Sensibility, and Prehension). A remote version (rGRASSP) was created in response to the growing needs of the field of Telemedicine. OBJECTIVE: The purpose of this study was to assess the psychometric properties of rGRASSP, establishing concurrent validity and inter-rater reliability. METHODS: Individuals with tetraplegia (n = 61) completed 2 visits: 1 in-person and 1 remote. The first visit was completed in-person to administer the GRASSP, and the second visit was conducted remotely to administer the rGRASSP. The rGRASSP was scored both by the administrator of the rGRASSP (Examiner 1), and a second assessor (Examiner 2) to establish inter-rater reliability. Agreement between the in-person and remote GRASSP evaluations was assessed using the intraclass correlation coefficient (ICC) and Bland-Altman agreement plots. RESULTS: The remote GRASSP demonstrated excellent concurrent validity with the GRASSP (left hand intraclass correlation coefficient (ICC) = .96, right ICC = .96). Concurrent validity for the domains was excellent for strength (left ICC = .96, right ICC = .95), prehension ability (left ICC = .94, right ICC = .95), and prehension performance (left ICC = .92, right ICC = .93), and moderate for sensibility (left ICC = .59, right ICC = .68). Inter-rater reliability for rGRASSP total score was high (ICC = .99), and remained high for all 4 domains. Bland-Altman plots and limits of agreements support these findings. CONCLUSIONS: The rGRASSP shows strong concurrent validity and inter-rater reliability, providing a psychometrically sound remote assessment for the upper extremity in individuals with tetraplegia.


Asunto(s)
Traumatismos de la Médula Espinal , Humanos , Reproducibilidad de los Resultados , Cuadriplejía , Extremidad Superior , Sensación/fisiología
6.
Bioengineering (Basel) ; 10(3)2023 Mar 18.
Artículo en Inglés | MEDLINE | ID: mdl-36978764

RESUMEN

The purpose of this study was to investigate the influence of changes in muscle length on the torque fluctuations and on related oscillations in muscle activity during voluntary isometric contractions of ankle plantar flexor muscles. Eleven healthy individuals were asked to perform voluntary isometric contractions of ankle muscles at five different contraction intensities from 10% to 70% of maximum voluntary isometric contraction (MVIC) and at three different muscle lengths, implemented by changing the ankle joint angle (plantar flexion of 26°-shorter muscle length; plantar flexion of 10°-neutral muscle length; dorsiflexion of 3°-longer muscle length). Surface electromyogram (EMG) signals were recorded from the skin surface over the triceps surae muscles, and rectified-and-smoothed EMG (rsEMG) were estimated to assess the oscillations in muscle activity. The absolute torque fluctuations (quantified by the standard deviation) were significantly higher during moderate-to-high contractions at the longer muscle length. Absolute torque fluctuations were found to be a linear function of torque output regardless of muscle length. In contrast, the relative torque fluctuations (quantified by the coefficient of variation) were higher at the shorter muscle length. However, both absolute and relative oscillations in muscle activities remained relatively consistent at different ankle joint angles for all plantar flexors. These findings suggest that the torque steadiness may be affected by not only muscle activities, but also by muscle length-dependent mechanical properties. This study provides more insights that muscle mechanics should be considered when explaining the steadiness in force output.

7.
Am J Phys Med Rehabil ; 102(9): 795-802, 2023 09 01.
Artículo en Inglés | MEDLINE | ID: mdl-36946368

RESUMEN

OBJECTIVE: The aim of this study is to determine the effects of bilateral trunk support during walking on trunk and leg kinematics and neuromuscular responses in children with cerebral palsy. DESIGN: Fourteen children with spastic cerebral palsy (Gross Motor Function Classification System level I to III) participated in this study. Children walked on a treadmill under four different conditions, that is, without support (Baseline), with bilateral support applied to the upper trunk (upper trunk support), the lower trunk (lower trunk support), and combined upper and lower trunk (combined trunk support). The trunk and leg kinematics and muscle activity were recorded. RESULTS: Providing bilateral support to the trunk had a significant impact on the displacement of the pelvis and trunk ( P < 0.003) during walking. Children's weaker leg showed greater step length ( P = 0.032) and step height ( P = 0.012) in combined trunk support compared with baseline and greater step length in upper trunk support ( P = 0.02) and combined trunk support ( P = 0.022) compared with lower trunk support. Changes in soleus electromyographic activity during stance phase of gait mirrored the changes in step length across all conditions. CONCLUSIONS: Providing bilateral upper or combined upper and lower trunk support during walking may induce improvements in gait performance, which may be due to improved pelvis kinematics. Improving trunk postural control may facilitate walking in children with cerebral palsy.


Asunto(s)
Parálisis Cerebral , Humanos , Niño , Proyectos Piloto , Caminata/fisiología , Marcha/fisiología , Equilibrio Postural/fisiología , Fenómenos Biomecánicos
8.
J Electromyogr Kinesiol ; 66: 102680, 2022 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-35843049

RESUMEN

The purpose of this study was to investigate the potential effects of key neuromuscular factors on muscle activation-force relationships, thereby helping us understand abnormal EMG-force relationships often reported in chronic stroke-impaired muscles. A modified Hill-type muscle model was developed to calculate muscle force production for a given muscle activation level and musculotendon length. Model parameters used to characterize musculotendon unit properties of medial gastrocnemius were adjusted to simulate known stroke-related changes in neuromuscular factors (e.g., voluntary activation and muscle mechanical properties). The muscle activation-force slope (i.e., muscle activation over force) was computed as a function of ankle joint angle. A Monte Carlo simulation approach was implemented to understand which neuromuscular factors are closely associated with the activation-force slope. Our simulations showed that a reduction in factors linked to voluntary activation capacity and to maximum force-generating capacity may be the primary contributors that increase the activation-force slope in dorsiflexed positions, and that a narrower active force-length curve appears to be the most significant factor that increases the slope in plantar flexed positions. In addition, our Monte Carlo simulation results demonstrated that an increase in the activation-force slope is strongly correlated with a reduction in voluntary activation capacity, in the maximum force-generating capacity, and in the active force-length curve width. These findings will help us to better interpret altered EMG-force relationships following chronic stroke.


Asunto(s)
Músculo Esquelético , Accidente Cerebrovascular , Simulación por Computador , Electromiografía/métodos , Humanos , Contracción Isométrica/fisiología , Músculo Esquelético/fisiología , Rango del Movimiento Articular , Accidente Cerebrovascular/complicaciones
9.
J Neural Eng ; 19(3)2022 06 20.
Artículo en Inglés | MEDLINE | ID: mdl-35671714

RESUMEN

Objective. Botulinum toxin (BT) induced cholinergic denervation of hyperactive motor units (MUs) is a clinically accepted and extensively practiced way of managing focal spasticity after stroke. The denervation potentially initiates a temporary reorganization of the MU activation patterns and structures by inducing the emergence of a large number of newly innervated muscle fibers. In this study, we quantify the effect of the BT on MU action potential (MUAP) amplitudes and on the MU territory areas (MUTAs) as seen on the surface of the skin over the biceps brachii (BB) muscle.Approach. We have used a 128-channel high-density surface electromyography (HDsEMG) grid on the spastic and contralateral BB muscle and recorded the myoelectric activity along with the contraction force during isometric contraction of the elbow muscles. We have decomposed the recorded EMG signal into individual MU potentials and estimated the MUAP amplitudes and territory areas before and two weeks after a BT injection.Main result. There were significantly larger median (47 ± 9%) MUAP amplitudes as well as reduction of MUTA (20 ± 2%) two weeks after the injection compared to the respective pre-injection recording.Significance. The observed covariation of the amplitude and the territory area indicates that the large amplitude MUs that appeared after the BT injection have a relatively smaller territory area. These results provide a rare insight into the BT-induced changes of MU characteristics and have the potential to improve spasticity treatment. We discuss the potential contributing factors to these changes subsequent to the injection in the context of the investigated subject cohort.


Asunto(s)
Toxinas Botulínicas , Contracción Isométrica , Potenciales de Acción/fisiología , Electromiografía/métodos , Humanos , Contracción Isométrica/fisiología , Espasticidad Muscular/tratamiento farmacológico , Músculo Esquelético/fisiología
10.
J Electromyogr Kinesiol ; 61: 102609, 2021 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-34689116

RESUMEN

The purpose of this study was to investigate the influence of changes in ankle joint angle on the mechanomyogram (MMG) amplitude of the human medial gastrocnemius (MG) muscle during voluntary isometric plantarflexion contractions. Ten healthy individuals were asked to perform voluntary isometric contractions at six different contraction intensities (from 10% to 100%) and at three different ankle joint angles (plantarflexion of 26°; plantarflexion of 10°; dorsiflexion of 3°). MMG signals were recorded from the surface over the MG muscle, using a 3-axis accelerometer. The relations between root mean square (RMS) MMG and isometric plantarflexion torque at different ankle joint angles were characterized to evaluate the effects of altered muscle mechanical properties on RMS MMG. We found that the relation between RMS MMG and plantarflexion torque is changed at different ankle joint angles: RMS MMG increases monotonically with increasing the plantarflexion torque but decreases as the ankle joint became dorsiflexed. Moreover, RMS MMG shows a negative correlation with muscle length, with passive torque, and with maximum voluntary torque, which were all changed significantly at different ankle joint angles. Our findings demonstrate the potential effects of changing muscle mechanical properties on muscle vibration amplitude. Future studies are required to explore the major sources of this muscle vibration from the perspective of muscle mechanics and muscle activation level, attributable to changes in the neural command.


Asunto(s)
Articulación del Tobillo , Tobillo , Electromiografía , Humanos , Contracción Isométrica , Músculo Esquelético , Torque
11.
Exp Brain Res ; 239(10): 3091-3104, 2021 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-34401936

RESUMEN

When lifting or moving a novel object, humans are routinely able to quickly characterize the nature of the unknown load and swiftly achieve the desired movement trajectory. It appears that both tactile and proprioceptive feedback systems help humans develop an accurate prediction of load properties and determine how associated limb segments behave during voluntary movements. While various types of limb movement information, such as position, velocity, acceleration, and manipulating forces, can be detected using human tactile and proprioceptive systems, we know little about how the central nervous system decodes these various types of movement data, and in which order or priority they are used when developing predictions of joint motion during novel object manipulation. In this study, we tested whether the ability to predict motion is different between position- (elastic), velocity- (viscous), and acceleration-dependent (inertial) loads imposed using a multiaxial haptic robot. Using this protocol, we can learn if the prediction of the motion model is optimized for one or more of these types of mechanical load. We examined ten neurologically intact subjects. Our key findings indicated that inertial and viscous loads showed the fastest adaptation speed, whereas elastic loads showed the slowest adaptation speed. Different speeds of adaptation were observed across different magnitudes of the load, suggesting that human capabilities for predicting joint motion and manipulating loads may vary systematically with different load types and load magnitudes. Our results imply that human capabilities for load manipulation seems to be most sensitive to and potentially optimized for inertial loads.


Asunto(s)
Adaptación Fisiológica , Movimiento , Aceleración , Humanos , Propiocepción , Sujetos de Investigación
12.
J Electromyogr Kinesiol ; 56: 102475, 2021 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-33242750

RESUMEN

Electromechanical delay (EMD) is the time delay between the onset of muscle activity and the onset of force/joint torque. This delay appears to be linked to muscular contraction efficiency. However, to our knowledge, limited evidence is available regarding the magnitude of the EMD in stroke-impaired muscles. Accordingly, this study aims to quantify the EMD in both paretic and non-paretic triceps surae muscles of chronic hemispheric stroke survivors, and to investigate whether the EMD is related to voluntary force-generating capacity in this muscle group. Nine male chronic stroke survivors were asked to perform isometric plantarflexion contractions at different force levels and at different ankle joint angles ranging from maximum plantarflexion to maximum dorsiflexion. The surface electromyograms were recorded from triceps surae muscles. The longest EMD among triceps surae muscles was chosen as the EMD for each side. Our results revealed that the EMD in paretic muscles was significantly longer than in non-paretic muscles. Moreover, both paretic and non-paretic muscles showed a negative correlation between the EMD and maximum torque-generating capacity. In addition, there was a strong positive relationship between the EMD and shear wave speed in paretic muscles as well as a negative relationship between the EMD and passive ankle joint range of motion. These findings imply that the EMD may be a useful biomarker, in part, associated with contractile and material properties in stroke-impaired muscles.


Asunto(s)
Electromiografía/métodos , Contracción Isométrica/fisiología , Debilidad Muscular/fisiopatología , Músculo Esquelético/fisiología , Accidente Cerebrovascular/fisiopatología , Sobrevivientes , Anciano , Enfermedad Crónica , Humanos , Masculino , Persona de Mediana Edad , Debilidad Muscular/etiología , Rango del Movimiento Articular/fisiología , Accidente Cerebrovascular/complicaciones , Torque
13.
J Physiol ; 598(22): 5183-5194, 2020 11.
Artículo en Inglés | MEDLINE | ID: mdl-32818308

RESUMEN

KEY POINTS: Maximum fascicle shortening/rotation was significantly decreased in paretic medial gastrocnemius (MG) muscles compared to non-paretic MG muscles. The fascicle gear ratio on both sides decreased as the ankle became dorsiflexed, but the slope of the fascicle gear ratio over ankle joint angle was significantly lower on the paretic side. The side-to-side slope difference was strongly correlated with the relative maximum joint torque and with the relative shear wave speed, suggesting that variable gearing may explain muscle weakness after stroke. ABSTRACT: The present study aimed to understand variable fascicle gearing during voluntary isometric contractions of the medial gastrocnemius (MG) muscle in chronic stroke survivors. Using ultrasonography, we characterized fascicle behaviour on both paretic and non-paretic sides during plantarflexion contractions at different intensities and at different ankle joint angles. Shear wave speed was also recorded from the MG muscle belly under passive conditions. Fascicle gear ratios were then calculated as the ratio of muscle belly shortening velocity to fascicle shortening velocity, and variable fascicle gearing was quantified from the slope of gear ratio vs. joint angle relations. This slope was used to establish associations with maximum joint torques and with shear wave speeds. At all measured angles, we found a significant reduction in both maximum fascicle shortening and maximum fascicle rotation on the paretic side compared to the non-paretic side on our stroke survivor cohort. The fascicle rotation per fascicle shortening on the paretic side was also significantly smaller than on the non-paretic side, especially at plantarflexed positions. Furthermore, the fascicle gear ratio on both sides decreased as the ankle became dorsiflexed, but the change in the fascicle gear ratio was significantly lower on the paretic side. The side-to-side difference in the gear ratio slope was also strongly correlated with the relative maximum joint torque and with the relative shear wave speed, suggesting that variable gearing may explain muscle weakness after stroke. Further studies are needed to investigate how muscular changes after stroke may impede variable gearing and adversely impact muscle performance.


Asunto(s)
Contracción Isométrica , Accidente Cerebrovascular , Articulación del Tobillo/diagnóstico por imagen , Humanos , Masculino , Músculo Esquelético/diagnóstico por imagen , Accidente Cerebrovascular/diagnóstico por imagen , Sobrevivientes , Ultrasonografía
15.
Front Neurol ; 11: 224, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32318013

RESUMEN

The slope of the EMG-torque relation is potentially useful as a parameter related to muscular contraction efficiency, as a greater EMG-torque slope has often been reported in stroke-impaired muscles, compared to intact muscles. One major barrier limiting the use of this parameter on a routine basis is that we do not know how the EMG-torque slope is affected by changing joint angles. Thus, the primary purpose of this study is to characterize the EMG-torque relations of triceps surae muscles at different ankle joint angles in both paretic and non-paretic limbs of chronic hemispheric stroke survivors. Nine male chronic stroke survivors were asked to perform isometric plantarflexion contractions at different contraction intensities and at five different ankle joint angles, ranging from maximum plantarflexion to maximum dorsiflexion. Our results showed that the greater slope of the EMG-torque relations was found on the paretic side compared to the non-paretic side at comparable ankle joint angles. The EMG-torque slope increased as the ankle became plantarflexed on both sides, but an increment of the EMG-torque slope (i.e., the coefficient a) was significantly greater on the paretic side. Moreover, the relative (non-paretic/paretic) coefficient a was also strongly correlated with the relative (paretic/non-paretic) maximum ankle plantarflexion torque and with shear wave speed in the medial gastrocnemius muscle. Conversely, the relative coefficient a was not well-correlated with the relative muscle thickness. Our findings suggest that muscular contraction efficiency is affected by hemispheric stroke, but in an angle-dependent and non-uniform manner. These findings may allow us to explore the relative contributions of neural factors and muscular changes to voluntary force generating-capacity after stroke.

16.
Artículo en Inglés | MEDLINE | ID: mdl-31518566

RESUMEN

This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.

17.
Eur J Neurosci ; 50(8): 3221-3234, 2019 10.
Artículo en Inglés | MEDLINE | ID: mdl-31161634

RESUMEN

People with incomplete spinal cord injury (iSCI) usually show impairments in lateral balance control during walking. Effective interventions for improving balance control are still lacking, probably due to limited understanding of motor learning mechanisms. The objective of this study was to determine how error size and error variability impact the motor learning of lateral balance control during walking in people with iSCI. Fifteen people with iSCI were recruited. A controlled assistance force was applied to the pelvis in the medial-lateral direction using a customized cable-driven robotic system. Participants were tested using 3 conditions, including abrupt, gradual, and varied forces. In each condition, participants walked on a treadmill with no force for 1 min (baseline), with force for 9 min (adaptation), and then with no force for additional 2 min (post-adaptation). The margin of stability at heel contact (MoS_HC) and minimum value moment (MoS_Min) were calculated to compare the learning effect across different conditions. Electromyogram signals from the weaker leg were also collected. Participants showed an increase in MoS_Min (after effect) following force release during the post-adaptation period for all three conditions. Participants showed a faster adaptation and a shorter lasting of after effect in MoS_Min for the varied condition in comparison with the gradual and abrupt force conditions. Increased error variability may facilitate motor learning in lateral balance control during walking in people with iSCI, although a faster learning may induce a shorter lasting of after effect. Error size did not show an impact on the lasting of after effect.


Asunto(s)
Equilibrio Postural , Traumatismos de la Médula Espinal/rehabilitación , Caminata , Adaptación Fisiológica , Adulto , Anciano , Fenómenos Biomecánicos , Electromiografía , Femenino , Humanos , Aprendizaje , Pierna , Masculino , Persona de Mediana Edad , Músculo Esquelético/fisiopatología , Rehabilitación Neurológica/métodos , Equilibrio Postural/fisiología , Robótica , Traumatismos de la Médula Espinal/fisiopatología , Terapia Asistida por Computador , Resultado del Tratamiento , Caminata/fisiología , Adulto Joven
18.
Front Neurol ; 10: 468, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-31133971

RESUMEN

Cortical and subcortical plastic reorganization occurs in the course of motor recovery after stroke. It is largely accepted that plasticity of ipsilesional motor cortex primarily contributes to recovery of motor function, while the contributions of contralesional motor cortex are not completely understood. As a result of damages to motor cortex and its descending pathways and subsequent unmasking of inhibition, there is evidence of upregulation of reticulospinal tract (RST) excitability in the contralesional side. Both animal studies and human studies with stroke survivors suggest and support the role of RST hyperexcitability in post-stroke spasticity. Findings from animal studies demonstrate the compensatory role of RST hyperexcitability in recovery of motor function. In contrast, RST hyperexcitability appears to be related more to abnormal motor synergy and disordered motor control in stroke survivors. It does not contribute to recovery of normal motor function. Recent animal studies highlight laterality dominance of corticoreticular projections. In particular, there exists upregulation of ipsilateral corticoreticular projections from contralesional premotor cortex (PM) and supplementary motor area (SMA) to medial reticular nuclei. We revisit and revise the previous theoretical framework and propose a unifying account. This account highlights the importance of ipsilateral PM/SMA-cortico-reticulospinal tract hyperexcitability from the contralesional motor cortex as a result of disinhibition after stroke. This account provides a pathophysiological basis for post-stroke spasticity and related movement impairments, such as abnormal motor synergy and disordered motor control. However, further research is needed to examine this pathway in stroke survivors to better understand its potential roles, especially in muscle strength and motor recovery. This account could provide a pathophysiological target for developing neuromodulatory interventions to manage spasticity and thus possibly to facilitate motor recovery.

19.
J Neural Eng ; 15(1): 016014, 2018 02.
Artículo en Inglés | MEDLINE | ID: mdl-28994667

RESUMEN

OBJECTIVE: Chronic muscle weakness impacts the majority of individuals after a stroke. The origins of this hemiparesis is multifaceted, and an altered spinal control of the motor unit (MU) pool can lead to muscle weakness. However, the relative contribution of different MU recruitment and discharge organization is not well understood. In this study, we sought to examine these different effects by utilizing a MU simulation with variations set to mimic the changes of MU control in stroke. APPROACH: Using a well-established model of the MU pool, this study quantified the changes in force output caused by changes in MU recruitment range and recruitment order, as well as MU firing rate organization at the population level. We additionally expanded the original model to include a fatigue component, which variably decreased the output force with increasing length of contraction. Differences in the force output at both the peak and fatigued time points across different excitation levels were quantified and compared across different sets of MU parameters. MAIN RESULTS: Across the different simulation parameters, we found that the main driving factor of the reduced force output was due to the compressed range of MU recruitment. Recruitment compression caused a decrease in total force across all excitation levels. Additionally, a compression of the range of MU firing rates also demonstrated a decrease in the force output mainly at the higher excitation levels. Lastly, changes to the recruitment order of MUs appeared to minimally impact the force output. SIGNIFICANCE: We found that altered control of MUs alone, as simulated in this study, can lead to a substantial reduction in muscle force generation in stroke survivors. These findings may provide valuable insight for both clinicians and researchers in prescribing and developing different types of therapies for the rehabilitation and restoration of lost strength after stroke.


Asunto(s)
Simulación por Computador , Debilidad Muscular/fisiopatología , Reclutamiento Neurofisiológico/fisiología , Accidente Cerebrovascular/fisiopatología , Humanos , Debilidad Muscular/diagnóstico , Debilidad Muscular/etiología , Umbral Sensorial/fisiología , Accidente Cerebrovascular/complicaciones , Accidente Cerebrovascular/diagnóstico
20.
Pediatr Phys Ther ; 29 Suppl 3: S48-S56, 2017 07.
Artículo en Inglés | MEDLINE | ID: mdl-28654477

RESUMEN

PURPOSE: To review lower-limb technology currently available for people with neurological disorders, such as spinal cord injury, stroke, or other conditions. We focus on 3 emerging technologies: treadmill-based training devices, exoskeletons, and other wearable robots. SUMMARY OF KEY POINTS: Efficacy for these devices remains unclear, although preliminary data indicate that specific patient populations may benefit from robotic training used with more traditional physical therapy. Potential benefits include improved lower-limb function and a more typical gait trajectory. STATEMENT OF CONCLUSIONS: Use of these devices is limited by insufficient data, cost, and in some cases size of the machine. However, robotic technology is likely to become more prevalent as these machines are enhanced and able to produce targeted physical rehabilitation. RECOMMENDATIONS FOR CLINICAL PRACTICE: Therapists should be aware of these technologies as they continue to advance but understand the limitations and challenges posed with therapeutic/mobility robots.


Asunto(s)
Trastornos Neurológicos de la Marcha/rehabilitación , Extremidad Inferior/fisiopatología , Modalidades de Fisioterapia/instrumentación , Robótica , Traumatismos de la Médula Espinal/rehabilitación , Rehabilitación de Accidente Cerebrovascular/instrumentación , Rehabilitación de Accidente Cerebrovascular/métodos , Humanos
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