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      Associations between lower-limb muscle activation and knee flexion in post-stroke individuals: A study on the stance-to-swing phases of gait

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          Abstract

          Reduced knee flexion is a leading feature of post-stroke gait, but the causes have not been well understood. The purpose of this study was to investigate the relationship between the knee flexion and the lower-limb muscle activation within the stance-to-swing phases of gait cycle in the post-stroke hemiplegic patients. Ten stroke patients and 10 age- and gender-matched healthy subjects participated in the experiment. The lower-limb kinematic signals and the surface electromyography (sEMG) signals of the left and right rectus femoris (RF), biceps femoris (BF) and lateral gastrocnemius (GS) were recorded during walking. The angle range (AR) of knee flexion, the root mean square (RMS) and the mean frequency (MNF) of sEMG signals were calculated from the terminal stance (TSt) to the initial swing (ISw) phases of gait cycle. Stroke patients showed lower bilateral AR of knee flexion and lower RMS of GS on the paretic side, but higher MNF of RF on the non-paretic side compared with the controls. Within the stroke patients, significant differences were found between their paretic and non-paretic limbs in the AR of knee flexion, as well as in the RMS and MNF of GS ( p < 0.05). Regression analysis showed that the RMS of BF, MNF of BF and MNF of GS explained 82.1% of variations in AR of knee flexion on paretic side ( r 2 = 0.821). But the RMS and MNF of all the muscles (including the RF, GS and BF) could explain 65.6% of AR of knee flexion variations on the non-paretic side ( r 2 = 0.656), and 45.2% of variations for the healthy subjects ( r 2 = 0.452). The reduced knee flexion during gait was associated with altered magnitude and frequency of muscle contractions and with simplified muscle synergy in the post-stroke hemiplegic patients. Identifying the muscles that are responsible for knee stiffness may facilitate improvement of rehabilitation strategy for post-stroke gait.

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          Most cited references27

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          The extraction of neural strategies from the surface EMG.

          This brief review examines some of the methods used to infer central control strategies from surface electromyogram (EMG) recordings. Among the many uses of the surface EMG in studying the neural control of movement, the review critically evaluates only some of the applications. The focus is on the relations between global features of the surface EMG and the underlying physiological processes. Because direct measurements of motor unit activation are not available and many factors can influence the signal, these relations are frequently misinterpreted. These errors are compounded by the counterintuitive effects that some system parameters can have on the EMG signal. The phenomenon of crosstalk is used as an example of these problems. The review describes the limitations of techniques used to infer the level of muscle activation, the type of motor unit recruited, the upper limit of motor unit recruitment, the average discharge rate, and the degree of synchronization between motor units. Although the global surface EMG is a useful measure of muscle activation and assessment, there are limits to the information that can be extracted from this signal.
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            Classification of walking handicap in the stroke population.

            The limited walking ability that follows a stroke restricts the patient's independent mobility about the home and community, a significant social handicap. To improve the in-hospital prediction of functional outcome, the relationships between impairment, disability, and handicap were assessed with clinical measures in 147 stroke patients. The patients' level of functional walking ability at home and in the community was assigned by expert clinicians to one of the six categories of a modified Hoffer Functional Ambulation scale at least 3 months after discharge. A 19-item questionnaire was further used to assess current customary mobility of the subjects. Functional muscle strength and proprioception were tested, and walking velocity was measured. The significant indicators of impairment, upright motor control knee flexion and extension strength, differentiated household from community ambulators. The addition of velocity improved the functional prediction. Proprioception was clinically normal in all walkers. The validity of the criteria for the six levels of walking handicap was confirmed statistically. Stepwise discriminant analysis reduced the ambulation activities on the questionnaire from 19 to 7. Redefinition of the criteria for patient classification using the coefficients and constants of the seven critical functions improved the prediction of patient walking ability to 84%. The results of this study offer a quantitative method of relating the social disadvantage of stroke patients to the impairment and disability sustained. The measurement of therapeutic outcome in relation to the social advantage for the patient would allow more efficient standardization of treatment and services.
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              The relationship between spatiotemporal gait asymmetry and balance in individuals with chronic stroke.

              Falls are common after stroke and often attributed to poor balance. Falls often occur during walking, suggesting that walking patterns may induce a loss of balance. Gait after stroke is frequently spatiotemporally asymmetric, which may decrease balance. The purpose of this study is to determine the relationship between spatiotemporal gait asymmetry and balance control. Thirty-nine individuals with chronic stroke walked at comfortable and fast speeds to calculate asymmetry ratios for step length, stance time, and swing time. Balance measures included the Berg Balance Scale, step width during gait, and the weight distribution between legs during standing. Correlational analyses determined the relationships between balance and gait asymmetry. At comfortable and fast gait speeds, step width was correlated with stance time and swing time asymmetries (r = 0.39-0.54). Berg scores were correlated with step length and swing time asymmetries (r = -0.36 to -0.63). During fast walking, the weight distribution between limbs was correlated with stance time asymmetry (r = -0.41). Spatiotemporal gait asymmetry was more closely related to balance measures involving dynamic tasks than static tasks, suggesting that gait asymmetry may be related to the high number of falls poststroke. Further study to determine if rehabilitation that improves gait asymmetry has a similar influence on balance is warranted.
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                Author and article information

                Contributors
                Role: Data curationRole: Formal analysisRole: InvestigationRole: VisualizationRole: Writing – original draftRole: Writing – review & editing
                Role: ConceptualizationRole: Funding acquisitionRole: InvestigationRole: MethodologyRole: Project administrationRole: ResourcesRole: SupervisionRole: ValidationRole: VisualizationRole: Writing – review & editing
                Role: ResourcesRole: ValidationRole: Writing – review & editing
                Role: Data curationRole: MethodologyRole: ResourcesRole: SoftwareRole: VisualizationRole: Writing – review & editing
                Role: ConceptualizationRole: MethodologyRole: ResourcesRole: Writing – review & editing
                Role: Editor
                Journal
                PLoS One
                PLoS ONE
                plos
                plosone
                PLoS ONE
                Public Library of Science (San Francisco, CA USA )
                1932-6203
                8 September 2017
                2017
                : 12
                : 9
                Affiliations
                [1 ] Laboratory of Motor Control and Rehabilitation, Institute of Biomedical Engineering, School of Control Science and Engineering, Shandong University, Jinan, China
                [2 ] Department of Physical Medicine and Rehabilitation, Qilu Hospital, Shandong University, Jinan, China
                [3 ] Department of Geriatrics, Qilu Hospital, Shandong University, Jinan, China
                University of L'Aquila, ITALY
                Author notes

                Competing Interests: The authors have declared that no competing interests exist.

                Article
                PONE-D-16-48729
                10.1371/journal.pone.0183865
                5590852
                28886079
                dee29dc0-5585-49e2-aad9-a883ed7295ed
                © 2017 Wang et al

                This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

                Page count
                Figures: 6, Tables: 2, Pages: 13
                Product
                Funding
                Funded by: funder-id http://dx.doi.org/10.13039/501100001809, National Natural Science Foundation of China;
                Award ID: 31200744
                Award Recipient :
                Funded by: Key Research and Development Programs of Shandong Province
                Award ID: 2015GSF118127
                Award Recipient :
                Funded by: funder-id http://dx.doi.org/10.13039/501100002858, China Postdoctoral Science Foundation;
                Award ID: 2014M560558
                Award Recipient :
                Funded by: funder-id http://dx.doi.org/10.13039/501100002858, China Postdoctoral Science Foundation;
                Award ID: 2015T80723
                Award Recipient :
                Funded by: Postdoctoral Innovation Foundation of Shandong Province
                Award ID: 201401012
                Award Recipient :
                Funded by: Young Scholars Program of Shandong University
                Award Recipient :
                Funded by 31200744, http://www.nsfc.gov.cn/, National Natural Science Foundation of China, KL 2015GSF118127, http://www.sdstc.gov.cn/, Key Research & Development Programs of Shandong Province, KL 2014M560558, 2015T80723, http://jj.chinapostdoctor.org.cn/V1/Program3/Default.aspx, China Postdoctoral Science Foundation, KL 201401012, http://www.sdhrss.gov.cn/, Postdoctoral Innovation Foundation of Shandong Province, KL NA, http://www.sdu.edu.cn, Young Scholars Program of Shandong University, KL. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
                Categories
                Research Article
                Biology and Life Sciences
                Anatomy
                Musculoskeletal System
                Limbs (Anatomy)
                Legs
                Knees
                Medicine and Health Sciences
                Anatomy
                Musculoskeletal System
                Limbs (Anatomy)
                Legs
                Knees
                Medicine and Health Sciences
                Neurology
                Cerebrovascular Diseases
                Stroke
                Medicine and Health Sciences
                Vascular Medicine
                Stroke
                Biology and Life Sciences
                Anatomy
                Musculoskeletal System
                Joints (Anatomy)
                Knee Joints
                Medicine and Health Sciences
                Anatomy
                Musculoskeletal System
                Joints (Anatomy)
                Knee Joints
                Biology and Life Sciences
                Physiology
                Biological Locomotion
                Walking
                Medicine and Health Sciences
                Physiology
                Biological Locomotion
                Walking
                Biology and Life Sciences
                Physiology
                Muscle Physiology
                Muscle Contraction
                Medicine and Health Sciences
                Physiology
                Muscle Physiology
                Muscle Contraction
                Research and Analysis Methods
                Mathematical and Statistical Techniques
                Statistical Methods
                Regression Analysis
                Physical Sciences
                Mathematics
                Statistics (Mathematics)
                Statistical Methods
                Regression Analysis
                Physical Sciences
                Physics
                Classical Mechanics
                Kinematics
                Biology and Life Sciences
                Physiology
                Biological Locomotion
                Gait Analysis
                Medicine and Health Sciences
                Physiology
                Biological Locomotion
                Gait Analysis
                Custom metadata
                All relevant data are within the paper and its Supporting Information files.

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