{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,21]],"date-time":"2026-07-21T13:58:17Z","timestamp":1784642297731,"version":"3.55.0"},"reference-count":72,"publisher":"ASME International","issue":"1","content-domain":{"domain":["asmedigitalcollection.asme.org"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[2020,1,1]]},"abstract":"<jats:title>Abstract<\/jats:title>\n               <jats:p>Because of its simplicity, static optimization (SO) is frequently used to resolve the muscle redundancy problem (i.e., more muscles than degrees-of-freedom (DOF) in the human musculoskeletal system). However, SO minimizes antagonistic co-activation and likely joint stiffness as well, which may not be physiologically realistic since the body modulates joint stiffness during movements such as walking. Knowledge of joint stiffness is limited due to the difficulty of measuring it experimentally, leading researchers to estimate it using computational models. This study explores how imposing a synergy structure on the muscle activations estimated by optimization (termed \u201csynergy optimization,\u201d or SynO) affects calculated lower body joint stiffnesses during walking. By limiting the achievable muscle activations and coupling all time frames together, a synergy structure provides a potential mechanism for reducing indeterminacy and improving physiological co-activation but at the cost of a larger optimization problem. To compare joint stiffnesses produced by SynO (2\u20136 synergies) and SO, we used both approaches to estimate lower body muscle activations and forces for sample experimental overground walking data obtained from the first knee grand challenge competition. Both optimizations used a custom Hill-type muscle model that permitted analytic calculation of individual muscle contributions to the stiffness of spanned joints. Both approaches reproduced inverse dynamic joint moments well over the entire gait cycle, though SynO with only two synergies exhibited the largest errors. Maximum and mean joint stiffnesses for hip and knee flexion in particular decreased as the number of synergies increased from 2 to 6, with SO producing the lowest joint stiffness values. Our results suggest that SynO increases joint stiffness by increasing muscle co-activation, and furthermore, that walking with a reduced number of synergies may result in increased joint stiffness and perhaps stability.<\/jats:p>","DOI":"10.1115\/1.4044310","type":"journal-article","created":{"date-parts":[[2019,7,25]],"date-time":"2019-07-25T08:31:10Z","timestamp":1564043470000},"update-policy":"https:\/\/doi.org\/10.1115\/crossmarkpolicy-asme","source":"Crossref","is-referenced-by-count":33,"title":["Muscle Synergies Modify Optimization Estimates of Joint Stiffness During Walking"],"prefix":"10.1115","volume":"142","author":[{"given":"Mohammad S.","family":"Shourijeh","sequence":"first","affiliation":[{"name":"Department of Mechanical Engineering, Rice University, 6100 Main Street, Houston, TX 77005"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Benjamin J.","family":"Fregly","sequence":"additional","affiliation":[{"name":"Department of Mechanical Engineering, Rice University, 6100 Main Street, Houston, TX 77005"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"33","published-online":{"date-parts":[[2019,10,1]]},"reference":[{"issue":"2","key":"2019100112384356200_bib1","doi-asserted-by":"crossref","first-page":"131","DOI":"10.1016\/j.clinbiomech.2006.09.005","article-title":"Model-Based Estimation of Muscle Forces Exerted During Movements","volume":"22","year":"2007","journal-title":"Clin. Biomech."},{"issue":"3","key":"2019100112384356200_bib2","doi-asserted-by":"crossref","first-page":"201","DOI":"10.1080\/10255849908907988","article-title":"A Dynamic Optimization Solution for Vertical Jumping in Three Dimensions","volume":"2","year":"1999","journal-title":"Comput. Methods Biomech. Biomed. Eng."},{"issue":"6","key":"2019100112384356200_bib3","doi-asserted-by":"crossref","first-page":"1055","DOI":"10.1016\/j.jbiomech.2009.12.012","article-title":"Optimality Principles for Model-Based Prediction of Human Gait","volume":"43","year":"2010","journal-title":"J. Biomech."},{"issue":"3","key":"2019100112384356200_bib4","doi-asserted-by":"crossref","first-page":"31018","DOI":"10.1115\/1.4026266","article-title":"Forward Dynamic Optimization of Human Gait Simulations: A Global Parameterization Approach","volume":"9","year":"2014","journal-title":"ASME J. Comput. Nonlinear Dyn"},{"key":"2019100112384356200_bib5","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1007\/978-1-4020-8829-2","article-title":"Physiological Methods to Solve the Force-Sharing Problem in Biomechanics","volume-title":"Multibody Dynamics","author":"Bottasso","year":"2009"},{"issue":"5","key":"2019100112384356200_bib6","doi-asserted-by":"crossref","first-page":"051005","DOI":"10.1115\/1.4036195","article-title":"Forward Static Optimization in Dynamic Simulation of Human Musculoskeletal Systems: A Proof-of-Concept Study","volume":"12","year":"2017","journal-title":"ASME J. Comput. Nonlinear Dyn."},{"issue":"2","key":"2019100112384356200_bib7","doi-asserted-by":"crossref","first-page":"153","DOI":"10.1016\/S0021-9290(00)00155-X","article-title":"Static and Dynamic Optimization Solutions for Gait Are Practically Equivalent","volume":"34","year":"2001","journal-title":"J. Biomech."},{"issue":"10","key":"2019100112384356200_bib8","doi-asserted-by":"crossref","first-page":"2922","DOI":"10.1007\/s10439-016-1591-9","article-title":"Evaluation of Direct Collocation Optimal Control Problem Formulations for Solving the Muscle Redundancy Problem","volume":"44","year":"2016","journal-title":"Ann. Biomed. Eng."},{"issue":"11","key":"2019100112384356200_bib9","doi-asserted-by":"crossref","first-page":"759","DOI":"10.1016\/0021-9290(81)90032-4","article-title":"EMG to Force Processing II: Estimation of parameters of the Hill Muscle Model for the Human Triceps Surae by Means of a Calfergometer","volume":"14","year":"1981","journal-title":"J. Biomech."},{"issue":"6","key":"2019100112384356200_bib10","doi-asserted-by":"crossref","first-page":"765","DOI":"10.1016\/S0021-9290(03)00010-1","article-title":"An EMG-Driven Musculoskeletal Model to Estimate Muscle Forces and Knee Joint Moments In Vivo","volume":"36","year":"2003","journal-title":"J. Biomech."},{"issue":"4","key":"2019100112384356200_bib11","doi-asserted-by":"crossref","first-page":"367","DOI":"10.1123\/jab.20.4.367","article-title":"Neuromusculoskeletal Modeling : Estimation of Muscle Forces and Joint Moments and Movements From Measurements of Neural Command","volume":"20","year":"2004","journal-title":"J. Appl. Biomech."},{"issue":"12","key":"2019100112384356200_bib12","doi-asserted-by":"crossref","first-page":"e52618","DOI":"10.1371\/journal.pone.0052618","article-title":"EMG-Driven Forward-Dynamic Estimation of Muscle Force and Joint Moment About Multiple Degrees of Freedom in the Human Lower Extremity","volume":"7","year":"2012","journal-title":"PLoS One"},{"key":"2019100112384356200_bib13","first-page":"e0179698","article-title":"Lower Extremity EMG-Driven Modeling With Automated Adjustment of Geometry","volume-title":"PLoS One","year":"2016"},{"issue":"4","key":"2019100112384356200_bib14","doi-asserted-by":"crossref","first-page":"1486","DOI":"10.1152\/japplphysiol.01070.2003","article-title":"The Extraction of Neural Strategies From the Surface EMG","volume":"96","year":"2004","journal-title":"J. Appl. Physiol."},{"issue":"1","key":"2019100112384356200_bib15","doi-asserted-by":"crossref","first-page":"15","DOI":"10.1016\/1050-6411(94)90023-X","article-title":"Crosstalk in Surface Electromyography: Theoretical and Practical Estimates","volume":"4","year":"1994","journal-title":"J. Electromyogr. Kinesiol."},{"issue":"8","key":"2019100112384356200_bib16","doi-asserted-by":"crossref","first-page":"1573","DOI":"10.1016\/j.jbiomech.2010.01.027","article-title":"Filtering the Surface EMG Signal: Movement Artifact and Baseline Noise Contamination","volume":"43","year":"2010","journal-title":"J. Biomech."},{"issue":"5","key":"2019100112384356200_bib17","doi-asserted-by":"crossref","first-page":"567","DOI":"10.1111\/j.1469-8986.1986.tb00676.x","article-title":"Guidelines for Human Electromyographic Research","volume":"23","year":"1986","journal-title":"Psychophysiology"},{"issue":"3","key":"2019100112384356200_bib18","doi-asserted-by":"crossref","first-page":"343","DOI":"10.1080\/00140139108967318","article-title":"The Quantification of EMG Normalization Error","volume":"34","year":"1991","journal-title":"Ergonomics"},{"issue":"9","key":"2019100112384356200_bib19","doi-asserted-by":"crossref","first-page":"1718","DOI":"10.1016\/j.jbiomech.2016.04.007","article-title":"A Forward-Muscular Inverse-Skeletal Dynamics Framework for Human Musculoskeletal Simulations","volume":"49","year":"2016","journal-title":"J. Biomech."},{"issue":"10","key":"2019100112384356200_bib20","doi-asserted-by":"crossref","first-page":"1179","DOI":"10.1016\/0021-9290(94)00181-3","article-title":"The Control of Shoulder Muscles During Goal-Directed Movements, an Inverse Dynamic Analysis","volume":"28","year":"1995","journal-title":"J. Biomech."},{"issue":"2","key":"2019100112384356200_bib21","doi-asserted-by":"crossref","first-page":"021005","DOI":"10.1115\/1.4024911","article-title":"Optimal Control and Forward Dynamics of Human Periodic Motions Using Fourier Series for Muscle Excitation Patterns","volume":"9","year":"2014","journal-title":"ASME J. Comput. Nonlinear Dyn."},{"issue":"11","key":"2019100112384356200_bib22","doi-asserted-by":"crossref","first-page":"1940","DOI":"10.1109\/TBME.2007.901024","article-title":"OpenSim: Open Source to Create and Analyze Dynamic Simulations of Movement","volume":"54","year":"2007","journal-title":"IEEE Trans. Biomed. Eng."},{"issue":"2","key":"2019100112384356200_bib23","doi-asserted-by":"crossref","first-page":"217","DOI":"10.1016\/0025-5564(92)90071-4","article-title":"Predictions of Antagonistic Muscular Activity Using Nonlinear Optimization","volume":"111","year":"1992","journal-title":"Math. Biosci."},{"issue":"1","key":"2019100112384356200_bib24","doi-asserted-by":"crossref","first-page":"83","DOI":"10.1016\/0025-5564(93)90034-8","article-title":"Cocontraction of Pairs of Antagonistic Muscles: Analytical Solution for Planar Static Nonlinear Optimization Approaches","volume":"118","year":"1993","journal-title":"Math. Biosci."},{"issue":"3","key":"2019100112384356200_bib25","doi-asserted-by":"crossref","first-page":"224","DOI":"10.1016\/0966-6362(95)01045-9","article-title":"Gait Characterization Via Dynamic Joint Stiffness","volume":"4","year":"1996","journal-title":"Gait Posture"},{"issue":"9","key":"2019100112384356200_bib26","doi-asserted-by":"crossref","first-page":"2604","DOI":"10.1109\/TBME.2012.2207895","article-title":"Model-Based Estimation of Knee Stiffness","volume":"59","year":"2012","journal-title":"IEEE Trans. Biomed. Eng."},{"issue":"4","key":"2019100112384356200_bib27","doi-asserted-by":"crossref","first-page":"2509","DOI":"10.1152\/jn.00989.2014","article-title":"Modeling and Simulating the Neuromuscular Mechanisms Regulating Ankle and Knee Joint Stiffness During Human Locomotion","volume":"114","year":"2015","journal-title":"J. Neurophysiol."},{"issue":"9","key":"2019100112384356200_bib28","doi-asserted-by":"crossref","first-page":"1282","DOI":"10.1016\/j.jbiomech.2009.03.009","article-title":"Modular Control of Human Walking: A Simulation Study","volume":"42","year":"2009","journal-title":"J. Biomech."},{"issue":"12","key":"2019100112384356200_bib29","doi-asserted-by":"crossref","first-page":"2157","DOI":"10.1016\/j.jbiomech.2012.05.037","article-title":"Three-Dimensional Modular Control of Human Walking","volume":"45","year":"2012","journal-title":"J. Biomech."},{"issue":"3","key":"2019100112384356200_bib30","doi-asserted-by":"crossref","first-page":"031009","DOI":"10.1115\/1.4042185","article-title":"A Synergy-Based Motor Control Framework for the Fast Feedback Control of Musculoskeletal Systems","volume":"141","year":"2019","journal-title":"ASME J. Biomech. Eng."},{"key":"2019100112384356200_bib31","doi-asserted-by":"crossref","first-page":"84","DOI":"10.1016\/j.jbiomech.2019.04.038","article-title":"Can Altered Muscle Synergies Control Unimpaired Gait?","volume":"90","year":"2019","journal-title":"J. Biomech."},{"issue":"6","key":"2019100112384356200_bib32","doi-asserted-by":"crossref","first-page":"697","DOI":"10.1016\/j.clinbiomech.2013.06.003","article-title":"The Influence of Merged Muscle Excitation Modules on Post-Stroke Hemiparetic Walking Performance","volume":"28","year":"2013","journal-title":"Clin. Biomech."},{"issue":"3","key":"2019100112384356200_bib33","doi-asserted-by":"crossref","first-page":"412","DOI":"10.1016\/j.jbiomech.2009.10.009","article-title":"Modular Control of Human Walking: Adaptations to Altered Mechanical Demands","volume":"43","year":"2010","journal-title":"J. Biomech."},{"key":"2019100112384356200_bib34","first-page":"1","article-title":"A Musculoskeletal Model of Human Locomotion Driven by a Low Dimensional Set of Impulsive Excitation Primitives","volume":"7","year":"2013","journal-title":"Front. Comput. Neurosci."},{"issue":"2","key":"2019100112384356200_bib35","doi-asserted-by":"crossref","first-page":"21031","DOI":"10.1115\/1.4026428","article-title":"Muscle Synergies May Improve Optimization Prediction of Knee Contact Forces During Walking","volume":"136","year":"2014","journal-title":"ASME J. Biomech. Eng"},{"key":"2019100112384356200_bib36","first-page":"1","article-title":"A Novel Computational Framework for Deducing Muscle Synergies From Experimental Joint Moments","volume":"8","year":"2014","journal-title":"Front. Comput. Neurosci."},{"issue":"7","key":"2019100112384356200_bib37","doi-asserted-by":"crossref","first-page":"2102","DOI":"10.1152\/jn.00769.2013","article-title":"Consequences of Biomechanically Constrained Tasks in the Design and Interpretation of Synergy Analyses","volume":"113","year":"2015","journal-title":"J. Neurophysiol."},{"issue":"77","key":"2019100112384356200_bib38","first-page":"1","article-title":"Muscle Synergies Facilitate Computational Prediction of Subject-Specific Walking Motions","volume":"4","year":"2016","journal-title":"Front. Bioeng. Biotechnol."},{"issue":"8","key":"2019100112384356200_bib39","doi-asserted-by":"crossref","first-page":"81001","DOI":"10.1115\/1.4033673","article-title":"Neuromusculoskeletal Model Calibration Significantly Affects Predicted Knee Contact Forces for Walking","volume":"138","year":"2016","journal-title":"ASME J. Biomech. Eng"},{"issue":"1","key":"2019100112384356200_bib40","doi-asserted-by":"crossref","first-page":"267","DOI":"10.1113\/jphysiol.2003.057174","article-title":"Five Basic Muscle Activation Patterns Account for Muscle Activity During Human Locomotion","volume":"556","year":"2004","journal-title":"J. Physiol."},{"issue":"6","key":"2019100112384356200_bib41","doi-asserted-by":"crossref","first-page":"3426","DOI":"10.1152\/jn.00081.2006","article-title":"Motor Patterns in Human Walking and running","volume":"95","year":"2006","journal-title":"J. Neurophysiol."},{"key":"2019100112384356200_bib42","doi-asserted-by":"crossref","first-page":"36","DOI":"10.1016\/j.jelekin.2015.12.001","article-title":"An Approach for Improving Repeatability and Reliability of Non-Negative Matrix Factorization for Muscle Synergy Analysis","volume":"26","year":"2016","journal-title":"J. Electromyogr. Kinesiol."},{"issue":"1","key":"2019100112384356200_bib43","doi-asserted-by":"crossref","first-page":"011011","DOI":"10.1115\/1.4038199","article-title":"Can Measured Synergy Excitations Accurately Construct Unmeasured Muscle Excitations?","volume":"140","year":"2018","journal-title":"ASME J. Biomech. Eng"},{"key":"2019100112384356200_bib44","doi-asserted-by":"crossref","first-page":"158","DOI":"10.1016\/j.jelekin.2016.04.008","article-title":"Use of Muscle Synergies and Wavelet Transforms to Identify Fatigue During Squatting","volume":"28","year":"2016","journal-title":"J. Electromyogr. Kinesiol."},{"issue":"1","key":"2019100112384356200_bib45","first-page":"89","article-title":"Inter\u2010Subject Variability of Muscle Synergies During Bench Press in Power Lifters and Untrained Individuals","volume":"25","year":"2014","journal-title":"Scand. J. Med. Sci. Sports"},{"issue":"4","key":"2019100112384356200_bib46","doi-asserted-by":"crossref","first-page":"503","DOI":"10.1002\/jor.22023","article-title":"Grand Challenge Competition to Predict In Vivo Knee Loads","volume":"30","year":"2012","journal-title":"J. Orthop. Res."},{"issue":"2","key":"2019100112384356200_bib47","doi-asserted-by":"crossref","first-page":"269","DOI":"10.1007\/s10439-009-9852-5","article-title":"A Model of the Lower Limb for Analysis of Human Movement","volume":"38","year":"2010","journal-title":"Ann. Biomed. Eng."},{"issue":"9","key":"2019100112384356200_bib48","doi-asserted-by":"crossref","first-page":"1447","DOI":"10.1016\/j.jbiomech.2003.12.017","article-title":"Moment Arms and Musculotendon Lengths Estimation for a Three-Dimensional Lower-Limb Model","volume":"37","year":"2004","journal-title":"J. Biomech."},{"key":"2019100112384356200_bib49","article-title":"What Is a Moment Arm? Calculating Muscle Effectiveness in Biomechanical Models Using Generalized Coordinates","volume-title":"ASME","year":"2013"},{"key":"2019100112384356200_bib50","article-title":"MATLAB Version 9.4 (R2018a)","year":"2018"},{"issue":"4","key":"2019100112384356200_bib51","first-page":"359","article-title":"Muscle and Tendon: Properties, Models, Scaling, and Application to Biomechanics and Motor Control","volume":"19","year":"1989","journal-title":"CRC Crit. Rev. Biomed. Eng"},{"issue":"6755","key":"2019100112384356200_bib52","doi-asserted-by":"crossref","first-page":"788","DOI":"10.1038\/44565","article-title":"Learning the Parts of Objects by Non-Negative Matrix Factorization","volume":"401","year":"1999","journal-title":"Nature"},{"key":"2019100112384356200_bib53","first-page":"556","article-title":"Algorithms for Non-Negative Matrix Factorization","year":"2000","journal-title":"Adv. Neural Inf. Process. Syst."},{"issue":"4","key":"2019100112384356200_bib54","doi-asserted-by":"crossref","first-page":"2199","DOI":"10.1152\/jn.00222.2005","article-title":"Matrix Factorization Algorithms for the Identification of Muscle Synergies: Evaluation on Simulated and Experimental Data Sets","volume":"95","year":"2006","journal-title":"J. Neurophysiol."},{"issue":"1","key":"2019100112384356200_bib55","doi-asserted-by":"crossref","first-page":"609","DOI":"10.1152\/jn.00681.2004","article-title":"A Limited Set of Muscle Synergies for Force Control During a Postural Task","volume":"93","year":"2005","journal-title":"J. Neurophysiol."},{"issue":"3","key":"2019100112384356200_bib56","doi-asserted-by":"crossref","first-page":"1530","DOI":"10.1152\/jn.00810.2005","article-title":"Muscle Synergy Organization Is Robust Across a Variety of Postural Perturbations","volume":"96","year":"2006","journal-title":"J. Neurophysiol."},{"key":"2019100112384356200_bib57","volume-title":"Statistics for High-Dimensional Data: Methods, Theory and Applications","year":"2011"},{"issue":"2","key":"2019100112384356200_bib58","doi-asserted-by":"crossref","first-page":"19","DOI":"10.1177\/003754976400200212","article-title":"Optimization of Multiparameter Systems by Hybrid Computer Techniques\u2014Part I","volume":"2","year":"1964","journal-title":"Simulation"},{"issue":"2","key":"2019100112384356200_bib59","doi-asserted-by":"crossref","first-page":"844","DOI":"10.1152\/jn.00825.2009","article-title":"Merging of Healthy Motor Modules Predicts Reduced Locomotor Performance and Muscle Coordination Complexity Post-Stroke","volume":"103","year":"2010","journal-title":"J. Neurophysiol."},{"issue":"6862","key":"2019100112384356200_bib60","doi-asserted-by":"crossref","first-page":"446","DOI":"10.1038\/35106566","article-title":"The Central Nervous System Stabilizes Unstable Dynamics by Learning Optimal Impedance","volume":"414","year":"2001","journal-title":"Nature"},{"issue":"2","key":"2019100112384356200_bib61","doi-asserted-by":"crossref","first-page":"1047","DOI":"10.1152\/jn.2001.86.2.1047","article-title":"Impedance Control and Internal Model Formation When Reaching in a Randomly Varying Dynamical Environment","volume":"86","year":"2001","journal-title":"J. Neurophysiol."},{"issue":"3","key":"2019100112384356200_bib62","doi-asserted-by":"crossref","first-page":"164","DOI":"10.5435\/00124635-200405000-00004","article-title":"Stiffness After Total Knee Arthroplasty","volume":"12","year":"2004","journal-title":"JAAOS-J. Am. Acad. Orthop. Surg."},{"key":"2019100112384356200_bib63","unstructured":"Tonietti, \nG., \nSchiavi, \nR., and \nBicchi, \nA., 2005, \u201c\nDesign and Control of a Variable Stiffness Actuator for Safe and Fast Physical Human\/Robot Interaction,\u201d IEEE International Conference on Robotics and Automation (ICRA), Barcelona, Spain, Apr. 18\u201322, pp. 526\u2013531.10.1109\/ROBOT.2005.1570172"},{"issue":"9","key":"2019100112384356200_bib64","doi-asserted-by":"crossref","first-page":"917","DOI":"10.1016\/j.clinbiomech.2005.06.002","article-title":"Muscle Force-Stiffness Characteristics Influence Joint Stability: A Spine Example","volume":"20","year":"2005","journal-title":"Clin. Biomech."},{"issue":"5","key":"2019100112384356200_bib65","doi-asserted-by":"crossref","first-page":"3097","DOI":"10.1152\/jn.00364.2004","article-title":"Impedance Control Balances Stability With Metabolically Costly Muscle Activation","volume":"92","year":"2004","journal-title":"J. Neurophysiol."},{"issue":"6","key":"2019100112384356200_bib66","doi-asserted-by":"crossref","first-page":"493","DOI":"10.1109\/10.581944","article-title":"Identification of Intrinsic and Reflex Contributions to Human Ankle Stiffness Dynamics","volume":"44","year":"1997","journal-title":"IEEE Trans. Biomed. Eng."},{"issue":"2","key":"2019100112384356200_bib67","doi-asserted-by":"crossref","first-page":"331","DOI":"10.1113\/jphysiol.1974.sp010613","article-title":"The Short Range Stiffness of Active Mammalian Muscle and Its Effect on Mechanical Properties","volume":"240","year":"1974","journal-title":"J. Physiol."},{"issue":"3","key":"2019100112384356200_bib68","doi-asserted-by":"crossref","first-page":"796","DOI":"10.1152\/japplphysiol.01451.2006","article-title":"Motor Unit Composition Has Little Effect on the Short-Range Stiffness of Feline Medial Gastrocnemius Muscle","volume":"103","year":"2007","journal-title":"J. Appl. Physiol."},{"issue":"2","key":"2019100112384356200_bib69","doi-asserted-by":"crossref","first-page":"79","DOI":"10.1080\/08990220.2016.1178636","article-title":"Ankle Muscle Coactivation and Its Relationship With Ankle Joint Kinematics and Kinetics During Gait in Hemiplegic Patients After Stroke","volume":"33","year":"2016","journal-title":"Somatosens. Mot. Res."},{"key":"2019100112384356200_bib70","first-page":"1","article-title":"Balance Dysfunction in Parkinson's Disease","volume":"2015","year":"2015","journal-title":"Biomed Res. Int."},{"issue":"7","key":"2019100112384356200_bib71","doi-asserted-by":"crossref","first-page":"1390","DOI":"10.1016\/j.clinph.2013.02.006","article-title":"Persons With Parkinson's Disease Exhibit Decreased Neuromuscular Complexity During Gait","volume":"124","year":"2013","journal-title":"Clin. Neurophysiol."},{"issue":"7","key":"2019100112384356200_bib72","doi-asserted-by":"crossref","first-page":"539","DOI":"10.1016\/0021-9290(88)90217-5","article-title":"Human Ankle Joint Stiffness Over the Full Range of Muscle Activation Levels","volume":"21","year":"1988","journal-title":"J. Biomech."}],"container-title":["Journal of Biomechanical Engineering"],"original-title":[],"language":"en","link":[{"URL":"http:\/\/asmedigitalcollection.asme.org\/biomechanical\/article-pdf\/doi\/10.1115\/1.4044310\/5173049\/bio-19-1133.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"http:\/\/asmedigitalcollection.asme.org\/biomechanical\/article-pdf\/doi\/10.1115\/1.4044310\/6030844\/bio_142_01_011011.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2019,10,1]],"date-time":"2019-10-01T12:40:06Z","timestamp":1569933606000},"score":1,"resource":{"primary":{"URL":"https:\/\/asmedigitalcollection.asme.org\/biomechanical\/article\/doi\/10.1115\/1.4044310\/955411\/Muscle-Synergies-Modify-Optimization-Estimates-of"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2019,10,1]]},"references-count":72,"journal-issue":{"issue":"1","published-print":{"date-parts":[[2020,1,1]]}},"URL":"https:\/\/doi.org\/10.1115\/1.4044310","relation":{},"ISSN":["0148-0731","1528-8951"],"issn-type":[{"value":"0148-0731","type":"print"},{"value":"1528-8951","type":"electronic"}],"subject":[],"published":{"date-parts":[[2019,10,1]]},"article-number":"011011"}}