{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,12]],"date-time":"2026-02-12T15:13:23Z","timestamp":1770909203094,"version":"3.50.1"},"reference-count":39,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2016,6,20]],"date-time":"2016-06-20T00:00:00Z","timestamp":1466380800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science foundation of China","doi-asserted-by":"publisher","award":["61273359"],"award-info":[{"award-number":["61273359"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science foundation of China","doi-asserted-by":"publisher","award":["91520201"],"award-info":[{"award-number":["91520201"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Entropy"],"abstract":"<jats:p>Aging alters muscular coordination patterns. This study aimed to investigate aging-related changes in the coordination of agonist and antagonist muscles from two aspects, the activities of individual muscles and the inter-muscular coupling. Eighteen young subjects and 10 elderly subjects were recruited to modulate the agonist muscle activity to track a target during voluntary isometric elbow flexion and extension. Normalized muscle activation and fuzzy entropy (FuzzyEn) were applied to depict the activities of biceps and triceps. Mutual information (MI) was utilized to measure the inter-muscular coupling between biceps and triceps. The agonist activation decreased and the antagonist activation increased significantly during elbow flexion and extension with aging. FuzzyEn values of agonist electromyogram (EMG) were similar between the two age groups. FuzzyEn values of antagonist EMG increased significantly with aging during elbow extension. MI decreased significantly with aging during elbow extension. These results indicated increased antagonist co-activation and decreased inter-muscular coupling with aging during elbow extension, which might result from the reduced reciprocal inhibition and the recruitment of additional cortical-spinal pathways connected to biceps. Based on FuzzyEn and MI, this study provided a comprehensive understanding of the mechanisms underlying the aging-related changes in the coordination of agonist and antagonist muscles.<\/jats:p>","DOI":"10.3390\/e18060229","type":"journal-article","created":{"date-parts":[[2016,6,20]],"date-time":"2016-06-20T12:51:28Z","timestamp":1466427088000},"page":"229","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":17,"title":["Investigating Aging-Related Changes in the Coordination of Agonist and Antagonist Muscles Using Fuzzy Entropy and Mutual Information"],"prefix":"10.3390","volume":"18","author":[{"given":"Wenbo","family":"Sun","sequence":"first","affiliation":[{"name":"Key Laboratory of Sensing Technology and Biomedical Instrument of Guang Dong province, School of Engineering, Sun Yat-sen University, Guangzhou 510275, China"},{"name":"Guangdong Provincial Engineering and Technology Center of Advanced and Portable Medical Devices, Guangzhou 510275, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jingtao","family":"Liang","sequence":"additional","affiliation":[{"name":"Key Laboratory of Sensing Technology and Biomedical Instrument of Guang Dong province, School of Engineering, Sun Yat-sen University, Guangzhou 510275, China"},{"name":"Guangdong Provincial Engineering and Technology Center of Advanced and Portable Medical Devices, Guangzhou 510275, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yuan","family":"Yang","sequence":"additional","affiliation":[{"name":"Key Laboratory of Sensing Technology and Biomedical Instrument of Guang Dong province, School of Engineering, Sun Yat-sen University, Guangzhou 510275, China"},{"name":"Guangdong Provincial Engineering and Technology Center of Advanced and Portable Medical Devices, Guangzhou 510275, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yuanyu","family":"Wu","sequence":"additional","affiliation":[{"name":"Key Laboratory of Sensing Technology and Biomedical Instrument of Guang Dong province, School of Engineering, Sun Yat-sen University, Guangzhou 510275, China"},{"name":"Guangdong Provincial Engineering and Technology Center of Advanced and Portable Medical Devices, Guangzhou 510275, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Tiebin","family":"Yan","sequence":"additional","affiliation":[{"name":"Department of Rehabilitation Medicine, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou 510120, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3662-116X","authenticated-orcid":false,"given":"Rong","family":"Song","sequence":"additional","affiliation":[{"name":"Key Laboratory of Sensing Technology and Biomedical Instrument of Guang Dong province, School of Engineering, Sun Yat-sen University, Guangzhou 510275, China"},{"name":"Guangdong Provincial Engineering and Technology Center of Advanced and Portable Medical Devices, Guangzhou 510275, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2016,6,20]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"858","DOI":"10.1002\/mus.10113","article-title":"Contractile muscle volume and agonist\u2013antagonist coactivation account for differences in torque between young and older women","volume":"25","author":"Macaluso","year":"2002","journal-title":"Muscle Nerve"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"543","DOI":"10.1007\/s00421-006-0205-x","article-title":"Voluntary activation during maximal contraction with advancing age: A brief review","volume":"100","author":"Klass","year":"2007","journal-title":"Eur. J. Appl. Physiol."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"899","DOI":"10.1007\/s11357-014-9616-5","article-title":"Is co-contraction responsible for the decline in maximal knee joint torque in older males?","volume":"36","author":"Billot","year":"2014","journal-title":"Age"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"29","DOI":"10.1097\/00003677-200601000-00007","article-title":"Mechanisms responsible for the age-associated increase in coactivation of antagonist muscles","volume":"34","author":"Devita","year":"2006","journal-title":"Exerc. Sport. Sci. Rev."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1010","DOI":"10.1152\/jn.00569.2013","article-title":"Altered activation of the antagonist muscle during practice compromises motor learning in older adults","volume":"112","author":"Chen","year":"2014","journal-title":"J. Neurophysiol."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"355","DOI":"10.1016\/j.gaitpost.2009.12.005","article-title":"Effects of age and walking speed on coactivation and cost of walking in healthy adults","volume":"31","author":"Peterson","year":"2010","journal-title":"Gait Posture"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"101","DOI":"10.1016\/S0966-6362(02)00200-X","article-title":"Aging, muscle activity, and balance control: Physiologic changes associated with balance impairment","volume":"18","author":"Laughton","year":"2003","journal-title":"Gait Posture"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"117","DOI":"10.1016\/S1050-6411(99)00026-7","article-title":"Muscle pre-and coactivity during downward stepping are associated with leg stiffness in aging","volume":"10","author":"DeVita","year":"2000","journal-title":"J. Electromyogr. Kinesiol."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"2231","DOI":"10.1016\/j.jbiomech.2009.06.038","article-title":"Dynamics and stability of muscle activations during walking in healthy young and older adults","volume":"42","author":"Kang","year":"2009","journal-title":"J. Biomech."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"901","DOI":"10.1016\/j.jelekin.2012.06.005","article-title":"Sample entropy analysis of surface EMG for improved muscle activity onset detection against spurious background spikes","volume":"22","author":"Zhang","year":"2012","journal-title":"J. Electromyogr. Kinesiol."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"476","DOI":"10.1109\/JBHI.2015.2398934","article-title":"Improvement in neural respiratory drive estimation from diaphragm electromyographic signals using fixed sample entropy","volume":"20","author":"Estrada","year":"2016","journal-title":"IEEE J. Biomed. Health Inform."},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Zhang, X., Ren, X., Gao, X., Chen, X., and Zhou, P. (2016). Complexity analysis of surface EMG for overcoming ECG interference toward proportional myoelectric control. Entropy, 18.","DOI":"10.3390\/e18040106"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1352","DOI":"10.1016\/j.archoralbio.2014.08.011","article-title":"Test\u2013retest reliability of electromyographic variables of masseter and temporal muscles in patients with cerebral palsy","volume":"59","author":"Giannasi","year":"2014","journal-title":"Arch. Oral Biol."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"805","DOI":"10.1007\/978-3-319-05582-4_71","article-title":"Application of the chaos theory in the analysis of EMG on patients with facial paralysis","volume":"274","author":"Xiong","year":"2014","journal-title":"Adv. Intell. Syst. Comput."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"266","DOI":"10.1109\/TNSRE.2007.897025","article-title":"Characterization of surface EMG signal based on fuzzy entropy","volume":"15","author":"Chen","year":"2007","journal-title":"IEEE Trans. Neural Syst. Rehabil. Eng."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"990","DOI":"10.1007\/s10439-014-1150-1","article-title":"Characterization of stroke- and aging-related changes in the complexity of EMG signals during tracking tasks","volume":"43","author":"Ao","year":"2014","journal-title":"Ann. Biomed. Eng."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"1013","DOI":"10.1109\/TNSRE.2013.2290017","article-title":"Complexity analysis of EMG signals for patients after stroke during robot-aided rehabilitation training using fuzzy approximate entropy","volume":"22","author":"Sun","year":"2014","journal-title":"IEEE Trans. Neural Syst. Rehabil. Eng."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"795","DOI":"10.1113\/jphysiol.2006.116939","article-title":"Transcranial direct current stimulation of the primary motor cortex affects cortical drive to human musculature as assessed by intermuscular coherence","volume":"577","author":"Power","year":"2006","journal-title":"J. Physiol."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"63","DOI":"10.2478\/v10078-008-0018-6","article-title":"Effects of aging on feedforward postural synergies","volume":"20","author":"Asaka","year":"2009","journal-title":"J. Hum. Kinetics"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"2866","DOI":"10.1152\/jn.01011.2011","article-title":"Sensitivity of EMG-EMG coherence to detect the common oscillatory drive to hand muscles in young and older adults","volume":"107","author":"Keenan","year":"2012","journal-title":"J. Neurophysiol."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"392","DOI":"10.1016\/j.clinph.2009.09.033","article-title":"Linear and nonlinear information flow based on time-delayed mutual information method and its application to corticomuscular interaction","volume":"121","author":"Jin","year":"2010","journal-title":"Clin. Neurophysiol."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"5721","DOI":"10.3390\/e16115721","article-title":"Applying information theory to neuronal networks: From theory to experiments","volume":"16","author":"Jung","year":"2014","journal-title":"Entropy"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"1039","DOI":"10.1016\/j.humov.2011.02.001","article-title":"Muscle coordination and force variability during static and dynamic tracking tasks","volume":"30","author":"Svendsen","year":"2011","journal-title":"Hum. Mov. Sci."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"277","DOI":"10.1111\/j.1600-0838.2009.01037.x","article-title":"Changes in the spatio-temporal organization of the trapezius muscle activity in response to eccentric contractions","volume":"21","author":"Madeleine","year":"2011","journal-title":"Scand. J. Med. Sci. Sports"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"478","DOI":"10.1007\/s00221-004-1970-6","article-title":"Proportional myoelectric control of a virtual object to investigate human efferent control","volume":"159","author":"Gordon","year":"2004","journal-title":"Exp. Brain Res."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"151","DOI":"10.1007\/s00221-007-1264-x","article-title":"The role of cocontraction in the impairment of movement accuracy with fatigue","volume":"185","author":"Missenard","year":"2008","journal-title":"Exp. Brain Res."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1023","DOI":"10.1016\/j.jelekin.2010.07.004","article-title":"How should we normalize electromyograms obtained from healthy participants? What we have learned from over 25 years of research","volume":"20","author":"Burden","year":"2010","journal-title":"J. Electromyogr. Kinesiol."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"45","DOI":"10.1016\/S0022-510X(00)00305-1","article-title":"Abnormal muscle activation characteristics associated with loss of dexterity after stroke","volume":"176","author":"Canning","year":"2000","journal-title":"J. Neurol. Sci."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"2318","DOI":"10.1103\/PhysRevE.52.2318","article-title":"Estimation of mutual information using kernel density estimators","volume":"52","author":"Moon","year":"1995","journal-title":"Phys. Rev. E."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"1341","DOI":"10.1152\/jappl.2001.91.3.1341","article-title":"Normalized force, activation, and coactivation in the arm muscles of young and old men","volume":"91","author":"Klein","year":"2001","journal-title":"J. Appl. Physiol."},{"key":"ref_31","unstructured":"Gordon, M.T. (2012). Effect of Age, Elbow Muscle Co-Contraction Level, and Elbow Moment Loading Characteristics on Elbow Angle Positional Variability in Postural Tasks by Positional Variability in Postural Tasks. [Ph.D. Thesis, University of Michigan]."},{"key":"ref_32","first-page":"637","article-title":"Age-related differences in pre-movement antagonist muscle co-activation and reaction-time performance","volume":"46","author":"Bautmans","year":"2011","journal-title":"Exp. Gerontol."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"525","DOI":"10.1152\/jn.1987.58.3.525","article-title":"Voluntary control of motor units in human antagonist muscles: coactivation and reciprocal activation","volume":"58","author":"Mambrito","year":"1987","journal-title":"J. Neurophysiol."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"575","DOI":"10.1113\/jphysiol.1993.sp019652","article-title":"The regulation of presynaptic inhibition during co-contraction of antagonistic muscles in man","volume":"464","author":"Nielsen","year":"1993","journal-title":"J. Physiol."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"1687","DOI":"10.1016\/S0531-5565(01)00143-7","article-title":"Changes in isokinetic torque and muscular activity of elbow flexors muscles with age","volume":"36","author":"Pousson","year":"2001","journal-title":"Exp. Gerontol."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"387","DOI":"10.1016\/S0531-5565(02)00265-6","article-title":"The influence of ageing on the force-velocity-power characteristics of human elbow flexor muscles","volume":"38","author":"Valour","year":"2003","journal-title":"Exp. Gerontol."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"752","DOI":"10.1016\/j.jelekin.2007.03.004","article-title":"Tennis players show a lower coactivation of the elbow antagonist muscles during isokinetic exercises","volume":"18","author":"Bazzucchi","year":"2008","journal-title":"J. Electromyogr. Kinesiol."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"697","DOI":"10.1016\/j.jelekin.2015.04.002","article-title":"Training-related changes in the EMG-moment relationship during isometric contractions: Further evidence of improved control of muscle activation in strength-trained men?","volume":"25","author":"Amarantini","year":"2015","journal-title":"J. Electromyogr. Kinesiol."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"238","DOI":"10.1139\/y04-017","article-title":"Spinal excitation and inhibition decrease as humans\u2019 age","volume":"82","author":"Kido","year":"2004","journal-title":"Can. J. Physiol. Pharmacol."}],"container-title":["Entropy"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1099-4300\/18\/6\/229\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T19:25:44Z","timestamp":1760210744000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1099-4300\/18\/6\/229"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2016,6,20]]},"references-count":39,"journal-issue":{"issue":"6","published-online":{"date-parts":[[2016,6]]}},"alternative-id":["e18060229"],"URL":"https:\/\/doi.org\/10.3390\/e18060229","relation":{},"ISSN":["1099-4300"],"issn-type":[{"value":"1099-4300","type":"electronic"}],"subject":[],"published":{"date-parts":[[2016,6,20]]}}}