{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,24]],"date-time":"2026-06-24T20:42:27Z","timestamp":1782333747700,"version":"3.54.5"},"reference-count":43,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2017,5,11]],"date-time":"2017-05-11T00:00:00Z","timestamp":1494460800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"the National Nature Science Foundation of China (NSFC)","award":["61431017 and 61671417"],"award-info":[{"award-number":["61431017 and 61671417"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Entropy"],"abstract":"<jats:p>This study aimed to investigate the fatiguing characteristics of muscle-tendon units (MTUs) within skeletal muscles during static isometric contraction tasks. The deltoid was selected as the target muscle and three head-related static isometric contraction tasks were designed to activate three heads of the deltoid in different modes. Nine male subjects participated in this study. Surface electromyography (SEMG) signals were collected synchronously from the three heads of the deltoid. The performances of five SEMG parameters, including root mean square (RMS), mean power frequency (MPF), the first coefficient of autoregressive model (ARC1), sample entropy (SE) and Higuchi\u2019s fractal dimension (HFD), in quantification of fatigue, were evaluated in terms of sensitivity to variability ratio (SVR) and consistency firstly. Then, the HFD parameter was selected as the fatigue index for further muscle fatigue analysis. The experimental results demonstrated that the three deltoid heads presented different activation modes during three head-related fatiguing contractions. The fatiguing characteristics of the three heads were found to be task-dependent, and the heads kept in a relatively high activation level were more prone to fatigue. In addition, the differences in fatiguing rate between heads increased with the increase in load. The findings of this study can be helpful in better understanding the underlying neuromuscular control strategies of the central nervous system (CNS). Based on the results of this study, the CNS was thought to control the contraction of the deltoid by taking the three heads as functional units, but a certain synergy among heads might also exist to accomplish a contraction task.<\/jats:p>","DOI":"10.3390\/e19050221","type":"journal-article","created":{"date-parts":[[2017,5,11]],"date-time":"2017-05-11T11:06:46Z","timestamp":1494500806000},"page":"221","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":13,"title":["Muscle Fatigue Analysis of the Deltoid during Three Head-Related Static Isometric Contraction Tasks"],"prefix":"10.3390","volume":"19","author":[{"given":"Wenxiang","family":"Cui","sequence":"first","affiliation":[{"name":"Department of Electronic Science and Technology, University of Science and Technology of China, Hefei 230026, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xiang","family":"Chen","sequence":"additional","affiliation":[{"name":"Department of Electronic Science and Technology, University of Science and Technology of China, Hefei 230026, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Shuai","family":"Cao","sequence":"additional","affiliation":[{"name":"Department of Electronic Science and Technology, University of Science and Technology of China, Hefei 230026, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1533-4340","authenticated-orcid":false,"given":"Xu","family":"Zhang","sequence":"additional","affiliation":[{"name":"Department of Electronic Science and Technology, University of Science and Technology of China, Hefei 230026, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2017,5,11]]},"reference":[{"key":"ref_1","first-page":"1","article-title":"Human muscle function and fatigue","volume":"82","author":"Edwards","year":"1981","journal-title":"Ciba Found. Symp."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"501","DOI":"10.1016\/j.jelekin.2012.02.019","article-title":"Electromyographic models to assess muscle fatigue","volume":"22","author":"Malanda","year":"2012","journal-title":"J. Electromyogr. Kinesiol."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"75","DOI":"10.1249\/JES.0000000000000043","article-title":"Skeletal muscle fatigue and decreased efficiency: Two sides of the same coin?","volume":"43","author":"Grassi","year":"2015","journal-title":"Exerc. Sport Sci. Rev."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"327","DOI":"10.1016\/j.clinbiomech.2009.01.010","article-title":"Surface emg based muscle fatigue evaluation in biomechanics","volume":"24","author":"Cifrek","year":"2009","journal-title":"Clin. Biomech."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"215","DOI":"10.1016\/j.gaitpost.2014.03.194","article-title":"Effects of unilateral leg muscle fatigue on balance control in perturbed and unperturbed gait in healthy elderly","volume":"40","author":"Toebes","year":"2014","journal-title":"Gait Posture"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"962","DOI":"10.1016\/j.gaitpost.2013.05.004","article-title":"Muscle fatigue during repetitive voluntary contractions: A comparison between children with cerebral palsy, typically developing children and young healthy adults","volume":"38","author":"Eken","year":"2013","journal-title":"Gait Posture"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1859","DOI":"10.3109\/09638288.2015.1107777","article-title":"Validity and everyday clinical applicability of lumbar muscle fatigue assessment methods in patients with chronic non-specific low back pain: A systematic review","volume":"38","author":"Villafane","year":"2016","journal-title":"Disabil. Rehabil."},{"key":"ref_8","first-page":"82","article-title":"The relation between muscle fatigue and some physiological and biomechanical parameters","volume":"12","author":"Sedeek","year":"2016","journal-title":"J. Am. Sci."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Becker, S., Fr\u00f6hlich, M., Kelm, J., and Ludwig, O. (2017). Change of muscle activity as well as kinematic and kinetic parameters during headers after core muscle fatigue. Sports, 5.","DOI":"10.3390\/sports5010010"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"2035","DOI":"10.1177\/0363546515588179","article-title":"Performance demands in softball pitching: A comprehensive muscle fatigue study","volume":"43","author":"Corben","year":"2015","journal-title":"Am. J. Sports Med."},{"key":"ref_11","unstructured":"Jarmey, C. (2008). Muscles of the shoulder and upper arm. The Concise Book of Muscles, Lotus Publishing and North Atlantic Books. [2nd ed.]."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"336","DOI":"10.1152\/jn.00049.2011","article-title":"The function of neuromuscular compartments in human shoulder muscles","volume":"107","author":"Wickham","year":"2012","journal-title":"J. Neurophysiol."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"066001","DOI":"10.1088\/1741-2560\/13\/6\/066001","article-title":"Muscle-tendon units localization and activation level analysis based on high-density surface emg array and nmf algorithm","volume":"13","author":"Huang","year":"2016","journal-title":"J. Neural Eng."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"794","DOI":"10.1002\/mus.24232","article-title":"Non-uniform surface electromyographic responses to change in joint angle within rectus femoris muscle","volume":"50","author":"Watanabe","year":"2014","journal-title":"Muscle Nerve"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"929","DOI":"10.1016\/j.jelekin.2011.08.006","article-title":"Are the myoelectric manifestations of fatigue distributed regionally in the human medial gastrocnemius muscle?","volume":"21","author":"Gallina","year":"2011","journal-title":"J. Electromyogr. Kinesiol."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"226","DOI":"10.1002\/mus.23739","article-title":"Region-specific myoelectric manifestations of fatigue in human rectus femoris muscle","volume":"48","author":"Watanabe","year":"2013","journal-title":"Muscle Nerve"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"69","DOI":"10.1515\/hukin-2015-0035","article-title":"Muscle fatigue in the three heads of the triceps brachii during a controlled forceful hand grip task with full elbow extension using surface electromyography","volume":"46","author":"Ali","year":"2015","journal-title":"J. Hum. Kinet."},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Naik, G.R., Kumar, D.K., Wheeler, K., and Arjunan, S.P. (2009, January 1\u20133). Estimation of Muscle Fatigue during Cyclic Contractions Using Source Separation Techniques. Proceedings of the 2008 Digital Image Computing: Techniques and Applications (2009), Melbourne, Australia.","DOI":"10.1109\/DICTA.2009.43"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"2652","DOI":"10.1016\/j.eswa.2013.11.009","article-title":"Extraction and analysis of multiple time window features associated with muscle fatigue conditions using semg signals","volume":"41","author":"Venugopal","year":"2014","journal-title":"Expert Syst. Appl."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"321","DOI":"10.1016\/j.ergon.2004.08.011","article-title":"The sensitivity of autoregressive model coefficient in quantification of trunk muscle fatigue during a sustained isometric contraction","volume":"35","author":"Kim","year":"2005","journal-title":"Int. J. Ind. Ergon."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"197960","DOI":"10.1155\/2014\/197960","article-title":"Computation and evaluation of features of surface electromyogram to identify the force of muscle contraction and muscle fatigue","volume":"2014","author":"Arjunan","year":"2014","journal-title":"Biomed. Res. Int."},{"key":"ref_22","unstructured":"Klug, J. (2015). Shoulders. Bodybuilding Anatomy, Human Kinetics. [2nd ed.]."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"219","DOI":"10.1016\/S0165-0270(97)02251-6","article-title":"Measurement of human muscle fatigue","volume":"74","year":"1997","journal-title":"J. Neurosci. Methods"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"543","DOI":"10.1080\/00140138108924875","article-title":"Work load and fatigue in repetitive arm elevations","volume":"24","author":"Hagberg","year":"1981","journal-title":"Ergonomics"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"361","DOI":"10.1016\/S1050-6411(00)00027-4","article-title":"Development of recommendations for semg sensors and sensor placement procedures","volume":"10","author":"Hermens","year":"2000","journal-title":"J. Electromyogr. Kinesiol."},{"key":"ref_26","unstructured":"(2015, December 12). Seniam. Available online: http:\/\/www.seniam.org\/."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1483","DOI":"10.1007\/s10439-010-9933-5","article-title":"Fuzzy approximate entropy analysis of chaotic and natural complex systems: Detecting muscle fatigue using electromyography signals","volume":"38","author":"Xie","year":"2010","journal-title":"Ann. Biomed. Eng."},{"key":"ref_28","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_29","doi-asserted-by":"crossref","first-page":"953","DOI":"10.1002\/mus.880170819","article-title":"Fractal dimension of electromyographic signals recorded with surface electrodes during isometric contractions is linearly correlated with muscle activation","volume":"17","author":"Anmuth","year":"1994","journal-title":"Muscle Nerve"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"179","DOI":"10.1016\/j.gaitpost.2008.04.002","article-title":"Assessment of force and fatigue in isometric contractions of the upper trapezius muscle by surface emg signal and perceived exertion scale","volume":"28","author":"Troiano","year":"2008","journal-title":"Gait Posture"},{"key":"ref_31","doi-asserted-by":"crossref","unstructured":"Garavito, F., Gonzalez, J., Cabarcas, J., Chaparro, D., Portocarrero, I., and Vargas, A. (September, January 30). Emg signal analysis based on fractal dimension for muscle activation detection under exercice protocol. Proceedings of the 2016 XXI Symposium on Signal Processing, Images and Artificial Vision (STSIVA), Bucaramanga, Colombia.","DOI":"10.1109\/STSIVA.2016.7743365"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"233","DOI":"10.1016\/j.jelekin.2009.03.011","article-title":"Emg spectral indices and muscle power fatigue during dynamic contractions","volume":"20","author":"Malanda","year":"2010","journal-title":"J. Electromyogr. Kinesiol."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"1097","DOI":"10.1016\/j.jelekin.2010.05.010","article-title":"Semg wavelet-based indices predicts muscle power loss during dynamic contractions","volume":"20","author":"Malanda","year":"2010","journal-title":"J. Electromyogr. Kinesiol."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"811","DOI":"10.1016\/j.jelekin.2011.05.002","article-title":"Emg-based muscle fatigue assessment during dynamic contractions using principal component analysis","volume":"21","author":"Rogers","year":"2011","journal-title":"J. Electromyogr. Kinesiol."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"578","DOI":"10.1109\/TNSRE.2011.2163527","article-title":"Measuring increase in synchronization to identify muscle endurance limit","volume":"19","author":"Kumar","year":"2011","journal-title":"IEEE Trans. Neural Syst. Rehabil. Eng."},{"key":"ref_36","doi-asserted-by":"crossref","unstructured":"Beretta-Piccoli, M., D\u2019Antona, G., Barbero, M., Fisher, B., Dieli-Conwright, C.M., Clijsen, R., and Cescon, C. (2015). Evaluation of central and peripheral fatigue in the quadriceps using fractal dimension and conduction velocity in young females. PLoS ONE, 10.","DOI":"10.1371\/journal.pone.0123921"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"851","DOI":"10.1016\/j.jelekin.2008.08.003","article-title":"A bi-dimensional index for the selective assessment of myoelectric manifestations of peripheral and central muscle fatigue","volume":"19","author":"Mesin","year":"2009","journal-title":"J. Electromyogr. Kinesiol."},{"key":"ref_38","first-page":"714","article-title":"Analysis of anterior, middle and posterior deltoid activation during single and multijoint exercises","volume":"55","author":"Franke","year":"2015","journal-title":"J. Sports Med. Phys. Fit."},{"key":"ref_39","first-page":"3590","article-title":"Muscle synergy analysis for similar upper limb motion tasks","volume":"2014","author":"Tang","year":"2014","journal-title":"Conf. Proc. IEEE Eng. Med. Biol. Soc."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"152","DOI":"10.1515\/msr-2015-0022","article-title":"Independence between two channels of surface electromyogram signal to measure the loss of motor units","volume":"15","author":"Arjunan","year":"2015","journal-title":"Meas. Sci. Rev."},{"key":"ref_41","doi-asserted-by":"crossref","unstructured":"Naik, G.R., Kumar, D.K., and Arjunan, S. (2012, January 9\u201311). Measure of Increase in Motor Unit Synchronisaton for Young and Old Using Semg. Proceedings of the Biosignals and Biorobotics Conference (BRC), Manaus, Brazil.","DOI":"10.1109\/BRC.2012.6222191"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"271","DOI":"10.1007\/BF00423403","article-title":"Human motor unit activity during the onset of muscle fatigue in submaximal isometric isotonic contraction","volume":"46","author":"Maton","year":"1981","journal-title":"Eur. J. Appl. Physiol."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"34","DOI":"10.1016\/j.compbiomed.2017.02.003","article-title":"Analysis of the semg\/force relationship using hd-semg technique and data fusion: A simulation study","volume":"83","author":"Carriou","year":"2017","journal-title":"Comput. Biol. Med."}],"container-title":["Entropy"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1099-4300\/19\/5\/221\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T18:35:31Z","timestamp":1760207731000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1099-4300\/19\/5\/221"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2017,5,11]]},"references-count":43,"journal-issue":{"issue":"5","published-online":{"date-parts":[[2017,5]]}},"alternative-id":["e19050221"],"URL":"https:\/\/doi.org\/10.3390\/e19050221","relation":{},"ISSN":["1099-4300"],"issn-type":[{"value":"1099-4300","type":"electronic"}],"subject":[],"published":{"date-parts":[[2017,5,11]]}}}