{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,25]],"date-time":"2026-01-25T07:48:16Z","timestamp":1769327296360,"version":"3.49.0"},"reference-count":49,"publisher":"MDPI AG","issue":"20","license":[{"start":{"date-parts":[[2022,10,14]],"date-time":"2022-10-14T00:00:00Z","timestamp":1665705600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Foundation for Science and Technology","award":["UIDB\/05757\/2020"],"award-info":[{"award-number":["UIDB\/05757\/2020"]}]},{"name":"Foundation for Science and Technology","award":["UIDP\/05757\/2020"],"award-info":[{"award-number":["UIDP\/05757\/2020"]}]},{"name":"Foundation for Science and Technology","award":["LA\/P\/0007\/2021"],"award-info":[{"award-number":["LA\/P\/0007\/2021"]}]},{"name":"national funds FCT\/MCTES (PIDDAC)","award":["UIDB\/05757\/2020"],"award-info":[{"award-number":["UIDB\/05757\/2020"]}]},{"name":"national funds FCT\/MCTES (PIDDAC)","award":["UIDP\/05757\/2020"],"award-info":[{"award-number":["UIDP\/05757\/2020"]}]},{"name":"national funds FCT\/MCTES (PIDDAC)","award":["LA\/P\/0007\/2021"],"award-info":[{"award-number":["LA\/P\/0007\/2021"]}]},{"name":"CeDRI","award":["UIDB\/05757\/2020"],"award-info":[{"award-number":["UIDB\/05757\/2020"]}]},{"name":"CeDRI","award":["UIDP\/05757\/2020"],"award-info":[{"award-number":["UIDP\/05757\/2020"]}]},{"name":"CeDRI","award":["LA\/P\/0007\/2021"],"award-info":[{"award-number":["LA\/P\/0007\/2021"]}]},{"name":"SusTEC","award":["UIDB\/05757\/2020"],"award-info":[{"award-number":["UIDB\/05757\/2020"]}]},{"name":"SusTEC","award":["UIDP\/05757\/2020"],"award-info":[{"award-number":["UIDP\/05757\/2020"]}]},{"name":"SusTEC","award":["LA\/P\/0007\/2021"],"award-info":[{"award-number":["LA\/P\/0007\/2021"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJERPH"],"abstract":"<jats:p>This pilot study aimed to explore a method for characterization of the electromyogram frequency spectrum during a sustained exertion task, performed by the upper limb. Methods: Nine participants underwent an isometric localized muscle fatigue protocol on an isokinetic dynamometer until exhaustion, while monitored with surface electromyography (sEMG) of the shoulder\u2019s external rotators. Firstly, three methods of signal energy analysis based on primer frequency contributors were compared to the energy of the entire spectrum. Secondly, the chosen method of analysis was used to characterize the signal energy at beginning (T1), in the middle (T2) and at the end (T3) of the fatigue protocol and compared to the torque output and the shift in the median frequencies during the trial. Results: There were statistically significant differences between T1 and T3 for signal energy (p &lt; 0.007) and for central frequency of the interval (p = 0.003). Moreover, the isometric peak torque was also different between T1 and T3 (p &lt; 0.001). Overall, there were no differences between the signal energy enclosed in the 40 primer frequency contributors and the analysis of the full spectrum energy; consequently, it was the method of choice. The reported fatigue and the decrease in the produced muscle torque was consistent with fatigue-induced alterations in the electromyogram frequency spectrum. In conclusion, the developed protocol has potential to be considered as an easy-to-use method for EMG-based analysis of isometric muscle exertion until fatigue. Thus, the novelty of the proposed method is to explore, in muscle fatigue, the use of only the main contributors in the frequency domain of the EMG spectrum, avoiding surplus information, that may not represent muscle functioning. However, further studies are needed to investigate the stability of the present findings in a more comprehensive sample.<\/jats:p>","DOI":"10.3390\/ijerph192013270","type":"journal-article","created":{"date-parts":[[2022,10,17]],"date-time":"2022-10-17T00:04:55Z","timestamp":1665965095000},"page":"13270","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":17,"title":["EMG Signal Processing for the Study of Localized Muscle Fatigue\u2014Pilot Study to Explore the Applicability of a Novel Method"],"prefix":"10.3390","volume":"19","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-2931-8971","authenticated-orcid":false,"given":"Sandra B.","family":"Rodrigues","sequence":"first","affiliation":[{"name":"FP-I3ID, FP-BHS, Escola Superior de Sa\u00fade Fernando Pessoa, Rua Delfim Maia 334, 4200-253 Porto, Portugal"}]},{"given":"Lu\u00eds Palermo","family":"de Faria","sequence":"additional","affiliation":[{"name":"FP-I3ID, FP-BHS, Escola Superior de Sa\u00fade Fernando Pessoa, Rua Delfim Maia 334, 4200-253 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4467-1722","authenticated-orcid":false,"given":"Ant\u00f3nio M.","family":"Monteiro","sequence":"additional","affiliation":[{"name":"Department of Sports Sciences and Physical Education, Instituto Polit\u00e9cnico de Bragan\u00e7a, 5300-253 Bragan\u00e7a, Portugal"},{"name":"Research Center in Sports, Health and Human Development, 5001-801 Vila Real, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7902-1207","authenticated-orcid":false,"given":"Jos\u00e9 Lu\u00eds","family":"Lima","sequence":"additional","affiliation":[{"name":"Research Centre in Digitalization and Intelligent Robotics (CeDRI), Instituto Polit\u00e9cnico de Bragan\u00e7a, Campus de Santa Apol\u00f3nia, 5300-253 Bragan\u00e7a, Portugal"},{"name":"Laborat\u00f3rio Para a Sustentabilidade e Tecnologia em Regi\u00f5es de Montanha (SusTEC), Instituto Polit\u00e9cnico de Bragan\u00e7a, Campus de Santa Apol\u00f3nia, 5300-253 Bragan\u00e7a, Portugal"},{"name":"INESC Technology and Science, 4200-465 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7071-2116","authenticated-orcid":false,"given":"Tiago M.","family":"Barbosa","sequence":"additional","affiliation":[{"name":"Department of Sports Sciences and Physical Education, Instituto Polit\u00e9cnico de Bragan\u00e7a, 5300-253 Bragan\u00e7a, Portugal"},{"name":"Research Center in Sports, Health and Human Development, 5001-801 Vila Real, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4756-5917","authenticated-orcid":false,"given":"Jos\u00e9 A.","family":"Duarte","sequence":"additional","affiliation":[{"name":"CIAFEL, Faculty of Sports, Porto University, Rua Dr. Pl\u00e1cido Costa 91, 4200-450 Porto, Portugal"},{"name":"TOXRUN, University Institute of Health Sciences, Rua Central de Gandra 1317, 4585-116 Gandra, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2022,10,14]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"299","DOI":"10.1007\/s004210100454","article-title":"Static and dynamic myoelectric measures of shoulder muscle fatigue during intermittent dynamic exertions of low to moderate intensity","volume":"85","author":"Nussbaum","year":"2001","journal-title":"Eur. 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