{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,11]],"date-time":"2026-03-11T06:58:00Z","timestamp":1773212280527,"version":"3.50.1"},"reference-count":32,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2026,3,10]],"date-time":"2026-03-10T00:00:00Z","timestamp":1773100800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"FCT\u2014Foundation for Science and Technology","award":["UID\/04045\/2025"],"award-info":[{"award-number":["UID\/04045\/2025"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Applied Sciences"],"abstract":"<jats:p>Resistance training machines are designed to provide either constant or variable resistance, with the latter intended to generate a machine resistive torque (MRT) that mirrors the natural fluctuations in human torque capability (HTC) across joint angles. Yet, achieving a precise match between MRT and HTC remains a persistent challenge. This study aimed to validate a novel variable-cam resistance system, the Variable Moment Arm Cam\u00ae (VMAC\u00ae), by examining torque output and muscle activation during leg extension across the full range of motion (100\u20130\u00b0), using repeated testing and direct comparison with an isokinetic dynamometer. Twenty-two young men completed four randomized sessions, two on the variable-cam system and two on the dynamometer, each separated by 72\u201396 h. Torque and muscle activity were recorded during six isometric contractions at 100\u00b0, 80\u00b0, 60\u00b0, 40\u00b0, 20\u00b0, and 0\u00b0. The variable-cam system produced torque and activation patterns broadly comparable to the dynamometer, with acceptable agreement across angles. Validity was highest at 60\u00b0, aligning with the region of peak torque, whereas greater variability emerged at the extremes of flexion and extension. Muscle activation profiles were similar between devices, though more variable than torque, underscoring the inherent complexity of neuromuscular assessment.<\/jats:p>","DOI":"10.3390\/app16062633","type":"journal-article","created":{"date-parts":[[2026,3,10]],"date-time":"2026-03-10T08:43:31Z","timestamp":1773132211000},"page":"2633","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Validation of a Novel Variable-Cam System: Electromyographic and Kinetic Analysis"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0009-0006-3405-9053","authenticated-orcid":false,"given":"Renato","family":"da Costa-Machado","sequence":"first","affiliation":[{"name":"Sport Sciences School of Rio Maior, Polytechnic Institute of Santar\u00e9m, 2040-413 Rio Maior, Portugal"},{"name":"Department of Sport Sciences, University of Beira Interior, 6201-001 Covilh\u00e3, Portugal"},{"name":"Research Centre in Sports, Health and Human Development (CIDESD), 6201-001 Covilh\u00e3, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6653-0616","authenticated-orcid":false,"given":"Diogo L.","family":"Marques","sequence":"additional","affiliation":[{"name":"Department of Sport Sciences, University of Beira Interior, 6201-001 Covilh\u00e3, Portugal"},{"name":"Research Centre in Sports, Health and Human Development (CIDESD), 6201-001 Covilh\u00e3, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5248-7717","authenticated-orcid":false,"given":"Runer A.","family":"Marson","sequence":"additional","affiliation":[{"name":"Brazilian Army, Preparatory School for Army Cadets, Campinas 13070-091, SP, Brazil"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5635-2476","authenticated-orcid":false,"given":"Hugo","family":"Louro","sequence":"additional","affiliation":[{"name":"Sport Sciences School of Rio Maior, Polytechnic Institute of Santar\u00e9m, 2040-413 Rio Maior, Portugal"},{"name":"Research Centre in Sports, Health and Human Development (CIDESD), 6201-001 Covilh\u00e3, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2351-3047","authenticated-orcid":false,"given":"Daniel A.","family":"Marinho","sequence":"additional","affiliation":[{"name":"Department of Sport Sciences, University of Beira Interior, 6201-001 Covilh\u00e3, Portugal"},{"name":"Research Centre in Sports, Health and Human Development (CIDESD), 6201-001 Covilh\u00e3, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8109-4875","authenticated-orcid":false,"given":"Ana","family":"Concei\u00e7\u00e3o","sequence":"additional","affiliation":[{"name":"Sport Sciences School of Rio Maior, Polytechnic Institute of Santar\u00e9m, 2040-413 Rio Maior, Portugal"},{"name":"Research Centre in Sports, Health and Human Development (CIDESD), 6201-001 Covilh\u00e3, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2026,3,10]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1069","DOI":"10.1007\/s00421-012-2526-2","article-title":"Neuromuscular fatigue in young and older men using constant or variable resistance","volume":"113","author":"Walker","year":"2012","journal-title":"Eur. 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