{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,26]],"date-time":"2026-02-26T18:05:28Z","timestamp":1772129128998,"version":"3.50.1"},"reference-count":46,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2021,1,20]],"date-time":"2021-01-20T00:00:00Z","timestamp":1611100800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"UNetBA project, Erasmus Mundus","award":["UN15PD0005"],"award-info":[{"award-number":["UN15PD0005"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The purpose of this study was to examine the changes in co-activation around the knee joint during different walking speeds in healthy females using the co-activation index. Ten healthy females (age: 21.20 \u00b1 7.21 years, height: 164.00 \u00b1 4.00 cm, mass: 60.60 \u00b1 4.99 kg) participated in this study and performed three walking speeds (slow, normal, and fast). A Qualisys 11-camera motion analysis system sampling at a frequency of 200 Hz was synchronized with a Trigno EMG Wireless system operating at a 2000 Hz sampling frequency. A significant decrease in the co-activation index of thigh muscles was observed between the slow and fast, and between the normal and fast, walking speeds during all walking phases. A non-significant difference was observed between the slow and normal walking speeds during most walking phases, except the second double support phase, during which the difference was significant. A negative relationship was found between walking speed and the co-activation index of thigh muscles in all speeds during walking phases: first double support (r = \u22120.3386, p &lt; 0.001), single support (r = \u22120.2144, p &lt; 0.01), second double support (r = \u22120.4949, p &lt; 0.001), and Swing (r = \u22120.1639, p &lt; 0.05). In conclusion, the results indicated high variability of thigh muscle co-activation in healthy females during the different walking speeds, and a decrease in the co-activation of the thigh muscles with the increase of speed.<\/jats:p>","DOI":"10.3390\/s21030677","type":"journal-article","created":{"date-parts":[[2021,1,21]],"date-time":"2021-01-21T00:53:41Z","timestamp":1611190421000},"page":"677","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":14,"title":["Muscle Co-Activation around the Knee during Different Walking Speeds in Healthy Females"],"prefix":"10.3390","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8292-3113","authenticated-orcid":false,"given":"Abdel-Rahman","family":"Akl","sequence":"first","affiliation":[{"name":"Faculty of Physical Education-Abo Qir, Alexandria University, Alexandria 21913, Egypt"},{"name":"Porto Biomechanics Laboratory (LABIOMEP-UP), Faculty of Sport (CIFI2D), University of Porto, 4099-002 Porto, Portugal"}]},{"given":"Pedro","family":"Gon\u00e7alves","sequence":"additional","affiliation":[{"name":"Porto Biomechanics Laboratory (LABIOMEP-UP), Faculty of Sport (CIFI2D), University of Porto, 4099-002 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4885-4924","authenticated-orcid":false,"given":"Pedro","family":"Fonseca","sequence":"additional","affiliation":[{"name":"Porto Biomechanics Laboratory (LABIOMEP-UP), Faculty of Sport (CIFI2D), University of Porto, 4099-002 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2053-7644","authenticated-orcid":false,"given":"Amr","family":"Hassan","sequence":"additional","affiliation":[{"name":"Department of Sports Training, Faculty of Sports Education, Mansoura University, Mansoura 35516, Egypt"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4109-2939","authenticated-orcid":false,"given":"Jo\u00e3o Paulo","family":"Vilas-Boas","sequence":"additional","affiliation":[{"name":"Porto Biomechanics Laboratory (LABIOMEP-UP), Faculty of Sport (CIFI2D), University of Porto, 4099-002 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1636-2685","authenticated-orcid":false,"given":"Filipe","family":"Concei\u00e7\u00e3o","sequence":"additional","affiliation":[{"name":"Porto Biomechanics Laboratory (LABIOMEP-UP), Faculty of Sport (CIFI2D), University of Porto, 4099-002 Porto, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2021,1,20]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"294","DOI":"10.1016\/j.gaitpost.2020.09.023","article-title":"Leg and lower limb dynamic joint stiffness during different walking speeds in healthy adults","volume":"82","author":"Akl","year":"2020","journal-title":"Gait Posture"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"78","DOI":"10.1016\/S0966-6362(01)00206-5","article-title":"Speed dependence of averaged EMG profiles in walking","volume":"16","author":"Hof","year":"2002","journal-title":"Gait Posture"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1451","DOI":"10.1016\/j.jelekin.2013.06.002","article-title":"Walking speed effects on the lower limb electromyographic variability of healthy children aged 7\u201316 years","volume":"23","author":"Tirosh","year":"2013","journal-title":"J. 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