{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,16]],"date-time":"2026-03-16T05:09:43Z","timestamp":1773637783296,"version":"3.50.1"},"reference-count":30,"publisher":"Wiley","issue":"8","license":[{"start":{"date-parts":[[2021,7,6]],"date-time":"2021-07-06T00:00:00Z","timestamp":1625529600000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["physoc.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Experimental Physiology"],"published-print":{"date-parts":[[2021,8]]},"abstract":"<jats:sec><jats:title>New Findings<\/jats:title><jats:p><jats:list list-type=\"bullet\">\n<jats:list-item><jats:p><jats:bold>What is the central question of this study?<\/jats:bold><\/jats:p>\n<jats:p>What are the <jats:italic>in vivo<\/jats:italic> operating lengths of the gastrocnemius muscle in children who idiopathically toe\u2010walk?<\/jats:p><\/jats:list-item>\n<jats:list-item><jats:p><jats:bold>What is the main finding and its importance?<\/jats:bold><\/jats:p>\n<jats:p>Children who idiopathically toe\u2010walk operate at more plantarflexed positions but at longer fascicle lengths than typically developing children during gait. However, these ranges utilised during gait correspond to where children who idiopathically toe\u2010walk are optimally strong. This should be considered when prescribing clinical treatments to restore typical gait.<\/jats:p><\/jats:list-item>\n<\/jats:list><\/jats:p><\/jats:sec><jats:sec><jats:title>Abstract<\/jats:title><jats:p>Children who idiopathically toe\u2010walk (ITW) habitually operate at greater plantarflexion angles than typically developing (TD) children, which might result in shorter, sub\u2010optimal gastrocnemius fascicle lengths. However, currently no experimental evidence exists to substantiate this notion. Five children who ITW and 14 TD children completed a gait analysis, whilst gastrocnemius fascicle behaviour was simultaneously quantified using ultrasound. The moment\u2013angle (hip, knee and ankle) and moment\u2013length (gastrocnemius) relationships were determined from isometric maximum voluntary contractions (MVC) on an isokinetic dynamometer combined with ultrasound. During gait, children who ITW operated at more plantarflexed angles (\u0394\u00a0=\u00a020\u00b0; <jats:italic>P<\/jats:italic>\u00a0=\u00a00.013) and longer muscle fascicle lengths (\u0394\u00a0=\u00a012\u00a0mm; <jats:italic>P<\/jats:italic>\u00a0=\u00a00.008) than TD children. During MVC, no differences in the peak moment of any joint were found. However, peak plantarflexor moment occurred at significantly more plantarflexed angles (\u221216 <jats:italic>vs<\/jats:italic>. 1\u00b0; <jats:italic>P<\/jats:italic>\u00a0=\u00a00.010) and at longer muscle fascicle lengths (44 <jats:italic>vs<\/jats:italic>. 37\u00a0mm; <jats:italic>P<\/jats:italic>\u00a0=\u00a00.001) in children who ITW than TD children. Observed alterations in the moment\u2013angle and moment\u2013length relationships of children who ITW coincided with the ranges used during gait. Therefore, the gastrocnemius muscle in children who ITW operates close to the peak of the force\u2013length relationship, similarly to TD children. Thus, this study indicates that idiopathic toe\u2010walking is truly an ankle joint pathology, and children who ITW present with substantial alterations in the gastrocnemius muscle functional properties, which appear well adapted to the characteristic demands of equinus gait. These findings should be considered when prescribing clinical treatments to restore typical gait.<\/jats:p><\/jats:sec>","DOI":"10.1113\/ep089658","type":"journal-article","created":{"date-parts":[[2021,6,23]],"date-time":"2021-06-23T04:33:13Z","timestamp":1624422793000},"page":"1806-1813","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":8,"title":["<i>In vivo<\/i> operating lengths of the gastrocnemius muscle during gait in children who idiopathically toe\u2010walk"],"prefix":"10.1113","volume":"106","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-6093-365X","authenticated-orcid":false,"given":"Carla","family":"Harkness\u2010Armstrong","sequence":"first","affiliation":[{"name":"Research Institute for Sport and Exercise Sciences Liverpool John Moores University  Liverpool 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for Sport and Exercise Sciences Liverpool John Moores University  Liverpool UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Thomas D.","family":"O'Brien","sequence":"additional","affiliation":[{"name":"Research Institute for Sport and Exercise Sciences Liverpool John Moores University  Liverpool UK"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"311","published-online":{"date-parts":[[2021,7,6]]},"reference":[{"key":"e_1_2_8_2_1","doi-asserted-by":"publisher","DOI":"10.1098\/rstb.2010.0345"},{"key":"e_1_2_8_3_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.jbiomech.2011.06.008"},{"key":"e_1_2_8_4_1","doi-asserted-by":"publisher","DOI":"10.1002\/mus.21287"},{"key":"e_1_2_8_5_1","doi-asserted-by":"publisher","DOI":"10.1002\/mus.21530"},{"key":"e_1_2_8_6_1","doi-asserted-by":"crossref","DOI":"10.1080\/17518423.2021.1899326","article-title":"Investigation of muscle strength, motor coordination and balance in children with idiopathic toe walking: A 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