{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,5]],"date-time":"2026-02-05T21:21:32Z","timestamp":1770326492049,"version":"3.49.0"},"reference-count":0,"publisher":"Georg Thieme Verlag KG","issue":"09","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Int J Sports Med"],"published-print":{"date-parts":[[2018,9]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>This study aimed to examine longitudinal changes in isometric strength of the knee extensors (ImKE) and knee flexors (ImKF) at 30\u00b0 and 60\u00b0. The sample was composed of 67 players aged 11.0\u201313.9 years at baseline over five years. Stature, body mass, skinfolds, and isometric strength (ImKE30\u00b0, ImKF30\u00b0, ImKE60\u00b0 and ImKF60\u00b0) were measured. Fat mass and fat-free mass (FFM) were derived from skinfolds. Skeletal age was obtained using TW2 RUS. Multilevel random effects regression analyses extracted developmental polynomial models. An annual increment on chronological age (CA) corresponded to 5.6\u2009N (ImKE30\u00b0), 2.7\u2009N (ImKF30\u00b0), 4.6\u2009N (ImKE60\u00b0) and 1.5\u2009N (ImKF60\u00b0). An increment of 1\u2009kg in FFM predicted isometric strength as follows: 1.2\u2009N (ImKE30\u00b0), 2.1\u2009N (ImKF30\u00b0), 3.1\u2009N (ImKE60\u00b0) and 2.0\u2009N (ImKF60\u00b0). The following equations were obtained: ImKE30\u00b0=5.759\u00d7CA+1.163\u00d7FFM; ImKF30\u00b0=\u221219.369+2.691\u00d7CA+0.693\u00d7CA2+2.108\u00d7FFM; ImKE60\u00b0=4.553\u00d7CA+3.134\u00d7FFM; and, ImKF60\u00b0=-19.669+1.544\u00d7CA+2.033\u00d7FFM. Although skeletal maturity had a negligible effect on dependent variables, age and body size, based on FFM, were relevant longitudinal predictors. During adolescence, systematic assessment of knee extensors and knee flexors are strongly recommended to prevent impairment of knee muscle groups.<\/jats:p>","DOI":"10.1055\/s-0044-100389","type":"journal-article","created":{"date-parts":[[2018,6,20]],"date-time":"2018-06-20T22:56:31Z","timestamp":1529535391000},"page":"688-695","source":"Crossref","is-referenced-by-count":13,"title":["Developmental Changes in Isometric Strength: Longitudinal Study in Adolescent Soccer Players"],"prefix":"10.1055","volume":"39","author":[{"given":"Joao","family":"Duarte","sequence":"additional","affiliation":[{"name":"Faculty of Sports Sciences and Physical Education, University of Coimbra, Coimbra, Portugal"},{"name":"uid\/dtp\/04213\/2016, University of Coimbra, Coimbra, Portugal"}]},{"given":"Jo\u00e3o","family":"Valente-dos-Santos","sequence":"additional","affiliation":[{"name":"uid\/dtp\/04213\/2016, University of Coimbra, Coimbra, Portugal"},{"name":"Faculty of Physical Education and Sport, Lusofona University of Humanities and Technologies, Lisbon, Portugal"}]},{"given":"Manuel","family":"Coelho-e-Silva","sequence":"additional","affiliation":[{"name":"Faculty of Sports Sciences and Physical Education, University of Coimbra, Coimbra, Portugal"},{"name":"uid\/dtp\/04213\/2016, University of Coimbra, Coimbra, Portugal"}]},{"given":"R.","family":"Malina","sequence":"additional","affiliation":[{"name":"Faculty of Physical Education and Sport, Lusofona University of Humanities and Technologies, Lisbon, Portugal"}]},{"given":"Dieter","family":"Deprez","sequence":"additional","affiliation":[{"name":"Department of Kinesiology and Health Education, University of Texas, Austin, Texas, USA"}]},{"given":"Renaat","family":"Philippaerts","sequence":"additional","affiliation":[{"name":"Club Brugge KV, Brugge, Belgium"}]},{"given":"Matthieu","family":"Lenoir","sequence":"additional","affiliation":[{"name":"Department of Movement and Sports Science, Ghent University, Ghent, Belgium"}]},{"given":"Roel","family":"Vaeyens","sequence":"additional","affiliation":[{"name":"Club Brugge KV, Brugge, Belgium"},{"name":"Department of Movement and Sports Science, Ghent University, Ghent, Belgium"}]}],"member":"194","published-online":{"date-parts":[[2018,6,20]]},"container-title":["International Journal of Sports Medicine"],"original-title":[],"language":"en","link":[{"URL":"http:\/\/www.thieme-connect.de\/products\/ejournals\/pdf\/10.1055\/s-0044-100389.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2018,8,1]],"date-time":"2018-08-01T22:37:48Z","timestamp":1533163068000},"score":1,"resource":{"primary":{"URL":"http:\/\/www.thieme-connect.de\/DOI\/DOI?10.1055\/s-0044-100389"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2018,6,20]]},"references-count":0,"journal-issue":{"issue":"09","published-online":{"date-parts":[[2018,8,1]]},"published-print":{"date-parts":[[2018,9]]}},"URL":"https:\/\/doi.org\/10.1055\/s-0044-100389","relation":{},"ISSN":["0172-4622","1439-3964"],"issn-type":[{"value":"0172-4622","type":"print"},{"value":"1439-3964","type":"electronic"}],"subject":[],"published":{"date-parts":[[2018,6,20]]}}}