{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,5,14]],"date-time":"2025-05-14T02:12:43Z","timestamp":1747188763087,"version":"3.40.5"},"reference-count":30,"publisher":"Human Kinetics","issue":"9","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2023,9,1]]},"abstract":"<jats:p><jats:italic><jats:bold>Purpose<\/jats:bold>:<\/jats:italic> To longitudinally investigate the development of physical characteristics and function during 3\u00a0years of high school among Japanese junior rugby players and examine the differences in these parameters between the positions. <jats:italic><jats:bold>Methods:<\/jats:bold><\/jats:italic> In 83 junior rugby players (forwards: n\u2009=\u200946, backs: n\u2009=\u200937) from one Japanese high school team who had participated in national high school competitions, anthropometric variables (height, body mass, fat and lean body mass, and body mass index), upper- and lower-body strength (eg,\u00a01-repetition-maximum [1RM] bench press, isokinetic knee muscle strength at 60\u00b0\/s and 180\u00b0\/s), and sprint and jump performance were measured. Upper- and lower-body strength relative to body mass and lean body mass were also calculated. <jats:italic><jats:bold>Results:<\/jats:bold><\/jats:italic> All anthropometric indices improved with increasing age, and the values were higher in forwards than in backs (all <jats:italic>P<\/jats:italic>\u2009&lt;\u2009.05). The 1-repetition maximum bench press (forwards: 40.8%, backs: 52.5%) and isokinetic knee strength (eg,\u00a0extension at 60\u00b0\/s, forwards: 15.4%, backs: 10.0%) improved with age (from 16 to 18\u00a0y), and they were higher in forwards than in backs (all <jats:italic>P<\/jats:italic>\u2009&lt;\u2009.05). Meanwhile, the 1RM bench press relative to lean body mass did not differ between the positions. Isokinetic knee muscle strength at 60\u00b0\/s and 180\u00b0\/s relative to lean body mass and sprint and jump performance did not improve with age. <jats:italic><jats:bold>Conclusion:<\/jats:bold><\/jats:italic> These results indicate that Japanese junior rugby players need to develop larger physiques and continuously increase their lower-body strength to improve sprint and jump performance.<\/jats:p>","DOI":"10.1123\/ijspp.2023-0114","type":"journal-article","created":{"date-parts":[[2023,7,27]],"date-time":"2023-07-27T10:45:37Z","timestamp":1690454737000},"page":"1038-1046","source":"Crossref","is-referenced-by-count":1,"title":["Longitudinal Development of Physical Characteristics and Function in Japanese Junior Rugby Union Players"],"prefix":"10.1123","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-3201-3810","authenticated-orcid":true,"given":"Akira","family":"Kumazaki","sequence":"first","affiliation":[{"name":"Department of Health and Sports, Niigata University of Health and Welfare, Niigata, Japan"},{"name":"Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1676-4921","authenticated-orcid":true,"given":"Tomomi","family":"Fujimoto","sequence":"additional","affiliation":[{"name":"Department of Health and Sports, Niigata University of Health and Welfare, Niigata, Japan"},{"name":"Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3397-1140","authenticated-orcid":true,"given":"Yuiko","family":"Matsuura","sequence":"additional","affiliation":[{"name":"Department of Health and Sports, Niigata University of Health and Welfare, Niigata, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"100","reference":[{"issue":"1","key":"r1","series-title":"BMJ Open Sport Exerc Med","article-title":"Trends in player body mass at men\u2019s and women\u2019s rugby world cups: a plateau in body mass and differences in emerging rugby nations","volume":"7","author":"Tucker R","year":"2021","unstructured":"Tucker R, Lancaster S, Davies P, et\u00a0al. 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