{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,2]],"date-time":"2026-09-02T12:14:26Z","timestamp":1788351266217,"version":"build-2803163510"},"reference-count":40,"publisher":"BMJ","issue":"2","license":[{"start":{"date-parts":[[2026,4,9]],"date-time":"2026-04-09T00:00:00Z","timestamp":1775692800000},"content-version":"unspecified","delay-in-days":8,"URL":"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/"}],"funder":[{"name":"IdrettsCampus Bergen"},{"name":"The University and College Network for Western Norway"},{"DOI":"10.13039\/501100009729","name":"Norwegian Fund for Post-Graduate Training in Physiotherapy","doi-asserted-by":"publisher","award":["\u200b\u200b286661"],"award-info":[{"award-number":["\u200b\u200b286661"]}],"id":[{"id":"10.13039\/501100009729","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["BMJ Open Sport Exerc Med"],"accepted":{"date-parts":[[2026,3,25]]},"published-print":{"date-parts":[[2026,4]]},"abstract":"<jats:sec>\n                    <jats:title>Objectives<\/jats:title>\n                    <jats:p>Spondylolysis is a common source of low back pain (LBP) among adolescent athletes. We aimed to investigate the occurrence of LBP and spondylolysis, and the potential associations of weekly training and match exposure, and maturity status with spondylolysis among male youth football players.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>Male players (n=98) from six teams were followed over three consecutive seasons (U15\u2013U17). Training and match exposure (min), and pain\/injuries were self-reported weekly. Clinical examinations were conducted if a player reported LBP and abstained from football training\/matches for 1\u2009week or reported LBP for 4 consecutive weeks despite participating. MRI was used to determine if the LBP was due to spondylolysis. The maturity level was estimated biannually by X-ray of the left hand, along with body height and weight. Risk factor analyses estimated the association between an increase in total weekly training and match exposure and the risk of spondylolysis, and between maturity factors and the risk of spondylolysis.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>Of 98 players, 46 reported back pain at least once, 18 fulfilled the criteria for a clinical examination and 13 underwent an MRI scan, identifying 12 cases of spondylolysis. Risk factor analyses showed a significant association between increased total weekly training and match exposure and the risk of spondylolysis. No association was shown between any maturity measure and the occurrence of spondylolysis.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>Increased training and match exposure in the weeks before injury was significantly related to a diagnosis of spondylolysis. Maturity measures were not related to increased risk.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1136\/bmjsem-2026-003222","type":"journal-article","created":{"date-parts":[[2026,4,9]],"date-time":"2026-04-09T16:10:20Z","timestamp":1775751020000},"page":"e003222","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":0,"title":["Incidence and risk factors of spondylolysis in youth football: a longitudinal study among male Norwegian players"],"prefix":"10.1136","volume":"12","author":[{"ORCID":"https:\/\/orcid.org\/0009-0005-2522-5702","authenticated-orcid":false,"given":"Nicolay","family":"Morland","sequence":"first","affiliation":[{"name":"Western Norway Center for Sports Medicine, Bergen, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0001-5030-9159","authenticated-orcid":false,"given":"David","family":"Tovi","sequence":"additional","affiliation":[{"name":"Haraldsplass Deaconess Hospital Department of Surgery, Bergen, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3713-8938","authenticated-orcid":false,"given":"Benjamin","family":"Clarsen","sequence":"additional","affiliation":[{"name":"FIFA Medical, F\u00e9d\u00e9ration Internationale de Football Association, Z\u00fcrich, Switzerland"},{"name":"Norwegian School of Sport Sciences, Department of Sports Medicine, Oslo Sports Trauma Research Center, Oslo, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Cecilie B","family":"Rygh","sequence":"additional","affiliation":[{"name":"Department of Radiology, Haukeland University Hospital, Bergen, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9466-7003","authenticated-orcid":false,"given":"Lena Kristin","family":"Bache-Mathiesen","sequence":"additional","affiliation":[{"name":"Oslo Sports Trauma Research Center, Norwegian School of Sports Sciences, Oslo, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0096-4032","authenticated-orcid":false,"given":"Hege Havstad","family":"Clemm","sequence":"additional","affiliation":[{"name":"Department of Pediatric and Adolescent Medicine, Haukeland University Hospital, Bergen, Norway"},{"name":"Department of Sports Medicine, Norwegian School of Sports Sciences, Oslo, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hilde","family":"Gundersen","sequence":"additional","affiliation":[{"name":"Department of Sport, Food and Natural Sciences, Western Norway University of Applied Sciences, Bergen, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"239","published-online":{"date-parts":[[2026,4,9]]},"reference":[{"key":"2026090204251081000_12.2.e003222.1","doi-asserted-by":"publisher","DOI":"10.1136\/bjsports-2021-104749"},{"key":"2026090204251081000_12.2.e003222.2","doi-asserted-by":"crossref","first-page":"37","DOI":"10.1053\/radi.2000.0299","article-title":"The prevalence of spondylolysis and spondylolisthesis in symptomatic elite athletes: radiographic findings","volume":"7","author":"Rossi","year":"2001","journal-title":"Radiography (Lond)"},{"key":"2026090204251081000_12.2.e003222.3","doi-asserted-by":"crossref","first-page":"67","DOI":"10.3233\/BMR-140491","article-title":"Low back pain in young elite field hockey players, football players and speed skaters: Prevalence and risk factors","volume":"28","author":"van Hilst","year":"2015","journal-title":"J Back Musculoskelet Rehabil"},{"key":"2026090204251081000_12.2.e003222.4","doi-asserted-by":"crossref","first-page":"2540","DOI":"10.1007\/s00167-014-3069-3","article-title":"Low back pain in female elite football and handball players compared with an active control group","volume":"23","author":"Tun\u00e5s","year":"2015","journal-title":"Knee Surg Sports Traumatol Arthrosc"},{"key":"2026090204251081000_12.2.e003222.5","doi-asserted-by":"crossref","first-page":"1088","DOI":"10.23736\/S0022-4707.21.12696-9","article-title":"Low back pain prevalence and risk factors in Italian adolescent male soccer players: results from an online survey","volume":"62","author":"Cugusi","year":"2022","journal-title":"J Sports Med Phys Fitness"},{"key":"2026090204251081000_12.2.e003222.6","doi-asserted-by":"crossref","first-page":"421","DOI":"10.1097\/JSM.0000000000000546","article-title":"Prevalence of Spondylolysis in Symptomatic Adolescent Athletes: An Assessment of Sport Risk in Nonelite Athletes","volume":"29","author":"Selhorst","year":"2019","journal-title":"Clin J Sport Med"},{"key":"2026090204251081000_12.2.e003222.7","doi-asserted-by":"crossref","first-page":"3","DOI":"10.5114\/biolsport.2023.109961","article-title":"Injury incidence and risk factors in youth soccer players: a systematic literature review. 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