{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,29]],"date-time":"2026-09-29T06:21:01Z","timestamp":1790662861005,"version":"4.1.0"},"reference-count":21,"publisher":"BMJ","issue":"13","content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["Br J Sports Med"],"accepted":{"date-parts":[[2014,4,23]]},"published-print":{"date-parts":[[2014,7]]},"abstract":"<jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>Physical activity improves bone strength and reduces the risk for osteoporotic fractures. However, there are substantial gaps in our knowledge as to when, how and how much activity is optimal for bone health.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Purpose<\/jats:title>\n                    <jats:p>In this cohort study, we examined developmental trajectories of objectively measured physical activity from childhood to adolescence to discern if moderate-and-vigorous intensity physical activity (MVPA) predicts bone strength.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>Starting at age 5 and continuing at 8, 11, 13, 15 and 17\u2005years, Iowa Bone Development Study participants (n=530) wore an accelerometer for 3\u20135\u2005days. At age 17, we assessed dual X-ray energy absorptiometry outcomes of mass and estimated geometry (femoral neck cross-sectional area and section modulus). We also assessed geometric properties (bone stress index and polar moment of inertia) of the tibia using peripheral computer quantitative tomography. Latent class modelling was used to construct developmental trajectories of MVPA from childhood to late adolescence. General linear models were used to examine the trajectory groups as predictors of age 17 bone outcomes.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>Girls and boys who accumulated the most MVPA had greater bone mass and better geometry at 17\u2005years when compared to less active peers. The proportion of participants achieving high levels of MVPA throughout childhood was very low (&lt;6% in girls) and by late adolescence almost all girls were inactive.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>Bone health benefits of physical activity are not being realised due to low levels of activity for most youth, especially in girls.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1136\/bjsports-2014-093574","type":"journal-article","created":{"date-parts":[[2014,5,17]],"date-time":"2014-05-17T02:55:19Z","timestamp":1400295319000},"page":"1032-1036","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":90,"title":["Objectively measured physical activity trajectories predict adolescent bone strength: Iowa Bone Development Study"],"prefix":"10.1136","volume":"48","author":[{"given":"Kathleen F","family":"Janz","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Elena M","family":"Letuchy","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Trudy L","family":"Burns","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Julie M","family":"Eichenberger Gilmore","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"James C","family":"Torner","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Steven M","family":"Levy","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"239","published-online":{"date-parts":[[2014,5,16]]},"reference":[{"key":"2024051409513559000_48.13.1032.1","doi-asserted-by":"publisher","DOI":"10.1097\/JES.0b013e318236e5ee"},{"key":"2024051409513559000_48.13.1032.2","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMp038101"},{"key":"2024051409513559000_48.13.1032.3","doi-asserted-by":"publisher","DOI":"10.1002\/jbmr.323"},{"key":"2024051409513559000_48.13.1032.4","doi-asserted-by":"crossref","first-page":"479","DOI":"10.1002\/jbmr.2055","article-title":"Does physical activity in adolescence have site and sex specific benefits on young adult bone size, content and estimated strength?","volume":"29","author":"Duckham","year":"2013","journal-title":"J Bone Miner Res"},{"key":"2024051409513559000_48.13.1032.5","doi-asserted-by":"publisher","DOI":"10.1177\/0049124106292364"},{"key":"2024051409513559000_48.13.1032.6","unstructured":"Physical Activity Surveillance Systems http:\/\/www.cdc.gov\/physicalactivity\/data\/surveillance.html (accessed 27 Dec 2013)."},{"key":"2024051409513559000_48.13.1032.7","doi-asserted-by":"publisher","DOI":"10.1249\/mss.0b013e31815a51b3"},{"key":"2024051409513559000_48.13.1032.8","unstructured":"Physical Activity Guidelines Advisory Committee. Physical Activity Guidelines Advisory Committee Report. Washington, DC: U.S. Department of Health and Human Services, 2008."},{"key":"2024051409513559000_48.13.1032.9","unstructured":"US Department of Health and Human Services. The 2004 Surgeon General's report on bone health and osteoporosis: what it means to you. Washington, DC: U.S. Department of Health and Human Services, 2004."},{"key":"2024051409513559000_48.13.1032.10","doi-asserted-by":"publisher","DOI":"10.1111\/j.1752-7325.2001.tb03369.x"},{"key":"2024051409513559000_48.13.1032.11","doi-asserted-by":"publisher","DOI":"10.1542\/peds.107.6.1387"},{"key":"2024051409513559000_48.13.1032.12","doi-asserted-by":"publisher","DOI":"10.1016\/j.bone.2007.05.001"},{"key":"2024051409513559000_48.13.1032.13","first-page":"1557","article-title":"Calibration of two objective measures of physical activity for children","volume":"24","author":"Evenson","year":"2006","journal-title":"J Sports Sci"},{"key":"2024051409513559000_48.13.1032.14","doi-asserted-by":"publisher","DOI":"10.1249\/MSS.0b013e318206476e"},{"key":"2024051409513559000_48.13.1032.15","doi-asserted-by":"publisher","DOI":"10.1359\/jbmr.1997.12.4.652"},{"key":"2024051409513559000_48.13.1032.16","doi-asserted-by":"publisher","DOI":"10.1016\/0021-9290(84)90010-1"},{"key":"2024051409513559000_48.13.1032.17","doi-asserted-by":"publisher","DOI":"10.1097\/00004424-199001000-00004"},{"key":"2024051409513559000_48.13.1032.18","doi-asserted-by":"publisher","DOI":"10.1097\/00005768-200204000-00020"},{"key":"2024051409513559000_48.13.1032.19","doi-asserted-by":"crossref","first-page":"34","DOI":"10.1123\/pes.15.1.34","article-title":"Measuring children's vertical ground reaction forces with accelerometry during walking, running, and jumping: the Iowa Bone Development Study","volume":"15","author":"Janz","year":"2003","journal-title":"Ped Exerc Sci"},{"issue":"(4 Suppl 1)","key":"2024051409513559000_48.13.1032.20","doi-asserted-by":"crossref","first-page":"S3","DOI":"10.1016\/j.amjmed.2005.12.017","article-title":"Preventing osteoporosis-related fractures: an overview","volume":"119","author":"Gass","year":"2006","journal-title":"Am J Med"},{"key":"2024051409513559000_48.13.1032.21","doi-asserted-by":"publisher","DOI":"10.1002\/jbmr.412"}],"container-title":["British Journal of Sports Medicine"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/syndication.highwire.org\/content\/doi\/10.1136\/bjsports-2014-093574","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2024,5,14]],"date-time":"2024-05-14T12:51:58Z","timestamp":1715691118000},"score":1,"resource":{"primary":{"URL":"https:\/\/bjsm.bmj.com\/lookup\/doi\/10.1136\/bjsports-2014-093574"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2014,5,16]]},"references-count":21,"journal-issue":{"issue":"13","published-online":{"date-parts":[[2014,6,11]]},"published-print":{"date-parts":[[2014,7]]}},"alternative-id":["10.1136\/bjsports-2014-093574"],"URL":"https:\/\/doi.org\/10.1136\/bjsports-2014-093574","relation":{},"ISSN":["0306-3674","1473-0480"],"issn-type":[{"value":"0306-3674","type":"print"},{"value":"1473-0480","type":"electronic"}],"subject":[],"published":{"date-parts":[[2014,5,16]]}}}