{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,27]],"date-time":"2025-10-27T08:45:00Z","timestamp":1761554700308,"version":"build-2065373602"},"reference-count":28,"publisher":"BMJ","issue":"4","license":[{"start":{"date-parts":[[2025,10,23]],"date-time":"2025-10-23T00:00:00Z","timestamp":1761177600000},"content-version":"unspecified","delay-in-days":22,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["BMJ Open Sport Exerc Med"],"accepted":{"date-parts":[[2025,10,1]]},"published-print":{"date-parts":[[2025,10]]},"abstract":"<jats:sec>\n                    <jats:title>Objectives<\/jats:title>\n                    <jats:p>To describe the characteristics of COVID-19 among elite Japanese athletes and their return-to-play (RTP) time.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>We retrospectively reviewed clinical records at the Japan Institute of Sports Sciences between June 2022 and May 2023. Elite athletes who underwent periodic health examinations were examined by a physician to confirm COVID-19 history, symptoms and the RTP time.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>Of 994 athletes, 456 had a COVID-19 history (mean\u00b1SD, 23.3\u00b14.6 years; 56% male). Most infections occurred during the sixth wave (Omicron variant), followed by the seventh and eighth waves, with 88% recorded after the fifth wave. Indoor athletes were more frequently affected than outdoor athletes (306 vs 150, p&lt;0.05). Badminton athletes were the most commonly affected athletes (16%), followed by volleyball (10%) and handball (7%). Among those with a history of COVID-19, 89% reported symptoms, while 11% were asymptomatic. Fever was the most common symptom (80%), followed by sore throat (58%) and cough (44%). The median (IQR) RTP time was 10 (7\u201314) days. Overall, 472 athletes resumed play within 28 days, while 20 returned after 28 days. RTP delays were more frequent before Omicron (9\/59 athletes) than after (11\/433 athletes, p&lt;0.05).<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>COVID-19 was more common among indoor sports athletes, primarily during the Omicron wave, with most cases being symptomatic but resolving quickly. These findings likely reflect factors such as close-contact training, immune changes during intensive training and international travel and may help characterise COVID-19 outcomes in elite athletes.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1136\/bmjsem-2025-002731","type":"journal-article","created":{"date-parts":[[2025,10,27]],"date-time":"2025-10-27T08:40:14Z","timestamp":1761554414000},"page":"e002731","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":0,"title":["COVID-19 infection and return-to-play outcomes of elite athletes in Japan: a retrospective descriptive study"],"prefix":"10.1136","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0009-0001-2004-628X","authenticated-orcid":false,"given":"Kazutaka","family":"Fukushima","sequence":"first","affiliation":[{"name":"Department of Sport Medicine, Japan Institute of Sports Sciences, Japan High Performance Sport Center, Tokyo, Japan"},{"name":"Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Kazuyuki","family":"Kamahara","sequence":"additional","affiliation":[{"name":"Department of Sport Medicine, Japan Institute of Sports Sciences, Japan High Performance Sport Center, Tokyo, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Anna","family":"Tomori","sequence":"additional","affiliation":[{"name":"Department of Sport Medicine, Japan Institute of Sports Sciences, Japan High Performance Sport Center, Tokyo, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0888-4440","authenticated-orcid":false,"given":"Yoshio","family":"Nakata","sequence":"additional","affiliation":[{"name":"Institute of Health and Sport Sciences, University of Tsukuba, Ibaraki, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"239","published-online":{"date-parts":[[2025,10,27]]},"reference":[{"key":"2025102701400736000_11.4.e002731.1","doi-asserted-by":"publisher","DOI":"10.1016\/j.jsams.2021.07.003"},{"key":"2025102701400736000_11.4.e002731.2","doi-asserted-by":"publisher","DOI":"10.1136\/bjsports-2021-104644"},{"key":"2025102701400736000_11.4.e002731.3","doi-asserted-by":"crossref","first-page":"341","DOI":"10.1111\/sms.14265","article-title":"Short and mid-term characteristics of COVID-19 disease course in athletes: A high-volume, single-center study","volume":"33","author":"Juh\u00e1sz","year":"2023","journal-title":"Scand J Med Sci Sports"},{"key":"2025102701400736000_11.4.e002731.4","doi-asserted-by":"crossref","DOI":"10.3390\/ijerph19095400","article-title":"Effects and Causes of Detraining in Athletes Due to COVID-19: A Review","volume":"19","author":"C\u00f3rdova-Mart\u00ednez","year":"2022","journal-title":"Int J Environ Res Public Health"},{"key":"2025102701400736000_11.4.e002731.5","doi-asserted-by":"publisher","DOI":"10.1136\/bjsports-2021-104392"},{"key":"2025102701400736000_11.4.e002731.6","doi-asserted-by":"publisher","DOI":"10.1136\/bjsports-2012-091395"},{"key":"2025102701400736000_11.4.e002731.7","doi-asserted-by":"crossref","unstructured":"Gattoni C , Conti E , Casolo A , et al . 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Date of onset and Ct and antigen quantification values in nosocomial cluster measures and case analyses with SARS-CoV-2 B.1.1.529 strain (omicron strain) association - yamaguchi prefecture. Available: https:\/\/id-info.jihs.go.jp\/niid\/ja\/2019-ncov-e\/11117-508p01.html [Accessed 17 Jul 2024]."},{"key":"2025102701400736000_11.4.e002731.25","doi-asserted-by":"crossref","unstructured":"Harmon K , de St Maurice AM , Brady AC , et al . Surveillance testing for SARS-COV-2 infection in an asymptomatic athlete population: a prospective cohort study with 123 362 tests and 23 463 paired RT-PCR\/antigen samples. 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