{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,5]],"date-time":"2026-10-05T19:28:42Z","timestamp":1791228522358,"version":"4.1.0"},"reference-count":33,"publisher":"PeerJ","license":[{"start":{"date-parts":[[2022,12,16]],"date-time":"2022-12-16T00:00:00Z","timestamp":1671148800000},"content-version":"unspecified","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100002449","name":"Jeju National University","doi-asserted-by":"crossref","id":[{"id":"10.13039\/501100002449","id-type":"DOI","asserted-by":"crossref"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"abstract":"<jats:sec>\n               <jats:title>Background<\/jats:title>\n               <jats:p>At least 60 min of moderate-intensity physical activity per day is recommended for physical and mental health of adolescents. Schools are one of the most suitable places for promoting students\u2019 health as it is a place where vigorous physical activity occurs. However, the physical activity of students is threatened because schools are closed worldwide owing to the coronavirus disease (COVID-19) outbreak in 2019. Therefore, this study aimed to analyze the physical fitness changes in 27,782 Korean adolescents during the pandemic and present alternative education and health policies to the school.<\/jats:p>\n            <\/jats:sec>\n            <jats:sec>\n               <jats:title>Methods<\/jats:title>\n               <jats:p>We included 29,882 middle school students (age: 13\u201315 years; males: 14,941, females: 12,841) in Korea from 2019 to 2021 . Participants\u2019 physical fitness at school was measured using the physical activity promotion system (PAPS) manual developed to measure students\u2019 physical fitness. Physical fitness variables included body mass index (BMI), 20 m shuttle run, handgrip strength, sit-and-reach, and 50 m run.<\/jats:p>\n            <\/jats:sec>\n            <jats:sec>\n               <jats:title>Results<\/jats:title>\n               <jats:p>The COVID-19 pandemic has had a negative impact on the BMI and cardiorespiratory endurance of Korean middle school students. Specifically, male students\u2019 BMI increased, while body composition, cardiorespiratory endurance, and grip strength decreased significantly. Female students showed significant decreases in BMI and sit-and-reach test scores. It is clear that the physical fitness level of adolescents decreased by a greater degree after the COVID-19 pandemic than before, and the decrease in the physical fitness level of male students was noticeable. Therefore, a lesson strategy should be prepared that considers the contents and methods of physical education classes to improve the physical fitness level of male and female adolescents.<\/jats:p>\n            <\/jats:sec>\n            <jats:sec>\n               <jats:title>Conclusions<\/jats:title>\n               <jats:p>Fitness-based classes suitable for online methods should be urgently added as alternative physical education classes to prepare for the second COVID-19 outbreak. In addition, it is necessary to create an environment in which physical activity is a possibility in physical education classes, in any situation using artificial intelligence and virtual reality.<\/jats:p>\n            <\/jats:sec>","DOI":"10.7717\/peerj.14494","type":"journal-article","created":{"date-parts":[[2022,12,16]],"date-time":"2022-12-16T08:27:54Z","timestamp":1671179274000},"page":"e14494","source":"Crossref","is-referenced-by-count":8,"title":["Physical fitness changes in adolescents due to social distancing during the coronavirus disease pandemic in Korea"],"prefix":"10.7717","volume":"10","author":[{"given":"Kwang-Jin","family":"Lee","sequence":"first","affiliation":[{"name":"Department of Physical Education, Chungbuk National University, Cheongju, South Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Se-Young","family":"Seon","sequence":"additional","affiliation":[{"name":"MSC Exercise Center, Seoul, South Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Byungjoo","family":"Noh","sequence":"additional","affiliation":[{"name":"Department of Kinesiology, Jeju National University, Jeju, South Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Keun-Ok","family":"An","sequence":"additional","affiliation":[{"name":"Sports Medicine Major, Division of Sports, Korea National University of Transportation,  Chungju, South Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"4443","published-online":{"date-parts":[[2022,12,16]]},"reference":[{"key":"10.7717\/peerj.14494\/ref-1","doi-asserted-by":"publisher","first-page":"e11431","DOI":"10.7717\/peerj.11431","article-title":"Eating habits, lifestyle behaviors and stress during the COVID-19 pandemic quarantine among Peruvian adults","volume":"9","author":"Agurto","year":"2021","journal-title":"PeerJ"},{"key":"10.7717\/peerj.14494\/ref-2","doi-asserted-by":"publisher","first-page":"1","DOI":"10.1017\/dmp.2021.48","article-title":"Impact of COVID-19 lockdown on body weight, eating habits, and physical activity of Jordanian children and adolescents","volume":"16","author":"Al Hourani","year":"2021","journal-title":"Disaster Medicine and Public Health Preparedness"},{"key":"10.7717\/peerj.14494\/ref-3","doi-asserted-by":"publisher","first-page":"768","DOI":"10.1080\/17430437.2016.1207756","article-title":"Sport, physical activity and educational achievement\u2014towards an explanatory model","volume":"20","author":"Bailey","year":"2017","journal-title":"Sociology of Sport"},{"issue":"10","key":"10.7717\/peerj.14494\/ref-4","doi-asserted-by":"publisher","first-page":"1088","DOI":"10.1080\/02640414.2022.2047504","article-title":"Changes in children\u2019s physical fitness, BMI and health-related quality of life after the first 2020 COVID-19 lockdown in England: a longitudinal study","volume":"40","author":"Basterfield","year":"2022","journal-title":"Journal of Sports Sciences"},{"key":"10.7717\/peerj.14494\/ref-5","doi-asserted-by":"publisher","first-page":"1","DOI":"10.1186\/s12966-019-0901-7","article-title":"The relationship between PA, mental wellbeing and symptoms of mental health disorder in adolescents: a cohort study","volume":"16","author":"Bell","year":"2019","journal-title":"International Journal of Behavioral Nutrition and Physical Activity"},{"key":"10.7717\/peerj.14494\/ref-6","doi-asserted-by":"publisher","first-page":"3141","DOI":"10.3390\/ijerph18063141","article-title":"Proposal for a fitness program in the school setting during the covid 19 pandemic: Effects of an 8-week crossfit program on psychophysical well-being in healthy adolescents","volume":"18","author":"Cataldi","year":"2021","journal-title":"International Journal of Environmental Research"},{"key":"10.7717\/peerj.14494\/ref-7","doi-asserted-by":"publisher","first-page":"399","DOI":"10.1136\/postgradmedj-2020-137738","article-title":"COVID-19 in South Korea","volume":"96","author":"Choi","year":"2020","journal-title":"Postgraduate Medical Journal"},{"key":"10.7717\/peerj.14494\/ref-8","doi-asserted-by":"publisher","first-page":"941","DOI":"10.1016\/j.adolescence.2012.01.002","article-title":"Do peers matter? A review of peer and\/or friends\u2019 influence on PA among American adolescents","volume":"35","author":"Fitzgerald","year":"2012","journal-title":"Journal of Adolescence"},{"key":"10.7717\/peerj.14494\/ref-9","doi-asserted-by":"publisher","first-page":"283","DOI":"10.1097\/fch.0000000000000115","article-title":"Consistency of moderate to vigorous PA in middle school physical education","volume":"39","author":"Gill","year":"2016","journal-title":"Family & Community Health"},{"key":"10.7717\/peerj.14494\/ref-10","doi-asserted-by":"publisher","first-page":"644235","DOI":"10.3389\/fpubh.2021.644235","article-title":"A COVID-19 crisis in child physical fitness: creating a barometric tool of public health engagement for the Republic of Slovenia","volume":"9","author":"Jurak","year":"2021","journal-title":"Frontiers in Public Health"},{"key":"10.7717\/peerj.14494\/ref-11","doi-asserted-by":"crossref","first-page":"33","DOI":"10.14333\/KJTE.2017.33.3.33","article-title":"Exploring the 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