Rosie Kwon ^{1 2}, Min Ji Koo ^{2 3}, Seung Won Lee ⁴, Yong Sung Choi ⁵, Youn Ho Shin ⁶, Jung U Shin ⁷, Ai Koyanagi 8 ⁹, Louis Jacob ^{8 10}, Lee Smith ¹¹, Sang Youl Rhee ^{2 12}, Hyug-Gi Kim ², Chanyang Min ², Seong Ho Cho ¹³, Abdullah Özgür Yeniova ¹⁴, So Young Kim ¹⁵, Jinseok Lee ¹⁶, Seung-Geun Yeo ^{16 17}, Jae Il Shin ¹⁸, Dong Keon Yon ^{2 5}

¹Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA.
²Center for Digital Health, Medical Science Research Institute, Kyung Hee University College of Medicine, Seoul, South Korea.
³Department of Human Biology, University of Toronto, Toronto, Ontario, Canada.
⁴Department of Precision Medicine, Sungkyunkwan University School of medicine, Suwon, South Korea.
⁵Department of Pediatrics, Kyung Hee University Medical Center, Kyung Hee University College of Medicine, Seoul, South Korea.
⁶Department of Pediatrics, CHA Gangnam Medical Center, CHA University School of Medicine, Seoul, Republic of Korea.
⁷Department of Dermatology, CHA Bundang Medical Center, CHA University School of Medicine, Seongnam, Republic of Korea.
⁸Research and Development Unit, Parc Sanitari Sant Joan de Deu, CIBERSAM, ISCIII, Barcelona, Spain.
⁹Catalan Institution for Research and Advanced Studies (ICREA), Pg. Lluis Companys, Barcelona, Spain.
¹⁰Faculty of Medicine, University of Versailles Saint-Quentin-en-Yvelines, Montigny-le-Bretonneux, France.
¹¹Centre for Health, Performance and Wellbeing, Anglia Ruskin University, Cambridge, UK.
¹²Department of Endocrinology and Metabolism, Kyung Hee University College of Medicine, Seoul, South Korea.
¹³Division of Allergy-Immunology, University of South Florida Morsani College of Medicine, Tampa, FL, USA.
¹⁴Division of Gastroenterology, Department of Internal Medicine, Tokat Gaziosmanpaşa University Faculty of Medicine, Tokat, Turkey.
¹⁵Department of Otorhinolaryngology-Head & Neck Surgery, CHA Bundang Medical Center, CHA University School of Medicine, Seongnam, South Korea.
¹⁶Department of Biomedical Engineering, Kyung Hee University, Yongin, South Korea.
¹⁷Department of Otolaryngology - Head & Neck Surgery, Kyung Hee University Medical Center, Kyung Hee University College of Medicine, Seoul, South Korea.
¹⁸Department of Pediatrics, Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea.

CORRESPONDING AUTHORS: Jinseok Lee, Jae Il Shin, Dong Keon Yon

Introduction: With the ongoing COVID-19 pandemic, several previous studies from different countries showed that physical activity (PA) decreased during the COVID-19 outbreak. However, few studies have examined the recent tendency of PA in the adolescent population. Thus, we aimed to investigate the long-term trend of PA in Korean youth and the prevalence changes between before and during the COVID-19 pandemic.

Methods: Data from Korea Youth Risk Behavior Web-Based Survey (KYRBS) was collected for consecutive years between 2009 and 2021. The period was separated into pre-pandemic (2009-2019), early-pandemic (2020), and mid-pandemic (2021). Self-reported amount of PA was categorized into four groups (insufficient, aerobic, muscle strengthening, and both physical activities) according to World Health Organization PA guidelines.

Results: A total of 840,488 adolescents aged 12-18 who fully responded to the survey were selected (response rate: 95.2%). The 13-year trends in the proportion of adolescents who reported aerobic and muscle-strengthening activities met or exceeded 2020 WHO exercise guidelines for adolescents plateaued (11.9% from 2009-2011, 14.2% from 2018-2019, 14.4% from 2020, and 14.0% from 2021); however, the slope decreased during the pandemic (βdiff , -0.076; 95% confidence interval [CI], -0.123 to -0.029). Proportion of sufficient aerobic exercise among adolescents sharply decreased midst the pandemic (28.0% from 2009-2011, 29.4% from 2018-2019, and 23.8% from 2020; βdiff , -0.266; 95% CI, -0.306 to -0.226) but increased again in 2021 (26.0% from mid-COVID19; 95% CI, 25.4 to 26.7). Similar patterns were observed in Metabolic Equivalent Task (MET) score (MET-min/week; 804.1 from 2018-2019, 720.9 from 2020, and 779.6 from 2021). The mean difference in MET score between pre-COVID and post-COVID was -55.4 MET-min/week (95% CI, -70.5 to -40.3).

Conclusions: Through a nationwide representative study, there was no significant difference with regard to the number of Korean adolescents who achieved the PA guidelines (pre-and-post-pandemic); however, the prevalence of recommended levels of PA needs to increase more based on the trend before the COVID-19 outbreak. The findings of this study suggest reinforcement of the importance of public health policies for Korean youths to be more physically active, especially during and after the pandemic. This article is protected by copyright. All rights reserved.