The present study aimed to describe the characteristics and rate of participation in sports activities, changes in sports, and the causes of these changes before and after the COVID-19 out-break in Korea using data from the 2020 Korea National Sports Participation Survey (KNSPS). Furthermore, evidence from this study could be used as basic data to maintain and promote sports activities given the current situation, in which the continued spread of infectious diseases, such as COVID-19, is likely. The KNSPS is an annual survey of subjective health and fitness, sports activities and conditions, and participation in sports activities, conducted among a sample comprising the entire Korean population. The current study analyzed data for 9000 participants, and descriptive statistical analysis was performed to calculate the frequency of each item and sample weight. The rate of regular participation in sports activities at least once a week was found to be 60.10% in 2020, representing a decrease of 6.48% from the rate observed in 2019. Among the types of sports facilities frequently used within the residential area, the most common facilities were private sports facilities (22.97%), other sports facilities (20.60%), and public sports facilities (18.97%), although the utilization rate for other sports facilities increased after the COVID-19 outbreak. After the COVID-19 outbreak, 34.12% of men and 29.72% of women responded that there had been a change in their participation in regular sports activities. Both before and after the COVID-19 outbreak, walking was the most common activity, although the participation rate increased from 29.23% in 2019 to 35.70% in 2020. The rankings and participation rates for indoor sports activities (bodybuilding, swimming, etc.) tended to decrease, while those for outdoor sports activities (climbing, cycling, etc.) tended to increase. These changes may be explained in part by the increasing concern regarding infection with increasing age, except among teenagers, and by economic factors. While participation in physical activity provides numerous health benefits, the COVID-19 pandemic has had a negative impact on regular participation in sports activities. The results of this survey suggest that government action is required to enhance participation in sports activities, even in the face of a pandemic.

The purpose of this study was to summarize the associations of physical activity (PA) and sedentary time (SED) with metabolic health and examine the effects of time reallocation on metabolic health in adolescents using accelerometer data. A literature search was conducted using PubMed, ScienceDirect, Web of Science, Cochran Library, and Google Scholar, and 27 articles were reviewed. Recent research generally confirms the associations of PA and SED with metabolic health. High PA levels and low SED levels had a positive relationship with metabolic health. Moreover, reallocating 10 min of daily SED to PA was associated with better metabolic health indicators. These results were stronger for moderate-to-vigorous physical activity than for light intensity PA. Thus, efforts to convert SED into PA of at least moderate intensity appear to be an effective strategy to prevent metabolic disease development in children and adolescents. However, some of the associations between PA and metabolic health indicators were inconsistent, depending on age, obesity degree, and PA intensity. Additionally, various accelerometer data collection and processing criteria impact the interpretation of the results. Therefore, consistent accelerometer data collection and analysis methods are needed in future studies. Further, intervention studies are required to verify the causality and effectiveness of the isotemporal substitution model.