Due to the COVID-19-induced social distancing restrictions, adolescents’ physical activity declined and their level of health and fitness decreased. In March 2023, the Korean government established the beginning of the post-COVID-19 era by declaring that indoor masks were now “recommended” rather than “mandatory”. Consequently, adolescents, whose physical activity decreased during COVID-19, began to participate in such activities again. This study aimed to verify the differences in adolescent physical activity during COVID-19 and after COVID-19. To achieve the study’s purpose, an online survey was conducted twice, using the International Physical Activity Questionnaire, for 1143 Korean adolescents in 2022 and 2023. The following results were derived through frequency analysis, descriptive statistical analysis, and an independent variables t-test. First, moderate-to-vigorous physical activity was higher during the post-COVID-19 period than during COVID-19 (p = 0.018). Second, high-intensity (p = 0.018), moderate-intensity (p = 0.030), and low-intensity (p = 0.002) physical activities and total leisure-time physical activities (p = 0.003) were all higher during the post-COVID-19 period than during COVID-19. Third, high-intensity (p = 0.005), moderate-intensity (p = 0.003), low-intensity (p = 0.003) activities and total physical activities in school (p = 0.001) were all higher during the post-COVID-19 period than during COVID-19. Fourth, there was no difference in the commuting times for cycling (p = 0.515) and walking (p = 0.484) and the total physical activities during commuting (p = 0.375) during and after COVID-19. Based on these results, the methods to help adolescents form correct habits for leading a healthy life are discussed.

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High-collar shoes are a biomimetic approach to preventing lateral ankle injuries during high-demand activities; however, the influence of collar stiffness (CS) on parameters related to lateral ankle sprain prevention during running remains unclear. In this study, we investigated the effects of a custom-designed shoe CS on muscular activity, dynamic stability, and leg stiffness (Kleg) during running using a biomimetic design approach inspired by the mechanisms of ankle sprain prevention. Sixteen healthy male participants ran on a treadmill while wearing a custom-designed high-collar shoe with low, medium, and high CS conditions, measured using circumferential ankle pressure (CAP). Lower extremity kinematics and electromyography (EMG) data were recorded simultaneously. One-way repeated-measures ANOVA was conducted to compare the CS conditions. Results indicate that high and medium CS conditions significantly reduce sagittal and frontal ankle ranges of motion (ROMs) compared to the low CS condition, providing improved stability and support against lateral ankle sprain; moreover, there was a trend towards higher dynamic stability and Kleg with increasing CS. Our study highlights the importance of considering the CAP in regulating high-collar stiffness properties and how higher CS may provide better support for the ankle during running. Nevertheless, additional research is necessary to validate the efficacy of the current design in preventing ankle sprains during high-demand activities.

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