Physical fitness before and during the COVID-19 pandemic: Results of annual national physical fitness surveillance among 16,647,699 Japanese children and adolescents between 2013 and 2021.

BACKGROUND: The primary aim was to examine the temporal trends in physical fitness (PF) for Japanese children and adolescents before and during the coronavirus disease 2019 pandemic. The secondary aim was to estimate the concurrent trends in body size (measured as body mass and height) and movement behaviors (exercise, screen, and sleep time). METHODS: Census PF data for children in Grade 5 (aged 10-11 years) and adolescents in Grade 8 (aged 13-14 years) were obtained for the years 2013-2021 from the National Survey of Physical Fitness, Athletic Performance, and Exercise Habits in Japan (n = 16,647,699). PF and body size were objectively measured, and movement behaviors were self-reported. Using sample-weighted linear regression, temporal trends in mean PF were calculated before the pandemic (2013-2019) and during the pandemic (2019-2021) with adjustments for age, sex, body size, and exercise time. RESULTS: When adjusted for age, sex, body size, and exercise time, there were significant declines in PF during the pandemic, with the largest declines observed in 20-m shuttle run (standardized (Cohen's) effect size (ES) =  - 0.109 p.a.) and sit-ups performance (ES = - 0.133 p.a.). The magnitude of the declines in 20-m shuttle run and sit-ups performances were 18- and 15-fold larger, respectively, than the improvements seen before the pandemic (2013-2019), after adjusting for age, sex, body size, and exercise time. During the pandemic, both body mass and screen time significantly increased, and exercise time decreased. CONCLUSION: Declines in 20-m shuttle run and sit-ups performances suggest corresponding declines in population health during the COVID-19 pandemic.

Associations of Voluntary Exercise and Screen Time during the First Wave of COVID-19 Restrictions in Japan with Subsequent Grip Strength among University Students: J-Fit+ Study

This study aimed to examine the combined effect of voluntary exercise and screen time during the first wave of the coronavirus disease 2019 (COVID-19) restrictions on subsequent grip strength among health and sports science students in Japan. The participants performed grip strength tests and had their weight assessed on 21 October 2020. Furthermore, they completed an online survey between 21 October and 28 October 2020, which included participants’current age, height, voluntary exercise, and screen time during the first wave of the COVID-19 pandemic (April and May 2020). In total, 380 participants provided complete data (mean age ±standard deviation [SD]: 18.8 ±0.6 years;233 males). Our results revealed that 87.6% of male students and 84.4% of female students performed voluntary exercise >1 day/week during the first wave of the pandemic. Moreover, 21.5% of male students and 23.1% of female students had >8 h/day of screen time. A trend toward greater grip strength was observed for both male and female students with high voluntary exercise and low screen time. In particular, grip strength (p < 0.05) was significantly greater in male students with high voluntary exercise and low screen time than those with low voluntary exercise and high screen time. In conclusion, this study revealed that during the first wave of COVID-19 restrictions, a combination of high voluntary exercise and low screen time positively affected the subsequent grip strength of health and sports science students.