Association between decreased grip strength in preschool children and the COVID-19 pandemic: an observational study from 2015 to 2021

BACKGROUND: Coronavirus disease 2019 (COVID-19) has reduced people’s physical activity. It is essential to accumulate knowledge regarding the influence of COVID-19 on the stimulation of physical fitness and physical functions. Several studies have reported the effects of COVID-19 on physical fitness; however, there are very few reports regarding preschoolers. This study aimed to compare the physical fitness of preschoolers before and during the COVID-19 pandemic to clarify the effects of curtailment of outings implemented to control the pandemic on physical fitness among preschoolers. METHODS: The subjects were 593 Japanese preschool children enrolled at a kindergarten during 2015–2019 and in 2021 who received a physical fitness test. Children enrolled in 2020 who did not receive a physical fitness test because of the COVID-19 pandemic were excluded. The physical fitness test included grip strength, standing long jump, and a 25-m run. The relationship between physical fitness level and survey year was analyzed using a general linear model, with grip strength and standing long jump as dependent variables, year of study as the independent variable, and sex and age in months as adjusted variables. Kruskal–Wallis test was used to analyze data for the 25-m run. Multiple comparisons were used to compare fitness levels between 2021 (during the COVID-19 pandemic) with levels in previous years. RESULTS: Significant relationships were found between survey year and each of grip strength (p < 0.001), standing long jump (p < 0.05), and 25-m run (p < 0.001) among the overall subjects. Grip strength was significantly lower in 2021 compared with the 2016–2019 period. Similarly, sub-stratification analysis by sex showed that grip strength was lower in 2021 than in previous survey years, in both sexes. However, there was no difference in standing long jump or 25-m run times between before and during the pandemic among the overall subjects or according to sex. CONCLUSIONS: These findings indicate that the COVID-19 pandemic has had a negative effect on the development of muscle strength in preschoolers, and suggest the need to develop strategies that could promote the development of muscle strength of preschool children when limitations are placed on activity during prolonged infectious disease pandemics. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s40101-023-00321-8.