Sex Differences in The Impact of COVID-19 Restrictions on Physical Fitness Changes Among Slovenian Schoolchildren

The COVID-19 pandemic and its related restrictions profoundly disrupted opportunities for physical activity among children worldwide, raising concerns about potential impacts on their physical fitness. This study investigated sex differences in changes of physical fitness among Slovenian schoolchildren before and during the pandemic (6th and 8th grade). Using a retrospective observational design, we analyzed data from the national SLOfit surveillance system, comparing two cohorts: a pre-pandemic group (tested in 2017 and 2019) and a pandemic group (tested in 2019 and 2021). Analyses of covariance were conducted to examine changes over time and differences between sexes in 8th grade, adjusting for 6th grade performance. A total of 1553 children (746 pre-pandemic, 807 pandemic) were included. Boys consistently outperformed girls in tests of muscular strength, explosive power, coordination, and endurance, while girls performed better in flexibility. In the pre-pandemic cohort, boys largely maintained or improved their performance, whereas girls showed stagnation or decline, particularly in cardiorespiratory endurance (600 m run test: 146.8 s for boys vs. 168.7 for girls; p<0.001). In the pandemic cohort, boys jumped on average 189.9 cm compared to 168.0 cm in girls, completed 47.7 vs. 42.3 sit-ups, and finished the 600 m run in 156.1 s vs. 174.1 s (all p<0.001), while girls reached 50.7 cm vs. 40.6 cm in the stand-and-reach test (p<0.001). These patterns persisted even after adjustment for anthropometric variables, suggesting that the observed performance gaps are not solely explained by morphological differences but may reflect unequal opportunities for skill development during public health restrictions. The relative magnitude of between-sex differences became more pronounced for tapping, standing long jump, polygon backwards, and stand-and-reach, while narrowing slightly for the 60- and 600-meter run. These findings emphasize the importance of equitable and sex-sensitive physical activity to maintain children’s motor competence and physical fitness during societal disruptions.