Regular physical activity is a very important factor in the healthy development of an individual and an essential part of a healthy lifestyle. However, today's population still suffers from an insufficient amount of exercise caused mainly by technological progress and often inappropriate conditions for practising sports. In relation to this, we are grappling with a steady increase in obesity. During the COVID-19 pandemic, conditions for regular physical activity became even more unfavourable, with the declaration of a state of emergency and antipandemic measures leading to the closure of sports grounds and sporting competitions. Using a questionnaire survey of a sample of children (n = 1456), we found that, already before the pandemic, 69% of the observed sample had not met the recommended amount of physical activity, and only 67% of the sample was of normal weight. By comparing both groups after the end of pandemic restrictions, we found statistically significant differences at examined indicators of the children's Body Mass Index (BMI), their physical activity, and free time spending habits. We noticed the significant differences in BMI indicators in two different categories, normal weight (7.5%) and stage 1 obesity (1.66%). Simultaneously, we noticed differences in the children's physical activities, especially with children who attend sports playgroups connected to athletic development (8.74%). More differences were noticed in free time spending habits indicators; the most significant ones were with the children who spend their free time behind the personal computer for more than 14 h a week (5.4%) and with the children who spend their free time on social media for 8-14 h a week (18.56%).
Keywords: COVID-19; body mass index; health; lifestyle; obesity; physical activity; pupils; sport.