The aim of the study is to assess the impact of changes in daily physical activity during the blockade (March 2020–February 2021) on the mass and segmental composition of the body of young people. Material and research methods: In total, 120 people from the sports and medical university aged 19.8 (±0.8) years, average height 173.2 (±9.2) cm, body mass 66.1 (±12.8), and BMI 19.2 (±5.9) kg/m2. The research was carried out in two stages. The total and segmental body mass of the respondents and the change in physical activity during the pandemic were assessed twice (December 2019, February 2021). There was a statistically significant increase in body mass in men, an increase in total fat mass in women, and statistically significant changes in the distribution of fat mass in both sexes. Conclusions: In the studied group, there was a change in the forms of physical activity from strength and group activity to endurance activity (running forms, cycling.) and individual activity. The subjects showed a statistically significant increase in body fat, regardless of gender, and in the upper limbs in men.

Introduction. Physical activity is one of the best methods to prevent civilization diseases in modern times. Studies confirm that the appropriate dose reduces the risk of hypertension, heart diseases, cancer, depression, or overweight and obesity. Methods. The aim of the study was to assess the changes in individual physical fitness tests among children in early school age participating in karate training. A total of 59 children attending primary school were examined. Selected Eurofit tests were carried out before and after 10 weeks of karate training. Results and conclusions. Karate training induced positive changes in the fitness of the studied children. Higher improvements were observed among children with normal body mass as compared with the overweight or obese ones.

The aim of the study was to compare the segmental body composition with the use of fat–fat-free (FFF) index in children at early school age, depending on sex and place of residence, with particular emphasis on urban and rural areas. The study consisted of 329 children aged 7.78 (SD = 0.88; mean age in years). The study group was divided according to the place of residence and sex. The height and body mass, Body Mass Index (BMI), segmental body composition (Tanita BC-418MA), and FFF were calculated. A more frequent occurrence of excessive body weight was observed in children from rural areas (over 20%) compared to their peers from the urban area (10%). Statistically significant lower values of FFF index as well as in the lower limbs and torso were observed in the case of the examined children from the urban area as compared with their peers from the rural areas. The body composition of children living in metropolitan and rural areas is diverse. Lower values of FFF indexes were found in children from the city than in children living in villages. There are more children in the city with signs of being underweight and of normative body mass and paradoxically more overweight ones in the village.

Introduction: Our aim was to assess the ultrasound properties of bone measured at hand phalanges in 55 adolescent boys aged 13-15 years regarding the influence of pubertal status and level of physical efficiency including muscular strength. Material and methods: They were divided into two age groups: Group I (n = 37, boys aged 159-171 months) and Group II (n = 18, aged 172-184 months). The controls were 94 boys matched for age, recruited from 1,256 subjects undergoing bone measurement for screening purposes. The skeletal status (amplitude-dependent speed of sound -Ad-SoS) was assessed by quantitative ultrasound (QUS) at proximal phalanges with the use of DBM Sonic 1200. Physical efficiency was assessed using Zuchora's test, and pubertal development by Tanner's score. Results: There was no difference in mean Ad-SoS between the entire study group and controls. Ad-SoS values were greater in older than in younger boys, both in right and left hands. There were no differences between left and right hand measurements. There were positive correlations between Ad-SoS and shoulder muscle strength in boys. Negative correlations between Ad-SoS at phalanges of right and left hand and BMI were shown in younger adolescent boys only. Similarly, only in the younger group were positive correlations present between both hands Ad-SoS and overall physical efficiency and age. Ad-SoS correlated positively better with Tanner's scale scoring in the older group. Conclusions: QUS at hand phalanges in adolescent boys aged 13-15 years depends on pubertal development and shoulder muscle strength. The overall physical efficiency has limited influence on bone properties assessed by QUS.

The study aimed to personalize the classification of body weight using the fat–fat-free (FFF) index with the percentage of body fat and to develop classification standards for the FFF index for men aged 18–25 years. Moreover, 1,642 adolescents (1,200 ♀) were examined. Using body composition analyzers, weight was determined, as well as overall and segmental body composition. Based on the obtained values for fat mass and fat-free tissue mass, an overall FFF index was calculated. According to the BMI classification, 9% of ♀ and 6% of ♂ are underweight, 29% of ♀ and 13% of ♂ are overweight, and 5% of the subjects are obese. Women and men classified in the same group according to BMI differed statistically significantly in terms of body weight, FM%, and FFM. In contrast to BMI and FM%, the FFF used takes into account the ratio of fat mass to fat-free tissue and muscle tissue mass. The proposed classification of FFF was made taking into account the differences that arise with sexual development and physiological changes occurring in ontogeny. Assessment of body mass using the FFF index should be used as part of preventive screening for the early diagnosis and prevention of overweight and thus many chronic diseases for which overweight or obesity is a risk factor.