Background: The goal of this research is to identify correlations of motivation and physical self-concept with physical activity among students of younger school age, as well as the level of prediction of motivation and physical self-concept with physical activity of students in physical education classes. Methods: The sample of respondents consisted of 411 students of the third and fourth grades from the territory of the Zlatibor district. A modified Self-Regulation Questionnaire was used to assess students’ motivational orientations, while appropriate subscales of the Self-perception Profile for Children measuring instrument were used to assess physical self-concept. Physical activity is shown as volume and intensive physical activity (vigorous physical activity (VPA)), measured with a Suunto memory belt pedometer and heart-rate monitor. Results: Boys’ motivational predictor variables accounted for 14% (volume) and 28% (VPA) of their physical activity in class, with intrinsic motivation, introjective regulation (just for the level of physical activity), and identified regulation as the most important determinants of physical activity. For girls, the identified regulation variable (from the system of motivational predictor variables) was shown to be the primary predictor variable on both criterion variables (R2 = 0.34 and 0.36). Conclusion: The teaching of physical education for students of younger school age should be conceived by creating a motivational climate, in order to encourage physical activity.

The present study investigated effects of squat resistance training on intermuscular hypertrophy of quadriceps femoris muscles (i.e., rectus femoris, RF; vastus intermedius, VI; vastus medialis, VM; and vastus lateralis, VL). Eighteen university students (age: 24.1 ± 1.7 years, 9 females) underwent 7 weeks of parallel squat training (2 days/week) preceded by a 2-week familiarization period. Squat strength (1RM) and cross-sectional area (CSA) of four quadriceps muscles were assessed at baseline and at the end of the study. At posttest, 1RM and CSA of quadriceps muscles significantly increased (p < 0.01), with moderate-to-large effect (ES = 1.25–2.11) for 1RM (8.33 ± 6.64 kg), VM CSA (0.12 ± 0.08 cm²), and VL CSA (0.19 ± 0.09 cm²) and small effect (ES = 0.89–1.13) for RF CSA (0.17 ± 0.15 cm²) and VI CSA (0.16 ± 0.18 cm²). No significant differences were found in the changes of CSA between muscles (F = 0.638, p = 0.593). However, the squat 1RM gain was significantly associated only with the changes in CSA of the VL muscle (r = 0.717, p < 0.001). The parallel squat resulted in significant growth of all quadriceps muscles. However, the novelty of this study is that the increase in strength is associated only with hypertrophy of the VL muscle.

Background/Objectives: The aim of this research was to determine the differences in physical fitness according to the level of physical activity (PA) during physical education classes in 10-year-old school children. Methods: The research included 315 primary school children (age 10 ± 1.3 years), divided into three groups by level of PA: low, moderate and high. A Eurofit test battery was used to evaluate the physical fitness of children. Physical activity (volume (number of steps) and intensity) was measured using a Coach Gear pedometer and a Suunto Memory Belt heart rate monitor. Results: Presented results indicate that there are significant differences between groups of children of both genders in relation to the level of PA. Group of boys with low PA showed lower values in sit and reach (p = 0.01), standing long jump (p = 0.02), bent arm hang (p = 0.04) and polygon backwards (p = 0.01) compared to the remaining two groups. Girls with low physical activity showed significant differences in sit and reach (p = 0.01) and bent arm hang (p = 0.01) compared to the other two groups, while in hand tapping, the high PA group showed better results compared to the other two groups (p = 0.03). Conclusions: The results reported in this research support the significant effects of PA level on physical fitness in school children. Less active children generally showed poorer physical fitness in both genders.

The aim of this study was to investigate the association between morphological characteristics (body composition and anthropometric data) and gross motor coordination in preschool children (42 boys and 40 girls, aged 6.22 ± 0.43 years, height: 1.22 ± 0.48 m, body mass index: 20.22 ± 2.34 kg/m², muscle mass: 11.50 ± 2.08 kg, and fat mass: 5.43 ± 4.02 kg). Motor coordination was determined by the obstacle course backward test (OCB), while body composition was measured using the bioelectrical impedance (BIA) method. Sex differences in the OCB test and body morphology were determined by an independent t-test. Multiple linear regression was used to examine whether morphological characteristics could predict OCB scores. Boys were significantly taller, with greater muscle mass, protein mass, and total body water compared to girls (t = 2.01–3.73, p < 0.05). Inversely, mineral mass was greater in girls than in boys (t = 2.98, p = 0.01). No significant sex differences were observed in the results obtained for the OCB test (t = 0.74, p = 0.46). All morphological variables showed trivial-to-weak (r = 0.01–0.15) associations with the OCB results, without reaching statistical significance (p ≤ 0.16). The model of predictor variables did not have a statistically significant effect on the OCB scores in boys and girls (R² = 0.09, p = 0.91 and R² = 0.012, p = 0.92, respectively). These results indicate that sex dimorphism in body composition is present at an early age before puberty, while morphological characteristics have a negligible influence on motor coordination in 6-year-old children.

The aim of the conducted research was to determine scientifically, by applying experimental methods, whether an additional program of physical exercises, carried out under regular working conditions at preschool institutions, can result in significant changes in the morphological characteristics of preschool children, mean age 6.21 ± 0.56 years. A total of 64 preschool children, girls (n=28) and boys (n=36) attending preparatory preschool lessons in the preschool institution 'Čukarica' in Belgrade were included in the research. The researchers used a pre-experimental draft survey, namely the draft involving one pretest-posttest group. The sample of the morphological measuring instruments was designed by applying a reduced theoretical model (Viskić, 1972; Kurelić et al., 1975). The experimental factor was realised over a period of 24 weeks, in 48 sessions, each lasting 35 minutes. The research results indicate that, in the final measurement, the differences between the sexes went in favour of boys in terms of the lower average values of the volume and body mass, subcutaneous adipose tissue on the back and body mass index. It was also determined that the additional kinesiology program of activities, regardless of the sex of pupils, had also given good results in terms of the reduction of the subcutaneous adipose tissue, as well as the volume and body mass of children. The authors believe that a regular program of physical education in preschool institutions is insufficient for the preparatory preschool group and that additional kinesiological activities give better results in the reduction of body mass and subcutaneous fat, especially if they are directed towards the development of biotic motor skills.