This study aimed to explore whether a 16-week Teaching Games for Understanding (TGfU) volleyball intervention could improve primary school students’ physical fitness and body composition. Eighty-eight primary school students (age 13.3 ± 0.3 years) were randomized to a TGfU volleyball intervention group (VG) or a control group (CG). The CG attended three regular physical education (PE) classes per week, while the VG attended two regular PE classes and a TGfU volleyball intervention that was implemented in the third PE class. Body composition components (body weight, body mass index, skinfold thickness, body fat percentage, and muscle mass percentage) and physical fitness (flexibility, vertical jumps (squat and countermovement jump—SJ/CMJ), 30 m sprint, agility, and cardiorespiratory fitness) assessments were performed pre-and post-intervention period. Significant interaction effects between VG and CG and pre- and post-test were found for the sum of five skinfolds (p < 0.0005, ŋp² = 0.168), body fat % (p < 0.0005, ŋp² = 0.200), muscle mass % (p < 0.0005, ŋp² = 0.247), SJ (p = 0.002, ŋp² = 0.103), CMJ (p = 0.001, ŋp² = 0.120), 30 m sprint (p = 0.019, ŋp² = 0.062), agility T-test (p < 0.0005, ŋp² = 0.238), and VO_2max (p < 0.0005, ŋp² = 0.253). Further examination revealed a greater improvement among VG students compared to CG students in certain body composition and physical fitness outcomes. Implementing a TGfU volleyball intervention in the physical education curriculum appears to have effective stimuli for reducing adiposity and promoting physical fitness levels in seventh-grade primary school students.

Physical abilities modelling has a profound connection with long-term athlete development and talent identification. There is not enough data to support evidence about age-related changes in volleyball players’ isometric strength. This study aimed to define the age-related model of volleyball players multidimensional muscles’ contractile characteristics. The participants were divided according to gender (male n = 112, female n = 371) and according to age into four groups: under 15 (U15), under 17 (U17), under 19 (U19), and under 21 (U21) years old. Participants performed three isometric strength tests: handgrip, lumbar extensors, and ankle extensors. Maximal force and rate of force development results from all three tests were transformed into a single Score value as a representation of contractile potentials using principal component analysis. The main findings were that Score values of both genders showed significant differences between age groups (male: F = 53.17, p < 0.001; Female: F = 41.61, p < 0.001). Trends of those yearly changes were slightly more balanced for female subjects (3.9%) compared to male subjects (6.3%). These findings could help in strength training adjustments when working with volleyball players of a certain age, and enable coaches to detect ones that stand out positively, considering them as strong in regard to their age.

Background: This study aimed to explore the effectiveness of a 12-week circuit training program in improving local muscular endurance in normal-weighted primary school students. Methods: The study involved a parallel-group randomized trial with 606 primary school boys assigned to an experimental or a control group. The participants underwent a 12-week circuit training program that involved multi-joint, total-body workouts using body weight, resistance bands, and medicine ball exercises. The study measured the participants’ local muscular endurance during sit-ups, dynamic trunk extensions on a Roman bench (DTE), and push-ups. Results: After adjusting for the baseline, the treatment–grade interaction was significant for sit-ups (F = 7.74, p < 0.001, η_p² = 0.04), DTE (F = 6.49, p < 0.001, η_p² = 0.03), and push-ups (F = 9.22, p < 0.001, η_p² = 0.05), where the experimental treatment was more beneficial than the control. The treatment effect seemed to vary depending on the individual’s baseline local muscle endurance capacity. As the baseline local muscular endurance values increased, the treatment and grade effects became less beneficial. Conclusion: A 12-week circuit training program involving body weight, resistance bands, and medicine ball exercises suits school-based programs and can improve local muscular endurance in normal-weighted primary school boys. The experimental treatment was more effective than the control, and the individual baseline muscular endurance should be considered when designing training programs.

This research aimed to create a multidimensional equation for predicting an optimal body composition model for elite-level European male volleyball players. The subject sample consisted of 36 elite volleyball players: national team members from two European countries - Slovenia and Serbia - in the 2017 season. Measurement of body composition was carried out using electrical multichannel bioimpedance (BIA - InBody 720), in which 11 variables were used (body height as a longitudinal one, and the other 10 as a system of body composition indicators). Based on the results of descriptive statistics, we can state that elite European male volleyball players are tall, heavy, and with nutritional status at the level of 198.5?6.5 cm, 92.3?5.9 kg and 23.44?1.44 kg^•m-2, respectively. The percentage of body fat in the whole sample was 7.91?3.03 %, and the skeletal muscle mass index averaged 12.49?0.80 kg^•m-2. For the evaluation and prediction of an optimal body composition model of elite male volleyball players, a multidimensional score (BC_Score) was defined, based on a simple, but sport-specific and playing position-sensitive model equation based on three dominant body characteristics of elite volleyball players: BH, PBF, and SMMI. In this manner, coaches can have a tool for managing the body composition status of players according to position, in terms of a deterministic, fully controlled system.

The main goal of this research is to analyze the relationship between body composition and jump height of volleyball players. Jump height testing included vertical jumps: squat jump (SJ), countermovement jump (CMJ), and depth jumps (DJ25 and DJ45). To assess body composition, body mass index (BMI) was calculated, and a percentage of fat (%FAT), muscle mass (%MUS), and body water (%WAT) was measured. The sample of respondents consisted of 13 top male senior volleyball players of representative level (age: 25.4±3.3 years; weight: 93.0±4.2 kg; height: 199.1±6.7 cm). Canonical correlation analysis was applied to analyze the relationship between these two spaces. This analysis shows that only with the first canonical factor was a statistically significant connection between these two spaces observed (p= .039). In the area of body composition, the body mass index (BMI) has the highest projections on this factor (r: -0.80), while in the area of jumping, the countermovement jump (CMJ) has the highest correlation coefficient (r: -0.84). Other body composition parameters have very low projections on the first canonical factor, while in the area of jump height, depth jumps have relatively high projections (r: -0.78; r: -0.54). These results indicate that body mass index is an essential predictor for estimating the magnitude of vertical jumps, especially those with countermovement.