Branislav Majkić

High countermovement-jump (CMJ) height prediction may reflect mechanical reconstruction rather than independent neuromuscular information. This study separated mechanically proximal variables from mechanically restricted force-expression, movement-organization, and tensiomyography (TMG) predictors. Sixty-six elite youth football players completed force-platform CMJ and rectus femoris TMG assessments. Jump height was reconstructed from mean propulsion force and propulsion duration. After excluding these variables and direct mechanical equivalents, Ridge, Elastic Net, GAM, and random forest models were evaluated using repeated nested cross-validation, with predictor-set, ablation, and held-out permutation-importance analyses. The mechanical benchmark almost perfectly reconstructed jump height (RMSE = 0.0027 m; predictive R² = 0.998). After mechanical restriction, random forests were the strongest prespecified single model family (RMSE = 0.0510 m; predictive R² = 0.296), whereas the fully nested one-standard-error model-selection pipeline provided a more conservative estimate of generalization (RMSE = 0.0548 m; predictive R² = 0.187). Within the retained predictor set, movement organization provided more information than force expression (predictive R² = 0.214 vs. 0.078). The TMG-only prediction was worse than the mean-level benchmark (predictive R² = −0.039), and adding TMG did not improve the CMJ base model. CMJ height is readily reconstructed from proximal propulsion mechanics. After their removal, movement organization retains modest predictive information, whereas single-muscle rectus femoris TMG did not provide useful standalone or incremental value in this cohort.

Background: This study examined the effects of an individualized weighted vest sprint training program on sprint performance and countermovement jump (CMJ) outcomes in post-peak height velocity (PHV) male youth soccer players while accounting for maturation status. Methods: Fifty players (mean age 17.76 ± 0.95 years) were randomly assigned to a weighted vest sprint group (WVG; n = 25) or a traditional unloaded sprint group (TS; n = 25). Sprint performance (5, 10, 20, and 30 m) and CMJ-derived variables (jump height, peak power output, reactive strength index modified (RSI-modified), and eccentric rate of force development) were assessed before and after an 11-week intervention performed twice weekly, with the WVG completing sprint drills while wearing a weighted vest (~11% body mass). Results: Weighted vest sprint training produced greater improvements in 10 m sprint performance and RSI-modified (d = 1.37 and 1.55, respectively). However, after Benjamini–Hochberg adjustment for multiple comparisons, the effects were no longer statistically significant and should therefore be interpreted with caution. Maturity offset did not meaningfully moderate training-induced adaptations. Conclusions: These findings suggest that weighted vest sprint training may provide potential benefits for mid-acceleration performance and reactive strength in post-PHV youth soccer players, although the magnitude of these effects remains uncertain.

Football is a dynamic and physically demanding sport that requires specific biomechanical characteristics and abilities from players. The aim of this research was to analyze the differences in body composition and motor skills of football players depending on their position. The study involved 25 football players aged 12-15 years, competing at the highest level for their age group. The participants were divided based on their positions: defense (n=11; age - 15.13±0.39 years; height - 171.17±5.24 cm; body weight - 59.25±5.99 kg; BMI - 20.16±1.54), midfield (n=12; age - 15.14±0.40 years; height - 165.32±11.4 cm; body weight - 52.84±9.64 kg; BMI - 19.17±1.39), and attack (n=10; age - 15.11±0.37 years; height - 169.32±10.3 cm; body weight - 52.58±10.28 kg; BMI - 17.82±1.73). The results showed that there were no significant differences in muscle mass or subcutaneous fat between different positions (p > .05). Furthermore, there were no significant differences in sprint times for 5m, 10m, 30m, squat jump (SJ), countermovement jump with arm swing (CMJarm), slalom test, slalom test with the ball, Zig-Zag test, or Zig-Zag test with the ball (p > .05). Further research with a larger sample size could provide additional insights and explanations for the lack of differences. In conclusion, although positional differences were expected, the results indicate that at the age tested, there are still no significant changes when it comes to different positions on the team.

The main goal of this study was to examine the effects of an 11-week weighted vest sprint training (WVT) program and traditional sprint training (TST) on tensiomyography (TMG) parameters in young football players. Fifty young football players were divided into two groups: a group that performed WVT and a group that stopped the running session if the obtained time was higher than 3% (WVG - n=25; age: 17.92±1 yr; body mass: 71.25±7.9 kg; height: 178.79±6.4 cm) and a group that performed TST (TSG - n=25; age: 17.92±1; mass: 75.49±5.56; height: 178.75±3.83). The experimental program lasted for 11 weeks and was implemented twice a week at the start of the training sessions separated by at least 48 h. Anthropometry (standing height, sitting height and leg length) was measured, as well as body composition, on the basis of which graduation was later calculated, which served as a covariate. After that, the TMG parameters of m. rectus femoris, m. vastus lateralis, m. vastus medialis and m. tibialis anterior were assessed. Time × group effects were examined with the Bayesian linear mixed-effects ANCOVA model. Between‐group difference was expressed as the posterior mean standardized regression coefficient (β) with its 95% credible interval (95% CI) for each variable. Practical significance was evaluated using the Region of Practical Equivalence (ROPE). The results showed that the applied programs did not significantly contribute to changes in the TMG parameters, which indicates that this type of training stimulus may not have a sufficiently specific effect on the neuromuscular characteristics that can be measured by TMG.

Change of direction (COD) and technical skills are considered key parameters of performance in youth soccer, as they are highly demanded during a match. The aim of this study was to examine whether change of direction and Dribble deficit (DD) differ between younger soccer players from various consecutive age categories. Ninety young soccer players (mean age: 11.67 ± 1.29 years; body height: 154.84 ± 10.82 cm; body weight: 43.95 ± 9.62 kg) participated in the study and were divided into 5 age categories (Under 10, Under 11, Under 12, Under 13, and Under 14). All the participants performed change-of-direction tests (the Slalom and Zig-zag) with and without a ball. The DD is determined indirectly by reducing the time variation between the fastest trials with and without a ball. The results revealed that the U14 group is significantly better in the Slalom with and without a ball compared to the other groups, in the Slalom DD compared to the U12 group, and Zig-Zag DD compared to the U13 group (p < 0.05). On the other hand, as expected, the U10 group showed the lowest results, with the Slalom test results significantly lower compared to the other categories (p < 0.05). In conclusion, as was expected, the oldest group (U14) showed better results in both COD tests and in DD compared to their younger peers, with the youngest group (U10) exhibiting the lowest values in almost all the tests.

The goal of this study was to determine the dropout rate and the difference between football players born in different halves of the year. This study involved 101 sub-elite football players (14.4±2.9 yr, 168.2±9.4 cm, 60.1±5.3 kg, 21.7±2.2 BMI) divided into three age categories and two sub-groups for each of them (U-11a/b, U-14a/b and U-19a/b). The difference between the sub-groups was assessed using the T-test for independent groups and the Mann-Whitney U test with statistical significance set at the p < .05 level. The 10, 20 and 30 m running tests, SJ, CMJ, CMJmax, T-test, 9-3-6-3-9, and Slalom agility tests were used. Statistical difference for U-11 group was obtained for the SJ (p = .002), T-test (p = .012) and 9-3-6-3-9 test (p = .002). In U-14 group the statistical difference is shown in all speed and explosive strength tests (p < .05). Body fat did not show a statistically significant difference between groups while body height, body mass and muscle mass differ at a statistically significant level (p = .017, .041, .0.46, respectively). Compared to younger groups, U-19 group showed a significant difference on T-test and 10 m running (p = .017, .037, respectively). The main limitation is that this is not a longitudinal study with a single group followed throughout the process. In conclusion, it would be desirable for everyone to get an equal chance due to the different speed of development in order to be competent. Further recommendations are to divide youth categories into two separate leagues so that everyone gets the same playing time.

The aim of this study was to analyze the relationship between functional movement screen (FMS) individual scores and sports performance variables in elite women’s soccer players. Twenty elite women’s soccer players (age: 22.01 ± 3.64) took part in the study. Players were screened using the FMS protocol with seven movement patterns: deep overhead squat (DS), hurdle step left (HS L) and right (HS R), in-line lunge left (ILL L) and right (ILL R), shoulder mobility left (SM L) and right (SM R), active straight leg raise left (ASLR L) and right (ASLR R), trunk stability push-up (TSPU) and rotary stability (RS) and three tests of vertical jumps: the squat jump, countermovement jump and countermovement jump with arms, speed on the 20m and slalom and zig zag test. The results showed negative correlations between the 10m sprint and HSL L (p < 0.001, r = 0.587), HS R (p < 0.001, r = 0.566) and ASLR R (p < 0.001, r = 0.667) and between the Slalom test and ILL R (p < 0.005, r = 0.461) and ASLR L (p < 0.005, r = 0.454). This study found little evidence of the relationship between FMS results and predictors of sports performance in elite women’s soccer players. Strength and conditioning coaches may use these indicators as an assessment of the weakness of certain movements or muscle imbalance as one of the methods for correcting certain segments of sports performance which can later help them achieve better results on the field.

Maintaining the state achieved after the warm-up in modern soccer represents a significant problem. The main goal of this research was to determine the influence of a regular tracksuit on skin temperature and running speed during the pre-game routine. This study included 36 youth soccer players (15.61 ± 0.68 years, 175.16 ± 4.21 cm) divided into two groups. A two-way ANOVA was used with the level of significance set at p = 0.015, η_p² = 0.16], 20 [p = 0.001, η_p² = 0.26], and 30 [p = 0.005, η_p² = 0.20] meter sprint tests. A significant treatment (experimental vs. control) main effect was observed for 10 m [p = 0.042, η_p² = 0.35], 20 m [p = 0.020, η_p² = 0.55], and 30 m [p = 0.005, η_p² = 0.58] sprint tests. Moreover, a significant sequence-trial interaction effect for 10 m (p = 0.002), 20 m (p < 0.001), and 30 m (p < 0.001) sprints was observed. However, the main effects of the sequence or trial factors alone were insignificant. It is concluded that regular tracksuits may have a beneficial influence on Ts loss and running speed. This research’s most significant practical application is that it lasts for a short period of time and that it requires no extra effort.