The Influence of the Dominant Leg in Body Asymmetries in Children and Adolescent Male Soccer Players

The current study aimed to examine (a) whether the dominant leg (DL) was associated with the contralateral side of functional scoliosis and (b) if any of the postural asymmetries' evaluation variables may be a reliable predictor of the functional scoliosis development in young male soccer players. Six hundred-nine (n = 609) male soccer players (age: 10.8 ± 2.7 years; height: 147 ± 17 cm; weight: 43.4 ± 14.6 kg; DL: Right 81.6%, Left 14%, Both 4.4%) participated in this study. The spinal asymmetries evaluation included thoracic kyphosis, lumbar lordosis, truncal rotation, shoulders alignment from posterior view, anterior and posterior pelvic tilt, anterior superior iliac spine (ASIS), hamstring tightness, and lower extremities discrepancy. A significant association was observed between the DL and the truncal rotation side: χ2(4) = 30.84, p = 0.001, V = 0.16. Participants with longer left legs were likelier to present a spinal asymmetry (OR = 1.18). The participants with higher left shoulders were 2.13 times more likely to have spinal asymmetry than the participants with normal shoulders level. Participants with left ASIS higher were 3.08 times more likely to present asymmetry than those with normally aligned ASIS levels. There was also a significant association between the DL and the side of truncal rotation: χ2(2) = 13.30, p = 0.001, V = 0.449. Logistic regression analysis for the functional scoliotic group and truncal rotation side demonstrated that the taller participants and participants with shorter right legs were more likely to have asymmetry on the left side (OR = 1.29, OR = 0.32). Participants with greater right hamstring stiffness were likelier to have a truncal rotation on the right side (OR = 0.93). Participants with higher left shoulders were 0.20 times less likely to have a truncal rotation on the left side than the participants with normal shoulders level. In conclusion, leg dominance in children and in youth soccer players may be a factor causing truncal rotation on the contralateral side. Additional causes, such as leg length discrepancy and pelvic tilt, may progressively lead to functional scoliosis.

The Effects of Motor Imagery on Static and Dynamic Balance and on the Fear of Re-Injury in Professional Football Players with Grade II Ankle Sprains

Lateral ankle sprains are one of the most frequent athletic injuries in football, causing deficits in balance. Motor Imagery (MI) has been successively included in sports rehabilitation as a complementary therapeutic intervention. The aim of the present study was to explore the effects of MI on static and dynamic balance and on the fear of re-injury in professional football players with Grade II ankle sprains. Fifty-eight participants were randomly allocated into two groups: First-MI group (n = 29) and second-Placebo group (n = 29), and they each received six intervention sessions. The first MI group received MI guidance in addition to the balance training program, while the second Placebo group received only relaxation guidance. One-way ANOVA showed statistically significant results for all variables, both before and 4 weeks after the interventions for both groups. The t-test showed statistically significant differences between the two groups for static balance for the right lower extremity (t = 3.25, S (two-tailed) = 0.002, p < 0.05) and also for heart rate (final value) in all time phases. Further research is needed in order to establish MI interventions in sports trauma recovery using stronger MI treatments in combination with psychophysiological factors associated with sports rehabilitation.

Study on the Impact of Implementing an Exercise Program Using Fitlight Technology for the Development of Upper Limb Coordinative Abilities in Basketball Players

The aim of this study was to evaluate the impact of implementing a basketball-specific exercise program using Fitlight technology on the coordinative abilities (reactive coordination, reactive reaction time, and reactive movement combination capacity) of U14 and U16 junior basketball players. This study included 70 male basketball players, 36 subjects U14 and 34 subjects U16, divided into two equal groups for each age category: the experimental group (EG) and the control group (CG). This study included an initial and a final test, between which, training was conducted over a period of 18 weeks. For the EG, the program aimed to develop coordinative abilities through an experimental program that utilized Fitlight technology, while the control groups underwent an identically timed program, but their training did not include the use of technology. Four tests were adapted and applied: the Reactive Reaction Test, Choice Reactive Reaction Test, Reactive Hand-Eye Coordination Test, and a test to evaluate the reactive capacity for combining movements. The results of this study showed statistically significant progress between the initial and final tests for the experimental group, p < 0.05. The Cohen's d values for the experimental groups were above 0.8, indicating a very large effect size, while for the control group, these values were small to medium. The comparative analysis of the experimental groups U14 and U16 and control groups shows statistically significant differences in favor of the experimental groups U14 and U16. This study highlights the effectiveness of implementing specific training programs that use modern technologies in developing coordinative abilities in the training and evaluation process of junior basketball players.

Bilateral Asymmetry of Spatiotemporal Running Gait Parameters in U14 Athletes at Different Speeds

The assessment of leg asymmetries is gaining scientific interest due to its potential impact on performance and injury development. Athletes around puberty exhibit increased gait variability due to a non-established running pattern. This study aims to describe the asymmetries in the spatiotemporal running parameters in developmentally aged athletes. Forty athletes under 14 (U14) (22 females and 18 males) were assessed running on a treadmill at constant speeds of 12 and 14 km·h-1 for 3 min. Step length, step frequency, along with contact (CT) and flight time, both in absolute values and as a percentage of step time, were recorded using a RunScribe sensor attached to the laces of each shoe. U14 runners exhibited high bilateral symmetry in the spatiotemporal parameters of running, with mean asymmetry values (1-5.7%) lower than the intra-limb coefficient of variation (1.7-9.6%). Furthermore, bilateral asymmetries did not vary between the two speeds. An individual-based interpretation of asymmetries identified subjects with consistent asymmetries at both speeds, particularly in terms of CT and contact ratio (%, CT/step time). This study confirms the high symmetry of pubertal runners and paves the way for the application of portable running assessment technology to detect asymmetries on an individual basis.

The Relationship Among Acceleration, Deceleration and Changes of Direction in Repeated Small Sided Games

The change of direction (COD) ability is perhaps the most significant fitness component in team sport games. One of the best ways to develop COD as well as other components of the game in soccer is the regular inclusion of small sided games (SSGs) in the training process. Therefore, the aim of this research was to determine changes in physiological and kinematic variables in repeated SSGs in youth soccer players. Additionally, we investigated the relationship between selected IMA variables such as acceleration, deceleration and changes of direction. Participants included sixteen U17 soccer players from a 2^nd league professional team with a high aerobic capacity. The study design involved six 3-min 4 × 4 SSGs with goalkeepers and with a 3-min rest interval between games, during two training sessions played on a field of 25 x 35 m. The results showed that the intervention protocol consisting of repeated SSGs generated an intensity below the anaerobic threshold. This allowed for the maintenance of all variables (Heart Rate, Total Distance Covered, Velocity, Acceleration, Deceleration, Change of Direction) at a similar level throughout the subsequent six SSGs. The analysis revealed that in the six SSGs, players performed the most Acc and Dec, then COD Right and the least COD Left. From the third game on, a decrease in the number of COD Right was noticed. We hypothesized that progressive neuromuscular fatigue on the dominant side caused a more symmetrical trend in COD.

Video-Based Behaviorally Coded Movement Assessment for Adolescents with Intellectual Disabilities: Application in Leg Dribbling Performance

Measuring motor performance in individuals with intellectual disabilities (ID) is quite challenging. The objective of this study was to compare the motor performances of individuals with ID and those with typical development (TD) during soccer dribbling through video-based behavior-coded movement assessment along with a wearable sensor. A cross-sectional research design was adopted. Adolescents with TD (N = 25) and ID (N = 29) participated in the straight-line and zigzag soccer dribbling tests. The dribbling performance was videotaped, and the footage was then analyzed with customized behavior-coding software. The coded parameters were the time for movement completion, the number of kicks, blocks, steps, the number of times the ball went out of bounds, the number of missed cones, and the trunk tilt angle. Participants with ID exhibited significantly poorer performance and demonstrated greater variances in many time and frequency domain parameters. It also revealed that participants with ID kicked with both feet while dribbling, whereas those with TD mainly used the dominant foot. The present findings demonstrated how the ID population differed from their peers in lower-extremity strategic control. The customized video-based behavior-coded approach provides an efficient and effective way to gather behavioral data and calculate performance parameter statistics in populations with intellectual disabilities.

Relationship between sprint, jump, dynamic balance with the change of direction on young soccer players' performance

The aim of the present paper was to determine the relationship between linear sprinting and jump performance, dynamic balance and change of direction on young soccer players. Ninety-four healthy young highly trained male soccer players belonging to the same high-performance academy agreed to participate in the study [twenty-seven soccer players U16 (14.8 ± 0.4 years; height: 170.6 ± 5.6 cm; body mass 64.7 ± 8.4 kg)] and [sixty-seven soccer players U19 (16.6 ± 1.3 years; height: 173.7 ± 7.2 cm; body mass 66.7 ± 8.0 kg)]. Participants completed 3 testing sessions, 7 days apart. Data from a CMJ, Crossover Hop Test, 10-m sprint test, 505 COD tests and the 90° COD test were collected. Moderate correlations were found in some of the cases (r values were between 0.2 and 0.5 in all cases, being p < 0.05), indicating that linear sprinting, jumping performance and dynamic balance are influential factors in agility but are not the main limiting factor. The highest correlation was found between the cross-over hop test and the 505 COD test (r = 0.44; p < 0.001). The main evidence from the current study suggested that linear sprinting, jumping performance and dynamics balance are determinants of COD, namely explaining the variations in such a skill. The current study revealed that short-distance sprint and jumping performance significantly explain the variations of COD performance on young soccer players.

Effects of Three Preseason Training Programs on Speed, Change-of-Direction, and Endurance in Recreationally Trained Soccer Players

Background: Modern coaches experience a drastic reduction of the available training time with an increasingly large number of competitions during the competitive season. Thus, they must choose wisely the most efficient methods to improve the physical fitness of their players during the preseason. Among all the methods, this study compared the effects of plyometric training (PT), sprint interval training (SIT), and small-sided games (SSGs) on the performance of recreationally trained soccer players.

Methods: Seventy-three participants were randomly assigned in one of the three experimental groups (i.e., PT [n = 23], SIT [n = 26] or SSGs [n = 24]) and completed two sessions per week for a total of 3 weeks. Meanwhile, the whole group maintained their habitual soccer-specific training program who do not interfere in the preparation of the season. Repeated sprint ability (RSA), maximal aerobic speed (MAS), and a 30-m sprint were assessed at baseline (PRE) and post-training (POST).

Results: Performance in SSGs decreased for the average speed from 0 to 10 m (V_0−10m; −0.84 km h⁻¹, −4 ± 5%, p < 0.001), the maximal distance (D_max) covered in the 30-s RSA test (−3.65 m, −3 ± 6%, p < 0.01) and MAS (−0.52 km h⁻¹, −3 ± 6%, p < 0.01). PT increased the mean distance (D_mean) covered in the 30-s RSA test (+5.98 m, 5 ± 4%, p < 0.001) and MAS (+0.58 km h⁻¹, 7 ± 5%, p < 0.01) while an improvement of all parameters but the maximal sprint speed reached during the 30-m trip (V_max) was found in the SIT group (V_0−10m: +1.462 km h⁻¹, 8 ± 5%, p < 0.001; D_max: +7.89 m, 6 ± 5%, p < 0.001; D_mean: +8.69 m, 7 ± 5%, p < 0.001 and MAS: +1.74 km h⁻¹, 12 ± 8%, p < 0.001). All SSG POST values were significantly lower than PT and SIT (p < 0.01). D_mean and MAS in POST were also significantly higher in SIT than in the PT group (p < 0.001).

Conclusion: This study suggests that both PT and SIT could be a better alternative to SSGs to boost performances during preseason. Moreover, SIT seems to produce higher improvements in physical performances than PT.

Relationship between Asymmetries Measured on Different Levels in Elite Basketball Players

In this study, we investigated the association of magnitude and agreement in direction between asymmetries measured on single-joint (hip and trunk), complex movement (jumping), and skill (change of direction (CoD)) levels. The study sample comprised 43 junior- and senior-level (age = 20.5 ± 6.0 years; height = 194.5 ± 7.2 cm; body mass = 86.8 ± 10.1 kg) elite male basketball players. Both limbs/sides were tested in hip and trunk isometric strength; passive range of motion (RoM); unilateral, horizontal, and vertical jumping; and CoD tests, from which asymmetry indexes were calculated. The associations between asymmetry magnitudes were calculated with Spearman’s ρ correlation coefficient. The agreement between the direction of asymmetries on different levels was calculated with Cohen’’s Kappa (κ) coefficient. The average magnitude of asymmetry varied substantially (2.9–40.3%). Most associations between asymmetry magnitudes measured on different levels were small and statistically non-significant, with a few exceptions of moderate and large associations. Asymmetry in single-leg countermovement jump parameters was strongly associated with hip abduction maximal strength (ρ = 0.58 and 0.50, p < 0.01). Agreement between asymmetry directions was slight to fair, with a few moderate exceptions. Results indicate that multiple tests are needed to obtain a comprehensive picture of athletes’ asymmetries and that universal thresholds and golden standard tests for return to play should be reconsidered and reinvestigated.

Relationship of regional and whole body morphology to vertical jump in elite soccer players: a data-driven approach

BACKGROUND

This study aimed to analyse the relationship of regional and whole body morphology to vertical jump performance and to compare the morphological features outlining high and low performers in professional soccer players.

METHODS

Twenty-one male soccer players were recruited. Whole and regional (upper and lower limbs) features were obtained in the form of body dimensional measurements. Then, all players were tested for vertical jump performance. A data-driven approach was used to group players according to their jump performance parameters (high vs low).

RESULTS

The regional morphological features presented higher correlations with vertical jump than whole body features. High and low performers were significantly different among upperand lower-limb morphology. No differences were observed among whole body features.

CONCLUSIONS

These findings indicate that, rather than the whole body, the use of morphological features linked to specific body regions may ensure a better interpretation of the soccer players' physical potential in jump performance.

Change of direction asymmetry across different age categories in youth soccer

Background

In youth, the development of change of direction (COD) and sprint performance is a key component for successfully competing in soccer across age. During a COD, the presence of directional asymmetries may be detrimental due to the unpredictable nature of the sport. Therefore, the aims of the study were to investigate asymmetries in COD ability and to examine the differences in COD and sprint performance across age in young soccer players.

Methods

Sixty-eight sub-elite soccer players of different age categories (U18, U17, U16, U15) were tested on a 10-m linear sprint test and 90°COD (5-m entry and exit) test in both directions. Asymmetric index (AI) of COD deficit was obtained for dominant (fastest) and non-dominant directions (slowest).

Results

The results showed that U16 were more asymmetrical than U18, U17, and U15 from large to moderate effects. The sprint time improved linearly across age with U18 and U15 displaying the fastest and slowest 10-m sprint performance (p < 0.01), respectively. Moreover, COD ability measured by COD deficit did not change across age (p > 0.05).

Conclusion

Given the results of this study, practitioners are encouraged to assess asymmetries between dominant and non-dominant directions rather than solely players’ COD ability in young soccer players.