Relationships of lower extremity and trunk asymmetries in elite soccer players.

In light of previous research highlighting the prevalence of asymmetries in soccer players and possible links to injury risks, there is a crucial gap in the biomechanical understanding of complex relationships between lower extremity and trunk asymmetries in elite soccer players. The purpose of this study was to investigate the level, relationships, and differences among twelve different parameters of strength, morphological, and neuromuscular asymmetries in elite soccer players. Methods: Elite male soccer players (n = 25, age 21.7 ± 3.9 years) were tested in the following tests: bilateral fluid distribution, hip flexor range of motion, postural stability, isokinetic strength of knee extensors and flexors, isometric lateral trunk rotation strength, eccentric strength of knee flexors, isometric bilateral strength of hip adductors, and vertical ground reaction force in counter-movement jump-free arms, counter-movement jump, squat jump, and drop jump tests. One-way ANOVA, Pearson's coefficient (r), and partial eta squared (η p 2) were used for data analysis. Results: Significant differences in asymmetries were found in elite soccer players (F11,299 = 11.01, p < .01). The magnitude of asymmetry over 10% was in postural stability and drop jump parameters. The lowest magnitudes of asymmetries were in the fluid distribution of the lower limbs and the vertical ground reaction force during the take-off phase in squat jumps. The highest asymmetries between the dominant and non-dominant sides were found in postural stability and drop jump. A total of eleven significant correlations (p < 0.05, r = 0.41-0.63, R2 = 0.17-0.40) were detected between the analyzed asymmetries in elite soccer players. The lateral trunk rotation asymmetries were significantly correlated to vertical ground reaction force asymmetries and knee extensors. Conclusion: Long-term exposure in elite soccer leads to unilateral biomechanical loading that induces abnormal strength and morphological adaptations in favor of the dominant side while linking lower limb and trunk strength asymmetries. By unraveling these complex relationships, we strive to contribute novel methods that could inform targeted training regimens and injury prevention strategies in the elite soccer community. The data should encourage future researchers and coaches to monitor and develop trunk strength linked to lower body kinematics.

Weekly Training Load Differences between Starting and Non-Starting Soccer Players.

The aim of this study was to examine the differences in the weekly training load between starters and non-starters classified based on the match starting line-up, with respect to the playing position and a training day. Notably, 31 young adult soccer players (age: 18.79 ± 1.04 years) competing in the 3rd Czech division were monitored across the season. The weekly training load was measured using a GPS system as follows: total distance covered (TD), high-speed running distance (HSR), sprint running distance (SR), and acceleration and deceleration distance (ACDC). We found higher values in three out of four observed variables (HSR, SR, and ACDC, excluding TD) for starters compared to non-starters (p < 0.05), with small to moderate effect sizes (d = 0.40-0.49). Differences were observed especially in players who were fullbacks, offensive midfielders, and forwards. Moreover, the largest differences were found in training prior to a match day for HSR, SR, and ACDC (p < 0.05). Non-starters experienced lower weekly external loads in offensive player positions, predominantly in high-intensity variables, which are essential for their physical performance. It seems that non-starters may experience potential under-loading in the training process. Coaches and practitioners should be aware of this potential risk and find an appropriate method to compensate for load discrepancies, particularly in terms of high-intensity activities.

Differences in external load among indoor and beach volleyball players during elite matches.

The aim of this cross-sectional study was to examine relationships of external load variables between beach and indoor volleyball amongst individual positions on the team. The movements of eight beach and fourteen indoor female volleyball players were recorded during elite playoff matches; in total, 2,336 three-dimensional trajectories were analyzed. Time-outs and intervals between rallies or sets were excluded from active play time. In both beach and indoor volleyball, 80% of rallies lasted up to 10 s, and players covered 4.5 to 10 m of court during 60% of rally play. Differences in dependent variables of external load were found between independent variables of sports and player positions (p < 0.05). The distance covered in beach volleyball rallies and Player Load™ parameters was significantly higher by up to 23%. The unstable court surface with sand in beach volleyball elevated explosive Player Load™ (accelerations in all three orthogonal planes of motion higher than 3.5 m/s3) in beach volleyball players compared to those of players on stable flooring in indoor. While beach volleyball blocker and defender positions showed no significant difference in parameters between each other, they differed in all parameters when compared to player positions in indoor volleyball. Indoor blocker and libero reached higher loads than setter, outside and opposite positions in various parameters. Factors that influence external load include the larger relative court areas covered by each player in beach volleyball, complexity of players' roles, and game strategy. This data adds to the knowledge of elite match demands in female volleyball. Specified agility-drill distances and times are essential for training optimization and must be supported by scientific observation. Researchers, coaches, and conditioning specialists should find this helpful for achieving a higher degree of training regulation.

Elite young soccer players have smaller inter-limb asymmetry and better body composition than non-elite players.

Body composition (BC) and inter-limb anthropometric asymmetries (LA) may influence the physical performance of soccer players. This study aimed to determine differences in BC and LA among soccer across four performance levels. The study involved 110 male soccer players participating in Czech senior teams who were grouped into four different performance levels (i.e. G1: national team, G2: 1st division, G3: 2nd division, G4: 3rd division). The following BC and LA parameters were compared among groups: body height, body mass, absolute fat-free mass, relative fat-free mass (FFMrel), percentage of fat mass (FM), total body water (TBW), intracellular water (ICW), extracellular water (ECW), phase angle, and bilateral muscle mass differences in the upper and lower extremities. Significant differences were observed in BC parameters among all groups (λ = 0.06, F75,246 = 5.38, p = 0.01, ηp 2 = 0.62). High-performance players (i.e. G1, G2) had significantly (p < 0.01) lower FM than lower performance players (i.e. G3, G4). The lowest values of FFMrel, relative TBW, relative ICW and ECW were detected in the lowest-performance players (i.e. G4). Significantly lower bilateral muscle mass differences were detected in G1 players (2.71 ± 1.26%; p < 0.01) compared with G4 players (3.95 ± 1.17%). G1 and G2 players had a higher proportion of muscle mass in the torso (p < 0.01) and upper limbs than G3 and G4 (p < 0.01). Elite and high-performance players have better BC and lower inter-limb anthropometric asymmetries compared with low-performance level players.

Anthropometric, Body Composition, and Morphological Lower Limb Asymmetries in Elite Soccer Players: A Prospective Cohort Study.

The aim of this study was to identify and compare parameters related to anthropometry, body composition (BC), and morphological asymmetry in elite soccer players in nine age categories at the same soccer club (n = 355). We used a bio-impedance analyzer to measure the following indicators of BC: body height (BH); body mass (BM); relative fat-free mass (FFMr); percentage of fat mass (FM); and bilateral muscle mass differences in the lower extremities (BLD∆). Age showed a significant influence on all parameters observed (F64,1962 = 9.99, p = 0.00, λ = 14.75, η2p = 0.25). Adolescent players (from U16 through adults) had lower FM values (<10%) compared to players in the U12-U15 categories (>10%). The highest FFMr was observed in the U18 category. Players in the U12 and U13 categories showed more homogenous values compared to older players. With increasing age, significantly higher FFMr was observed in the lower extremities. An inter-limb comparison of the lower extremities showed significant differences in the U17 category (t27 = 2.77, p = 0.01) and in adult players (t68 = 5.02, p = 0.00). Our results suggest that the end of height growth occurs around the age of 16 years, while weight continues to increase until 20 years. This increase is not linked to decreasing FM, nor to the FFMr, which remains stable. We found morphological asymmetries between limbs in players of the U17 category and in adult players.

Body composition and morphological limbs asymmetry in competitors in six martial arts / Composición corporal y asimetría morfológica de miembros en competidores en seis artes marciales

The aim of this study was to compare body composition (BC) and morphological symmetry differences among elite athletes (n = 132) in six martial arts (judo, karate, fencing, wrestling, taekwondo, kickboxing). Multivariate analysis of variances (MANOVA) was used to compare the following variables: absolute (FFM) and relative (FFMrel) value of fat free mass, percentage of fat mass (FMp), bone mass, protein mass, basal metabolic rate, absolute (TBW) and percentual (TBWp) value of total body water, segmental proportion of muscle mass, phase angle, and percent-age differences between the upper and lower limbs. MANOVA revealed significant differences in BC among the groups (λ = 0.01, F104, 256 = 10.01, p< 0.01, ηp2 = 0.67). No significant differences were observed for FMp, FFMrel, and TBWp (p>0.05). In all other BC variables, significant differences were detected (p<0.05). The comparison of paired differences between limbs revealed significantly greater fluid volume in the preferred arm compared to the non-preferred arm in karate and fencing athletes. Significant differences (p<0.05) in favour of the preferred leg in all combat athletes were detected. This study revealed morphological differences among practitioners of different martial arts and between paired limbs.

El objetivo de este estudio fue comparar la composición corporal (CC) y las diferencias de simetría morfológica entre atletas de élite (n = 132) en seis artes marciales (judo, karate, esgrima, lucha, taekwondo, kickboxing). Se utilizó el análisis multivariado de varianzas (MANOVA) para comparar las siguientes variables: valor absoluto (FFM) y relativo (FFMrel) de la masa libre de grasa, porcentaje de masa grasa (FMp), masa ósea, masa proteica, tasa metabólica basal, absoluto (TBW) y el valor porcentual (TBWp) de líquido corporal total, la proporción segmentaria de la masa muscular, el ángulo de fase y las diferencias porcentuales entre los miembros superiores e inferiores. MANOVA reveló diferencias significativas en BC entre los grupos (λ = 0,01, F104, 256 = 10,01, p <0,01, ηp2 = 0,67). No se observaron diferencias significativas para FMp, FFMrel y TBWp (p>0,05). En todas las demás variables de BC, se detectaron diferencias significativas (p<0,05). La comparación de las diferencias pareadas entre los miembros reveló un volumen de líquido significativamente mayor en el brazo dominante en comparación con el brazo no dominante en karate y atletas de esgrima. Se detectaron diferencias significativas (p<0,05) a favor de la pierna dominante en todos los atletas de combate. Este estudio reveló diferencias morfológicas entre los practicantes de diferentes artes marciales y entre las miembros emparejadas.

Morphological and Isokinetic Strength Differences: Bilateral and Ipsilateral Variation by Different Sport Activity.

BACKGROUND: The purpose of this study was to investigate the morphological and isokinetic strength asymmetry and magnitude in young athletes. METHODS: One hundred and thirty nine male subjects (soccer, floorball, non-athletes) were measured for proportion of muscle mass between upper extremities (BADΔ) and lower extremities (BLDΔ). Moreover, the peak muscle torque of knee extensors (PTE) and flexors (PTF), ipsilateral (H:Q) and bilateral strength ratio (Q:Q, H:H) were measured. RESULTS: We found significant differences in observed parameters with respect to different sport activities (F = 13.02, p = 0.00, η p 2 = 0.80). Higher values of BADΔ were observed in the non-active (0.19 ± 0.11 kg) group compared with soccer players (0.10 ± 0.11 kg). We found a lower value of BLDΔ in floorball players (0.32 ± 0.11 kg) compared with soccer players (0.58 ± 0.27 kg) and non-active boys (0.63 ± 0.28 kg). Results revealed significantly higher PTE in soccer players compared with non-active boys and floorball players and higher Q:Q ratio in soccer players (10.99 ± 7.75%) compared with non-active boys (7.47 ± 5.92%). CONCLUSIONS: This study revealed that there are morphological and strength asymmetries in the observed groups, which may have potential maladaptive effects (e.g. uncompensated overload of extremity) in athletes affected by specific load.

Effect of Muscular Strength, Asymmetries and Fatigue on Kicking Performance in Soccer Players.

The aim of this study was to determine the effect of muscular strength, strength asymmetries, and fatigue on the speed and accuracy of an instep kick in soccer players. We measured ball velocity (BV) and kicking accuracy (KA) in the preferred (PL) and non-preferred leg (NPL) before (PRE) and after (POST) physical load in the PL. Maximum peak muscle torque of the knee extensors and flexors in the PL and NPL as well as ipsilateral knee flexors and knee extensors ratio (H:Q ratio) for both legs were assessed. BV was significantly decreased in POST physical load (5.82%, BVPRE=30.79±1.70 m·s-1, BVPOST=29.00±1.70 m·s-1, t19=3.67, p=0.00, d=1.05). Instep kick accuracy after the physical load worsened by an average of 10% in the most accurate trials. Results revealed a significant decrease in instep kick accuracy after physical loading (KAPRE=2.74±0.70 m, KAPOST=3.85±1.24 m, t19=-3.31, p=0.00, d=1.10). We found an insignificant correlation between H:Q ratio and KA in PRE test value, whereas a lower ipsilateral ratio (higher degree of strength asymmetry) in the POST physical load significantly correlated with KA in all angular velocities (r=-0.63 up to -0.67, p=0.00).

Kinematic Analysis of Volleyball Attack in the Net Center with Various Types of Take-Off.

The aim of the study was to describe and compare kinematics in two types of execution of attack hit, the goofy approach and regular approach. The research group consisted of players from the Czech Republic's top league (n = 12, age 28.0 ± 4.3 years, body height 196.6 ± 5.6 cm, body mass 89.7 ± 6.7 kg) divided into two groups according to the individual type of approach in the attack. Analysis of movement was performed by 3D kinematics video analysis, space coordinates were calculated by the DLT (Direct Linear Transformation) method together with interpretation software TEMA Bio 2.3 (Image Systems AB, Sweden). The players started their run-up from a distance of about 4 - 4.5 m from the net with similar maximal vertical velocity (2.91 - 2.96 m⋅s-1). The trajectory of players with goofy approach seemed to be convenient for the rotation of shoulders and hips in the moment of ball contact. Differences between both groups were observed. Players with a goofy approach had a longer flight phase compared to regularly approaching players.

Unilateral and ipsilateral strength asymmetries in elite youth soccer players with respect to muscle group and limb dominance / Asimetría de fuerzas unilateral e ipsilateral en jugadores de fútbol de elite juveniles con respecto al grupo muscular y a la dominancia de miembros

The purpose of study was to identify the presence of strength asymmetries (SA) in young elite soccer players in relation to muscle group (knee extensors (KE) and flexors (KF)) and limb preference (dominant vs. non-dominant limb). Forty-one U16 national team soccer players (mean age 15.7±0.3 years, body height 177.9±6.6 cm, body weight 68.2±7.9 kg) participated in this study. Assessments were performed on a Cybex Humac Norm isokinetic dynamometer in concentric contraction. We noted the degree of SAs in the bilateral ratio of quadriceps and hamstrings and in the ipsilateral ratio of the dominant (DL) and non-dominant (NL) legs. Bilateral deficits of KFs were higher (9.02­12.61 %) than those of KFs (6.32­7.15 %). The percentage of SA (>10 %) in knee extensors was 19.5­31.7 %. The percentage of SA (>10 %) in knee flexors was 36.6­51.2 %. At the lowest velocity, there was asignificantly higher prevalence of SAs in KFs than in KEs (c2= 4.11, p<.05). The ipsilateral ratio was lowest at the lowest velocity regardless of limb dominance (DL: 58.95­63.27 %, NL: 56.58­60.11 %). At each velocity, the percentage of SA was higher for the non-dominant limb (12.2­24.4 %) than for the dominant one (4.9­14.6 %). Despite these differences, we did not find any significantly higher prevalence of SA in the non-dominant limb than in the dominant one (c2= .35­2.04, p>.05). The results of the study suggest that more than 73.2 % of players have at least one SA. More attention should be paid to knee flexors, where a higher percentage of strength asymmetries were observed; furthermore, a higher percentage of strength asymmetry was seen in the non-dominant lower limb.

El objetivo de este estudio fue identificar la presencia de asimetría de fuerzas (AF) en jóvenes jugadores de fútbol de élite en relación con el grupo de músculos extensores de la rodilla (ER) y flexores (FR) y la preferencia de los miembros (miembro dominante frente al miembro no dominante). Participaron en este estudio 41 jugadores sub-16 del equipo nacional de fútbol (edad media de 15,7±0,3 años; altura 177,9 ± 6,6 cm; peso corporal 68,2±7,9 kg). Las evaluaciones se llevaron a cabo en un dinamómetro isocinético Cybex Humac Norm en contracción concéntrica. Se registró el grado de AF en la relación bilateral de los músculos cuádriceps y los tendones y en la relación ipsilateral del miembro dominante (MD) y el miembro no dominante (MND). Los déficits bilaterales fueron más altos en FR (9,02 a 12,61 %) que en ER (6,32-7,15 %). El porcentaje de AF (> 10 %) en los músculos extensores de la rodilla fue de 19,5 a 31,7 %. El porcentaje de AF (> 10 %) en los músculos flexores de la rodilla fue de 36,6 a 51,2 %. A la velocidad más baja, había una mayor prevalencia de AF en FR que en ER (c2 = 4.11, p <0,05). La relación ipsilateral fue la más baja a la velocidad más baja, independientemente de la dominancia de los miembros (MD: 58,95 a 63,27 %, MND: 56, 58-60, 11 %). En cada velocidad, el porcentaje de AF fue mayor para el miembro no dominante (12,2 a 24,4 %) que para el miembro dominante (4,9 a 14,6 %). A pesar de estas diferencias, no hemos encontrado ningún prevalencia significativamente mayor de AF en el miembro no dominante en comparación al miembro dominante (c2 = 0,35 a 2,04, p> 0,05). Los resultados del estudio sugieren que más de 73,2 % de los jugadores tienen al menos una AF. Más se debe prestar atención a los músculos flexores de la rodilla, donde se observó un mayor porcentaje de asimetría de fuerzas. Por otra parte, un mayor porcentaje de asimetría de fuerzas se observó en el miembro inferior no dominante.

Body composition of elite female players in five different sports games.

The goal of this study was to identify and compare body composition (BC) variables in elite female athletes (age ± years): volleyball (27.4 ± 4.1), softball (23.6 ± 4.9), basketball (25.9 ± 4.2), soccer (23.2 ± 4.2) and handball (24.0 ± 3.5) players. Fat-free mass (FFM), fat mass, percentage of fat mass (FMP), body cell mass (BCM), extracellular mass (ECM), their ratio, the percentage of BCM in FFM, the phase angle (α), and total body water, with a distinction between extracellular (ECW) and intracellular water, were measured using bioimpedance analysis. MANOVA showed significant differences in BC variables for athletes in different sports (F60.256 = 2.93, p < 0.01, η2 = 0.407). The results did not indicate any significant differences in FMP or α among the tested groups (p > 0.05). Significant changes in other BC variables were found in analyses when sport was used as an independent variable. Soccer players exhibited the most distinct BC, differing from players of other sports in 8 out of 10 variables. In contrast, the athletes with the most similar BC were volleyball and basketball players, who did not differ in any of the compared variables. Discriminant analysis revealed two significant functions (p < 0.01). The first discriminant function primarily represented differences based on the FFM proportion (volleyball, basketball vs. softball, soccer). The second discriminant function represented differences based on the ECW proportion (softball vs. soccer). Although all of the members of the studied groups competed at elite professional levels, significant differences in the selected BC variables were found. The results of the present study may serve as normative values for comparison or target values for training purposes.

The bilateral strength and power asymmetries in untrained boys.

The aim of the study was to identify the level of isokinetic strength and power of lower limbs in 13-year-old untrained boys (n=22, height: 158.5±8.0 cm, mass: 49.1±12.6 kg), to determine bilateral deficit between the limbs in the tests and examine their mutual relationship. Maximum peak muscle torque of knee extensors (PTQ) and flexors (PTH) on dominant (DL) and non-dominant leg (NL) were measured by isokinetic dynamometer. Three types of a vertical jump: countermovement jump with (CMJFA) and without arms (CMJ) and squat jump (SJ) were performed on two force platforms. We found the significant effect (p<.01) of independent variables (knee extensors, flexors, AV) and their interaction on PT. AV did not indicate any significant effect on bilateral ratio of knee extensors (F4,84=.74, p>.05, ηp2=0.03), however a significant effect of AV was found in knee flexors (F4,84=2.70, p<.05, ηp2=.114). The type of jump had no effect on the difference between force exerted by DL and NL (F1,21=.102, p>.05, ηp2=.01). Bilateral deficit (Q:Q, H:H) did not significantly correlate with bilateral deficit in jumps (p>.05). Despite the possibility of identifying muscle asymmetries in the sense of strength imbalances, their mutual relationship with results in isokinetic dynamometry and power jump tests is still unclear.