COLLEGIATE MALE SOCCER PLAYERS EXHIBIT BETWEEN-LIMB SYMMETRY IN BODY COMPOSITION, MUSCLE STRENGTH, AND RANGE OF MOTION

Asymmetry in kinematics of dominant/nondominant lower limbs in central and lateral positioned college and sub-elite soccer players

Change of direction, stops, and pivots are among the most common non-contact movements associated with anterior cruciate ligament (ACL) injuries in soccer. By observing these dynamic movements, clinicians recognize abnormal kinematic patterns that contribute to ACL tears such as increased knee valgus or reduced knee flexion. Different motions and physical demands are observed across playing positions, which may result in varied lower limb kinematic patterns. In the present study, 28 college and sub-elite soccer players performed four dynamic motions (change of direction with and without ball, header, and instep kick) with the goal of examining the effect of on-field positioning, leg dominance, and gender in lower body kinematics. Motion capture software monitored joint angles in the knee, hip, and ankle. A three-way ANOVA showed significant differences in each category. Remarkably, centrally positioned players displayed significantly greater knee adduction (5° difference, p = 0.013), hip flexion (9° difference, p = 0.034), hip adduction (7° difference, p = 0.016), and dorsiflexion (12° difference, p = 0.022) when performing the instep kick in comparison to their laterally positioned counterparts. These findings suggest that central players tend to exhibit a greater range of motion when performing an instep kicking task compared to laterally positioned players. At a competitive level, this discrepancy could potentially lead to differences in lower limb muscle development among on-field positions. Accordingly, it is suggested to implement position-specific prevention programs to address these asymmetries in lower limb kinematics, which can help mitigate dangerous kinematic patterns and consequently reduce the risk of ACL injury in soccer players.

Effect of a Ten-week Sensorimotor Exercise Program on the Side-to-Side LAM Asymmetry of Adolescent Football Players: A Randomized Control Trial

In this study we, evaluated the effects of a 10-week sensorimotor exercise program on the thickness and side-to-side asymmetry of the lateral abdominal muscles in adolescent soccer players. From among 120 initially recruited participants, we included 90 athletes (aged 10-17 years old) in our final analysis. Healthy athletes who met our inclusion criteria were randomly divided into comparative experimental and control groups. Sensorimotor exercises were conducted twice weekly for 10-weeks in the experimental group, and the control group received no intervention. We took ultrasound measurements when participants were in supine and standing rest positions. In the supine position, the experimental group (a) reduced the asymmetry of the internal oblique (IO) muscle by 0.4 mm (MD: 0.7; 95% CI 0.6-1.1); (b) increased the thickness of the external oblique (EO) muscle on the right by 0.7 mm (MD: 0.2; 95% CI 0.1-0.6) and on the left by 0.9 mm (MD: 0.2, 95% CI 0.2-0.7); and (c) increased the muscle on the IO right by 0.8 mm (MD: 0.3; 95% CI 0.2-0.9) and on the, left by 1.2 mm (MD: 0.4 95% CI 0.3-1.1). In a standing position the experimental group increased the thickness of the EO on the right by 1.5 mm (MD: 0.6; 95% CI 0.03-1.2) and on the left by 2.1 mm (MD: 0.6; 95% CI 0.1-1.3) and increased the IO on the right by 1.2 mm (MD: 0.7; 95% CI 0.2-1.7) and on the left by 1.1 mm (MD: 0.9; 95%CI 0.1-2.0). Thus, this 10-week program of additional sensorimotor exercises reduced the (side-to-side) asymmetry of the internal oblique muscle and increased the thickness of the EO and IO muscles in young football players.

DEXA Body Composition Asymmetry Analysis and Association to Injury Risk and Low Back Pain in University Soccer Players

Soccer is a laterally dominant sport owing to the repetitive nature of unilateral kicking. The relationship between functional and body composition asymmetries related to limb dominance in soccer players has yet to be established. When present, asymmetries can increase the risk of injury and low back pain. Our study investigated whether lateral dominance is associated with limb asymmetries in a comprehensive body composition assessment among varsity soccer players. Twenty-seven varsity soccer players (age 20.4 ± 1.7 years old; BMI 22.6 ± 4.6 kg/m2) participated in this study. Body composition was assessed through dual-energy X-ray absorptiometry scans. Results showed low lower limb asymmetry indices in both males (3.82%) and females (3.36%) compared to normal ranges. However, upper limb lean mass exhibited high asymmetry, surpassing thresholds in males (7.3%) and females (4.39%). Significant differences were found in total bone mass among males and total lean body mass among females. Male players exhibited higher asymmetry indices in both arm and trunk mass compared to females. Despite these asymmetries, no significant correlations were found between asymmetry indices and occurrences of lower limb injury or low back pain. The study suggests that while evaluating body composition for injury prevention in soccer shows potential, lateral dominance may be influenced by factors extending beyond sport-specific adaptations.

Tracking Body Composition Over a Competitive Season in Elite Soccer Players Using Laboratory- and Field-Based Assessment Methods

ABSTRACT

Bongiovanni, T, Lacome, M, Rodriguez, C, and Tinsley, GM. Tracking body composition over a competitive season in elite soccer players using laboratory- and field-based assessment methods. J Strength Cond Res 38(3): e104-e115, 2024-The purpose of this study was to describe body composition changes in professional soccer players over the course of a competitive playing season and compare the ability of different assessment methods to detect changes. Twenty-one elite male soccer players (age: 23.7 ± 4.8 years; height: 185.0 ± 5.2 cm; body mass: 80.7 ± 5.5 kg; body fat: 12.8 ± 2.2%) playing for an Italian national second league (Serie B) championship team were assessed at 4 time points throughout a competitive season: T0 (mid-October), T1 (mid-December), T2 (mid-February), and T3 (end of April). Dual-energy x-ray absorptiometry (DXA), skinfolds (SKF), and bioelectrical impedance analysis were performed at each time point, and multiple SKF-based equations were applied. A modified 4-compartment (4C) model was also produced. Data were analyzed using repeated measures analysis of variance, relevant post hoc tests, and Pearson's correlations. Dual-energy x-ray absorptiometry, 4C, and the SKF-based equations of Reilly and Civar detected differences in fat-free mass (FFM) between time points, with the most differences observed for DXA. Fat-free mass increased from T0 values to a peak at T2, followed by a decrease by T3, although FFM values remained higher than T0. Fat-free mass gain was primarily driven by increases in the lower limbs. Fat-free mass changes between all methods were significantly correlated, with correlation coefficients of 0.70-0.97. No significant differences between time points were observed for absolute fat mass or body fat percentage, although significant correlations between several methods for change values were observed. Select laboratory and field methods can detect changes in FFM over the course of a season in elite, professional soccer athletes, with a more limited ability to detect changes in adiposity-related variables. For SKF in this population, the equation of Reilly is recommended.

Forward step down test - clinical rating is correlated with joint angles of the pelvis and hip: an observational study

BACKGROUND

Clinical methods for assessing quality of movement and functional tests are important to clinicians. Typical deviations from normal kinematics during the clinical test of Forward Step Down Test (FSDT) are pelvic tilt and hip adduction which are associated with the risk of knee pain.

OBJECTIVES

(1) to examine the correlation between clinical assessment of the FSDT and joint angle measurements of pelvis, hip, knee and ankle joints in males and females; (2) to examine the differences in joint angles between individuals rated as good, fair or poor in a FSDT performance test.

METHODS

Ninety-two healthy individuals performing FSDT were video-taped with two-dimensional digital video cameras. The clinical assessment of the FSDT was rated by two experienced physical therapists as good, fair, or poor based on a Crossley et al. (2011) validated scale. Measurements of pelvic drop, hip adduction and knee valgus were taken using Image J software.

RESULTS

Out of 177 lower limbs, 74 (37 in each limb) were clinically rated as "good/fair" (41.80%) while 103 (52 in the dominant leg and 51 in the non-dominant leg) were rated as "poor" (58.19%). No significant differences were observed between dominant and non-dominant legs or between males and females in clinical rating of the FSDT. Pelvic drop angle was significantly higher and hip adduction angle was significantly lower for "poor" clinical rating compared to "good/fair" in both dominant and non-dominant legs (p < 0.001) in males and females. Females demonstrated higher pelvic drop, lower hip adduction and higher knee valgus angles compared with males (p < 0.05).

CONCLUSIONS

This study showed that the clinical rating of FSDT is correlated with joint angle measurements suggesting that this assessment can be utilized in clinical practice. Individuals with poor quality performance of FSDT showed higher pelvic drop and hip adduction movement. Further studies examining different populations with diverse disorders or pathologies are essential.

Difference Asymmetry between Preferred Dominant and Non-Dominant Legs in Muscular Power and Balance among Sub-Elite Soccer Players in Qatar

The objective of this study was to determine and compare leg asymmetry between preferred dominant and non-dominant legs in muscular power and balance among sub-elite soccer (football) players in Qatar. Thirty-two professional local soccer players from the Qatar Stars League (Second Division) participated in the study (23.1 ± 6.1 years). They were classified according to their preferred dominant leg (preferred leg to kick the ball). Twenty-two players had a right dominant leg, and the remaining ten had a left dominant leg. Countermovement jump (CMJ) was used to measure unilateral and bilateral vertical jump performances. The Y-balance test (YBT) was used to assess dynamic balance. No significant differences were found between the dominant and non-dominant leg for CMJ flight height (p > 0.05; asymmetry index (AI) = 1.83 ± 11.46) or the relative and absolute reach distance derived from the YBT (p > 0.05; AI (relative) = −0.45 ± 9.68, AI (absolute) = −0.60 ± 12.3). Bilateral asymmetry in dynamic balance was not significant for any of the anterior, posteromedial, or the posterolateral reaching directions (p > 0.05). The selected football players demonstrated an acceptable level of leg symmetry for power and dynamic balance. These findings may prove helpful for the assessment and evaluation of talents and should help to develop and optimize training regimes.

The Assessment of Ankle Range-of-Motion and Its Relationship with Overall Muscle Strength in a Cross-Section of Soccer Players

Soccer (football) practice can induce a limitation of ankle range of motion (ROM) that is a possible risk factor for injury and other negative consequences over time. The main objective of this research was to investigate the effects of soccer practice on ankle ROM throughout the entire period of a sports career of soccer players (SP). Furthermore, the relationship between ankle ROM and muscle strength in SP of different ages was studied. A total of 204 SP (range 6.7−45.1 years) and 87 controls (range: 7.5−45.2 years) matched for age, body mass index (BMI), and gender, were assessed. Ankle ROM in both plantar flexion (APF) and dorsiflexion (ADF) in addition to handgrip strength (HGS) were evaluated using an inclinometer and the Jamar hydraulic hand dynamometer, respectively. The comparison between SP and control groups showed a significant reduction in ankle ROM of both APF (26.3 ± 7.2° vs. 32.6 ± 7.4°; d = −0.90; p < 0.001) and ADF (95.5 ± 15.6° vs. 105.5 ± 15.8°; d = −0.66; p < 0.001). In SP, the results of the ANOVAs test indicate that age had a significant effect on ADF (F = 4.352, p = 0.038, partial eta-squared (ηp2) = 0.015) but not on APF (F = 0.430, p = 0.746, ηp2 = 0.001). Moreover, considering only the SP, a weak inverse correlation between ADF and HGS group ADF was found (rs = −0.27; p < 0.001). Factors such as the non-linear trend of growth in young SP could hinder the definition of the relationship between ankle ROM, age, and muscle strength. However, the appropriate consideration of age and muscle strength could facilitate the management of ankle ROM in PF of different ages.

Lower Extremity Flexibility Profile in Basketball Players: Gender Differences and Injury Risk Identification

Analysis of the flexibility profile of basketball players (BPs) can reveal differences in range of motion (ROM) by gender and also identify those players who are at higher risk for sports injuries. A descriptive observational study was conducted to determine the lower extremity flexibility profile of sixty-four basketball players and gender differences to identify players at higher risk of injury due to limited and asymmetric ROM in one or more movements. Participants: Sixty-four (33 male and 31 female) competitive athletes from the national leagues of the Spanish basketball league system participated in the present study (power of sample size ≥0.99). The eight passive ROM tests of the hip, knee and ankle were assessed using the ROM-SPORT battery. Each player completed a questionnaire on age, basic anthropometric data, dominant extremities, and training and sport-related variables. The lower extremity flexibility profile was established at 15° and 10° hip extension (HE), 39° and 38° ankle dorsiflexion with knee extended (ADF-KE), 40° and 39° ankle dorsiflexion with knee flexed (ADF-KF), 43° and 43° hip abduction (HAB), 75° and 61° hip abduction with the hip flexed (HAB-HF), 78° and 83° hip flexion with the knee extended (HF-KE), 134° and 120° knee flexion (KF), and 145° and 144° hip flexion (HF) by male and female basketball players, respectively. Sex differences in HE, HAB-HF, and KF were observed in BPs (p ≤ 0.01; Hedges’ g ≥ 1.04). Players reported limited ROM in ADF-KF, HE, HAB-HF, HF-KE, and KF; and asymmetric ROM mainly in HE, ADF-KE, KF, ADF-KF, and HF-KE. In conclusion, this study provides gender-specific lower extremity flexibility profile scores in BPs that can help athletic trainers and athletic and conditioning trainers to identify those players who are at higher risk of injury due to abnormal ROM scores.

Functional performance and interlimb asymmetries of young football players during single-leg jump tests

Background

Jumps are predominant components in football (soccer). Interlimb functional difference in single-leg jump performance is a risk factor for lower extremities injuries. Screening uninjured athletes is essential to design prevention strategies and implement individual training interventions. The aims of this cross-sectional study were (1) to provide age-specific mean values and limb symmetry index (LSI) in young football players, (2) to detect age effect on LSI and interlimb functional differences and (3) to investigate the association of age with single-leg functional performance and LSI.

Methods

A total of 146 male football players (age 14.2 ± 2.3) performed the countermovement jump, jump for distance, side hop and speedy jump tests. Descriptive statistics, mean values (dominant/non-dominant) and LSI were provided according to age groups (U11–U19). Two-way mixed analysis of variance (ANOVA), one-way ANOVA and Pearson’s correlation were used for the statistical analysis.

Results

Participants showed on average perfect LSI (103.8 ± 14.2%) amongst all tests and age groups. Interlimb functional differences occurred in three out of four tests (p < 0.05), without age interaction (p > 0.05). Age effect was positively associated with single-leg functional performance (p < 0.05), but not with LSI (p > 0.05), in all tests and age groups.

Conclusion

An LSI ≥100% in single-leg jump tests is proposed as a benchmark in young football players, but interlimb performance differences may occur without age interaction. Nevertheless, the growth process plays a crucial role in the development of functional capacities: older players may show a higher single-leg jump performance, but not a higher LSI, than younger players. In football practice, preventive intervention is advisable to counteract interlimb performance differences, for which unilateral strength, power and plyometric training is recommended.

Long-Term Patterns of Bone Mineral Density in an Elite Soccer Player

Changes in bone mineral density (BMD) have been associated with association football (soccer) participation. Seasonal changes in BMD of soccer players have been proposed as well. However, previous investigations were based on short-term observations. Actually, longitudinal investigation of BMD in soccer players is lacking, possibly because of frequent inter-club transfer, changes in club policy or continued availability of the relevant facilities. Dual-energy X-ray Absorptiometry (DXA)-measured areal BMD (aBMD) was obtained during the competitive season in an elite soccer player along 10 consecutive years. Findings showed that (1) aBMD tends to increase with age, independently of body mass; (2) The right (preferred, kicking) leg has higher aBMD than the left (non-preferred, support) one; (3) Meaningful (i.e., >least significant change, LSC) changes in aBMD take place along the season; and (4) The off-season (transition) period has no effect on aBMD. Findings prompt for future research aimed at clarifying the long-term and seasonal patterns of bone characteristics in soccer in relation with age and type/dose of training. Season-around, long-term scrutiny of bone status in soccer players would help controlling for possible changes/asymmetries in bone mineralization/strength.

Individual hop analysis and reactive strength ratios provide better discrimination of ACL reconstructed limb deficits than triple hop for distance scores in athletes returning to sport

BACKGROUND

The triple hop for distance test commonly uses a limb symmetry index (LSI) 'pass' threshold of >90% for total hop distance following anterior cruciate ligament reconstruction (ACLR). However, understanding the manner in which athletes generate and dissipate forces during consecutive hops within the test may provide greater insight into residual limb deficits. The aim of the study was to examine reactive strength ratios (RSR) of individual hops during a triple hop test in a cohort of ACLR patients at discharge prior to return-to-sport.

METHODS

Twenty male athletes (24.6 ± 4.2 years; height 175.3 ± 10.2 cm; mass 73.6 ± 14.5 kg) completed the test on both non-operated and operated limbs. Total distance hopped, contact times, flight times and RSR were collected for each hop using a floor-level optical measurement system.

RESULTS

Significant, small to moderate between-limb differences (p < 0.05; d = 0.45-0.72) were shown for triple hop distance, flight time and RSR for each hop, with lower performance consistently displayed in the operated limb. Large, significant differences in RSR were evident between hops one and two on the operated limb (p < 0.05; d = 0.97). Despite 80% of participants achieving >90% LSI for total hop distance, less than 50% of participants reached the >90% LSI threshold for RSR.

CONCLUSIONS

Standardised LSI 'pass' thresholds (>90% LSI) for triple hop distance may mask residual deficits in reactive strength performance of operated limbs; therefore, more detailed analyses of individual hop performance may be warranted to enhance return to sport criteria following ACLR.

Four meta-analyses across 164 studies on atypical footedness prevalence and its relation to handedness

Human lateral preferences, such as handedness and footedness, have interested researchers for decades due to their pronounced asymmetries at the population level. While there are good estimates on the prevalence of handedness in the population, there is no large-scale estimation on the prevalence of footedness. Furthermore, the relationship between footedness and handedness still remains elusive. Here, we conducted meta-analyses with four different classification systems for footedness on 145,135 individuals across 164 studies including new data from the ALSPAC cohort. The study aimed to determine a reliable point estimate of footedness, to study the association between footedness and handedness, and to investigate moderating factors influencing footedness. We showed that the prevalence of atypical footedness ranges between 12.10% using the most conservative criterion of left-footedness to 23.7% including all left- and mixed-footers as a single non-right category. As many as 60.1% of left-handers were left-footed whereas only 3.2% of right-handers were left-footed. Males were 4.1% more often non-right-footed compared to females. Individuals with psychiatric and neurodevelopmental disorders exhibited a higher prevalence of non-right-footedness. Furthermore, the presence of mixed-footedness was higher in children compared to adults and left-footedness was increased in athletes compared to the general population. Finally, we showed that footedness is only marginally influenced by cultural and social factors, which play a crucial role in the determination of handedness. Overall, this study provides new and useful reference data for laterality research. Furthermore, the data suggest that footedness is a valuable phenotype for the study of lateral motor biases, its underlying genetics and neurodevelopment.

Soccer Footedness and Between-Limbs Muscle Strength: Systematic Review and Meta-Analysis

Purpose: Limb dominance and consequent between-limbs muscle strength in soccer players should be explored to determine a standard musculoskeletal profile to maintain and establish during screening protocols and postinjury rehabilitation. The primary aim of this review was to identify dominant- vs non-dominant-lower-extremity muscle-strength characteristics of healthy soccer players, with secondary aims to consider available between-limbs outcome measures and directions for future research. Methods: Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. Five electronic databases were used for study identification with guidance from a medical librarian. Inclusion criteria consisted of studies employing a cross-sectional design assessing soccer players of all ages, genders, and levels of play that identified limb dominance and associated lower-extremity muscle strength as a main purpose of the experiment. Results: The literature search identified 3471 articles. After screening titles, abstracts, and full texts, 17 articles were included in the review. Peak torques and hamstring-to-quadriceps ratios via isokinetic dynamometry were commonly used, and subsequent meta-analyses were conducted to yield remarkable between-limbs symmetry. Additional results of individual studies also demonstrate symmetry, except 1 article of velocity-dependent measures that reported greater strength in the dominant limb. Conclusions: In soccer, between-limbs muscle strength measured by maximal isokinetic dynamometry demonstrates symmetry across ages, genders, and levels of play. Future testing using alternative measures that more specifically replicate the movement demands of soccer players may further classify between-limbs characteristics.