Article

Analysis of Lower Limb Asymmetries by Isokinetic and Vertical Jump Tests in Soccer Players

Laboratory of Sport Biomechanics, Federal University of Minas Gerais, Belo Horizonte, BRAZIL.
The Journal of Strength and Conditioning Research (Impact Factor: 2.08). 07/2012; 27(5). DOI: 10.1519/JSC.0b013e318265a3c8
Source: PubMed

ABSTRACT

Assessment of lower extremity bilateral asymmetries in soccer players is important for both injury prevention and performance. The purpose of this investigation was to compare isokinetic knee extensor assessment of asymmetry with a more specific countermovement jump (CMJ). Forty-six male Brazilian professional soccer players participated in this study. The maximal power, maximal force and impulse were determined during CMJ as well as the total work and peak torque at 60/s, 180/s and 300/s during isokinetic leg extension, separately for each leg. Factor analysis was performed for all investigated variables, and the diagnostic concordance between different criteria was analyzed by McNemar's Chi test. The factor analysis showed that the isokinetic and CMJ tests were widely independent methods for the assessment of bilateral differences. Concordance of the diagnostic information could only be found between the maximal force during CMJ and the total work and peak torque at 180°/s and 300/s during isokinetic leg extension. Impulse and maximal power during countermovement jump on a double force platform appear to be appropriate additional variables for the identification of bilateral differences. Therefore, it might be pertinent to perform, in addition to isokinetic assessment, a vertical jump test on a force platform to assure widespread and reliable diagnostic information.

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Available from: Hans-Joachim Menzel
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    • "Since its inception in the late 1960s, it has become an essential part in sports sciences and physiotherapy being applied both in research and training studies as well as in rehabilitation (for review see [1] [2] [3] [4]). Isokinetic devices are used for training and testing purposes due to their unique contraction conditions [5] [6] [7] [8], rehabilitative and preventive application possibilities [9] [10] [11] [12] [13] [14] as well as their predictive power in relation to several sport-specific capabilities [15] [16] [17] [18] [19]. Reliability represents an important quality criterion of measurement instruments for research and performance diagnostics. "
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    ABSTRACT: BACKGROUND: Although the reliability of isokinetic strength tests of knee flexors (flex) and extensors (ext) has been examined several times, statistical evidence about the influence of internal and external factors is missing. OBJECTIVE: This study aims to examine the impact of familiarisation, muscle group, contraction mode, angular velocity and test parameters on the reproducibility of findings derived from an isokinetic dynamometer (IsoMed 2000). METHODS: Thirty-three male subjects (mean age: 22.3 years) with no prior experience of isokinetic exercise participated in three identical test sessions (T1, T2, T3), each separated by 48–72 h. Peak moment (PM), angle of peak moment (APM) and contractional work (CW) were determined unilaterally (left and right) during maximum concentric (con) and eccentric (ecc) knee flexion (abdominal position) and extension (supine position) at 30, 90 and 150°/s, respectively. An ANOVA with repeated measures confirmed systematic bias. Reproducibility of consecutive tests (T1–T2, T2–T3) was assessed by calculating the intra-class correlation coefficient (ICC 2,1) (relative reliability) as well as the standard error of measurement (SEM) (absolute reliability). ICC values were averaged according to respective factors (Fisher’s z-transformation) and tested for significant differences by Steiger’s formulas. RESULTS: PM and CW demonstrated a high absolute reliability (SEM: 4.7–10.5%). Relative reproducibility varied considerably (p > 0.05) between muscles (ecc flex > ecc ext), contraction modes (con ext > ecc ext) and test parameters (PM = CW > APM), but did not depend on angular velocity (30 = 90 = 150°/s). Due to familiarisation the reliability of PM obtained from eccentric knee extensions significantly increased (T2–T3 > T1–T2). CONCLUSIONS: These results improve the development and execution of reliable isokinetic strength testing protocols for unilateral knee flexion and extension together with the interpretation of different test parameters.
    Full-text · Article · Dec 2014 · Isokinetics and exercise science
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    • "At the highest angular velocity (300°.s -1 ), our players from both groups achieved worse results in comparison to values presented by Menzel et al. (2013). Knee extensor performance in the dominant leg was better by 3.45 % (compared to Team 1) and 12.07 % (compared to Team 2) and in the non-dominant leg 2.34 % (compared to Team 1) and 9.94 % (compared to Team 2). "
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    ABSTRACT: Purpose: The purpose of research was to compare strength parameters of lower limbs (knee extensors and flexors) and their asymmetries (bilateral and unilateral) in elite and sub-elite professional soccer players. Material and method: The screened sample was composed of two professional soccer teams. The first team (Team 1 - elite professional players, n = 28, age = 24.31 ± 4.79 years) was a leader of the first Czech league the second team (Team 2 - sub-elite professional players, n = 24, age = 26.19 ± 3.67 years) was a leader of the second Czech league. Maximum peak torque (PT) and derived parameters (bilateral ratio [Q:Q and H:H] and unilateral ratio [H:Q]) were evaluated using Cybex isokinetic dynamometer at three angular velocities (60, 180, 300 °•s-1) for the dominant (DL) and non-dominant leg (NL) during the knee flexion (KF) and extension (KE) in concentric contraction. The four-way mixed-design ANOVA, Student's t-test and Cohen "d" index of effect size were used for statistical analyses. Results: The factor of P (performance) revealed a significant effect on the level of isokinetic strength of lower limbs in soccer players (F(1.596)= 91.74, p < 0.01, η2= 0.14). The factors of L (laterality) did not significantly influence the level of thigh muscular strength of lower extremities in soccer players (F(1.596)= 2.47, p > 0.05, η2= 0.01). The factor of the tested muscle group (KE, KF) showed a significant effect on the compared bilateral differences (F(1.288)= 11.13, p < 0.01, η2= 0.04). Post-hoc tests also showed significantly higher (p < 0.01) values of the bilateral deficit in KF compared to KE. A significant effect was also found in the unilateral ratio of the lower limbs (H:Q) on the basis of comparison of the performance criterion (F(1.288)= 15.51, p < 0.01, η2= 0.05) and angular velocity of movement (F(2.288)= 5.56, p < 0.01, η2= 0.04). The unilateral ratio (H:Q) was significantly higher in both the dominant and non-dominant limbs in favour of the higher performance Team 1 in comparison to Team 2 (H:Q ratio dominant limb: F(1.144)= 5.87, p < 0.05, η2= 0.04; non-dominant limb: F(1.144)= 11.21, p < 0.01, η2= 0.07). Discussions and conclusions: The results of the study suggest that more than 50 % of players have at least one strength asymmetry regardless of their performance level. Elite professional players have greater muscular strength of KE and KF, especially at higher angular velocity. Concerning sub-elite players, we found a lower unilateral H:Q ratio. The results of the study point to worse preparedness of KF (performance and prevention perspective) in the sub-elite players. Maladaptive effects in terms of different kinds of body strength asymmetries represent a potential risk of a player's injury; therefore the detected asymmetries should be systematically monitored and compensated using specific exercises.
    Full-text · Article · Jun 2014
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    ABSTRACT: Background: Effective execution of vertical jump depends on the explosive power of lower limbs and their symmetrical integration mainly. Assessment of lower extremity bilateral asymmetries in soccer players is important for both injury prevention and performance. Objective: The aim of this study was to identify and compare parameters of lower limb power in three different jump tests in elite soccer goalkeepers. The next aim was to describe and compare strength asymmetries of force exerted by lower limbs in the take-off phase in all tests. Method: The research group consisted of 25 elite soccer goalkeepers (age 26.5 ± 9.1 years, height 186.1 ± 7.8 cm, weight 86.7 ± 14.8 kg). Three types of a vertical jump - countermovement jump with arms included (CMJFA), countermovement jump with arms excluded (CMJ) and squat jump (SJ) were performed on two force platforms. Following parameters were assessed - maximum force during the take-off phase Fmax(N) and their relative value Frel(N • kg-1), jump height h (m) and force asymmetry between limbs (ΔFmax). RM ANOVA was used in statistical analysis. Results: The type of jump had a significant effect on jump height (F2, 48= 109.66, p <.01, η2=.82). The highest jump was reached in CMJFA. This result was higher by 11.1% (5.01 cm) in comparison to CMJ and by 19.9% (8.98 cm) than in SJ. Type of jump significantly influenced Fmax(F1.6, 38.7= 44.29, p <.01, η2=.65) and Frel(F2, 48= 50.33, p <.01, η2=.68). Force asymmetry between limbs (ΔFmax) was significantly different with respect to the type of jump performed (F1.3, 31.7= 5.14, p <.05, η2=.18). The highest force asymmetry was found in CMJFAtest (ΔFmax= 8.61%), while the difference in CMJ test was (7.06%) and in SJ test (ΔFmax= 3.95%). We found a significantly greater difference in ΔFmaxbetween CMJFAvs. SJ (p <.05) and CMJ vs. SJ (p <.01). Conclusion: The best results of jump height were achieved, as expected in the CMJFAbut in this test also the greatest force asymmetry was detected. Monitoring of power level and strength asymmetries at the beginning of the preparatory period enables identification of possible strength imbalances in elite soccer goalkeepers, which should be further reduced during the preparatory period. Screening examination of strength asymmetry may be thus a useful tool for both performance and injury prevention in goalkeepers.
    No preview · Article · Mar 2013
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