Comparação de dois critérios de classificação de jogadores de futebol profissional da assimetria lateral de força dos membros inferiores

Abstract

Prospective studies have indicated that assessing muscle function by the isokinetic test in the preseason is able to identify muscle strength variables that can be associated with injuries in the hamstring muscles of professional soccer players. However, the results are conflicting and could be related to the different cutoff points for the categorization of athletes in asymmetric or symmetric. Based on these conflicting results, the present study aims to: i) Identify the cutoff points of lateral asymmetry (LA) of the 95% confidence interval for the peak torque in soccer players, evaluated by the isokinetic test, taking into consideration the mean population value; ii) Compare LA between 15% cutoff point proposed in literature and the upper limit of 95% confidence interval (UP) of the study population. Sixty-four professional soccer players performed five knee flexion and extension repetitions at rate of 60°/s, with a one-minute interval. To determine the cutoff point for strength asymmetries, the UP was used, and for the purpose of diagnostic concordance of information among the different values, the McNemar’s χ² test was applied. The proportion between symmetric and asymmetric athletes was not different from the 15% cutoff point and the general population, both for knee flexors (χ² = 0.5, p = 0.250) and the knee extensors (χ² = 2.0, p = 0.125). It was concluded that the cutoff point of 15% referenced in literature for the general population provides similar diagnostic information for the classification of professional soccer players.

Cutoff Values for Strength Asymmetry Classification on Soccer Players

“…The results of the present study corroborate Impellizzeri, 15 Bell 10 and Araújo, 9 since through McNemar χ² test there was sufficient evidence to confirm the hypothesis, that the proportion of symmetric and asymmetric athletes would be statistically different between the 15% cut-off value and cut-off value based on the mean of the professional soccer players population. Reinforcing the results of the present study, Impellizzeri 15 affirm that tests with different coordinating and motor demands may result in different strength asymmetry values.…”

“…5 For professional soccer athletes, higher values of strength asymmetry may increase noncontact injury risks 6 along with a decrease in performance. 7 To set up normative values for strength asymmetry classification coaches should consider the selected outcome, 8 test or methodological approach 9 and sports characteristics. 10 Among soccer players isokinetic dynamometry has been used to measure lower limbs strength asymmetry 11,12 however, isokinetic assessment characteristics like knee angular velocity do not reflect lower limbs functional aspects of soccer.…”

“…16 Furthermore, the application of an arbitrary cut-off value might bias the sensitivity and specificity of the result. 8,9 With two force plates to assess CMJ performance, peak force and impulse can be measured separately for the left and right leg simultaneously 17 allowing robust asymmetry analysis. For example, Menzel 14 applied the lateral symmetry index (LSI) propose by Clark 18 on a cohort of 46 male professional soccer player and reported LSI of (5.58% ± 4.55) for peak force and LSI of (20.66% ± 14.60) for impulse.…”

“…8,14 Even though, LSI of 15% has been used as cutoff values to classify soccer athlete's asymmetry on CMJ regardless the chosen variable. 14,15 The same arbitrary cutoff values (LSI = 15%) applied for peak force and impulse may lead to misguided training strategies, in this regard, Araújo 9 employed the Upper Limit Value (ULV) of the 95% confidence interval from the sample mean as the cutoff value. This approach, take into consideration the characteristics inherent of the participants and may change the distribution of soccer athletes classified as asymmetric.…”

Valor De Corte Para Classificação Da Assimetria De Força Em Jogadores De Futebol

“…Para superar essas limitações, o teste de salto de contramovimento (CMJ) tem sido utilizado para avaliar a assimetria de força nos membros inferiores de jogadores de futebol 14,15 , visto que o desempenho no CMJ apresenta uma correlação forte e positiva (r= 0,72, r= 0,60) com o tempo de sprint de 10 m e 30 m, respectivamente 16 . Além disso, a aplicação de um valor de corte arbitrário pode enviesar a sensibilidade e especificidade do resultado 8,9 .…”