A influência da profundidade de agachamento no desempenho e em parâmetros biomecânicos do salto com contra movimento

Rodrigo Ghedini Gheller,Bruno Monteiro De Moura,Luis Antonio Pereira De Lima,Juliano Dal Pupo,Saray Giovana Dos Santos

doi:10.5007/1980-0037.2014v16n6p658

Abstract

The aim of this study was to analyze the effect of different squat depths in the performance and biomechanical parameters at counter movement jump (CMJ). Twenty-two male volleyball or basketball players volunteered to participate in this study and all were currently competing at the college level. The CMJ was performed in three different conditions: 1) with relative knee flexion at the end of counter movement phase smaller than 90° ( 90°), and; 3) preferred position (PREF). During the CMJ, kinematic, kinetic, and electromyography parameters were assessed. ANOVA for repeated measures with post-hoc Bonferroni´s test was used for variables comparison, with a significance level set at p≤0.05. The higher performance was on PREF and 90°. Average and peak power, as well as absolute and normalized peak forces, were higher in >90° CMJ. The peak velocity of CG and angular velocities of hip and knee were higher in the 90°. Recuts femoris and biceps femoris did not show difference in any jump phases. In conclusion, the knee flexion interferes the performance and the biomechanical variables at the CMJ. The highest jumps were got at a deeper squat, so this technique could be used for athletes in order to optimize the vertical jump performance in the training and competitions.

Highlights

Vertical jump has been one of the tests most used by coaches and researchers to assess the muscle power of the lower limbs of athletes from different sport modalities[1,2]
The results showed that the heights obtained in jumps performed with maximum knee flexion preferred or less than 90° are larger than those obtained in lower squat depth (>90°)
According to Moran and Wallace[16], countermovement jumps (CMJ) performance improves 17% when the jump is performed with knee flexion of 90° compared to 70° (0° represents full extension)

Summary

Introduction

Vertical jump has been one of the tests most used by coaches and researchers to assess the muscle power of the lower limbs of athletes from different sport modalities[1,2]. In the case of vertical jump, the modulation of the level of knee flexion, in other words, the magnitude of squat preceding jump and hip movement change the length of thigh muscles. These segmental movements will reflect in changes in the length-tension relationship and in the generation of impulse[4]. According to the theory of cross bridges[6], there seems to be an “optimum” muscle length for force production. When the muscle fibers are much shortened or elongated reductions in force production may be observed because there is less interaction between cross bridges[6]

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Conclusion