Efeito agudo do alongamento passivo-estático dos extensores do joelho na força de reação vertical do solo e na técnica de movimento durante saltos verticais

Abstract

Flexibility training is often prescribed before physical activities, although there has already been shown that maximal strength can decrease right after stretch exercises. Studies which investigated the influence of acute stretching exercises on vertical jump performance reported non-conclusive results. The aim of this study was to analyse theacute effects of knee extensors stretching in the ground reaction force and movement technique during vertical jumps. Thirty male Physical Education students (age: 24,6 ± 4,4 years; body mass: 71,2 ± 8,2 kg; height: 175,3 ± 7,2 cm) performed vertical jumps in two different sessions: before and after a knee extensors stretching session (experimental protocol) and before and after a 20 minutes rest period (control protocol). The vertical jump techniques were Squat Jump (SJ), Countermovement Jump (CMJ) and Drop Jump (DJ). No significant difference was found in peak of force, rate of force development, vertical velocity of center of gravity, joint angles and maximal angular velocities during the SJ and CMJ. During the DJ a significant increase in ground contact time (before: 211 ± 20 ms; after: 223 ± 25 ms), greater dorsiflexion range of motion (before: 94,3 ± 5,7º; after: 92,8 ± 4,0º) and knee flexion range of motion (before: 115,7 ± 6,9º; after: 113,8 ± 7,2º) was observed. After stretching, a significant increase was found in knee maximal angular velocities during the eccentric (before: 363,4 ± 81,6º/s; after: 380,4 ± 83,3º/s) and concentric (before: 526,5 ± 62,9º/s; after: 541,8 ± 65,8º/s) phases. However, no change in the vertical velocity at take off was observed, resulting in the same performance. The results suggest that a flexibility training session with the applied load did not induce changes in performance during the three jumping techniques.