The acute passive stretching does not affect the maximal muscular activity of the hamstrings
AbstractThe acute stretching may influence the force production in different tasks and sports performances. The aim of this study was to investigate the influence of acute passive stretch on the electrical activity of the biceps femoris (BF) and hamstring muscle (HS) strength. Fourteen young adults, sedentary took part of this study. The subjects were asked to produce the maximal isometric contractions before and after a passive stretching protocol. The stretching protocol consisted of three attempts at 60 seconds and resting 15 seconds between each attempt. The subjects were analyzed using the following techniques: maximal isometric force (MIF), integrated electromyography (IEMG) and median frequency (Fmed) of the EMG signal of the BF before and after stretching. We performed the MIF, IEMG and Fmed of the EMG signal under these conditions and compared using a paired Student t test. The MIF of the biceps femoris (14.1 ± 4.9 e 13.1 ± 4.5 Kgf, respectively, p = .12), IEMG (208.4 ± 89.9 e 189.3 ± 75 V.s, respectively, p = .059), and FMed (22.7 ± 4 e 23.4 ± 5.5 Hz, respectively, p = .52) showed no significant differences between conditions before and after stretching. The acute effects of passive stretching did not significantly influence the pattern of electrical activation of the BF and the maximal isometric force produced by the HS.
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