Efeito da velocidade de alongamento na rigidez relativizada pela área de secção transversa muscular de indivíduos pouco flexíveis e muito flexíveis

Abstract

The aim of the present study was to investigate the effect of two stretching velocities on passive stiffness normalized by cross sectional area of hamstrings muscles in subjects with different levels of flexibility. Eighteen men and eighteen women were distributed in two groups, according to their joint range of motion determined by increased electromyography activity (ROMemg). The subjects with either less than 90° or more than 95° of passive knee extension on Flexmachine were allocated in Low flexibility group or High flexibility group, respectively. The tests followed four stages: 1st) familiarization; 2nd) ROMemg and passive torque measurement in velocity 5°/s; 3rd) ROMemg and passive torque measurement in velocity 50°/s; e 4th) cross sectional area (CSA) of hamstrings muscles measurement. The ROMemg and passive torquewere measured by Flexmachine and the CSA were measured by Magnetic resonance. Both lower limbs were assessed, reaching a total of 72 samples. Passive stress was calculated dividing passive torque by CSA. Normalized stiffness was calculated in the third portion of passive stress ROMemg curve. The results demonstrated an ICC = 0,98 and SEM = 0,59cm² for CSA, and an ICC = 0,91 to 0,98 and SEM = 0,11 to 0,26N.m.cm-2/° for normalized stiffness in all groups and all velocities. In comparison between the stretch velocity 50°/s to 5°/s, the normalizedstiffness was not significantly different. Normalized stiffness was greater for the Low flexibility group than for the High flexibility group (p < 0,05). Thus, the procedures used to calculate CSA and normalized stiffness presented high reliability; the increase of stretch velocity of 5°/s to 50°/s did not alter significantly the normalized stiffness in both groups; and the normalized stiffness was statistically different according to the subjects flexibility level in both velocities.