Impacto de diferentes intensidades no treinamento de flexibilidade sobre as propriedades biomecânicas, sensoriais e estruturais da unidade músculo-tendão

Abstract

Flexibility is an important component of physical performance, being decisive in the rehabilitation process and for good performance in various sports. Unlike other physical capacities, little is known about the impact of manipulating different training intensities, and their forms of control, to enhance biomechanical, sensory and structural adaptations to training. Thus, the present study aimed to: compare the effect of 12 weeks of flexibility training of the hamstring muscles at low and high stretching intensities on maximum range of motion (ROMmax), maximum torque (torquemax), ROM at the first perception of stretching (FPS), stiffness, energy and fascicle length and compare the effect of quantitative and qualitative control of the same intensities on the same variables mentioned. The study was approved by the Research Ethics Committee of the Federal University of Minas Gerais. The study included 39 male individuals, aged between 18 and 35 years, with no history of flexibility or strength training for at least 6 months. The volunteers were divided into three groups: Control, Low Intensity (ROMFPS) and High Intensity (ROM85%). All volunteers went through an initial assesment of flexibility levels and fascicle length (baseline) and were allocated in a balanced way in their respective groups (balance made by age and physical activity). After this division, the training groups performed 6 series of 30s of stretching of the hamstring muscles, in the intensities ROMFPS or ROM85%, 3 times a week, for 12 weeks, in the Flexmachine device, with one of the lower limb controlling the intensity in a quantitative way and the other in a qualitative way. Every three weeks, the volunteers were reassessed as to the flexibility measures to adjust the absolute intensity. At the end of 12 weeks, all volunteers were reassessed for flexibility and fascicle length. ANCOVA showed that, in the post-test, the variables ROMmax, torquemax, ROMFPS and fascicle length were greater in the training groups compared to the Control group and energy was smaller in the training groups compared to the Control group. In addition, ROMmax and torquemax were higher in the High Intensity group compared to the Low Intensity group. Only for the ROMFPS the qualitative control showed higher values than the quantitative control, but with a trivial effect size (0.19). The stiffness did not change after the intervention. In this way, we can conclude that the intensity modulates the adaptations of the flexibility training, with a high intensity leading to values of flexibility after intervention greater than a low intensity. In addition, controlling the intensity in a quantitative way led to the same adaptations as controlling it in a qualitative way.