Alterações morfo-funcionais do músculo quadríceps femoral de humanos lesado pelo exercício excêntrico.
Serrão, Fábio Viadanna
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studies about muscle regeneration and injury used invasive methods in animals. Although the muscle regeneration process in many mammals is similar to the one found in humans, it is necessary to improve the application of non-invasive procedures used in the evaluation of the muscle regeneration and injury in humans. Non-invasive techniques such as surface electromyography, isokinetic dynamometry and nuclear magnetic resonance (NMR) for imaging have been used in studies in humans for the evaluation of the skeletal muscle. However, studies in which all these procedures are used together, allowing a more detailed evaluation of the muscle morphology and function, are rare.Thus, the aim of this study was to evaluate the behaviour of the medium maximal isometric torque, the electrical activity and the muscle pain before the injury, during the 7 days after the injury and also between the 21st and 30th days after the injury, when the muscle has already regenerated. For this, a injury was induced in the quadriceps femoris muscle through intense eccentric exercise. To confirm if the model utilized was effective to produce the muscle injury, the plasma activity of the creatine kinase (CK) was also evaluated and the NMR for imaging of the quadriceps femoris muscle was realized. Ten university student volunteers (21,9±1,5), sedentary and without musculoskeletal dysfunction in the lower right limb participated in this study. The extensor medium maximal isometric torque was evaluated through maximal isometric contraction with the knee joint at 90º of flexion, in the isokinetic dynamometer (Biodex Multi-joint System 2 da BIODEX MEDICAL SYSTEM Inc). The electrical activity (Root Mean Square-RMS and Median Frequency) of the vastus medialis oblique (VMO), vastus lateralis (VL) and rectus femoris (RF) muscles was analysed simultaneously to mensuration of the isometric torque, utilizing a Digital Analogue Conversor A/D (LYNX) and single differential active electrodes of surface (LYNX). The quantitative and qualitative analysis of the pain were realized by Visual Analogue Scale (VAS) and by Brazilian Version of Short-Form McGill Pain Questionnaire. The activity of CK was measured utilizing the Kit CK-NAC UV unitest (Wiener lab) and the NMR was realized in the ToRM 0.5 equipment. For the induction of quadriceps femoris muscle injury, the volunteers were submitted to 4 series of 15 maximal eccentric isokinetic contractions, at angle velocity 5º.s-1. The results of this study demonstrated that the medium maximal isometric torque reduced significantly until the 4th day after the eccentric exercise (immediately after and 1st - 4th days after, p<0.01; 4th day after, p<0.05). The RMS of the VMO, VL and RF muscles reduced significantly the 2nd day after (p<0.01, p<0.01 e p<0.05, respectively). However, the RMS of the VL and RF muscles between the 21st and 30th days was significantly greater than before the exercise (p<0.01). There wasn t alteration in the median frequency after tthe eccentric exercise (VMO, p= 0.90; VL, p= 0.55 e RF, p= 0.89). The intensity of pain was greater until the 3rd day, and the peak occurred in the 2nd day after (p<0.01). The McGill Pain Questionnaire demonstrated that the word heavy was the most used to describe the pain after the induced injury by eccentric exercise. The peak of activity of the CK occurred in the 2nd day after the eccentric exercise(p<0.05). The evaluation by NMR demonstrated that the greatest extension of injury occurred in the 2nd and 7th days after, and some voluteers still showed injury sign between the 21st and 30th days. In conclusion, the eccentric exercise reduced the medium maximal isometric torque, increased the activity of the CK, changed the RMS and resulted in pain, which were gradually recovered in one week, despite the presence of muscle injury.