Adaptacoes neuromusculares ao treino da forca Com especial referencia para as adaptacoes do padrao electromiografico induzidas pelo treino e destreino

Abstract

The purpose of this study was to investigate the effects of power training with stretch-shortening cycle (SSC) exercises, on the electromyographic (EMG) pattern of the leg extensor muscles, during a sequential period of training - detaining - training. Thirteen active males participated in a eight training weeks process, followed by a detaining period of four weeks and a new training period of four weeks. The subjects performed tree to four sessions per week, using drop jumps (DJ) as the basic exercise. Beside the initial evaluation, the subjects where tested every four weeks. Testing procedures included Squat Jumps (SJ), Counter-Movement Jumps (CMJ), a battery of DJ (25 to 0 cm) and an isometric leg press movement. The signals of the vertical component of the ground reactions forces (Fz), the angular displacement of the knee and ankle joints, together with the EMG recordings of the vastus medialis (VM), biceps femoris (BF), gastrocnemius (GE) and soleos(SOL) muscles, were stored in a computer for further analysis. The results showed that when quality of the training stimulus where controlled, the changes on the EMG pattern showed an increased on the IEMG of the Late EMG Response phase. The increase of the activation during the Reflex Induced Activation phase, reflects the contribution of the stretch reflex system to the neural input to the muscle. The positive changes on the Reflex Induced Activation phase were correlated with the changes on the total contact time with the ground and with the height to rise of the centre of gravity. The force-length relationship of the triceps surah muscles, showed that the training process induced adaptations on the elastic behaviour of the muscle tendon-complex, with a positive energy balance between the eccentric and concentric phases of the jump. The decrease on the length range suggested that, al least, part of the eccentric action may have taken place within the limits of the short range elastic stiffness. The changes on the slope of the stretch phase, also suggested that muscle stiffness increased as an adaptation due to a better neural controlAvailable from Fundacao para a Ciencia e a Tecnologia, Servico de Informacao e Documentacao, Av. D. Carlos I, 126, 1200 Lisboa / FCT - Fundação para o Ciência e a TecnologiaSIGLEPTPortuga