Electromyographical study of the pectoralis major (sternocostal part) and deltoid muscles (middle fibers) in volleyball sequential actions.

UNLABELLED: The Pectoralis Major muscles (Sternocostal part) and Deltoid (middle fibers) had been studied using electromyography in 8 male individuals, who practice volleyball, youth category, (age between 15 and 17 average +/- 16,25 years old), right-handed, those involved in volleyball for about one year. The objective was to analyze the potential of action of these muscles engaged in the volleyball movements: service, spike, pass, set and blocking with and without ball. The work was developed in the Electromyography and Biomechanics of Posture Laboratory(Physical Education Faculty--State University of Campinas--UNICAMP). To caption the muscle action potential, surface electrodes were set with conductive gel and fixed on the skin, in the center of the muscles. It was used an electromyography Lynx with 6 channels. The apparatus calibration was 2.500 microV, 1199.760 Hz. The low and high pass filter was set at 600-10 Hz. The sequential experiments without ball were performed for 10 seconds, and the sequential experiments with ball in 12 seconds. RESULTS: The Pectoralis Major muscle (Sternocostal part) revealed active during the basic movements of volleyball, (service and spike) in all movements of the extension of the arm, as well as the arm abduction during the pass movement. The Deltoid muscle (middle fibers), in spite of being primary in the abduction, showed the potential of action in all movements practiced in volleyball, however, they were more intense, in the spike and block actions. It is interesting to observe, that the general average and the standard deviation of the Deltoid muscle (middle fibers), were higher in the sequential movements executed without ball.

Electromyography study of the hamstring muscles while exercising on a bicycle and the Roman table.

During the past few years electromyography has been used a lot in developing research in the science of sports; it has made a great contribution to what is called muscle biomechanics. The Biceps Femoris (long head), Semitendinosus and Semimembranosus bi-articulated muscles make up the muscle group called Hamstring; they act in articulated movements of the hip (extensors) and in articulated movement of the knee (flexors). In this sense, the Hamstring have been the object of many investigations, precisely because they are bi-articulated. All the Hamstring pass through the knee's articulation producing flexing as well as leg rotation and their effectiveness as hip extensors depends on the positioning of the knee's articulation, Hamill, Knutzen (1999). The knee's flexor muscles (Biceps Femoris - long head, Semimembranosus and Semitendinosus) were studied using electromyography with surface electrodes in 10 male subjects between 19 and 25 years old. They included five who used a stationary bicycle and five doing activities on the roman table. Knee flexing on the roman table (concentric and eccentric action) was performed in the ventral decubitus position. Surface electrodes with electro-conductive gel were used to register the action potentials; they we fixed on the skin covering the areas of interest to this study in each ventral muscle. For each type of experiment, a laboratory with all the apparatus needed for the study was created. Results, expressed in RMS, demonstrate that on the bicycle the Biceps Femoris (long head) showed an RMS of 31.81 (+/- 10.15), the Semimembranosus 65.15 (+/- 18.76) and the Semitendinosus 44.33 (+/- 44.33 (+/- 22.34). In flexing the knee the values were 188.54 (+/- 46.10) for the Biceps Femoris (long head) muscle, 480.00 (+/- 130.13) for the Semimembranosus and 303.50 (+/- 63.31) for the Semitendinosus. The verified data demonstrated greater values for the bicycle activities. The Semimembranosus muscle showed greater values in RMS for all activities studied, followed by the Semitendinosus and Biceps Femoris (long head).