Characteristics Of EMG Parameter Change And Its Mechanism During Isotonic And Isometric Exercises For Athletes In Different Events

Objective :The purpose of this study was to investigate characteristics of EMG parameter change during isotonic and isometric exercises for athletes in different events and discuss the relationship of EMG parameter change between Athletes and Rowers during the exercise.Methods:27 male subjects participated in the study. The subjects were divided into 2 teams. One is 14 rowing athletes , others is jumping or short-distant running athletes(events of speed-power). Two exercising styles were designed in the study, one is isotonic exercises, which loaded 2/3MVC (maximal voluntary contraction), and the other is isometric exercise(performed as explosively as possible) loaded the maximal voluntary contraction .The frequency of the isometric exercise is once in 3 seconds. The subjects performed isometric and isotonic exercises until they refused because of fatigueResults:(1) When work loads of 2/3MVC were sustained to fatigue over the isotonic exercise period ,IEMG and E/T ratio was increased(P <0.05)and the center frequency of the power spectra(FC) progressively decreased (P <0.01).In contrast, IEMG was decreased during the isometric exercise (P >0.05) (2)Loaded isotonic exercise :Compare with the rowing athletes ,the center frequency of athletes was decreased more quickly. The E/T ratio indicated Significantly difference between the different events(P<0.05) (3)Loaded isometric exercise :Results indicate that there is much difference in the Maximal Contraction Time (MCT) of different events(P<0.01).Compare with the rowing athletes , MCT of athletes was less.Conclusion: IEMG was increased because central nerve system must recruit new motor unit to sustain the work loaded over the isotonic exercise period . IEMG was decreased because of fatigue in central nerve system over the isometric exercise period. It can be shown that rowing athletes'muscle has excellent strength endurance .we can investigate the relationship of EMG parameter change between Athletes and Rowers during the exercise by the record of E/T radio. There is a direct correlation on the MCT and speed of sport performance. It can be shown that athletes'muscle has excellent speed by the index of MCT.