2004 年 17 巻 p. 57-68
The purpose of this study was to investigate muscle damage and reinforcement by electrical muscle stimulation (EMS).
The first experiment involved two groups of athletes (Group 1 and Group 2) and one group of healthy volunteers who did not engage in daily exercises (Group 3 served as the control). The subjects’ triceps brachii muscles were stimulated electrically (EMS, subject&RSQUO;s variable tolerance: Group 1) and mechanically (concentric- and eccentric-resistance training of 60% MVC, RT: Group 2). For one of the subjects with EMS, the serum CPK levels of 3 and 4 days after the stimulation were approximately six times as high as that before the stimulation. The serum CPK levels of other subjects with EMS increased to twice or less of those before the stimulation. The serum CPK levels of subjects with RT did not change. The levels showed significant difference between subjects with EMS and RT, 2 and 5 days after the stimulation (Mann-Whitney test, p<0.05).
In the second experiment, the quadriceps femoris muscles were stimulated. EMS generating a force of 60% MVC was applied to each subject in Group 4 for 30 minutes every other day for a week. RT of 60% MVC was applied to each subject in Group 5. The subject did 30 trials, with 60 s resting time between every 10 trials, every other day for a week. The serum CPK levels of the subjects with EMS increased, but the increase rate varied with subjects. One of the subjects had more than six times as high serum CPK levels as that before the stimulation. Another subject had only one and half times as high serum CPK levels as that before the stimulation. There were significant changes with time after the stimulation (Friedman test, p<0.05). However, there were no significant differences between subjects with EMS and the control. For subjects with RT, the serum CPK levels increased slightly but there were no significant changes with time after the stimulation (p>0.05).
In the third experiment, EMS was applied to the triceps brachii muscles of Group 1 and Group 3 for eight weeks. The non-athletes with EMS showed 30% increase of the maximum voluntary contractile force and they showed 38-54% improvement of endurance. The maximum voluntary contractile force of athletes with EMS did not change but the endurance showed 59% improvement. However the maximum voluntary contractile force of athletes without EMS decreased and the endurance did not change.
In conclusion, we suggest that EMS could cause more severe muscle damage than concentric-, eccentric-resistance training. EMS reinforced the muscles of both athletes and non-athletes. Moreover, EMS showed stronger effects on non-athletes compared with the athletes.