The present study aimed to investigate the level of muscular activities such as postural mainte nance and change, and body weight transfer during daily physical activities, through electromyogram (EMG) recordings. In each of 27 prescribed movements, EMGs of a total of 8 muscles located in the upper arms, trunk and lower limbs were recorded in 12 young adult men and women using a portable surface electromyograph apparatus. The percentage of integrated EMG per time (mEMG) to that during isometric maximum voluntary contraction (MVC) was calculated as an index by assessing the muscular activity level in each of the prescribed movements. In most of the prescribed movements, the muscular activity level of every muscle corresponded to about 2030% of MVC, and tended to be higher in women than men. However, some actions induced an activity level of 40% and more of MVC in the soleus muscle. The activity levels of the lower limb muscles in going up and down stairs and a slope at a fast speed, and jogging were higher compared to other prescribed movements. Thus, the results indicate that body weight transfer actions in daily life raise the activities of the lower limb muscles to a level sufficient for maintaining and increasing their function.

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In brief: Aerobic dancing is a popular fitness activity in Japan, primarily among young women. To identify and characterize the injuries associated with aerobic dance, 161 instructors and 800 students from 13 Japanese fitness facilities were surveyed. Results showed an injury rate of 72.4% for instructors and 22.8% for students. The lower leg and foot were the most common injury sites for instructors and students, respectively. Though these results seem to indicate that aerobic dance is hazardous, the number of injuries per 100 hours of participation was only 0.17 for instructors and 0.15 for students. Most aerobic dance injuries seem to be caused by overuse; thus, moderating the frequency and duration of participation and individualizing programs could reduce the number of injuries that occur.

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