Abstract
[Purpose] We investigated the characteristics of the deltoid muscle (anterior, middle and posterior fibers) using surface electromyography. [Subjects] The subjects were 16 healthy young males, average age 22.9 ± 2.9. [Method] At maximum isometric voluntary contraction (MVC), 50% MVC and 25% MVC we obtained integrated electromyograms (IEMG) and median power frequencies (MdPF), and compared them. [Results] We found significant decreases in IEMG with decrease in %MVC for all of the muscle fibers. For the anterior and middle fibers, we found significant increases in MdPF with decrease in %MVC; however, no significant differences were found for the anterior fibers among the muscular contractions. [Conclusion] Since the deltoid muscle has a unique relationship with MdPF, we conjecture that it cannot be seen as having a role as an `outer muscle' but rather has activities that are both continuous and preparatory at the same time.
