Getting up from a Side-Lying Position at Different Angles of the Shoulder Joint: Electromyography of Muscles Surrounding the Shoulder Joint and Abdominal Muscles

Abstract

[Purpose] The purpose of this study was to examine the relationship between the positions of the shoulder joint that enable easy getting-up from a side-lying position, and the muscle activity that occurs at the same time. [Subjects] Thirty (25.8 ± 4.3 years) and ten (26.6 ± 4.9 years) healthy adult men participated in this study. [Methods] Research on positions of the shoulder joint that enabled easy getting-up was conducted, while getting up from right side-lying with support from the right elbow, with the shoulder bent at the five different angles of 10 degrees, 30 degrees, 60 degrees, 90 degrees, and 120 degrees. Then the most favorable posture for getting-up was selected and statistically verified by χ². Next, to investigate the correlation with muscular dynamics, surface electrodes were applied to the posterior fibers of the deltoid, the triceps muscle, the infraspinatus muscle and the rectus abdominal muscle, and rising-up from a right side-lying position to the right hand palm support position was performed. The independent χ² test and the Spearman rank-difference correlation were performed for the statistical evaluation. [Results] For ease of getting up, no statistically significant differences were found, but there was a strong tendency towards easiness in the 60 and 90 degree shoulder angle positions. For muscle action, significant differences were found in the posterior fibers of the deltoid and the rectus abdominis muscle, depending on the angle set. The muscle activity decreased as the angle increased. [Conclusion] In getting up from a side-lying position, the relation between angles at which it was subjectively easy to get up and muscle activity of the muscles surrounding the shoulder joint and abdominal muscles was unclear, but the possibility that weight transfer exerted an influence was suggested.