Comparison of Muscle Activity of the Erector Spinae according to Thoracic Spine Extension Mobility

Abstract

Background During trunk extension, the thoracic extensor is decreased and the lumbar extensor is excessively activated, which is a factor inducing low back pain. Purpose The purpose of this study is to compare the muscle activity of the erector spinae of the thoracis and the lumborum during trunk extension according to the thoracic spine extension mobility. Study design Cross-sectional study. Methods 94 participants measured thoracic spine extension mobility and assigned low mobility group (n=31) and high mobility group (n=31) according to the mean and standard deviation. The muscle activity of the erector spinae was measured when participants maintained their trunk extension at the prone position. An independent <italic>t</italic>-test was used to compare the muscle activity between the low and high mobility groups. Results The muscle activity of longissimus thoracis, the ratio of longissimus thoracis:iliocostalis lumborum pars lumborum, and iliocostalis lumborum pars thoracis:iliocostalis lumborum pars lumborum was significantly different between the high and low mobility group (<italic>p</italic>&lt;0.05). Conclusions The muscle activity of longissimus thoracis and ratio between the thoracis and the lumborum of the erector spinae are reduced in the low mobility group than the high mobility group during trunk extension.