Selective recruitment of the thoracic erector spinae during prone trunk-extension exercise.

Abstract

This study examined the effect of modified prone trunk-extension (PTE) exercises on selective activity of the thoracic erector spinae. Thirty-nine healthy subjects performed four modified PTE exercises, involving location of the edge of the table (iliac crests [IC] vs. xiphoid process [XP]) and the degree of trunk extension (horizontal vs. hyperextension). Electromyography signals were collected bilaterally from the longissimus thoracis (LT), iliocostalis thoracis (ICT), and iliocostalis lumborum (ICL). Normalized LT:ICL and ICT:ICL ratios were calculated. The data were analyzed using a repeated measures two-way analysis of variance. The LT:ICL and ICT:ICL ratios were significantly higher under the XP than the IC condition (p < 0.05); however, the degree of trunk extension did not affect the ratio (p > 0.05). Activity in the lumbar erector spinae and left ICT muscles was greater when subjects were in the hyperextended position than in the horizontal position. Moreover, activity in the thoracic erector spinae was greater when the table edge was aligned with the IC compared with the XP (p < 0.05). Our findings suggest that PTE exercise with the XP aligned with the table edge increased the selective activation of the thoracic erector spinae muscles.