Comparisons of Trunk Muscle Activity During Arm Lift in Prone and Standing Positions With and Without Abdominal Drawing-in Maneuver

The aim of this study is to compare the effect of abdominal drawing-in maneuver (ADIM) on lower trapezius (LT), serratus anterior (SA), and erector spinae (ES) muscle activity during arm lifts in prone and standing positions. Twenty healthy subjects were recruited, and NoraxonTeleMyo 2400T was used to collect electromyographic signals from the LT, SA, and ES muscles. A two-way repeated analysis of variance (ANOVA) used a significance level of .05. If a significant interaction was found, pairwise comparisons were performed with a Bonferroni adjustment (.05/4=.013). The results of the study were as follows: 1) In LT, no significant ADIM by position interaction was found ($F_{1,19}$=.356, p=.558). There was a significant main effect for ADIM. LT muscle activity with ADIM was significantly greater compared with muscle activity without ADIM ($F_{1,19}$=82.863, p<.001). There was also a significant main effect for position. LT muscle activity in the prone position was greater compared with muscle activity in the standing position ($F_{1,19}$=116.401, p<.001). 2) In SA, significant ADIM by position interaction was found ($F_{1,19}$=8.687, p=.008). There were significant differences in all pairwise comparisons. The greatest SA muscle activity was observed in the standing position with ADIM. 3) In ES, significant ADIM by position interaction was found ($F_{1,19}$=122.473, p<.001). The lowest ES muscle activity was elicited in the standing position with ADIM. Based on these results, ADIM is advocated in the prone position to increase LT muscle activity. In addition, it is concluded that arm lifts in the standing position with ADIM offer the most favorable combination for reducing ES muscle activity and increasing SA muscle activity.