Draw-in is a promising intervention for regaining isolated control of the transverse abdominis (TrA). Exercises to stimulate isolated contractions are needed; however, the appropriate methods are unclear. The objec-tives of this study were to examine how the muscle activity and muscle activity ratio of abdominal muscles change with various verbal instruc-tions and to determine the onset of the abdominal muscles during draw-in. The participants were 21 healthy men. TrA electromyography was performed using fine-wire electrodes, and the internal oblique (IO), ex-ternal oblique (EO), and rectus abdominis (RA) were determined using surface electrodes. The participants performed seven abdominal exer-cises according to verbal instructions and isolated voluntary contrac-tion of the TrA for more than 5 sec. The TrA showed higher activity in bracing. IO and EO activities were highest in bracing, whereas RA showed the highest activity in maximum bracing. TrA/IO and TrA/EO were not significantly different between conditions. The results of the onset activity analysis of the abdominal muscles during the draw-in maneuver showed that the TrA was significantly earlier than the other muscles. The activity ratios of TrA to IO and EO were highly individual-ized and did not differ according to the verbal instruction. Maximum draw-in showed more significant IO activity, and bracing showed co-contraction of the superficial and deep abdominal muscles. During draw-in, the TrA initiated the earliest activity among the abdominal muscles and then isolated activity for 1.1 sec.
ASJC Scopus subject areas