Comparison of changes in the contraction of the lateral abdominal muscles between the abdominal drawing-in maneuver and breathe held at the maximum expiratory level.

The abdominal drawing-in maneuver (ADIM) is commonly used as a fundamental component of lumbar stabilization training programs. One potential limitation of lumbar stabilization programs is that it can be difficult and time consuming to train people to perform the ADIM. The transverse abdominis (TrA), internal oblique (IO), and external oblique (EO) muscles are the most powerful muscles involved in expiration. However, little is known about the differences in the recruitment of the abdominal muscles between the ADIM and breathe held at maximum expiratory level (maximum expiration). The thickness of the TrA and IO muscles was measured by ultrasound imaging, and the activity of the EO muscle was measured by electromyography (EMG) in 33 healthy male performing the ADIM and maximum expiration. Maximum expiration produced a significant increase in the thickness of the TrA and IO muscles compared to the ADIM (p < 0.001). The EMG activity of the EO muscle was significantly higher during maximum expiration than during the ADIM (p < 0.001). The intensity of the EMG activity of the EO muscle was approximately 30% of the maximal voluntary contraction during maximum expiration. Thus, maximum expiration may be an effective method for training of co-activation of the lateral abdominal muscles.