Background : The one-leg standing (OLS) test is a method of evaluating trunk stability. The transverse abdominis (TrA) is an important muscle that contributes to trunk stability during functional movement through abdominal draw-in maneuver (ADIM). The gluteus medius (Gmed) is also important for functional movement and for stability of the hip joints in the muscles that prevent lateral deviation of the trunk in OLS. During ADIM, the Gmed, TrA and internal oblique (IO) muscles are activated. It has been reported that ADIM is an effective method of training co-activation of these muscles for trunk stability. To our knowledge, there is no study that applies ADIM to OLS. Objectives : The purpose of this study was to investigate TrA/IO and Gmed activity, as well as lateral trunk deviation, during OLS with ADIM. Methods : Fourteen healthy male subjects were recruited. Activity of the Gmed and TrA/IO muscles was measured for all subjects in OLS. Muscle activity of all subjects was then re-measured in OLS with ADIM. Muscle activity was measured using surface EMG, and lateral deviation was measured using Image J. The differences in outcome measures in OLS and in OLS with ADIM were analyzed using a paired t-test. Results : Compared to OLS, OLS with ADIM showed significantly increased activity in the TrA/IO (p < 0.001) and in the Gmed (p < 0.001). Compared to OLS, OLS with ADIM also showed significant decreases in trunk (p = 0.001) and pelvic displacement (p = 0.003). Conclusions : These results show that TrA/IO and Gmed activities were significantly higher in OLS with ADIM than in OLS without ADIM. Additionally, trunk and pelvic displacement were significantly lower in OLS with ADIM than in OLS on its own. OLS with ADIM may therefore be utilized as a training method for co-contraction of TrA/IO and Gmed for trunk stability.