The purpose of this study was to investigate the effect of Abdominal Enhancement (AE) on the muscle activation of vastus medialis obliquus (VMO), vastus lateralis (VL) and rectus femoris (RF) muscle activation levels during eccentric, isometric and concentric phases of single leg raise (SLR), single leg wall squat (SLWS) and forward lunge (FL) exercises. Sixteen healthy individuals (Age: 24.6 +/- 1.7 years) were included in the study. Internal Obliques/Transversus Abdominis (IO/TA), VMO, RF and VL muscle activation levels were measured by surface EMG during the exercises in two conditions: with and without AE. The abdominal drawing-in technique was used for AE. Repeated-measures analysis of variance was performed for statistical analysis. With AE, the average of IOTA muscle activation level was 28.9%. VMO and VL muscle activation levels were significantly greater with AE during SLR (p = .02), SLWS (p < .001) and FL (VMO, p = .008, VL, p = .04) exercises. The effect of AE on VMO muscle activation level ranged from 2.5% to 5% (Effect size range: 0.54 to 0.91) and VL muscle activation level ranged from 2.1% to 5.5% (Effect size range: 0.35-1.24). RF muscle activation level did not change with AE (p > .05). The results of this study showed that AE increased VMO and VL muscle activities during SLR, SLWS and FL exercises but the corresponding changes were small. Even if this is not enough for muscle strengthening, exercises with AE may be used to enhance knee joint stability while controlling lumbopelvic stability.