Figure 1. Schematic illustrations of the asymmetric abdominal exercises. (a) sit-up twist (SUT) in the frontal plane (left) and sagittal plane (right); (b) oblique leg raise (OLR) in the frontal plane (left) and sagittal plane (right); (c) side bridge (SB) in the frontal plane; (d) side bridge roll out with the elbow (SBE) in the frontal plane; and (e) side bridge roll out with the foot (SBF) in the frontal plane.