Bent-leg Side Plank Target Muscles: internal and external obliques, transverse abdominis. Begin by lying on your right side with your right knee bent to 90 degrees on the floor. (Your foot should be behind you.) Action: Place your right palm and forearm flat on the floor as shown, then lift your left leg from the ground. Hold this position for 30 seconds, rest, then repeat on the other side. Complete this move a total of three times on each side.