The seated oblique twist exercise, sometimes erroneously called a Russian twist but actually a variation of it (a proper Russian Twist is executed while standing with one weight plate held by both hands), is a very effective exercise for strengthening the abdominal muscles. If you are a beginner use no weight; if you are advanced, perform the exercise using a medicine ball.
1. To begin, sit on the floor with your knees bent and feet flat on the floor (easier) or raise up off the floor (more difficult). If you have difficulty holding the position and your feet shift around, tuck your feet beneath a stable object.
2. Next, contract your abs and sit at about a 45 degree angle while holding the medicine ball with both hands, directly in front of you. While contracting your abs, twist slowly from your torso to your right/left and touch the medicine ball to the floor beside you. Pause to hold the position a moment.
3. Then, quickly, but smoothly, contract your abs and twist your torso back to the center position, and then proceed on to touch the medicine ball to the floor on the opposite side and move back to starting position, i.e., center. Repeat as denoted in your program.