The russian twist is a challenging abdominal exercise that incorporates all the muscles of the core: low back, abs, obliques, diaphragm, and inner thighs. Unlike crunches in which your rest your back on the floor between reps, the russian twist forces you to hold your spine off the floor the entire time.
1- To begin, sit with your feet on the floor and knees bent and your torso at a 45 degree angle. Keep your abs engaged to hold this angle.
2- Hold your fists together with your elbows tucked into your body. Like a boxer holding a pose.
3- Twist your torso from side to side. As you twist, exhale to better pull your abs in and support the spine.
For added intensity, hold a light weight, medicine ball, or lift your feet a few inches from the floor. This will not only add arm strength, but also strengthens the torso and obliques ( waistline or sides of the torso).