This is a variation of the Sit-Up. Twisting alternatively from side to side will additionally involve the intercoastal muscles as well as the obliques
How to do: 1. Lie on your back on the floor and hook your toes under a heavy piece of furniture. Even better, use an ab board and hook your toes under the ankle constraints.
2. Bend your knee comfortably and keep them bent throughout the entire set. This helps to relieve concentrated back strain.
3. Place your hands behind your head and lock your fingers together.
4. Curl your head, shoulders, upper back and lower back slowly in succession off the floor until your torso is perpendicular to the floor.
5. Hold the upright position for a second and reverse the movement slowly until reaching the starting point.
6. Resistance may be added by varying the degree of incline if you are using an ab bench or by holding a weighed barbell plate behind your head. Advanced athletes may want to do both!
7. Do a second repetition however during this rep twist to the right as you raise yourself.
8. Do a third repetition twisting to the left.
9. Continue reps straight, right, left until the end of the set.