Chair crunch

This exercise tones your rectus abdominis. By using a chair, you keep your hips at a 90° angle and this helps keep your spine stable.

Beginner
3 sets of 10 reps
1 min recovery in between

Intermediate
4 sets of 16 reps
45 sec recovery in between  

Advanced
5 sets of 26 reps
35 sec recovery in between

Very Advanced
6 sets of 34 reps
30 sec recovery in between