This is one of the most effective ways to strengthen, flatten and tone the abs. Doing the exercise using a Balance Ball or stability ball eliminates the impact of a hard surface on the spine, which helps you perform the movement more precisely.It also helps increase lower back strength, support the spine, promote better posture and prevent lower back injury.
The twisting sit-up is an advanced form of sit-up. You can either use an incline sit-up bench or perform them on the floor. The technique is similar to the basic sit-up, but you twist the torso as your raise it to bring in the internal oblique on the side contracted and the external oblique on the other side (as well as the other flexors).