It is a classic and builds tremendous flexibility within the spinal muscles as well as build core strength for people that aren't used to exercise. (ashotofadrenaline.net)
And it's going to develop incredible core strength in you. (thebestexercises.com)
The first month's core workout focuses on core stability, the second month focuses on core strength, and the third month focuses on core power. (ab-core-and-stomach-exercises.com)