Are the muscles responsible for twisting rotation the same ones responsible for body flexion (abs, sides)?

Yes: "are the muscles responsible for twisting rotation the same ones responsible for body flexion ( abs, sides)? The answer is yes. Each side of the core/trunk of the body has these abdominus obliques muscles. When they work individually, the body turns in that direction. Working together and simultaneously, they help the rectus abdominus muscles, to bend (ie, flexion) the body.