Add Yahoo as a preferred source to see more of our stories on Google. Your favorite ab-building machine at the gym may be causing you more harm than good. That's right—we're talking about the torso ...

Add Yahoo as a preferred source to see more of our stories on Google. Credit: Getty The Russian twist is a dynamic abdominal exercise that's more than just a twist — it's a core-strengthening ...

Russian twists tend to be a staple in many core workouts, and for good reason: This exercise boosts the strength and stability of your obliques, which can actually improve your running performance.