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 ...

According to experts, it takes just four core workouts to absolutely rip your top half to shreds, so you can get stronger.

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.