Get Washboard Abs With This 5-Minute, No-Equipment Workout

"This move is so great because it stabilizes your entire core holding the standing plank position, where your hands are under your shoulders like the push-up position," said Erica. "Then you bring your right knee toward the right elbow in a Spider-Man-looking position to engage the oblique." Alternate sides to hit both sides of the obliques.

• In plank, open your knee to the side and bring your knee to your elbow and alternate sides. To modify, just lift leg open to the side.
• Repeat for 60 seconds.