"This continues to work your abdominals, but also involves the quads and a little extra oblique work," Jetter says.
Starting in your plank position, exhale as you take one foot off the floor and bend your knee toward your chest. Inhale as you step back into your plank position. Repeat on the second side.
Be mindful to keep everything on your body still, with the exception of the leg you're moving — no booty in the air!