Jun 27, 2013 6:14am
Planks (hop out planks, planks with leg lifts)
I used some of these exercises in workouts (Core Blast, Sexy Booty, 20x10). I built it from exercises I found here and at ab-workouts-guide.com
Also, checkout Multi-Plank Challenge, Core Abs & Stretches, P90x: Ab Ripper X, Core & Glute Kicks, All-Around Abs they'll challenge your core I different ways so you wont get bored.
And give the burpee challenge a try. A lot of you lower abs are about how you challenge your hips.
Good luck and God Bless!