Add a leg kick to your plank.

We all know that the plank is a great core move, but it gets even better when you add in a few simple tweaks. Typical plank form has you on your elbows and toes. Your core is engaged to keep your hips off the ground, and your head is looking at your hands to help maintain a straight spine throughout.

But here's where it can get fun: Using your abdominals, bend your right knee into your chest without raising your hips. Then extend your leg behind you and up slightly to engage the glutes. Place the foot back on the floor, then repeat the action using your left leg. Now, this isn't a quick move. Breathe in for two seconds as you bring in the knee, breathe out for two as you extend. Try three sets of 5 repetitions (one repetition concludes after you bend and extend each leg once). Work your way up from there. Increase sets and reps until your doing, oh...say five sets of ten.

It sounds easy, but it's really not! And if you're looking for more ways to challenge your planking skills, you could also try the following:

• Inclined plank with elbows on a stability ball, BOSU or bench
• Declined plank with feet on a stability ball, BOSU or bench
• Reverse plank with your arms beneath you, body facing toward the ceiling (or sky!)
• Reverse plank with a light weight on your stomach
• Side plank, balancing on one elbow
• Standard plank on just one foot
• Standard plank with arms on a stability ball and feet on a bench

Am I forgetting a variation? Let me know if there's something you do in your plank that I haven't mentioned above!