Planks and Leg Raises: This version of a suped-up plank engages nearly every muscle. As you get stronger, you can integrate leg raises, which work the glues and hamstrings as well.
Plank Pedestal Routine
Start in a plank position, balancing on your forearms and toes. Keep your body in a straight line; suck in your tummy, and make sue your butt isn't sticking up in the air. Lift your left leg up and down 15 times, and repeat on the right leg 15 times.
Flip over so you're balancing on your heels and forearms, with your chest facing skyward. Again, work to keep your body in a straight line. Lift your left leg 15 times, then your right leg 15 times.
Turn to the right, and balance on your right forearm and the side of your right foot. Stack your hips so your left leg is resting on top of the right. Keep everything tight and sucked in, and don't let your hips sag to the floor. Lift your left leg up and down 15 times.
Turn to the left, and repeat sequence, this time lifting your right leg up and down 15 times.
Glutes and Hamstrings
Back Bridge: Lie on your back, pressing the small of your back flat to the floor to engage the core, knees bent in the air, feet on the ground a fair distance from your bum. Squeeze your glutes and lift your butt into the air until your body, from your knees to your shoulder blades, is in a straight line. Lower back down, and complete two to three sets of 10 to 15 reps.
Hamstring Ball Roll: Lie with your back on the floor, arms at both sides, legs straight ahead. Place your feet on top of an exercise ball. Lift your torso up so that only your shoulder blades are on the floor. Your arms should remain on the floor for support. Bring your knees to your chest by rolling the ball inward towards your butt, and then roll back out. Complete two to three sets of 10 to 15 reps.
Toe Touch Balance: Stand straight, balancing on your left foot. Keep your left leg straight, and reach down to your left foot, leading with your right arm (so the right arm crosses the body). The trick here is to keep your balance without putting your right leg on the floor. Raise back up to the starting position and repeat 10 times. Change sides, balancing on the right foot, and repeat toe touch 10 times.