staggering push ups : by staggering them with a ball or a stack of books,
you are throwing your center of balance off, and forcing your core to do more work!
tricep dips : perform these against a solid and stable surface, and kick a single
leg out on the bottom portion of the move to again increase the amount of work the core
has to do. keep your shoulders back and down to really get the triceps going.
kitty kat pike : get yourself into a plank position with your feet up on the bed, and your hands directly below your shoulders. just like a plank works the core muscles the best, a pike will add a spike to that by having you squeeze your abs together forcing your bum into the air. the slower your perform this move, the better.
tummy tucks : this is best performed against a desk or a solid chair - remember to keep your elbows in, and to kick one leg up at a time, bringing it as close to your elbow as possible! slow and steady wins.