Find a comfortable spot on the floor and sit with a wall behind you. (Magazine and coffee optional.)
Prop your back up against the wall, bend your right leg, and extend your left leg in front of you with your foot flexed.
Pull your belly button in to engage your abs and raise your left leg off the floor as high as you can without arching your back. Lower the leg (don’t let it touch the ground), and do 15 continuous reps. Switch sides, then go on back to relaxing.