With a tall spine, sit towards the edge of your seat with your hands placed lightly next to your hips. Draw your belly button into your spine to engage your core, and then slowly lift your right leg up off of the floor. Lower your right leg. Repeat the movement with your left. For a more advanced version, lift both legs off the ground at the same time. Repeat for 10-20 reps to strengthen your hip-flexor and core muscles.