A strong core equals better posture, period. The muscles around your spine spend a lot of energy all day keeping you upright. The stronger the muscles of your abs and lower back, the less your body has to rely on altering the shape of your skeleton. Keep in mind that ideally you want to maintain a long, “lifted” spine, with your ears over your shoulders, over your hips, over your ankles. Minimize excessive sway in your lower back and too much “hunching” in your upper back by imagining a string tied to the crown of your head. This string “lifts” you toward the sky as if it were tied to a balloon.