Very important to understand what type of posture you have, before you begin trying to correct it. There are different "side effects" and pain associated to each type of posture. Also to note: Anterior pelvic tilt typically (not always) has externally rotated hips (your feet turn out more than 10 degrees) while posterior pelvic tilt typically has internally rotated hips (your feet turn inward) each "side effect" can cause improper alignment to the joints, increasing wear and tear, and limited range of motion.
Also known as hyperlordosis, this posture causes many patients low back pain, glute pain and sciatica. Correcting this posture reduces your risk of back injury, spondylothesis and disk herniations. By strengthening your "core" you are not only strengthening the abdominal muscles, but also the small deep core muscles that attach to the spine; multifid and rotatores (tiny muscles that span from one vertebrae to the other). Don't get discouraged, it took you your whole life to obtain this posture, it will take time to correct it.
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Very common with office workers, equipment operators, etc. This type of posture can be seen with both the hyperlordosis, swayback and kyphotic postures. Symptoms associated to this type of posture include chronic tension headaches, malalignment of the vertebrae, increased wear and tear on facet joints (the joints of the vertebrae), neck pain, chest pain, mid back pain, and trigger points.