Neither your ribs nor your lungs can draw in a single breath without help. Your basic chest-box is brought to life by the performance of MUSCLES sandwiched between your ribs in partnership with the wide, powerful DIAPHRAGM that stretches like an elastic floor across the bottom of your ribcage.
Lung tissue is completely dedicated to delivering oxygen to your blood and to carting away carbon dioxide and other spent gases. The expansion and release of your ribcage is what draws in fresh air and dumps out depleted air. Lung tissue is far too busy to share in that responsibility! Your major breathing muscles turn your chest into a kind of accordion - squeeze and release.
So these primary-breathing muscles must have FREEDOM to do their very important work. When primary breathing muscles are cramped and restricted, you process less and less oxygen. Less oxygen makes you feel more and more like slumping.
EFFECTIVE POSTURE PRODUCES THE GREATEST AMOUNT OF OXYGEN WHILE INVESTING THE LEAST EXPENDITURE OF ENERGY. Effective posture translates AS BONE BALANCED LIGHTLY ON BONE, with as few muscles involved as possible in the support of that balance.
We first do the slump but eventually the slump does us. Muscles across the front of the chest grow short and tight while muscles across the back become
overstretched and useless. Spinal discs and vertebrae are eventually worn down by rag-doll posture. What began as a muscle habit eventually becomes a crisis of bones and joints.
The human body is simply not designed to sit on a chair. Sitting still for long periods threatens your circulation, your digestion, your concentration and your respiration.
To make the best of a bad situation, keep your weight evenly distributed along the backs of your thighs from your bottom to the backs of your knees. Keep equal weight on your right and left sit bones (those bony points that hurt when you sit a long time on a hard bench). Never allow your tailbone to touch down on the chair seat. Balance your head directly above your tailbone. "Float" the top of your head lightly toward the sky. Whenever possible, let your elbows stay in line with the side seams of your shirt.
Notice how your breathing capacity improves when your bones are properly balanced. You look like a dancer or cellist in this position and people may tell you to "sit back and relax." You are actually MORE relaxed than those people who lean back in their chairs (tailbones touching the seat).
The spine shortens and curls forward as we age, almost as if we are returning to a fetal position. The loss of bone calcium, especially in women, is a major villain coupled with years of lazy posture.
Since the main support-pillar of your torso is the stack of spinal vertebrae toward the rear of your ribcage, the breakdown of bone quality in that area will rob you of your youthful and functional carriage as well as your easy, free breathing. Remember the LUNGS ARE ONLY AS GOOD AS THE CAGE THEY ARE CARRIED IN.
Long years of straining forward to read the computer screen, of carrying a heavy purse on one shoulder, of bending over the sink or desk, of sitting like a wilted daisy, is finally written permanently on your body and can no longer be erased. As usual, prevention is the best medicine.
Refuse to shrink as you age. Stretch. Bend. Research your hormones and your nutrition. Your body remains totally deaf to all your best intentions regardless of how frequently, loudly and elegantly you state them.