What exactly is meant by having good posture? Good posture occurs when your musculoskeletal system is in alignment to guard against injury and deformity over time as a result of needless muscular strain. Your muscles work more efficiently when your body is in a state of balance and equilibrium whether in a standing, lying, squatting, bending, or sitting position. Good posture can be assumed when drawing your chin back, relaxing your shoulders, stretching your chest forward, tucking your navel toward your spine, sitting with your knees lower than your hips, and having both feet planted firmly on the floor. Good posture means standing or sitting "tall', shoulders pulled back (chest pushed out) with your stomach pulled in. Assuming good posture does require isometric contraction of your stomach and lumbar muscles but the result will be good spinal alignment, reducing upper and lower back pain caused by slouching and hunching. Having good core strength in your abdominal, lumbar, hamstring, and gluteal muscles will certainly help in maintaing good posture. (See elsewhere in this blog for information regarding core exercises.)
BOTTOM LINE: Strengthening your core muscles as well as stretching tight chest and shoulder muscles will be helpful in maintaining good posture. And don't forget there's a bonus to having good posture: you will look much more attractive!
Brian Danley, CFT
"Motivation is what gets you started. Habit is what keeps you going."