Final answer:
Posture relates to how we position our spine and pelvis, with good posture marked by the center of gravity being above the hips, avoiding back strain. The core muscles, including abdominal muscles, actively maintain this posture by balanced contraction and relaxation, directed by the brain.
Step-by-step explanation:
The question refers to the action by which tightening the stomach muscles and flattening the back can result in a pelvis tilt. This involves the mechanics of good posture, which is a function developed from infancy and is crucial for balanced upright walking and standing. Good posture is characterized by having the center of gravity directly above the pivot point at the hips, which avoids unnecessary strain on the back and potential disc damage.
Many muscles contribute to maintaining this balance, with the core muscles, including the abdominal muscles, playing a significant role. These muscles work in harmony, controlled by electrical impulses from the brain that contract and relax them alternatively, preventing any single muscle group from becoming overly fatigued.
The pelvis supports the upper body's weight and serves as an attachment point for muscles; it is naturally tilted anteriorly in the anatomical standing position. Proper posture involves aligning the pelvis and spine to maintain this natural curvature without excessive stress.