What type of posture is characterized by hyperkyphosis?

Hyperkyphosis is characterized primarily by an exaggerated curve of the thoracic spine, which leads to a hunched or slumped appearance. This condition results in an increased thoracic curve, often accompanied by rounded shoulders. The hallmark of hyperkyphosis is this abnormal curvature that disrupts the natural alignment of the spine and shoulders, resulting in a posture that significantly alters the body's structural integrity.

The other posture types described do not align with hyperkyphosis. A flat back presents with a reduced lumbar curve, which does not reflect an increased thoracic curve. Overextension of the cervical curve does not relate directly to the thoracic area affected by hyperkyphosis. Balanced posture is marked by proper alignment of vertebrae and would not present the signs of slumping typical of hyperkyphosis. Thus, the correct choice accurately describes the distinctive features of hyperkyphosis.