Final answer:
Kyphosis-lordosis posture is associated with tight hip flexors and weak upper back muscles due to changes in normal spine curvature. This altered posture can lead to muscle strain and imbalance.
Step-by-step explanation:
Disorders associated with the curvature of the spine, such as kyphosis and lordosis, create postural imbalances due to the alteration of normal spine curvature. Kyphosis, characterized by an excessive posterior curvature of the thoracic spine, can lead to a kyphosis-lordosis posture, which commonly includes tight hip flexors and weak upper back muscles. The shift to maintain balance causes certain muscles to become tight while others weaken, contributing to muscle strain and altered posture.