Which muscles are typically underactive in association with upper crossed syndrome?

In upper crossed syndrome, there's a specific pattern of muscle imbalances that typically arise due to prolonged postural habits, especially those involving forward head posture and rounded shoulders. The correct answer identifies the lower trapezius as one of the commonly underactive muscles.

The lower trapezius plays a crucial role in stabilizing the scapula and supporting proper shoulder mechanics. When this muscle is underactive, it can lead to an imbalance between the overactive muscles, such as the upper trapezius and pectoralis major, which are often overly tense. In this scenario, the lower trapezius does not maintain adequate support, contributing to the characteristic postural deformities associated with upper crossed syndrome.

In analyzing other muscles mentioned: the upper trapezius is typically overactive and tight due to forward shoulder posture, while the rhomboids also tend to be underactive but often do not represent the primary issue as significantly as the lower trapezius. The pectoralis major is similarly prone to overactivity, contributing to the typical presentation of upper crossed syndrome. Therefore, recognizing the lower trapezius as underactive in this condition underscores the necessity of strengthening this muscle to help restore balance and improve posture.