Which muscle is a weak muscle in Upper Cross Syndrome?

• A. Deep neck flexors (longus coli and capitis)
• B. Pectoralis major
• C. Scalenes
• D. Levator scapulae

Answer: (A)

Weak deep stabilizers of the neck, specifically the deep neck flexors like longus coli and longus capitis, are the muscle group that tends to be underactive in Upper Cross Syndrome. These deep muscles normally provide precise cervical spine stabilization and control of craniocervical flexion, helping keep the head balanced over the spine. When they are weak, the head tends to sit forward, and the more superficial muscles—such as the upper trapezius and sternocleidomastoid—become overactive to lift and move the head, while the scapular stabilizers on the lower side (like the serratus anterior and lower trapezius) may also lag. This imbalance manifests as forward head posture with rounded shoulders, a pattern driven by overactivity of tight muscles like pectoralis major, scalenes, and levator scapulae rather than weakness. So the muscle most characteristically weak in this syndrome is the deep neck flexor group.