Final answer:
To counteract upper cross syndrome, patients should focus on strengthening the posterior thorax muscles - specifically the rhomboids and serratus anterior - which help improve posture by retracting and stabilizing the scapula.
Step-by-step explanation:
To counteract upper cross syndrome, a patient should focus on training the muscles that will help correct their rounded shoulders and forward head posture, typically caused by prolonged sitting and poor ergonomic practices. The muscles that need strengthening are primarily those of the posterior thorax, which include the rhomboids and the lower portion of the trapezius. These muscles help retract and depress the scapula, thus opening up the chest and improving posture. Strengthening the rhomboids causes the scapula to move medially, pulling the shoulder and upper limb posteriorly, directly counteracting the protracted shoulder position found in upper cross syndrome. Additionally, a focus on the serratus anterior can help stabilize and properly position the scapula. Therefore, the correct answer to the question is a) Rhomboids and serratus anterior.