Causes of upper crossed syndrome formation include poor posture and improper exercise methods. Upper crossed syndrome is mainly caused by anterior muscle tone (i.e., chest muscle tone) and posterior muscle laxity (i.e., back muscle laxity). When the muscle lines of both sides cross each other, then it will be called upper crossed syndrome. 1. Chronic poor posture: Poor posture (shrugging, head tilting forward, etc.) leads to passive elongation and relaxation of the back muscles and tension in the front muscles. Maintaining poor posture for a long period of time can cause upper crossed syndrome to form. 2. Exercise method error: excessive exercise chest muscles (such as pectoralis major) leads to excessive strength, while neglecting the exercise of back muscles (rhomboid muscle) leads to back muscle strength is insufficient, then the formation of the upper cross syndrome. It is recommended to go to the hospital for examination and treatment when upper crossed syndrome occurs.