Many people have such a bad posture that the upper neck muscles have to cramp up to the extent that they compress the base of the skull onto the top of the neck just to keep the eyes looking straight ahead, this is a common cause of tension headaches. In-fact most of us have too much forward hunching curvature in our upper mid-back due to our habit of sitting, stress, and the way we walk. In order to compensate for this, we tend to extend and compress the back of our upper neck, overall this posture compresses the length of the neck. Our necks have gotten so tight that we can no longer move our neck joints in the way they were designed, and this tight posture can even affect the blood flow to your brain. This head hangs exercise can gently increase the range of motion of the head and neck by restoring the length of these tissues at the base of the skull and the nape of the neck.
Stand with the feet shoulder width apart with your toes facing forward, then stack your body up vertically straight so that the shoulders are over your hips and your hips are over your ankles, then let the head tuck forward so that chin gets close to you air-pipe. Make sure to keep your midback and chest tall and your shoulders relaxed into a backwards and down posture. Slowly let the head drop further and further with deep relaxed breathing, you can keep this posture for up to a minute. Alternatively, you can do this exercise sitting just make sure to keep a tall posture in your upper midback.
Work your way up to 60 sec and repeat 3 times per day for best result.