Every Inch!

Every Inch!

For every inch your head is forward, your upper back and neck muscles have to hold an extra 10 lbs (~4.5 kg), as they have to work harder to keep the head (chin) from dropping to your chest. This also forces the sub-occipital muscles (they raise the chin) to remain in constant contraction, putting pressure on the three sub-occipital nerves. This nerve compression may cause headaches at the base of the skull or mimic sinus (frontal) headaches.
Kapandji, Physiology of the Joints, Volume III