According to Dr. Adalbert I. Kapandji, an orthopedic surgeon and the author of "Physiology of the Joints, Volume Three," for every inch your head is craned forward, 10 lbs. of effective weight is added. The additional force on your upper back and neck tissues caused by a forward head position—anterior head carriage—places significant stain on your muscles, joints, ligaments and nerves, and can result in the onset of muscle tension headaches and other musculoskeletal problems
Muscle Tension Headaches
In an April 29, 2009 "National Post" article by Rob Williams, a Vancouver, British Columbia-based kinesiologist and posture specialist, he states that tight levator scapulae muscles, which connect your neck to your shoulder blades, frequently contribute to tension headaches. With anterior head carriage, the muscle tone of your levator scaplae muscles, along with your upper trapezius and suboccipital muscles, increases, and "trigger points" —hyperirritable nodules within a band of muscle—can form and produce local and referred pain. The increased tone of your suboccipital muscles puts pressure on your suboccipital nerves, which can produce headaches originating at the base of your skull. Increased pressure on your suboccipital nerves also can imitate sinus headaches. Muscle tension headaches or tension-type headaches are the most common type of headache disorder, according to the World Health Organization.
Loss of Lung Vital Capacity
According to Dr. Rene Cailliet, an emeritus professor of Physical Medicine and Rehabilitation at the David Geffen School of Medicine at UCLA and the author of numerous books on musculoskeletal medicine, anterior head carriage can add up to 30 pounds of leverage on your cervical spine, which can pull your spine out of alignment. Dr. Cailliet states that anterior head carriage can lead to the loss of 30 percent of your lung's vital capacity (the total amount of air you can expel from your lungs after a maximum inspiration). Anterior head carriage-related loss of vital capacity is due to your loss of cervical lordosis or neck curvature, which negates the action of your hyoid muscles, especially your inferior hyoid muscle, which is responsible for elevating your first rib during a deep breath in. Postural exercises are an effective way to restore your normal neck curvature and regain your lung vital capacity.