How the Neck is Affected From a Musculoskeletal Standpoint
The point of this is not to get into topics like sleep apnea or facial wrinkles and their relation to sleeping on the stomach, but to give a couple of reasons (which may seem obvious) why your aches and pains may be related to or aggravated by sleeping on the stomach.
Sleeping habits are often very hard habits to change because ultimately we need to be able to get a good night's sleep so that we can feel awake and focused the next day to take on our daily routine. If sleeping on the stomach provides the best position for someone to be able to achieve this state of relaxation and go through the stages of the sleep cycle so that they can feel rejuvenated the next day, then it hard to convince that person to sleep on their side or back. UNLESS they are experiencing musculoskeletal pain that may be aggravated by or related to this sleeping position.
In the prone or face down sleeping position, it is almost impossible to not have our head turned in one direction or the other. Over time, muscles on one side of the neck are stretched and lengthened while the muscles on the other side are contracted and shortened. The curve, which is supposed to be a reversed C-shape, slowly straightens over time in this position. This most likely will translate to aches and pains in this area over time as the muscles and joints of the neck will have a hard time finding a normal resting position. Most of the rotational range of motion of our spine is present in the neck. If compromised, we start to compensate with moving other areas of our spine to make up for the lack of range of motion.
The neck holds up the head, and the curved spine provides shock absorption and muscle attachments that serve as levers to move our head around. The joints take on more stress as our head moves forward with straightening of the curve and our muscles start to pull in less natural plains, causing strain to the whole joint complex. Losing the curve in the spine actually increases the load on the spine! Think about holding a 10 pound bowling ball straight up in the air supported by your wrist and forearm. Now flex your wrist forward slightly and feel how much the stress on your wrist and forearm increases. Imagine this daily while upright with your head (bowling ball) on your spine (wrist and forearm). Not only will the stress of the load irritate the joints and muscles, the muscles in the back of the neck will have to work harder and more often just to hold the head upright. Then, when we get into daily activities like texting, looking down at the computer, working out, or playing a sport, the joint complex has to work that much harder.
With the joint complexes taking on more stress, we face a higher risk of musculoskeletal injury and earlier onset degeneration/arthritis. Most of us do not have perfect spines or perfect cervical curvatures, whether it is congenital, from a sports injury, or due to a fender bender, but we can help ourselves by improving our sleeping posture.