1) RIP position is on the back not the sides or stomach....it's a natural position...
2) Infant SIDS tells parents not to place their infant on their stomach...it interferes with their breathing and circulation, leading to death.
3) The fetal position is being curled up on the side. This restricts circulation and blood flow.
4) Like a water hose is twisted or bent to increase water pressure, the body reacts the same way.
Laying on your stomach with your head turned to the side is a perfect example that correlates to the twisted or bent water hose.

Also, I've recently (within the past 2 or 3 weeks) tried to focus on sleeping on my back to increase circulation and reduce stiffness, tingling, and pain. It's easier if I don't use pillows at the head because it's my natural reaction to put it under my head. Instead I use my pillows at the foot of my bed foot for elevation. As a result, the complexion of my face is clearer each morning I succeed. I also noticed that my skin is more supple and my face is oily not dry. Another benefit is reduced aging because a dry body or face wrinkles like a raisin that was once a grape til it loses it's water supply.

Words of advice, if you wear contacts to bed, take them out. You can do it. It will get easier and easier. Trust me. I'm speaking from experience. Since taking them out, I have reduced bags & eye puffiness, in addition to dryness.

Furthermore, I've noticed that when I lay with a pillow under my head excluding my shoulders, similar to an older person walking with their head forward in front of their body. I feel an uncomfortable sensation in the back of my neck. So sleeping like this causes the muscles to hold you in that position when you wake because that's what the body's muscles were trained to do.

When walking upright, if the body is not horizontal to the ground, even by 1-3%, it adds a surprising amount of weight to the body as a result of the force of gravity. ((I don't remember the amount exactly. I'd say 30-35 lbs. (I'll let the researches look it up and get back to me) )) In other words this unnatural forward bend requires more energy expenditure. The head should be directly above with the chest cavity and pelvic region aligned.

Another benefit I've noticed by sleeping on my back without a pillow is that gravity pushes my shoulders back naturally realigning my spine, as well shifting and reducing any unnatural forward or back pelvic tilt. Consequently, I feel loose and limber upon waking.

5) Exercise increases blood flow to the extremeties or peripheral circulation due to larger oxygen intake.
When someone feels depressed they dont want to move a lot because they don't feel they have the energy. A reason for lack of energy is lack of circulation. If the blood can circulate it can carry the needed nutrients throughout the body.

A little over 2 yrs ago, I was completely bald. I was working out at the gym 5 days a week. I would go home and soak in a hot tub and break another sweat. Then I would put Dr. Miracle's feel it working formula on my head. After about 6 months, I had regrown about 80% of my own hair. Needless to say, I got impatient, started applying an oil of his, which resulted in a chemical burned at the nape of my neck. As a result I was out of the gym for a while and my stress levels went up. Hair slowly began to fall out again and about a year later I was completely bald again. I just started working out again about 2 weeks ago and this time I'm much more patient,

I'm sure I could elaborate more, but for now I will leave it at that. What do you think about the body's posture and circulation as a possible cause of alopecia?