When you sleep, where do your elbows go ?

All the above.

None of the above…side sleeper, elbows bent, bottom hand tucked under pillow, top hand tucked between knees. Occasionally back sleeper, arms crossed on chest, elbows at side (the "Egyptian Mummy" position).

Well if you're collecting explanations as I recall it's also the position recommended for a good night's sleep by Aliester Crowley.

I'm all over the place. On my back, my arms may be straight by my sides, or sometimes I slide my hands up inside the sleeve of my opposite arm which tends to hold my arms in place across my chest mummy-style and also keeps my hands warmer. On my side, I mostly tend to put one hand under my head as extra pillowing and the other cross body.

About 12" away from wherever my hands go. ;)

More seriously, though. 90% of my sleeping is on my side, curled up. Hands tend to go either in between my knees or under/on the pillow in front of my face. The latter position I seem to prefer, but it leaves the top elbow hanging in space. At home I stick a pillow next to my chest to prop it up. When camping I use a stuff sack filled with some spare gear. Those rare times I'm on my back, I tend to rest my hands on my stomach.

On my side, my hands either go under my pillow or between my thighs.
On my back, they lie at my side or kinda cross over my torso.

A or C or if I'm really cold I lay on my stomach with my arms under my body. My biggest problem is I drool horribly when I'm out there so I almost always have to sleep on my back. I can only sleep in other positions if I stay dehydrated so I won't drool.

I'm not a big guy, not by a long shot, but I can't sleep with my elbows tucked. So they always tend to fall just outside the 20" matt. For this reason I wish manufacturers would extend their mummy-style inflatables to 24-25" just above the hip and tape back to head and foot widths. Instead, I buy Large or Extra-Large mats and cut them down to size. I just purchased the Large "NeoAir XTherm" for winter use and will try the cut/seal process on this $200+ pad. Wish me luck!

I've been known to sleep in all the positions mentioned in one night. I'm a very restless sleeper. I love the sounds of the outdoors in the wild, so I just can't seem to fall asleep. After a couple of nights with no sleep, I'm so exhausted that I could sleep standing up if need be.

I recall a time when I was in the ARMY, where none of us were permitted nearly enough sleep for 5 days. One of the guys started crying, and hugging a tree. He was delusional. He'd gotten into an argument with his wife before we went to the field and in his sleep deprived state, thought the tree was his wife.

A ways down the trail, I blinked, and when I opened my eyes again I noticed that we'd gone a couple of kilometers farther while my eyes were shut. Apparently, I'd fallen asleep while hiking down the trail. So, under the right conditions, I can sleep while carrying 120 pounds of gear. lol

I don't often sleep on my back, but when I do, I also have problems with my elbows falling off the sleeping pad. They stick off the pad when I'm sleeping on my stomach too.