Sometimes I think it might be fun to start recording everything I hear while walking around town or waiting in line at the store. At the farmer's market this morning, I heard a man tell his friends: "I think I slept on my kidney wrong. It's really sore this morning." I'm pretty sure that's not possible.
Sleep is a common prescription for good health today. Getting enough of it, that is. In the 19th century, many alternative health movements promoted things we now think of as common sense: eating a heathy diet, drinking water, getting fresh air, and exercising. But few health reformers actively promote sleep. It seems that sleep wasn't the same issue that it is today. Scientists and doctors speculated on what sleep was for and what happened while you slept (especially what you were dreaming) but didn't seem to worry so much about the amount of sleep people were getting.
In part, this may be due to technology. Electricity wasn't widespread until the 20th century so working late into the night or before dawn wasn't an issue in many cases. There were certainly many other things to keep people up at night, however, from lice and other bed bugs to stinky chamber pots.
Or maybe it was, as historian Roger Ekirch suggests, that sleeping through the night wasn't expected. He proposes that interrupted sleep was the norm and that it's only now that we equate a good night's rest with uninterrupted sleep. He says--and many others seem to agree--that artificial lighting has changed us. Harvard chronobiologist Charles A. Czeisler has compared artificial lighting to a drug in its physiological effects. Among other things, it alters our levels of melatonin, the hormone that regulates our circadian clock. In the past, we may have slept in segments, sleeping for a few hours, waking and doing something, and sleeping some more.
It's certainly always been possible to sleep in an awkward position and wake up with sore muscles. I'm just not sure that extends to body organs.