sacrum

Things like the SI joints and the sacrum which get zero movement from sitting.

In particular they’re focused on injury to the junction of the lumbar spine and sacrum.

I have a damaged disc between the sacrum and L5. After several years of back pain and a few visits to the emergency room, I took up deadlifting.

Exercise balls put your back into a C position and put pressure on your sacrum, neither of which are natural.

I was struck across the sacrum, crushing nerves and fracturing both the sacrum and tailbones, as well as a deal of laceration for good measure.

Unfortunately, sitting in a chair, as well as various other modern activities, completely messes up not only the alignment of the hip and sacrum, but conditions the soft tissue in those areas to hold a bad position.

[snip]> Craniosacral therapists claim to be able to detect a craniosacral "rhythm" in the cranium, sacrum, cerebrospinal fluid and the membranes which envelop the craniosacral system.

This has nothing to do with visibility, but rather from "the name of the purple-red ink, the sacrum encaustum, used by the Roman emperors to sign their documents; this was said to have been obtained from the ground remains of certain shellfish, formed into writing fluid by the application of fire or heat, which explained the name.