Aside: Pain

Pain is all in the brain. A nerve cell (axion?) somewhere triggers an impulse that wends it's way to the brain, which then interprets the data and passes the information to the conscious.

Generally, the information is correct and you can act based on it. If you feel pain in your ankle, you adjust your stride to minimize the pain signal from there. You can believe your brain, you don't wrap your wrist if you have a toothache.

Alas, as I understand it, nerve impulses from the hips and legs and lower back all travel to the brain via the spinal cord, which runs inside the spine. The spine is a remarkably flexible set of bones called vertebrae. Sometimes problems can occur with one or more vertebrae. Doctors count them, the ones up from the legs L1, L2, ..., and the ones down from the cranium C1, C2, .... They also have mapped which nerves get into the spinal cord at which vertebra.

Let's say a vertebra is damaged in some way (the lack of the membrane keeping bone from rubbing on bone, for example). The nerves passing through that damage can be affected. Moving a vertebra or two may pinch a nerve that reports you've been kicked in the hip, or that hip doesn't work and other muscles need to deal with it. The effect is a trivial movement in the spine causes a nerve to trigger an impulse that is only supposed to be triggered at the far end of that nerve. So the spine moves, and the left hip suddenly feels a monster was pretty bite for a second or two. Or a hip suddenly loses all feeling, which causes you to fall to that side, which sucks if you happen to be on a SUP, and fall in the water.

Working out regularly, there is a lot of pain that actually feels good, muscles that have been exercised fully and reporting such. But these random pains don't feel like that. It's weird how we live for some pains, and do whatever it takes to not feel other pains. And a lot of pain can be ignored for a while, but as the day goes on it's harder to ignore.

All in all, most pain is best avoided.