Oh boy, I can relate to this one quite well.
Around about the age of 20, I used the totally incorrect technique to lift a cylinder head off. I was leant forward from the hip at approx 45 degrees, knees against the bumper, arms fully stretched out, going for a 'clean-jerk-upwards-and-pull-it-towards-me' just as some of the other techs did....only I wasn't built as big as them.
Most of the time previously, when I'd asked for a hand I got one, eventually. Due to the shop being on an individual time-saved bonus scheme, "Yeah, in a minute" could easily turn into five or ten minutes standing around waiting for someone to actually turn up & help, since helping someone else is going to affect their own pocket.
Time ticked.
And ticked.
"Yeah, in a minute" for the second time.
It was a little bit larger than the other heads I'd removed previously, but not by much. Too much longer and I wasn't going to make much bonus from this job. I could probably handle it.
What I hadn't taken into consideration, was that the head was pretty tight on the locating dowels and with hindsight, I should have leant over each wing (fender for you US guys) and rocked it first to loosen it.
I went for the lift and it didn't budge, but something in my back did.
The doctor prescribed anti-inflammatories in the form of Brufen Retard and two weeks of bed rest.
The following year, at the end of January/beginning of February - nearing the end of the British winter - it 'went' again, resulting in four weeks off work, with the same prescription and bed rest for the duration.
The following year, at the end of January/beginning of February ........ blah blah ......... yep, same result.
I got referred to the hospital for some x-rays etc. Turns out that I had/have a (this is only from memory) "reversal of lower lordosis around L3 & L4 - a reversal of curves"
Basically, my spine now curves in normally just above the top of my buttocks, curves out briefly around L3/4, then curves back in & then continues normally ouward through my upper back to my neck.
Sitting for long periods is no fun. Standing for long periods is no fun. Sleeping-in is a no-no and that doesn't tend to happen anyway because I know it will worsen the feeling but if I'm ill in/on the bed/sofa with something else......such as man-flu.
The worst thing though, has to be the local weather. If I conciously catch myself sitting/standing in one position for too long, I can correct it by changing position or getting up and walking around, but I can't change the weather.
Living in a location which was chosen for it's ideal conditions for spinning cotton tells a story. If you live in a town which has/had a thriving cotton industry, you can bet your behind that for most of the year it will be cool and damp. Or slightly less cool in the summer, but still somewhat damp.
As a young apprentice, when an older guy said "It seeps into your bones" I dismissed it, but I now know what he was talking about.
Regards.