Usually with lower back pain, the cause isn't even looked for; it's just assumed it's due to muscle or joint strain.
Well some back problems are caused by muscle strain, so maybe by lifting you strengthened the muscles that were affected.
Do you know what Chronic fatigue syndrome is? I know that the fatigue is not because of exertion or some other medical condition. It's essentially unexplained. Any idea what causes it? Ive heard of it, and of course have felt fatigue just from everyday life, but I cant say its chronic.. No, doctors still do not know the cause.  It could be biology, genetics or in someone's head from what I understand anyways. Ive been looking into pain causes, has ive always dealt with back pain, been following some research being done by some doctors that are big into treating pain with weight lifting, it really has made a difference for me. alot of what they say is pain is mostly in your head. Apparently back pain and discomfort can go into the arms and legs. Has that happened to you? No, it was pretty much just back pain. Ive started lifting regularly and things have progressed more in the last 6 months then they have the last 4 years working with a chiro. Kind of feel like it was a big waste of money.
In most episodes of low back pain, a specific underlying cause is not identified or even looked for, with the pain believed to be due to mechanical problems such as muscle or joint strain.