If being careful it can be good for the back!
I was knocked out by a hernia for more than a year! While I cannot be sure about the reason, my guess is that sitting still at the office for ~7.5 hours pr day, plus a lot of sitting time when coming back home was the biggest reason.
During that year, most of the time I couldn't sit (for more than some few minutes), and simple mundane tasks (like putting on my socks) was very difficult. At the very worst, it was painful to walk, painful to lie down, painful to sit and painful to stand. Luckily it was in the summer time, so at least I was able to swim (but there was limits for how much I could swim - the sea was rather cold - later I bought myself a good wet suit). But I digress. Eventually I started doing some exercises, and eventually the problem gradually disappeared. I threw away the chair in the office and got myself a desk where I could stand and work.
This was before that drainage incident. I don't know how many cubic meters of soil and clay I was moving, but it for sure was a lot. I did feel a little bit of back pain, then I understood I would need a day or two of rest ... but in the end I'm positively sure I got out stronger from it!
RE: Let's Dig. (How-to)