For those suffering from back/ neck/ wrist, shoulder... etc pain from sitting long periods this book helped me a ton.
book: Pain Free at your PC
https://www.amazon.com/Pain-Free-Your-PC-Computer/dp/0553380524
It's basically about realigning/stretching your muscles that get tight in certain areas from sitting thus causing pain.
Most of the excercises you are just laying on the floor in various positions.
The book is an interesting read as well.
I had bad carpal tunnel and it fixed it. I was able to return back to full time computer work.
The catch is you have to do the stretches which take 15 - 60 min depending on how hard core you want to get
Bonus is if you do them at night before bed it's kind of a muscle tension release feeling which also helps with sleep!