Iused to use a TENS machine when I had lower back pain, when I was still working (as a gymnastic coach!!). Absolutely excellent, still have the machine, although do not use it much now.
Cannot say it totally got rid of the pain, but did enough to permit to operate more or less as normal. Only thing I discovered is not to have it on when I was driving, as if I accidently turned it up, it would make me jump very much. Apart from that would keep it on most of the day.
When I had a fall earlier this year resulting in a spinal stress fracture, could not use the TENS machine as would not able to move enough to get it into place. However, I did use a large heated pad which was marvellous and went everywhere with me those first few months. Even plugged it into my seat on the train when coming to visit my daughter in WestonSMare.