Hi Nina,
I use my TENS machine and my grain sack (get the sack very hot though - and use it down the centre of my spine) at the same time, that seems to do the trick, also put lavender oil on the sack which seems to helps re the TENS machine, you have to find the right setting and more importantly the right place for the pads.
Some people in the UK are prescribed a low dosage anti-depressant which acts as a muscle relaxant, trying to think of its name - amtryptaline, or something similar sounding to that.
Hope the spasms stops soon.
All the very best
Rob
Slimmer than I was!
