I have a small portable at home. Unfortunately it´s going on only 2/3 of it´s power because one of the elements broke, but it´s still making my muscles a bit softer and has a bit of a pain killing quality to it that can last for at least several hours. It doesn´t loosen up very stiff muscles though (lyme stiffness)but probably could help stiffness due to other circumstances. So I feel it has both some temporary pain killing ability as well as skin detox, especially if you have one that actually works so you can sweat a little.
I also have morgellons and they seem to love being in the sauna though (if anyone else has morgellons out there), so it needs to be cleaned with alcohol or something else in that case.