If you have ever had back spasms, you know how painful they can be. Right up there with kidney stones. I know, as I have had both, more than once. Two weeks ago, I had a back spasm. Heat and massage did little to relieve it. Remembering that back spasms are a form of cramps, I decided to try some Theraworx on it. Due to location, wife had to apply Theraworx. Within 30 minutes, some relief was taking place. Twice a day application (morning, and night) and two days later you wouldn't know i had ever had a back spasm. Now if they can just figure out something for kidney stones that you can rub on. , FYI, active ingredient in Theraworx is magnesium sulfate, AKA Epsom salts.