Actually, all the medical and physical therapy experts now recommend ice, not heat. The standard treatment prescribed for athletic injuries is RICE: Rest, Ice, Compression, Elevation.

My youngest son, the surfer, got lectured for using heat after messing up his back surfing, made worse by too much weight lifting before he recovered from the original injury (he got lectured for that, too!). We spent last weekend trading stories of similar back problems. Mine started 30 years ago when I was substituting for him on his paper route, and didn't have sense enough not to try to carry all the Sunday papers in one batch. I still have to do the exercises frequently to keep my back from hurting. Back in the early 1980's, heat was the recommended treatment, but that changed to cold by the middle of that decade.

Heat increases swelling and retards healing, while ice does just the opposite and also reduces pain. Of course don't leave the ice on too long, or you'll have frostbite to contend with along with the original injury! 20 minutes at a time is the maximum.