There are several different things or techniques that people use but in a very simple way, the muscles are being compressed. Compression is applied; the therapist is squeezing the muscles and squeezing out toxins and stimulating the release of contractions that might be there to help spasms. And "spasm" is a layman's terms, people use too generally, but it simply means "contractions that are not a conscious choice, or unconscious contractions," which we all have. Massaging helps to cause those spasms to release and therefore allows the blood to flow in and natural byproducts of the muscle or toxins to be flushed out. That in itself releases and reduces pain. A lot of times, people will find that when they have a little sore spot on their back, within just minutes of massaging, the soreness is either gone completely or diminished a lot. And that's mostly just because of that flushing aspect in many styles of massage.
