Workouts with intense activity produce "runners high" by pushing the body to it's max activates endorphin production. Endorphin production resembles a feeling of well-being. Releasing endorphins through massage can also replicate this euphoric high and endorphins work as "natural pain relievers."
With a massage endorphins are released during kneading of the skin and muscles.
Muscle manipulation with a massage triggers the production of endorphins and this explains a portion of the pain-relief experience.
