Peer-reviewed medical research has shown that the benefits of massage include pain relief, reduced trait anxiety and depression, and temporarily reduced blood pressure, heart rate, and state of anxiety. Additional testing has shown an immediate increase and expedited recovery periods for muscle performance. Theories behind what massage might do include blocking pain, activating the parasympathetic nervous system, which may stimulate the release of endorphin and serotonin, preventing fibrosis or scar tissue, increasing the flow of lymph, and improving sleep, but such effects are yet to be supported by well-designed clinical studies.
Massage is hindered from reaching the gold standard of scientific research, which includes placebo-controlled and double blind clinical trials. Developing a “sham” manual therapy for massage would be difficult since even light touch massage could not be assumed to be completely devoid of effects on the subject. It would also be difficult to find a subject that would not notice that they were getting less of a massage, and it would be impossible to blind the therapist. Massage can employ randomized controlled trials, which are published in peer reviewed medical journals. This type of study could increase the credibility of the profession because it displays that purported therapeutic effects are reproducible.