Medical Massage is a term that is very confusing in the massage profession since there has been no professional definition of what exactly medical massage is.
More people are turning to massage to help them heal from various conditions such as strains/sprains, repetitive strain syndromes like carpal tunnel, headaches, fibromyalgia and many other conditions. The term medical massage is being used to describe massage therapists who work in more of a 'medical' capacity and work with physicians and even bill insurance companies for the massage services.
Some schools and organizations are creating a medical massage therapist specialty where students get more training in working with various conditions and get training in how to bill insurance companies and work with physicians. There are some specialized techniques that some are referring to as medical massage but the fact is that it is not one or any specific technique or massage method. The thing is that anyone can become a medical massage therapist if you can show that there is improvement in a persons condition from your massage - whatever type of massage one does including relaxation massage.
While more training in specific diseases and conditions may be helpful in your understanding of working with clients with these conditions - it is not really necessary because of the extremely low incidence of massage doing any harm to people.
Since stress is one of the biggest causes of disease and health problems, ruling out relaxation massage from the medical massage category is damaging to the massage profession.