Shiatsu and Tuina are perhaps the most well recognized body works systems introduced to the west. And in many ways they are radically different than massage therapy.
Western Body work systems were developed out of a western medical tradition which analyzes movement and function of the body from a bio-mechanical standpoint. It studies the human body like if our body was a machine. The main science applied using this concept is physics: forces, vectors, torque etc.
Early massage therapy methods were based solely on the idea that by affecting the moving parts in the system (muscles and ligaments) they will resolve underlying problems that have to do with posture, movement and mechanical damages (such as injuries) through muscles.
With time this view was broadened to take into consideration other systems, like the nerves and to an extent even the hormonal system. However, the focus remains on the muscular system.
The Eastern traditions, on the other hand were developed way before modern anatomy and physiology were introduced in the East, and are following the eastern medicine approach, which is focused on the internal organs as the prime interest of the therapist.
A manual therapist, like an acupuncturist is seeking ways to affect the internal organs by finding areas on the surface of the body that will affect the organs lying deep inside, at times in places so far away from each other that we may wonder how did they even come up with these connections.
A traditional Tuina or Shiatsu therapist will try and affect an internal organ such as the lung, the stomach or the kidney by affecting superficial tissue that has an affinity with this underlying organ.
This does not mean that oriental body workers are not familiar with body mechanics. On the contrary. Many of these systems were developed side by side with martial arts that studied movement and the relationships between different body parts in a very precise and intimate manner.
However, the broader picture an oriental body worker is seeking incorporates a bigger picture. It looks for a connection between an injury site and the entire person that is injured.