Hi,
Try reading the book below if you can get a hold of it. It has focuses on muscle pain and has an indepth chapter on trigger points, with discussion backed by literature.

Mense S, Simons DG, 2001. Muscle Pain - understanding its nature, diagnosis and treatment. Lippincott Williams & Wilkins

Much of the research seems to come from older studies, and it's still not clear what the etiology of a trigger point is?

from memory, muscles with trigger points are more likely to fatigue demonstrated on surface EMG. There is also heightened responsiveness of the tissues adn acclerated fatigability, delayed recovery and relaxation of the muscle .

there isn't much literature on treatments of trigger points, so far most research have looked at ischaemic compression, which seems effective on its own or combined with other modalities. not much on PNF or MET techniques, or other manual therapies for it.

are you planning on doing research on MTrP?