When the masseuses was working around the shoulder/lats area I could feel that she was finding and sort of crackling (if that is the right word) hard little lumps under my skin.
When I asked he what they were afterwards she told me that they were trigger points.
Trigger points, also known as trigger sites or muscle knots, are described as hyperirritable spots in skeletal muscle that are associated with palpable nodules in taut bands of muscle fibers, according to Wikipedia.I developed something not dissimilar when I hurt my shoulder skiing years ago and I very occasionally do some foam rolling, but I really had no idea these knots were so prevalent.
What's intriguing is that trigger points arise at predictable places in the muscle and cause predictable patterns of referred pain. I have had one at such a predictable place on the back of my left calf for years and have always thought it was on old injury.