Many people suffer from sensitive spots in muscle, often called trigger points or muscle knots.
There are no actual knots involved, — it’s just a metaphor. Although their true nature is uncertain, the main theory is that a trigger point (TrP) is a small patch of tightly contracted muscle, an isolated spasm affecting just a small patch of muscle tissue. That small patch of knotted muscle cuts off its own blood supply, which irritates it even more — a vicious cycle called “metabolic crisis.”
A collection of too many nasty trigger points is called myofascial pain syndrome (MPS).
Individual trigger points and MPS can cause a shocking amount of discomfort — far more than most people believe is possible — as well as some surprising side effects.