A Trigger Point is defined as "a highly irritable localised spot of exquisite tenderness in a nodule in a "palpable-can feel it with your fingers" taut band of muscle tissue. " This means that a trigger point hurts like the devil when you push on it. The "nodule" knot- to your fingertips feels like a small lump that can range in size from a pinhead to a pea. In the larger muscles a trigger point can feel the size of your thumb.  

The place where contraction actually occurs in the muscle fibre is a microscopic unit called a sarcomere. Millions of sarcomeres have to contract in your muscles to make even the smallest of movement.  A Trigger Point exists when overstimulated sarcomeres become unable to release their contracted state. Normally, sarcomeres act like tiny pumps, contracting and releasing to circulate blood though the capillaries that supply their metabolic needs. When sarcomeres in a trigger point hold their contraction, blood flow essentially stops in the immediate area. The resulting oxygen starvation and accumulation of waste products irritate the trigger point. The trigger point responds to this emergency by sending out pain signals until the brain institutes a policy of rest for the muscle. You stop using the muscle, which then begins to shorten and tighten up.  

Trigger Points are remarkably common. They have been called the "scourge of mankind" or the missing link in medicine. No one escapes trigger points, not even children or babies. Trigger Points can develop in any of the two hundred pairs of muscles in the body.

The pain inflicted by trigger points may be the biggest cause of disability and loss of time in any workplace or office, in any professional or amateur sport, musicians, or simple in everyday life.

Solving the problem of myofascial pain hinges on locating the central trigger points, those that occur in the belly of the muscle. Trigger points always originate at the midpoint of a muscle's fibres. This is where the motor nerve enters, bringing the signals that tell the muscle to contract. This is also where sarcomeres get into trouble, locking up and forming a trigger point.