Tendons connect muscles to bone. There are groups of cells within a tendon, where the fibers of the muscle meet the tendon, called Golgi tendon bodies. Made up of strands of collagen, the Golgi organ also contains nerve tissue. The major function of this organ is to sense muscle tension when a muscle is contracted, sending signals to the brain about how much force is being exerted.
Golgi tendon organs and muscle spindle cells work together to prevent injury to muscles. The more the muscle tries to stretch and the faster it tries to stretch, the more the Golgi tendon organs cause it to contract.
These nerve cells and fibers can be influenced by massage. Golgi tendon organs react to sustained pressure such as trigger point therapy and stress point therapy, by telling the muscle to relax.