**2.2 Golgi's tendon organ (tendon spindle)**

The Golgi-tendon organ or tendon-spindle, localized at the origins and insertion of tendon, or rarely within the tendon. It is a mechanoreceptor that informs on muscle tension via its Ib afferent (**Figure 1**).

Structurally it consists of a capsule and within it there are loosely packed collagen fibers and muscle fibers (3–50). Among these elements there is a unique Ia afferent which branches to innervate the distal and the proximal parts of the organ [28, 47]. With respect to the skeletal muscle fibers the Golgi-tendon organ is in series between muscle and tendon.

The Golgi-tendon model react to "static and dynamic responses to activation of single motor units whose muscle fibers insert into the Golgi tendon organ, self and cross adaptation, non-linear summation when multiple motor units are active in the muscle, and the proportional relationship between the cross-adaptation and summation recorded for various pairs of motor units" [47, 48].
