Fig. 1.
Illustration of the perception of muscle length (L1) and force (F1) in static conditions based on 2 components: efferent (EFF) and afferent (AFF). The efferent process is associated with setting a value of λ, which plays the role of a referent coordinate (RC). Signals from many sources increase monotonically along the force-length curve (dashed line). These include signals along Ia, Ib, and II afferents as well as those from α-motoneurons. Muscle vibration leads to an increase in the activity of the primary spindle afferents; this increased activity corresponds to a new point along the muscle characteristic (filled circle) corresponding to misperception of an increased length (LV) and an increased force (FV).