After-effects of fusimotor stimulation on spindle la afferents' dynamic sensitivity, revealed during slow movements.

After-effects of fusimotor action on dynamic sensitivity of spindle primary afferents from soleus resulted from low rate stimulation of both static and dynamic gamma-axons. Sensitivity to small sinusoidal stretches superimposed on triangles was enhanced during triangular lengthening but not during shortening. These after-effects were elicited by fusimotor stimulation during preceding triangular shortening, but not during lengthening. Given these characteristics, they may be important functionally during alternating rhythmic movements.