Figure 2. The dynamic response of four muscle spindle afferents to ramp stretch during relaxation and voluntary contraction.

The unaveraged instantaneous firing rates (inst. rate) of three primary afferents (A-C) and a secondary afferent (D) are shown. Torque at the wrist joint and rectified EMG are also shown for each afferent. The left column is the response to stretch during relaxation. The right column is the response recorded while the subject maintained a steady contraction.