Selective Adequate Activation of Large Afferents from Muscle Spindles and Golgi Tendon Organs

An apparatus has been devised for brief stretching of muscles and a method is described for selective activation of I a and I b afferents. With muscles under light initial tension all I a afferents can be activated by a brief stretch of less than 100 μ without co‐activation of any I b afferents. A brief pull applied during contraction of an initially slack muscle activates I b afferents but not I a afferents. With intracellular recording from motoneurones brief stretches activating only I a fibres were found to evoke monosynaptic excitatory postsynaptic potentials almost indistinguishable from those resulting on stimulation of the muscle nerve.