H-reflex in nonhomonymous muscles in the human forearm.

In 6 healthy volunteers, stimulation of the median nerve at the elbow elicited H-reflexes in muscles innervated by the ulnar nerve (flexor digitorum profundus of the 4th and 5th digits of the hand) as well as the median nerve (flexor carpi radialis). This finding offers direct physiologic evidence in humans of monosynaptic excitation from group Ia afferents to nonhomonymous muscles, a phenomenon for which only limited indirect evidence existed previously.