[The postnatal development of EMG reactions of limb muscles to free fall stimulation. I. Studies in normal rabbits]

The ontogenetic development of the vestibulospinal reaction following the free fall was studied in 11 rabbits ("Deutscher Riese") 8 to 20 days old by means of myographical recordings (EMG) synchronously derived from 3 muscles (M. triceps brachii caput lateralis, M. brachialis, M. quadriceps femoris vastus lateralis) by chronically implanted steel wire electrodes. With increasing age, rabbits show a sustained rise of EMG activity during fall and develop the ability to change the generated EMG activity under the condition of repeated stimulation. It is concluded, firstly, that more typical EMG reactions are produced with growing age, and secondly, that the ability to modify the intensity of the response to repeated free falls increases during postnatal development.