HUMAN MYOTATIC REFLEX DEVELOPMENT OF THE LOWER-EXTREMITIES

Lower extremity (LE) myotatic reflexes were tested by percussion (taps ) to the patellar and Achilles tendons. Surface electromyographic reco rdings were obtained from 5 LE muscles during tendon taps. Results ind icated that LE myotatic reflexes underwent considerable change during early human development. The changes were non-linear and highly variab le, Reflex irradiation (the presence of reflex responses in muscles ot her than the one being directly stimulated by a tendon tap) was presen t in the newborn but to a lesser extent than was in evidence later on during the first year of life. The percentage of time reflex irradiati on was detected in heteronymous muscle groups appeared to achieve maxi mal levels during the first year and then progressively decline. The d ecline in reflex irradiation was most dramatic between the first and s econd years of life. Irradiated responses were still recorded from 2 y ear-old children but with less frequency than in children less than 1 year of age. With the exception of responses in muscles that were dire ct antagonists to the stimulated muscle, irradiation was not observed in children 3-5 years of age.