Control of Human Locomotion by Group I Reflex Pathways from Ankle Extensors

Abstract

It is generally accepted that the basic mechanism of the alternating activation of flexors and extensors in stepping is programmed by a central pattern generator. That in the cat spinal reflexes may regulate the working of this central generator has long been assumed, even though direct evidence was only obtained in 1975 by Forssberg et al. (5): they found that in walking spinal cats the same cutaneous stimulation which elicited an activity in flexor muscles during the swing phase elicited, by contrast, a reinforcement of extensor muscle activity during the stance phase. In 1969, Lundberg (6), while discussing the reflex control of stepping in the cat suggested that the complex connections of group I fibres found in the cat hindlimb had evolved to assist the soft feline gait. Accordingly, the special organization of group I reflex pathways that we have found in man will be discussed here with regard to the requirements of the bipedal gait.