Proprioceptive control of posture: a review of new concepts

The assumption that proprioceptive inputs from the lower legs are used to t rigger balance and gait movements is questioned in this review (an outgrowt h of discussions initiated during the Neural Control of Movement Satellite meeting held in Cozumel, Mexico, April 1997). Recent findings presented her e suggest that trunk or hip inputs may be more important in triggering huma n balance corrections and that proprioceptive input from the lower legs mai nly helps with the final shaping and intermuscular coordination of postural and gait movements. Three major questions were considered. First, what rol e, if any, do lower-leg proprioceptive inputs play in the triggering of nor mal balance corrections? If this role is negligible, which alternative prop rioceptive inputs then trigger balance corrections? Second, what is the eff ect of proprioceptive: loss on the triggering of postural and gait movement s? Third, how does proprioceptive loss affect the output of central pattern generators in providing the final shaping of postural movements? The autho rs conclude that postural and gait movements are centrally organized at two levels. The first level involves the generation of the basic directionally -specific response pattern based primarily on hip ol trunk proprioceptive i nput and secondarily on vestibular inputs. This pattern specifies the spati al characteristics of muscle activation, that is which muscles are primaril y activated, as well as intermuscular timing, or the sequence in which musc les are activated. The second level is involved in the shaping of centrally set activation patterns on the basis of multi-sensorial afferent input (in cluding proprioceptive input from all body segments and vestibular sensors) in order that movements can adapt to different task conditions. (C) 1998 E lsevier Science B.V. All rights reserved.