Editorial on the Research Topic
Current State of Postural Research – Beyond Automatic Behavior
Postural control requires regulating the neural circuitry of musculoskeletal mechanics to maintain and change body spatial orientation to fulfill changing demands specific to the task and the environment. Knowledge progression has closely followed our understanding of the dynamic interplay between organism, task, and environment. Initially, Magnus ( 1 ) focused on the reflexes elicited when decerebrate and decorticate animals righted themselves in space. As the science of posturography progressed, minimization of movement reflected through a small center of pressure footprint during quiet stance became the criterion value. A major theoretical shift occurred in the 1970’s with development of the dynamic force platform; reactive postural behaviors could be quantified and were found to be adaptive and modifiable. Thus, research began targeting sensory pathways triggering the postural reactions. Simplified mechanics were used to model the multisegmental body as an inverted pendulum with principal motion around the ankle. But recent studies implicate cognitive processing in the organization of postural behaviors. Thus, basic assumptions need to be challenged if posture control research is to continue to evolve. The papers presented in this special issue are evidence of the progress that has been made toward explaining and assessing effective postural control.
Sensory Information and Postural Control
To discern when multimodal sensory information impacts recovery of upright balance, Le Goic et al. examine subject-specific geometry and inertial parameters. Intrinsic properties of the lower limb, stiffness and damping, were the earliest influences; however, early muscle activity was insufficient to counteract the external forces. The head was the last segment to move; thus, active correction for a fall could not be initiated by vestibular and visual inputs. The authors conclude that proprioception serves as the sole source of information for up to 300 ms following onset of unexpected falls. Rather than improved anticipation with experience, they argue for improved efficiency of reactive behaviors.