Effects of temporal and spatial cueing on anticipatory postural control in a rapid interceptive task

Balance disruptions induced by voluntary focal arm actions are accommodated via anticipatory postural adjustments, but how this coordinated control is organized by the central nervous system remains unclear: either as combined or separate streams of postural-focal motor commands. For example, a focal arm task that dictates extremely tight temporal constraints may induce a focal response in absence of an anticipatory postural adjustment, providing evidence for separate focal-postural control streams. This study sought to probe the organization of focal-postural control via an interceptive task with very little available response time, and to determine whether focal-postural coordination depends on temporal and/or spatial foreknowledge of the task. Ten healthy young adults (5 males and 5 females; 20-29 years) reacted to catch a ball when standing under four conditions of temporal and spatial foreknowledge. Response onset was characterized by muscle activity from both postural and focal arm muscles. The catching task resulted in rapid muscle responses, but there was no difference between the fastest focal and postural muscle onsets. As expected, temporal cuing resulted in faster focal and postural onsets compared to spatial and control cuing trials. The accompaniment and time-locking of focal and postural muscle onsets, suggests that postural-focal coupling remains intact even under external time constraints and provides evidence for a single combined command stream of postural and focal control under such circumstances.