Support for the existence of open-loop and closed-loop regions in balance control

In this paper, we give evidence to support the claim that there are two regions in balance control characterized by open-loop and closed-loop behavior. Subjects were equipped with a skin-stretch feedback device (SSD) at the fingertip to provide sensory augmentation [1]. It was found that skin-stretch feedback based on sway angular velocity improved postural stability with respect to several parameters, including a significant decrease in z_(λ_2,AP) and a tendency (p = 0.07) of z_(λ_2,Rad) to decrease, which corresponded to a smaller open-loop region. Thus, it would seem that z_(λ_2,AP) could potentially be used to decompose the state-space into the open-loop {x|x≤z_(λ_2 )} and closed-loop {x|x>z_(λ_2 )} regions.