Quiet standing exhibits strongly intermittent variability that has inspired at least two interpretations. First, variability can be intermittent through the alternating engagement and disengagement of complementary control processes at distinct scales. A second and perhaps deeper way to interpret this intermittency is through the possibility that postural control depends on cascade-like interactions across many timescales at once, suggesting specific non-Gaussian distributional properties at different timescales. Multiscale probability density function (PDF) analysis shows that quiet standing on a stable surface exhibits a crossover from low, increasing non-Gaussianity (consistent with exponential distributions) at shorter timescales, reflecting inertial control, towards higher non-Gaussianity. Feedback-based control at medium to longer timescales yields a linear decrease that is characteristic of cascade dynamics. Destabilizing quiet standing with an unstable surface or closed eyes serves to attenuate inertial control and to elicit more of the feedback-based control over progressively shorter timescales. The result was to strengthen the appearance of the linear decay indicating cascade dynamics. Finally, both linear and nonlinear indices of postural sway also govern the relative strength of crossover or of linear decay, suggesting that tempering of non-Gaussianity across log-timescale is a function of both extrinsic constraints and endogenous postural control. These results provide new evidence that cascading interactions across longer timescales supporting postural corrections can even recruit shorter timescale processes with novel task constraints that can destabilize posture.

安静的站立表现出强烈的间歇性变化，至少激发了两种解释。首先，可变性可以通过不同规模的互补控制过程的交替参与和脱离而成为间歇性的。解释这种间歇性的第二种可能更深入的方法是，姿势控制可能同时依赖于多个时间尺度上的级联相互作用，这表明在不同时间尺度上具有特定的非高斯分布特性。多尺度概率密度函数 (PDF) 分析表明，安静地站立在稳定的表面上，在较短的时间尺度上表现出从低的、增加的非高斯性（与指数分布一致）（反映惯性控制）向更高的非高斯性的交叉。中等到较长时间尺度的基于反馈的控制产生线性下降，这是级联动力学的特征。用不稳定的表面或闭上眼睛破坏安静的站立有助于减弱惯性控制，并在越来越短的时间尺度上引发更多基于反馈的控制。结果是加强了表明级联动力学的线性衰减的外观。最后，姿势摇摆的线性和非线性指标也控制交叉或线性衰减的相对强度，这表明在对数时间尺度上非高斯性的回火是外在约束和内生姿势控制的函数。