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. Author manuscript; available in PMC: 2019 Feb 21.
Published in final edited form as: Neuroscience. 2017 Dec 23;372:97–113. doi: 10.1016/j.neuroscience.2017.12.018

Figure 1.

Figure 1

The plot shows a family of dependences of a force vector FX on a spatial vector variable X (the dashed line). The efferent process (EFF) defines a referent coordinate (RCX), while the afferent signals (AFF) inform on deviation of X from RCX. At a single-muscle level, RCX is equivalent to the stretch reflex threshold (λ), while FX is muscle force (F) and X is muscle length (L). For a given external load (the solid curves show a family of load characteristics), the system comes to an equilibrium point (EP) with a combination of F, L, and muscle activation (EMG), which is the point of intersection of two characteristics (shown as thick lines) defined by the actual external load and values of λ.