Fig 3.

(A) Viscoelastic model used to represent receptor muscle (Swerup & Rydqvist, 1996). Total extension is the sum of that from both linear (left-hand-side spring in A) and non-linear springs (right-hand-side spring in A). The spring constant of the non-linear spring is k  = k₂ × εⁿ. (B) General form of the ramp-and-hold extension. ε₀ is extension before ramp, t₁ is the end of extension rising phase, α is rate of rise, t₂ and t₃ define the falling phase of the ramp, β is the rate of fall.