Table 2.

Parameter estimations.

Model	$c_3$ (nm)	$\mathrm{\Delta }{L}_{\mathit{CB}}$ (nm)	$C_{\mathit{fil}}$ ($\text{nm}{\text{pN}}^{-1}$)
Model1	–	85.7	0.4
Model1${}^{\ast }$	–	198	0.0067${}^{\ast }$
Model2	1.2	–	–

In model2, the parameter $c_3$ represents the pole (at $L_{\mathit{CB}}=-c_3$) in the non-linear cross-bridge force–length relation $F_{\mathit{CB}}(L_{\mathit{CB}})$ (Coulomb drive in series to the serial elastic part representing S1, S2 and filaments), which is used to estimate $k_{\mathit{CB}}$, and eventually $k_{\mathit{hs}}$. In model1, the parameter $\mathrm{\Delta }{L}_{\mathit{CB}}$ (nm) represents the average elongation at a fixed force of each cross-bridge acting in series to the filament part with compliance $C_{\mathit{fil}}$. The parameter values of both model1 and model2 were determined with the Matlab curve fitting tool ‘cftool’. If the maximum isometric force of a half-sarcomere $F_{CB,max}$ is 445 pN, as estimated in this paper, then the original parameter values for model1 ([$\mathrm{\Delta }{L}_{\mathit{CB}}=1.56\text{nm}$ and $C_{\mathit{fil}}=1.77\text{nm}{T}_0^{-1}$]¹⁵) would translate to $k_{\mathit{CB}}=285\text{pN}{\text{nm}}^{-1}$ ($\frac{445pN}{1.56nm}$) and $k_{\mathit{fil}}=251\text{pN}{\text{nm}}^{-1}$ ($\frac{445pN}{1.77nm}$) at $F_{CB,max}$.

${}^{\ast }$ $\mathrm{\Delta }{L}_{\mathit{CB}}$ (nm) in model1 estimated with a fixed $k_{\mathit{fil}}=150\text{pN}{\text{nm}}^{-1}$ value ($C_{\mathit{fil}}=\frac{1}{k_{\mathit{fil}}}=\frac{1}{150pNn{m}^{-1}}=0.0067nmp{N}^{-1}$).