$\newcommand{\Dev}{\operatorname{Dev}}$ $\newcommand{\dev}{\operatorname{dev}}$ $\newcommand{\grad}{\operatorname{grad}}$ $\newcommand{\Grad}{\operatorname{Grad}}$ $\newcommand{\divg}{\operatorname{div}}$ $\newcommand{\Ei}{\operatorname{Ei}}$ $\newcommand{\tr}{\operatorname{tr}}$ $\newcommand{\Divg}{\operatorname{Div}}$ $\newcommand{\cay}{\operatorname{cay}}$ $\newcommand{\rot}{\operatorname{rot}}$

An isotropic active contractile stress is given by $$\begin{equation} \mathbf{S}^{a}=T^{a}\mathbf{I}\label{eq523} \end{equation}$$ and the corresponding Cauchy stress is $$\begin{equation} \boldsymbol{\sigma}^{a}=J^{-1}T^{a}\mathbf{B}\,.\label{eq524} \end{equation}$$ The material and spatial tangents are zero.