Table A1.

Variables only in appendix.

Symbol	Definition	Symbol	Definition
S0	surface of V0	${\widehat{n}}_0$	normal unit vector on S
V	current configuration	${\widehat{a}}_0$	normalized fibre orientation in V0
S	surface of V	t	applied traction
St	region of S with applied traction	κmus	bulk modulus muscle
Sd	region of S with applied displacement	κapo	bulk modulus aponeurosis
Vol	current volume	F	deformation tensor
A	area in V	I	identity tensor
t	time	B	left Cauchy tensor
q0	point in V0	Biso	isovolumetric left Cauchy tensor
q	point in V	σ	Cauchy stress tensor
Uvol	volumetric strain-energy potential	τ	Kirchhoff tensor
Uiso	isovolumetric strain-energy potential	I1	first invariant
Ubase	base material strain-energy potential	I3	third invariant
Ufibre	fibre strain-energy potential	I4	fourth invariant
Uapo,base	aponeurosis base material strain-energy potential	â	activation level in muscle fibres
Uapo,fibre	aponeurosis fibre strain-energy potential	σ0	maximum isometric stress of contractile elements
Umus,base	muscle base material strain-energy potential	σbase	base material stress
Umus,fibre	muscle fibre strain-energy potential	σmus,base	muscle base material stress
Uact	active muscle fibre strain-energy potential	σapo,base	aponeurosis base material stress
Upas	passive muscle fibre strain-energy potential	σfibre	fibre stress
ψvol	volumetric strain energy-density	σmus,fibre	muscle fibre stress
ψiso	isovolumetric energy-density	σapo,fibre	aponeurosis fibre stress
ψbase	base energy-density	${\widehat{\sigma }}_{\text{act}}$	active muscle fibre stress
ψfibre	fibre energy-density	${\widehat{\sigma }}_{\text{pas}}$	passive muscle fibre stress
ψapo,base	aponeurosis base material energy-density	∇0	gradient with respect to V0
ψapo,fibre	aponeurosis fibre energy-density	∇	gradient with respect to V
ψmus,base	muscle base material energy-density	div	tensorial divergence with respect to V
ψmus,fibre	muscle fibre energy-density	0	zero vector