Directional Dependence of Experimental Trunk Stiffness: Role of Muscle-Stiffness Variation of Nonneural Origin

Table 2

Muscles shortened following forward and backward position perturbations and their contribution to the trunk stiffness.

Muscle group		Forward perturbation		Backward perturbation
#	Name	Muscle designation		Muscle designation
1	Rectus abdominis	RA	18.4
2	External oblique	EO2; EO5; EO6	18.6
3	Thoracic multifidus	tmf_L1; tmf_L2	0.1	tmf_L3; tmf_L4; tmf_L5	0.5
4	Psoas major	pL1VB; pL1TP; pL1-L2IVD; pL2TP; pL2-L3IVD; pL3TP; pL3-L4IVD; pL4TP; pL4-L5IVD	0.6	pL5TP; pL5VB	0.05
5	Quadratus lumborum	T12-I,3; T12,1-I,3; T12,2-I,3; T12,3-I,3; I,3-L1; I,3-L3; I,2-L4	0.2	T12,1-I,2; L2-12,1; L3-12,1; L3-12,2; L3-12,3; L4-12,3; I,2-L2; I,3-L2; I,1-L3; I,2-L3	0.4
6	Longissimus thoracis			LT3; LT4; LT5; LT6; LT7; T8; LT9; LT10; LT11; LT12	22.9
7	Iliocostalis lumborum pars thoracis			IT5; IT6; IT7; IT8; IT9; IT10; IT11; IT12	10.0
8	Longissimus thoracis pars lumborum			l1; l2; l3; l4; l5	2.6
9	Iliocostalis lumborum pars lumborum			I1; I2; I3; I4	3.8
10	Multifidus			m1s; m1t1; mlt2; mlt3; m2s; m2t1; m2t2; m2t3; m3s; m3t1; m3t2; m3t3; m4s; m4t1; m4t2; m4t3; m5s; m5t1; m5t2; m5t3	6.3

Abbreviations are taken from [14].