Recently, experimental results have demonstrated that the load carrying capacity of the human spine substantially increases under the follower load condition. Thus, it is essential to prove that a follower load can be generated in vivo by activating the appropriate muscles in order to demonstrate the possibility that the stability of the spinal column could be maintained through a follower load mechanism. The aim of this study was to analyze the coordination of the trunk muscles in order to understand the role of the muscles in generating the follower load. A three-dimensional finite element model of the lumbar spine was developed from T12 to S1 and 117 pairs of trunk muscles (58 pairs of superficial muscles and 59 pairs of deep muscles) were considered. The follower load concept was mathematically represented as an optimization problem. The muscle forces required to generate the follower load were predicted by solving the optimization problem. The corresponding displacements and rotations at all nodes were estimated along with the follower forces, shear forces, and joint moments acting on those nodes. In addition, the muscle forces and the corresponding responses were investigated when the activations of the deep muscles or the superficial muscles were restricted to 75% of the maximum activation, respectively. Significantly larger numbers of deep muscles were involved in the generation of the follower load than the number of superficial muscles, regardless of the restriction on muscle activation. The shear force and the resultant joint moment are more influenced by the change in muscle activation in the superficial muscles. A larger number of deep trunk muscles were activated in order to maintain the spinal posture in the lumbar spine. In addition, the deep muscles have a larger capability to reduce the shear force and the resultant joint moment with respect to the perturbation of the external load or muscle fatigue compared to the superficial muscles.

1.
Moore
,
K. L.
, and
Dalley
,
A. F.
, 1999,
Clinically Oriented Anatomy
,
Lippincott Williams & Wilkins
,
Philadelphia
.
2.
White
,
A. A.
, III
,
Johnson
,
R. M.
,
Panjabi
,
M. M.
, and
Southwick
,
R. O.
, 1975, “
Biomechanical Analysis of Clinical Stability in the Cervical Spine
,”
Clin. Orthop. Relat. Res.
0009-921X,
109
, pp.
85
95
.
3.
Crisco
, III,
J. J.
, and
Panjabi
,
M. M.
, 1991, “
The Intersegmental and Multisegmental Muscles of the Lumbar Spine. A Biomechanical Model Comparing Lateral Stabilizing Potential
,”
Spine
0362-2436,
16
, pp.
793
799
.
4.
Wilke
,
H. J.
,
Wolf
,
S.
,
Claes
,
L. E.
,
Arand
,
M.
, and
Wiesend
,
A.
, 1995, “
Stability Increase of the Lumbar Spine With Different Muscle Groups. A Biomechanical In Vitro Study
,”
Spine
0362-2436,
20
, pp.
192
198
.
5.
Wilke
,
H. J.
,
Rohlmann
,
A.
,
Neller
,
S.
,
Graichen
,
F.
,
Claes
,
L.
, and
Begmann
,
G.
, 2003, “
A Novel Approach to Determine Trunk Muscle Forces During Flexion and Extension. A Comparison of Data from an In Vitro Experiment and In Vivo Measurements
,”
Spine
0362-2436,
28
, pp.
2585
2593
.
6.
Patwardhan
,
A. G.
,
Havey
,
R. M.
,
Meade
,
K. P.
,
Lee
,
B.
, and
Dunlap
,
B.
, 1999, “
A Follower Load Increases the Load-carrying Capacity of the Lumbar Spine in Compression
,”
Spine
0362-2436,
24
, pp.
1003
1009
.
7.
Patwardhan
,
A. G.
,
Havey
,
R. M.
,
Ghanayem
,
A. J.
,
Diener
,
H.
,
Meade
,
K. P.
,
Dunlap
,
B.
, and
Hodges
,
S. D.
, 2000, “
Load-carrying Capacity of the Human Cervical Spine in Compression is Increased Under a Follower Load
,”
Spine
0362-2436,
25
, pp.
1548
1554
.
8.
Beck
,
M.
, 1952, “
Die Knicklast des Einseitig Eingespannten, Tangential Gedrückten Stabes
,”
ZAMP
0044-2275,
3
, pp.
225
228
and
476
477
.
9.
Pflüger
,
A.
, 1955, “
Zur Stabilität des Tangential Gedrückten Stabes
,”
ZAMM
0044-2267,
35
, p.
191
.
10.
McGill
,
S.
,
Juker
,
D.
, and
Kropf
,
P.
, 1996, “
Quantitative Intramuscular Myoelectric Activity of Quadratus Lumborum during a Wide Variety of Tasks
,”
Clin. Biomech. (Bristol, Avon)
0268-0033,
11
, pp.
170
172
.
11.
Stokes
,
I. A. F.
, and
Gardner-Morse
,
M. G.
, 1995, “
Lumbar Spine Maximum Efforts and Muscle Rcruitment Ptterns Pedicted by a Model With Multijoint Muscles and Joints with Stiffness
,”
J. Biomech.
0021-9290,
28
, pp.
173
186
.
12.
Stokes
,
I. A. F.
, and
Gardner-Morse
,
M. G.
, 2001, “
Lumbar Spinal Muscle Activation Synergies Predicted by Multi-Criteria Cost Function
,”
J. Biomech.
0021-9290,
34
, pp.
733
740
.
13.
Kim
,
Y. H.
, and
Kim
,
K.
, 2004, “
Numerical Analysis on Quantitative Role of Trunk Muscles in Spinal Stabilization
,”
JSME Int. J., Ser. C
1340-8062,
47
, pp.
1062
1069
.
14.
Kim
,
K.
,
Kim
,
Y. H.
, and
Lee
,
S. K.
, 2007, “
Increase of Load Carrying Capacity under Follower Load Generated by Trunk Muscles in Lumbar Spine
,”
Proc. Inst. Mech. Eng. Part H: J. Eng. Med.
to be published.
15.
Bogduk
,
N.
,
Macintosh
,
J. E.
, and
Pearcy
,
M. J.
, 1992, “
A Universal Model of the Lumbar Back Muscles in the Upright Position
,”
Spine
0362-2436,
17
, pp.
897
913
.
16.
Stokes
,
I. A. F.
, and
Gardner-Morse
,
M. G.
, 1999, “
Quantitative Anatomy of the Lumbar Musculature
,”
J. Biomech.
0021-9290,
32
, pp.
311
316
.
17.
Gardner-Morse
,
M. G.
,
Laible
,
J. P.
, and
Stokes
,
I. A. F.
, 1990, “
Incorporation of Spinal Flexibility Measurements into Finite Element Analysis
,”
ASME J. Biomech. Eng.
0148-0731,
112
, pp.
481
483
.
18.
Schultz
,
A. B.
, 1990,
Biomechanical Analyses of Loads on the Lumbar Spine
,
The Lumbar Spine
,
W. B. Saunders Co.
,
Philadelphia
, pp.
160
171
.
19.
Lu
,
W. W.
,
Luk
,
K. D. K.
,
Holmes
,
A. D.
,
Cheung
,
K. M. C.
, and
Leong
,
J. C. Y.
, 2005, “
Pure Shear Properties of Lumbar Spinal Joints and the Effect of Tissue Sectioning on Load Sharing
,”
Spine
0362-2436,
30
, pp.
E204
E209
.
20.
Stokes
,
I. A. F.
, and
Frymoyer
,
J. W.
, 1987, “
Segmental Motion and Instability
,”
Spine
0362-2436,
12
, pp.
688
691
.
21.
McGill
,
S. M.
,
Hughson
,
R. L.
, and
Parks
,
K.
, 2000, “
Changes in Lumbar Lordosis Modify the Role of the Extensor Muscles
,”
Clin. Biomech. (Bristol, Avon)
0268-0033,
15
, pp.
777
780
.
22.
Norman
,
R.
,
Wells
,
P.
,
Neumann
,
P.
,
Frank
,
J.
,
Shannon
,
H.
,
Kerr
,
M.
, and the Ontario Universities Back Pain Study Group, 1998, “
A Comparison of Peak vs Cumulative Physical Work Exposure Risk Factors for the Reporting of Low Back Pain in the Automotive Industry
,”
Clin. Biomech. (Bristol, Avon)
0268-0033,
13
, pp.
561
573
.
23.
Wilke
,
H. J.
,
Neef
,
P.
,
Caimi
,
M.
,
Hoogland
,
T.
, and
Claes
,
L. E.
, 1999, “
New In Vivo Measurements of Pressures in the Intervertebral Disc in Daily Life
,”
Spine
0362-2436,
24
, pp.
755
762
.
24.
Wilke
,
H. J.
,
Nee
,
P.
,
Hinz
,
B.
,
Seidel
,
H.
, and
Claes
,
L.
, 2001, “
Intradiscal Pressure together With Anthropometric Data—A Data Set for the Validation of Models
,”
Clin. Biomech. (Bristol, Avon)
0268-0033,
16
, pp.
S111
S126
.
25.
Nachemson
,
A.
, and
Elfstrom
,
G.
, 1970, “
Intravital Dynamic Pressure Measurements in Lumbar Discs. A Study of Common Movements, Maneuvers and Exercises
,”
Scand. J. Rehabil. Med. Suppl.
0346-8720,
1
, pp.
1
40
.
26.
Schultz
,
A.
,
Andersson
,
G.
,
Ortengren
,
R.
,
Haderspeck
,
K.
, and
Nachemson
,
A.
, 1982, “
Loads on the Lumbar Spine. Validation of a Biomechanical Analysis by Measurements of Intradiscal Pressures and Myoelectric Signals
,”
J. Bone Jt. Surg., Am. Vol.
0021-9355,
64
, pp.
713
720
.
27.
White
, III,
A. A.
, and
Panjabi
,
M. M.
, 1990,
Clinical Biomechanics of the Spine
,
Lippincott Williams & Wilkins
,
Philadelphia
.
You do not currently have access to this content.