2-8 Biomechanics
TABLE 2.5 Architectural Properties of Human Lower Limb
a,b
Muscle Mass Muscle Fiber Length Pennation Cross-Sectional
Muscle (g) Length (mm) (mm) Angle (◦) Area (cm
2
) FL/ML Ratio
RF (n = 3) 84.3 ±14 316 ± 5.766.0 ±1.55.0 ±0.012.7 ±1.90.209 ±0.002
VL (n = 3) 220 ±56 324 ± 14 65.7 ±0.88 5.0 ± 0.030.6 ± 6.50.203 ± 0.007
VM (n = 3) 175 ± 41 335 ±15 70.3 ± 3.35.0 ± 0.021.1 ± 4.30.210 ± 0.005
VI (
n = 3) 160 ±59 329 ± 15 68.3 ±4.83.3 ±1.722.3 ±8.70.208 ±0.007
SM (n = 3) 108 ± 13 262 ±1.562.7 ±4.715±2.916.9 ± 1.50.239 ± 0.017
BF
L
(n = 3) 128 ± 28 342 ±14 85.3 ± 5.00.0 ± 0.012.8 ± 2.80.251 ±0.022
BF
s
(n = 3) — 271 ±11 139 ± 3.523±0.9—0.517 ±0.032
ST (n = 2) 76.9 ±7.7 317 ± 4 158 ± 2.05.0 ± 0.05.4 ± 1.00.498 ±0.0
SOL (n = 2) 215 (n = 1) 310 ± 1.519.5 ±0.525± 5.0 58.0 (n = 1) 0.063 ± 0.002
MG (n = 3) 150 ± 14 248 ±9.935.3 ±2.016.
7 ±4.432.4 ±3.10.143 ±0.010
LG (n = 3) — 217 ±11 50.7 ±5.68.3 ±1.7—0.233 ±0.016
PLT (n = 3) 5.30 ±14 85.0 ± 15 39.3 ± 6.73.3 ± 1.71.2 ±0.40.467 ±0.031
FHL (n = 3) 21.5 ± 3.3 222 ± 5.034.0 ±1.510.0 ± 2
.95.3 ±0.60.154 ±0.010
FDL (n = 3) 16.3 ±2.8 260 ±15 27.0 ±0.58 6.7 ± 1.75.1 ± 0.70.104 ± 0.004
PL (n = 3) 41.5 ±8.5 286 ± 17 38.7 ±3.210.0 ± 0.012.3 ± 2.90.136 ± 0.010
PB (n = 3) 17.3 ±2.5 230 ±13 39.3 ±
3.55.0 ± 0.05.7 ±1.0 0170 ± 0.006
TP (n = 3) 53.5 ± 7.3 254 ± 26 24.0 ±4.011.7 ± 1.720.8 ±30.095 ±0.015
TA (n = 3) 65.7 ± 10 298 ±12 77.3 ±7.85.0 ±0.09.9 ±1.50.258 ±0.015
EDL (n = 3) 35.2 ± 3.6 355 ± 13 80.3
± 8.48.3 ± 1.75.6 ±0.60.226 ±0.024
EHL (n = 3) 12.9 ±1.6 273 ± 2.487.0 ± 8.06.0 ± 1.01.8 ± 0.20.319 ± 0.030
SAR (n = 3) 61.7 ±14 503 ± 27 455 ±19 0.0 ±0.01.7 ±0.30.906 ± 0.017
GR (n = 3) 35.3 ± 7.4 335 ±
20 277 ± 12 3.3 ± 1.71.8 ±0.30.828 ±0.017
AM (n = 3) 229 ±32 305 ± 12 115 ±7.90.0 ± 0.018.2 ±2.30.378 ± 0.013
AL (n = 3) 63.5 ± 16 229 ± 12 108 ± 2.06.0 ± 1.06.8 ± 1.90.475 ±0.023
AB (n = 3) 43.8 ± 8.4 156 ± 12 103 ± 6.40.0
± 0.04.7 ± 1.00.663 ±0.036
PEC (n = 3) 26.4 ± 6.0 123 ± 4.5 104 ± 1.20.0 ± 0.02.9 ± 0.60.851 ± 0.040
POP (n = 2) 20.1 ±2.4 108 ± 7.029.0 ± 7.00.0 ± 0.07.9 ±1.40.265 ±0.048
a
Data from Wickiewicz et al., 1982.
b
AB, adductor brevis; AL, adductor longus; AM, adductor magnus; BF
L
, biceps femoris, long head; BF
S
, biceps femoris,
short head; EDL, extensor digitorum longus; EHL, extensor hallucis longus; FDL, flexor digitorum longus; GR, gracilis;
FHL, flexor hallucis longus; LG, lateral gastrocnemius; MG, medical gastrocnemius; PEC, pectineus; PB, peroneus
brevis; PL, peronius longus; PLT, plantaris; POP, popliteus; RF, rectus femoris; SAR, sartorius; SM, semimembranosus;
SOL, soleus; ST, semitendinosus; TA, tibialis anterior; TP, tibialis posterior; VI, vastus intermedius; VL, vastus lateralis;
VM, vastus medialis.
These equations can be solved analytically for the special case of confined compression against a porous
platen [Mow et al., 1980]. The surface displacement during creep under an applied load f
0
is
u
h
=
f
0
H
A
1 −
2
π
2
2
n=0
n +
1
2
−2
exp
−π
2
n +
1
2
2
H
A
kf
(1 +2a
0
)h
2
where h is the tissue thickness, and H
A
is the aggregate modulus (λ + 2μ). Those authors estimate k as
7.6 ± 3.0 × 10
−13
m
4
/Nsec and H
A
as 0.70 ± 0.09 MPa for bovine articular cartilage. Chen et al. [2001]
report strongly depth-dependent values for H
A
ranging between 1.16 ±0.20 MPa in the superficial zone to
7.75 ±1.45 MPa in the deep zone in human articular cartilage. The biphasic approach has been extended
to finite element modeling, resulting in the u–p class of models [Wayne et al., 1991].
2.3.2 Tendon and Ligament
The composition and structure of the tensile soft tissues is quite similar to that of cartilage, and the
biphasic theory can be applied to them as well. Fluid pressure serves a smaller role in tissues loaded in