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(a) (b)
(c)
(d)
FIGURE 2.1 Stability of the body parts depends on the shape of the base of support described by the position
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FIGURE 2.2 Tent analogy. The skeleton is the tent pole, the muscles are the guy ropes, and the soft tissues
are the canvas.
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Iordosis
Kyphosis
Cervical
oracic
Lumbar
Sacral
cc
b
a
Iordosis
d
FIGURE 2.3 The lumbar, thoracic, and cervical spines and the pelvis (a) and sacrum (b). The weight of theupper
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1
2
2
1
FIGURE 2.4 Function of (1) intervertebral disk and (2) facet joints. The disk resists the compressive load and
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A
C
B
(a) (b)
FIGURE 2.5 Intervertebral disk and vertebral body. (a) In this view, the superior vertebral body has been
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A
B
B
CC
A
BB
FIGURE 2.6 The pelvis as an arch. The pelvis viewed from the rear. A is the sacrum, B is the ilium, and C
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A
B
C
FIGURE 2.7 View of the sacroiliac joint from above. A represents the ligaments, B is the sacrum, and C is
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(a)
(b)
(c)
40° 15° –5°
FIGURE 2.8 Relationship between sacral and lumbar angles. (a) Sacral angle and lumbar lordosis, as
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Abdominals Erector
spinae
Hip
extensors
Hip
flexors
FIGURE 2.9 Schematic representation of the muscular system of the pelvis (sagittal view). When the abdom-
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(a) (b)
FIGURE 2.10 When the base of support is constrained, compensatory movements occur automatically to
maintain postural stability demonstrating that the “attitudinal as well as the righting reactions” are indeed
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reshold of damage
Time
(a) (b)
Demand on tissues
Demand on tissues
reshold of
damage
Time
(c)
Demand on tissues
reshold of damage
Time
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100
1000
20
3.0 6.1
4.6
7.6
24.4
m/s
40
Inertial forc
e
vector
G
Pulse duration t (s)
FIGURE 2.13 The tolerance to human whole-body impact for critical velocity change, critical acceleration
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0
Risk of pedestrian fatality
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Ashton data (all ages, front of cars, n = 358)
10 20 30 40
Impact speed (mph)
50 60
70
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FIGURE 2.17 Sample output of SSPP (University of Michigan). Lifting a mooring bollard weighing 38.6 kg.
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3
2
1
0
Not
uncomfortable
A little
uncomfortable
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