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Anthropometric Measurements
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Application of Anthropometry in Biomechanics
Measurement of Segment Length
Measurement of Segment Mass
Measurement of Center of Mass
Measurement of Moment of Inertia
Measurement of Physiological Cross-sectional Area
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After completing this topic, the students will be able to
- to define the scope of the anthropometry
- to calculate the parameters related to the body segment using anthropometric methods
- Winter, D.A., 1990. Biomechanics and Motor Control of Human Movement, 2nd ed.
New York, Wiley & Sons. pp. 11-50
- Chaffin, D.B., Andersson, G. B., Martin, D.J., 1999. Occupational Biomechanics,
3rd ed. New York, John Wiley & Sons. Chapter 3, pp. 65-130.
- Hall, 2003¡GChapter 3
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Application of Anthropometry in Biomechanics
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Definition of anthropometry
the study investigating the physical dimensions
or other properties of the human body
to determine the differences in the individuals and groups (Hall, 2003, p.3)
the science that deals with the measure of size, mass,
shape, and inertia properties of the human body
(Chaffin et al., 1999, p.65)
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Examples in movement science
length of body segment
trajectory of joint center of rotation
angle of pull of tendons
length and cross-sectional area of muscles
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Base of Knowledge needed in anthropometry
mathematics
physics
biomechanics
biostatistics
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Materials used in anthropometric research
living body
cadaver¡G fresh or frozen
fossil
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Measurement of Segment Length
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Length of body segment
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assumptions in motion analysis¡G
the human body is a system of mechanical links,
with each link of known physical size and form
the center of rotation
of each joint can be easily identified by bone landmark
determination of link¡G the line drawn along the
longitudinal axis of the segment
determination of center of rotation¡G the intersection of two segment links during motion
link length = the distance between two centers of rotation
error¡G < 5%
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Estimation of link length using bony landmarks
by Dempster, 1955
identification of bony landmarks located near the joint
axis of rotation
link length = the distance between two bony landmarks
R2 > 0.9
| segment |
link |
link-to-length ratio (%) |
| humerus |
acromion to lateral humeral epicondyle |
89.0% |
| radius |
lateral humeral epicondyle to ulnar styloid process
| 107.0% |
| hand |
ulnar styloid process to knuckle of 3nd metatarsal head
| 20.6% |
| femur |
greater trochanter to lateral femoral condyle |
91.4% |
| tibia |
lateral femoral condyle to lateral melleolus |
110.0% |
| foot |
lateral malleolus to 2nd metatarsal head
| 30.6% |
| * link-to-length ratio = link length / real bone length
´ 100% |
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Estimation of link length using body height
Drillis and Contini, 1966
| grouped link |
% of BH |
single link |
% of BH |
| total arm |
44% |
upper arm |
18.6% |
| forearm |
14.6% |
| hand |
10.8% |
| total leg at stance |
53.0% |
thigh |
28.5% |
| low leg |
24.6% |
| foot height at stance |
3.9% |
| Note¡G real foot length=15.2% |
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Measurement of Segment Mass
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Definition of mass
mass¡G a physical quantity of
matter composing a body
symbol¡G m
SI unit¡G kg (kilogram)
Can you distinguish mass from
weight?
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Estimation of density in human body
density¡G a physical quantity of
mass divided by volume
The human body consists of many types of tissue,
each with a different density
cortical bone > 1.8
muscle = ~1.0
fat < 1.0
average whole body density¡G a function of somatotype
d = 0.69 + 0.9 (h / w 1/3) where
the unit = kg/ l
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Measurement of segment density
density of distal segment > density of proximal density
immersion techniques
Di = mi / Vi
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Estimation of segment mass using total mass
If the location of the center of mass of the segment is known,
then the mass of each segment can easily be calculated.
Please see the next section.
segment mass¡G expressed by the percentage of the total mass (%M)
| grouped segment |
% of total body weight |
individual segment |
% of grouped segment |
| head and neck |
8.4% |
head |
73.8% |
| neck |
26.2% |
| torso |
50.0% |
thorax |
43.8% |
| lumbar |
29.4% |
| pelvis |
26.8% |
| total arm |
5.1% |
upper |
54.9% |
| forearm |
33.3% |
| hand |
11.8% |
| total leg |
15.7% |
thigh |
63.7% |
| shank |
27.4% |
| foot |
8.9% |
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Measurement of Center of Mass
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Definition of Center of Mass (COM)
definition
the point where the entire weight of the body is concentrated
the point in a body about which all the parts exactly
balance each other
Note¡GCan you distinguish the
center of mass
from the center of gravity (COG)
or from the center of pressure (COP)?
its precise location depending on
individual's anatomical structure
habitual standing posture
current position
external support
NOTE¡G Location of COM remains fixed as long as the body does NOT change the shape
methods to estimate the COM of an object
suspension method
moment subtraction method
segment zone approach¡G weighed average of every segment of the entire body
kinetic method¡G double integration of shear forces from the force platform
clinical method¡G measurement of the PSIS (posterior superior iliac spine) level in the sagittal plane
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Suspension Technique
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A body segment is suspended in a frame from only one point and then
the point where the gravity effect is equaled is the location of the
center of mass
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Methods to estimate COM
Moment Subtraction Method
developed by Williams & Lissner, 1977
example I¡G to measure the location of COM of a segment composed of the low leg and foot
given¡G segment weight W
- have the subject lie prone on a scale
- measure the length from head to scale, L
- read the value on the scale, S
- then have the subject bend one leg
- measure the length from head to knee, X'
- read the value on the scale, S'
- the location of the COM of the low leg and foot is equal to (X-X') from the knee joint
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example II¡G to measure the mass of the segment composed of the low leg and foot
given¡G location of the COM of the segment composed of the low leg and foot
the mass of the low leg and foot is
Methods to estimate COM
Segmental Zone Approach
developed by Miller & Nelson, 1976
for a single-segment¡G Please check Chaffin's book for details
for a multi-segment in 3D expression
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Methods to estimate COM
Ratios of location of COM to segment length
Different values have been reported form different studies due to
variations in the definition of segment length and different measurement techniques.
Please check Chaffin's book for details
| segment |
% from proximal end |
| upper arm |
43.6% |
| forearm |
43.0% |
| hand |
49.4% |
| thigh |
43.3% |
| shank |
43.3% |
| foot |
42.9% |
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Measurement of Moment of Inertia
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Definition
moment of inertia¡G
the physical quantity that an object resists to change or to action in response to angular velocity
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or |
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| where |
mi = mass of the ith segment |
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ri = perpendicular distance that the mass is located
from a given axis of rotation of the ith segment |
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Calculation of moment of inertia
moment of inertia acting around the axis of a joint
moment of inertia acting around the COM
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Radius of gyration
radius of gyration¡G the radial distance from the
axis of rotation at which the
mass of the segment can be concentrated
without altering the moment of inertia of the segment
I = mr 2
moment of inertia around a joint axis
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where I0 = moment of inertia about COM
x = distance between COM and center of rotation
m = mass of segment
r = radius of gyration
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Physiological Cross-Sectional Area
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Physiological cross-sectional area (PCSA) of a paralleled muscle
where m = mass of muscle fibers (g)
d = density of muscle (g/cm3) = ~1.056 g/cm3
l = length of muscle fibers (cm)
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Physiological cross-sectional area of a pennate muscle
pennation angle¡G
the angle between the longitudinal axis
of the muscle and the fiber angle of a
pennate-fiber muscle
where m = mass of muscle fibers (g)
d = density of muscle (g/cm3) = ~1.056g/cm3
l = length of muscle fibers (cm)
q = pennation angle
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