Chapter 3
Anthropometry
Anthropometry
• Deals with the measure of
size, mass, shape and
inertial properties of the
human body segments.
Biomechanical Models
• Facilitates prediction of a body’s
response and the design of the
workspace interface
• Physical
• crash test dummies
Biomechanical Models
• Facilitates prediction of a body’s
response and the design of the
workspace interface
• Physical
• crash test dummies
• Mathematical
• Joint moment of force
Biomechanical Models
• Facilitates prediction of a body’s
response and the design of the
workspace interface
• Physical
• crash test dummies
• Mathematical
• Joint moment of force
Biomechanical Models
• Facilitates prediction of a body’s
response and the design of the
workspace interface
• Physical
• crash test dummies
• Mathematical
• Joint moment of force
Biomechanical Models
• Facilitates prediction of a body’s
response and the design of the
workspace interface
• Physical
• crash test dummies
• Mathematical
• Joint moment of force
Measurement of Body-Segment
Physical Properties
• Segments defined by bony prominence
(landmarks) (fig 3.2)
• Human body: system of rigid links
• known physical size and form
• connected at identifiable joints
Caveat: Body-segment links
• No joint in the human body is a simple
single-axis hinge joints, but are considered
so in many analyses (1 Degree of Freedom)
• Assume
• segments are rigid links
• joints are frictionless and hinged
Body-segment links
• Link lengths can be
defined as the
distance between
projected centers
• Resulting error in
link length estimate
is < + 5%
Body-segment links
• Acceptable degree of model
simplification reflect analysis goal:
• Assumptions valid for most analyses
• Crash test dummies require consideration
of joint structure, ligaments, muscle
response, organs, etc.
• Injury risk (Lives!!) depends on the
validity of the model
Average
Segment
Lengths as
Proportion of
Total Body
Height (TBH)
[see Table 3.7]
Padding goalie stats no longer an option: NHL catalogues netminders' measurements
By DAVE STUBBS, © Copyright (c) The Montreal Gazette, November 17, 2009
Habs' Carey Price is slated to have his measurements taken next month for new equipment rules that will come into effect next season.
Kay Whitmore would make a pretty fair tailor or building contractor. For now, he's the National Hockey League's go-to guy with a tape measure.
Whitmore, the league's manager of hockey operations, is gradually working his way through NHL dressing rooms to catalogue the legs of 60-plus netminders. When fully collected, his data will be
applied to a formula providing new size-specific pad-length rules for the 2010-11 season.
Next fall, a few goalies might be wearing pads taller than the current 38-inch NHL maximum. The pads of others might be a little shorter; some should see no change at all.
It's part of the league's effort, in concert with the players' association, to streamline goaltenders - to maintain or improve their protection while putting them on a sheet of ice that's level for all.
"We're working with the union, dealing with fairness and the safety of the goalies, and trying not to upset equipment manufacturers," Whitmore said with a laugh.
The plan, approved last week by NHL general managers, asks: Why should a 6-foot-5 goalie like Nashville's Pekka Rinne look rink-length to, say, the Canadiens' Jaroslav Halak, who is six inches
shorter, but wearing pads of precisely the same size? While the NHL is satisfied that goalies are wearing sleeker upper-body protection - they're no longer the human spinnakers who billowed to fill the
net - the issue of pad size was less easily solved.
Body measurement of goalies was done last March by each team's equipment staff. But their leg measurements were sometimes wildly inconsistent. So Whitmore, a former NHL netminder, is now
taking his own tape measure to goalies' legs. He's the one who inspects equipment before its first NHL use to ensure its legality and does postgame spot-checks to make certain things have not been
tweaked beyond the rules.
The leg measurement is two-fold: it's taken from the floor, beneath a goalie's bare foot, up to the centre of his kneecap, the knee slightly bent; and from the knee to the pelvic bone.
Whitmore also is charting arm length, circumference of chest, waist and hips, and skate-boot size, as well as determining whether a goalie needs a pant-size allowance depending on how he wears his
chest and torso protection. Applied to a complex formula, the leg data will give a goalie the maximum length next season for his pad, which remains the current 11 inches wide. The aim is to have it
reach roughly mid-thigh, no longer above the crotch to almost navel-height.
But protection, Whitmore said, remains paramount. "If a guy is 6-foot-5 with really short legs (and thus would be wearing shorter pads), he'll have a longer upper-body pad to cover his longer torso,"
Whitmore said. "We can't ask guys not to play their style because some of the newer equipment created that style."
Whitmore, based in Toronto, figures he's scoped about 30 goalies so far. He expects to size up the Canadiens' Carey Price and Halak on Dec. 26, when the Habs are at the Air Canada Centre to play the
Maple Leafs. He tries to measure all goalies, shoulders to toes, before a game-day morning skate when the netminder is in undergarments and of normal bulk, neither waterlogged nor dehydrated.
"The goalies are willing to do their part to help everyone, as long as it's fair for all," Whitmore said. That's not to say goaltenders still won't try to bend the rules, even if there's little that would surprise a
fraternity brother. Whitmore has heard stories about netminders asking their pant suppliers to replace an XXL tag with an L, in a bid to detour the size police.
Whitmore, who can spot that ploy a mile away, expects to keep a close eye on resized goalies who might exercise a little, well, creativity to reclaim a lost half-inch. But this plan isn't about shrinking the
player; if a larger body needs longer leg coverage, he'll get it.
Vaughn Sports, which makes equipment for Price and about 30 NHL and AHL goaltenders, expects to have NHL/NHLPA-approved sizes in time to make pads for pro customers to use in summer
hockey."Goaltending is totally different than it was 20 years ago," said Jorg Achenbach, Vaughn's pro-services representative. "I believe goalies of today are much better athletes, mentally tougher and
superior in conditioning. "They understand the physics, dynamics and laws of averages of the position. They also have fantastic goalie coaches who are students of the game."
Indeed, much has changed since the days of harness-maker Emil (Pop) Kenesky, who from the mid-1920s almost until his death in 1974 sketched blueprints for his NHL customers and hand-stitched
their horsehide- and felt-stuffed leather pads on his Hamilton, Ont., workbench. Computers and synthetic materials are the production staples today, with a pair weighing less than just one of Kenesky's.
For now, at least, streamlining goalies has silenced talk of larger nets, a sacrilege discussed during the lockout.
"Maybe that's still out there in the sense that, 'Hey, if the (equipment) doesn't work, we always have larger nets,' " Whitmore said. "I don't know if there's a lot of appetite for that. I've learned to never
say never, but this game is probably in the best place it's ever been."
Given the choice of more net to protect or one less inch of pad to guard the status quo, goalies would agree that Whitmore's tape measure is the lesser of two evils. By far.
Padding goalie stats no longer an option: NHL catalogues netminders' measurements
By DAVE STUBBS, © Copyright (c) The Montreal Gazette, November 17, 2009
When fully collected, his data will be applied to a formula providing new size-specific pad-length rules for the 2010-11 season.
Next fall, a few goalies might be wearing pads taller than the current 38-inch NHL maximum. The pads of others might be a little
shorter; some should see no change at all.
It's part of the league's effort, in concert with the players' association, to streamline goaltenders - to maintain or improve their
protection while putting them on a sheet of ice that's level for all.
"We're working with the union, dealing with fairness and the safety of the goalies, and trying not to upset equipment manufacturers,"
Whitmore said with a laugh.
The plan, approved last week by NHL general managers, asks: Why should a 6-foot-5 goalie like Nashville's Pekka Rinne look rinklength to, say, the Canadiens' Jaroslav Halak, who is six inches shorter, but wearing pads of precisely the same size? While the NHL
is satisfied that goalies are wearing sleeker upper-body protection - they're no longer the human spinnakers who billowed to fill the
net - the issue of pad size was less easily solved.
Body measurement of goalies was done last March by each team's equipment staff. But their leg measurements were sometimes
wildly inconsistent. So Whitmore, a former NHL netminder, is now taking his own tape measure to goalies' legs. He's the one who
inspects equipment before its first NHL use to ensure its legality and does postgame spot-checks to make certain things have not been
tweaked beyond the rules.
The leg measurement is two-fold: it's taken from the floor, beneath a goalie's bare foot, up to the centre of his kneecap, the knee
slightly bent; and from the knee to the pelvic bone. Whitmore also is charting arm length, circumference of chest, waist and hips, and
skate-boot size, as well as determining whether a goalie needs a pant-size allowance depending on how he wears his chest and torso
protection. Applied to a complex formula, the leg data will give a goalie the maximum length next season for his pad, which remains
the current 11 inches wide. The aim is to have it reach roughly mid-thigh, no longer above the crotch to almost navel-height.
But protection, Whitmore said, remains paramount. "If a guy is 6-foot-5 with really short legs (and thus would be wearing shorter
pads), he'll have a longer upper-body pad to cover his longer torso," Whitmore said. "We can't ask guys not to play their style because
some of the newer equipment created that style.”
Body-segment mass and weight
• The mass of the body segments
adds additional stresses to the body
beyond those exerted by external
forces (resistance to acceleration)
• These weight related stresses can
be of considerable magnitude in
certain postures (a force)
Inertia
Resistance of an object to
changing its current state of
motion.
Body-segment inertial properties
When a segment can translate
and/or rotate during activity, the
inertial properties of the segment
must be considered in the
analysis
Two inertial properties to consider
• Mass: resistance to linear acceleration
• Moment of Inertia: resistance to angular
acceleration
Conversions
• Mass (kg) to Weight (lbs)
multiply by 2.2 (downward)
• Mass (kg) to Weight (N):
multiply by 9.81 (downward)
• Weight (lbs) to Weight (N):
multiply by 4.45
Body-segment mass and weight:
• Body segment mass (weight)
can be expressed as a
proportion of whole-body mass
(weight) without great loss of
accuracy
• TBM: total body mass
• Many sources exist (see p41 in text)
Table 3.4, p41
Recommended Values for Percentage
distribution of total body weight
Grouped segments, % of total body wt
Head and neck
8.4%
Torso
50%
Total arm
5.1%
Total leg
15.7%
data from Winter (1989)
based on Dempster (1956) data (overhead)
Percent distribution of total body mass
Grouped segments % of total body wt
Head and neck
8%
HAT
68 %
Total arm
5%
Total leg
16 %
One of the most common sources for anthropometric data.
Winter table
Winter table (cont’d)
Example
• TBM of individual is 82 kg (180 lbs)
• 82 kg x -9.81 = 804 Newtons
• What is mass of upper body?
• from Winter table: HAT (head-arms-trunk) =
67.8% of TBM
• Calculate: (82 kg) x (0.678) = 55.6 kg
• 180 lbs x 0.678 = 122 lbs
• 804 N x 0.678 = 545 Newtons
Body segment
center of mass location
• Insufficient to know only the mass (weight)
of a body segment to perform an analysis
• Must locate the center of mass for each
segment (and the entire body)
•
•
•
•
single point mass
point of application of the gravitational force
See Table 3.5 p43, Table 3.13 p.48
Better: off Winter overhead
Winter table
Example
• Total Arm of individual is 51 cm (20
inches) long
• 0.51 m long
• Locate Center of mass
• from Winter table: 0.53 (53% of arm length
from the proximal end)
• Calculate: (0.51 m) x (0.53) = 0.27 m from
the proximal end of arm
Importance
• Knowledge of
• mass center location in segment
• % TBM (weight)
• link length
• sufficient input for static analysis to
calculate forces and moments at each
joint for a given body posture.
Draw a FBD of Arm
(60 inches, 215 pound person)
Angular inertial properties
• This property is referred to as
• Inertia (linear motion)
• moment-of-inertia (angular motion)
• not only mass, but mass distribution
I=m
2
r
• Varies according to Axis
• Varies according to mass distribution
Moment of Inertia
• greater the moment of inertia
greater inertial load
Greater joint stress
Example flexed vs straight elbow
Anthropometric Data for Biomechanics
Studies in Industry:
• anthropometric data defines the
reach and space requirements of a
specified population or equipment
user
• modeling and simulation
• important consideration for
workplace design
Making anthropometric measurements in the modern world
Workplace Analyses
• The book includes tables of PERCENTILE
data for segment lengths, weights, masscenter location, and moment of inertia based
on the general population.
z=
- 1.645
95%
5%
50%
z = 1.645
Example application of
Percentile Tables ( Table 3.8& 3.9)
• Table 3.8: Segment lengths as % TBH
• Table 3.9: the mean (50th), 5th and 95th
percentile population heights.
• design must strive to accommodate the
5th to 95th percentiles (M & F)
• Importance: hand tools, workstation
surfaces and seat design
Example:
Using USAF men and women
•
•
•
•
New pliers with span of 11 cm (4.3”)
USAF women: average ht = 162.1 cm
USAF men: average ht = 177.2 cm
Calculate average hand length: (0.108
x height)
• Females: 162.1 x 0.108 = 17.5 cm (6.9 “)
• Males: 177.2 x 0.108 = 19.0 cm (7.5”)
• Male and female
differences
• Racial
differences
• (US vs
Japanese)
• Specific
population
• (ie source:
military,
NASA,
civilians)
• number of
subjects
• source of
variability (SD)
• (ie NASA vs
civilians)
Summary
• Knowledge of anthropometry is important
• Anthropometrics is basis of models
• mass, length, and center of mass of segments
• Design must accommodate 5th to 95th
• appropriate sex, race, specific population
• Will use the tables with future analysis