isssptzist

10

Vertical distance (inche«’ of C. 6G. from reference point

7 8 9 yO fl 12 13 14 #15) 16 7 18
Horizontal distdnce (inches) of C. 6. from reference point

* A

Frcuns 7. Position of body C. G. of pilot operatiny controls in various positjons; back erect,
Meat 108° g back lege bo to thighs, ;

~19—



sa

pap>

TABLE XIV
t of C. G. by 20 Ib. Back Pack

(C. G. of Pack 18%” above ischium, 6” Back)

in Sitting and Standing Positions

Horizontal &
Location of Vertical Range
Av. CG For Subjects
(8%, 9%) 1"
(7%, 10%) 1s”
(5, 5%) 23
(3%, 7%) Ke
J
Saat


SB ee aa a aes ae SEL
13 Be : fal ie
12 ee i
‘| eee EE = =
10

9 a if

Vertical distance (inches) of C. G6. from reference point
@

7 8 9 10 8 12 #13 #14 #15 46 17 18
Horizontal distance (inches) of C.G. from reference point

Frevag 4, ce Sa era giararns Sn wah et 9° to back,

“ -B-


13 sFepsrererr ecessttatu age cacs sate . seid etteteseefoteapedeapeteeg:
itt $ ge cresestee (eaadeesd ed SSE ea tet
SE eg See a ees Sega
e'? ee ee Hat eas See eae
2 + Bs Sev peta Sues ¥agrs 4
ey, s feuy istosrastesesy eaiiiuerisessy
2 i Ssigatais eset oia3s 5 Sine Seana abvaepesas
pisieeitiss egestas EEF esas conagiareesasast
B10 : Saati
e isregess tf HH bs Pada gases sages sees
3 :
- ir a +
° 8 ir
F =
S 7&E
= aay
eo
g 6
2 = =a
CJ
3 5 i
3 i
= 4
s
>
3
3 4 5 6 Tv 8 9 10 61} 12 13 14 «15

Horizontal distance (inches) of C. G. from Posterior body plane

1?)
Ficune 8: Displacement of budy C. G. hy anterior movements

—23~


Tr

direction, were made. In these tests the center
of gravity was measured vertically from the
ischium and horizontally from the posterior
body plane.

Only two tests were made for shifting center
of gravity toward the feet (caudad) (Fig. 13),
one with the subject standing with the trunk
flexed as far as possible without extending the
arms and the second with the arras extended.
Here the pelvis was allowed to rotate but the
vertical distance of the center of gravity was
measured from the position of the ischium be-
fore flexion of the trunk in order to show the
total caudad shift due to these movements.
The horizontal distance of the c.g. was meas-
ured from the posterior body plane.

Finally, tests to determine shifts of center
of gravity accompanying maximum abduction
of arms ard legs wore made (Fig. 14 and 15).
Individual tests were riucz to.) ‘er :.ine the
c.g. for abduction of the arms, for abduction ot
the legs and for simultaneous abduction of
arms and legs. For reference, the results of
these tests are presented first showing the shift
of the c.g, in the free body as measured from
the ischium qnd secondly the shift of the cg.
of man standing giving vertical height of the
c.g. from the ground.

ADDITION OF WEIGHTS TO BODY

Studies were made to locate the center of
gravity of man sitting and standing with a
twenty pound pack on his back (Fig. 16), with
the center of gravity of the pack 18-5/8 inches
above the ischjum and § inches posterior to
the back. The center off gravity of man wear-
ing this pack in the two positions studied was
found experimentally on the balancing equip-
ment and then checked, by mathematical calcu-
lations, using data préviously obtainéd in this
study for the center of gravity of without
the pack. We were pleased to find that the
calculated and the experimental data checked
within one-fourth inch. The significance of
these tests is obvious as they show that the
data presegted in this report may be used as a
basis for mathematical calculations of location
of the center of gravity of man in various posi-
tions with the addition of various weights to

the body; for example, parachutes, hack packs,
chest packs, etc.

RESULTS

T’... results are presented both in graphical
(Figs. 4 through 16) and tabular (Tables II
through X!¥) form with small diagramatic
figures representing the body positions of the
subjects. For any one position the geometrical
average of the centers of gravity of all five.
subjects is shown as a black dot in Figs. 4
through 16 along with an arc of a circle which,
if completed, would include the actual centers
of gravity of all subjects.

DISCUSSION AND CONCLUSION

Tt will be noted from 2 study of these graphs
that the variation between subjects in any one
position is sometimes greater than the shift of
the center of gravity of the group due to any
particular motion. Fig. 3 presents actual cen-
ters of gravity of each of the five sitting sub-
jects for three different arm positions and shows
the location of the geometrical averages of the
group. It will be noted from this graph that
the shifts of c.g. of all subjects follow a defin-
ite pattem. The completed circles in Figs. 4, 5,
6, and 7 enclose areas that include all subjects
and all arm positions. In Fig. 4 this area
has a two inch radius while a radius of one and
one-half inches suffices in Figs. 5, 6, and 7.

Analysis of tests of maximum shift shows
that man is capable of shifting his c.g. roughly
11-1/2 inches toward the kead (Fig. 12), 10
inches toward the feet (Fig. 13), 8 inches an-
teriorly (Fig. 9), 4-1/2 inches posteriorly
(Fig. 10), and 4-1/2 inches laterally (Fig. 11)
from that of ‘ari’ erect standing posture.

The maximam shift of cg. accompanying
the movement of all body parts in a given di-
tection is not the sum of the shifts produced
by moving each part separately. ‘

This study shows that in spite of the wide
variety of body sizes and mass distributions
there is surprisingly little variation in the loca-
tion of the body c.g. when measured from a
teference’ point on the pelvis, In a given body

a4


TABLE XII
Displacement of Body €. G. by Abduction of Arms and Legs
‘as Measured from Floor Level

Location of Vertical Range
Body Position Av. C.G. For Subjects
‘A. Body standing straight (0, 38%) 21"
B. Standing, arms abducted (0, 36%) 2"
C. Standing, both legs abducted (0, 36%) 2X"
D. Both arms and both legs (0, 37%) = ox"
abducted
‘ y
t b
i
‘
; ‘
s
: ‘
: ;
‘ / Scot


TABLE VI
Displacement of Body C. G. of Commercial Aitline Passeagers
, Horizontal &
ic Vertica] Range
Body Position Av. C. C. For Subjects
Treak 125°, Knees 1450
A. Hands in lap (9%, 7%)
B. Arms across chest (9%, 7x)
© One arm (9, 7%,
D. Both arms forword (10%, 8%)
E. Holding to sea: back (9%, G4}
F. Head and arms on forward seat (12%, 10-7736)
"et Heda (7% &%) r
in +
H. Ams acrose chest (8% 7%) 2x7
L One arm forward “(%, TR) =I"
J. Both ams forward (8%, 7%) 2%
K Holding to seat back (7%, 8%)

es



we

— —
TABLE 1X
Displacement of Body C. G. by Lateral Movements
Horizontal &
Location of Vertical Ran;
Body Position Av. C. G. For Subjects
A. Standing, body straight 40, 3%) +x"
B. Head flexed to side (1%, SK) =e
One arm extended C#, 6%) ze
D. One arm extended across chest ( % 6%) 2
E. Head and trunk in Jater. (1X, 5%) ax
flexion
F One teg abducted OS, 6%) 2x
G. Maximum lateral mcvement of (1%, 6%) 2K
both legs
H. All body parts moved laterally (4%, 7%) 21
y
. i
‘ ‘ ry yy
is vy y
es



TABLE Vii
Displacement of Body C. G. by Anterior Movements
vaoricantal &
Location «f fertical
Body Position Av. CG. For Subjects
A standing strai; (4, SX) +3”
B nea forwant est (45, 5%) =
G Both anns extended forward (5%, 7) =x
D. Head and trunk forward (38, 4) +i"
E. Both legs straight forward (9, 11) 21
SF, All body parts in maximum (12, 10x) =
anterior posit :
y
i i
' .
i ‘
v 4 +.
' J “

wa


A #
f HH
Suse HHH
Ee
Lda eH H i
zee
ean :
iy +]
3 Ee
Hy ti Hy ‘8
fergeasel eal adeeed cel td
Ses eecra ieasenesi EE q
teal Ht i
pellet Ht fazed Yeeen ead if
Frat eat ee af
reef asseititi te H
RTE Lge Reged ce

° a @
tv vt ed td

4co}} Wess 9 °D Jo (SeYyoU})

Lad © 0
Led Le) L2)

@0UDjSIP [Dd1;40eA,

-H-

Ficunx 15. Displacement’ of body C. G. by abduction of arms and legs ai measured from
floor level, :

wa



S43 EE i =f
o
o H
612 :
s
ar] “4
£
°o
= 10 z
. 6 i
ar)
3s
Ss
£
oo
c
= 7
3
c
5 6
&
uv
3s (5
2
$4
7 8 9 JO 11 12 13 14 15 16 17 18

Horizontal distance (inches) of C. G. .from reference point

fa

A 8 Cc
Freung 6. Position of body C. G, operating controls in various ions; back erect,
"seat Bo ee beet jeg 110° to thighs. Pos

-17-



Ficune 1h, Technique of reading horizontal distance of C. G, from reference point.

- age



eo

ppp
z

Body Position
Standing, body strai;
Both aise sbtoctal
Both legs abducted
and both arms

i

TABLE XO
Displacement of C, G. by Abduction of Arms and Legs

Location of
Av. C.C.

(0, 5%)

40, 7-1/16)
(0, 6%)
(0, 8%)



a

2

o

Nn

°o

Vertical distance (inches) of: C. 6G, from ischium

3 4 5 6 7 8 9 10 Th 12 643
Horizon rior body plane

Ficun 12, Displacement of boy C. G. by exphahul movements,

29

e



TABLE la
Anthropometric Measurements® of Original 5 Subjects
I B. M. NC
1. Age 39 39 29 6
2 Weight 152 152 225 177
3. Stature 68 R 69.75 69.5,
4. Sitting Height (Anthro) 34.75 375 385 37
5. Trunk Height 23 PAS a 225
6. Eye Level (Anthro.) 30 32.25 3 31.25
7. Buttocks Knee 23 245 245 23.5
8. Patella Height 21 22.25 22 20.75
9. Abdominal Girth 25 29 38 3
10. Thigh Circumference 18.75 18 mw 20.75
11. Chest Depth 8 8.25 10.75 95
12. Abdominal Depth 715 7s 10 95
“Weight in pounds; all other in inches
y

4 i

i

.t .

5
; ‘
: y ;
' / a

-6-——

113.25
64.75
BS

28.5
225
19.75

15.5
675


position the c.g, of at least 90% of the adult male
population falls within a sphere 2 inches in
diameter.

REFERENCES

1. Elbel, E. R., Leg strength and leg endur-
ance in relation to height, weight, and
other body measur. ~nts, Project No. 318,

Report No. 1, 27th AAF Base Unit, AAF

School of Aviation Medicine, Randolph

Field, Texas, 15 August 1945.

Swearingen, J. J., Determination o. the most
comfortable knee angle for pilots, Civil
Aeronautics Medical Research Laboratory,
Project No. Biotechnology 3-48, Report
No. 1.


TABLE V
Sitting Back Erect, Seat 108° to Back

Legs 180° to Thighs
Location of
Body Position Av. CG.
A. One hand on stick control, (9%, 8%)
‘one on control at side of seat
B, One hand on overhead control, (10x, 8%)
‘one on control at side of seat

C. Both hands on overhead control (10-9716, 8-15/16)

-18—

Horizontal &
Vertical Range
For Subjects
=I
+r

+


+

Frcunr la, Technique of reading vertical distance of C. G, from reference point.

-8—-


TABLE VII
Displacement of Body C. G. by Posterior Movements

Horizortal &
Location of Vertical Range
* “Body Position Av. C. G. For Subjects
‘A. Standing, body straight (5%, 8) on
B. Head back (5%, 5%) "
C.Anms back (5%, 6%)
D. Head & trunk back (7%, 5%)
& back (6%, 7) ~
Fr ‘body parts in maximum. (9%, 6%)
posterior position
’
. t
t ‘ « *
‘
, ‘
v y
’ / aad
' . '
oo iy
? \
+ .
.
« ~ —-A-

wa


APR 2 11989

DETERMINATION OF CENTERS

OF GRAVITY OF MAN

JOHN J. SWEARINGEN

Chief, Pretection and Surcicel Branch

GECENES

62-14

SQDERAL AVIATION AGENCY,
AVIATION’ MEDICAL SERVICE
AEROMEDICAL RESEARCH DIVISION
CIVIL AEROMEDICAL RESEARCH INSTITUTE
OKLAHOMA CITY, OKLAHOMA
August 1962


Vertical distance (inches) of C.G. from reference poir*

3
Nim

a
NI-

rh

1 ; n 1
73 8 85 9 93 10
Horizontal distonce (inches) of CG. 6. from reference point

sy © Arms at sides 4 One arm forward © One arm over head

Ficuns 3. Centers of gravity of all five subjects for three arm positions,
-he



Ficunr 8 Details of counterbalance system.

-10-


cae 0
SEEEE H i 0 -
Begesesrerpistessee i zt =
saH8 fit ttt tf H °
BESesCeesl eeaed pea d tess stata 7”
pertaessis fa
ate i E iat ®

# S
it

fssitaal aeetvaasainiettee

eel otal ET r?)
Fesstecest fetes stastars:

ar tg FE

EAT HSH Ht iH 0

pitttrrts ett

issay
4
Horizontal distance (inches) of C.G. from posterior body plane

Bea i
if
RHEE
i) re) + 9 n - oO =~ we ms _

+ + + + + + ' ' r t . »
WNIYdS! MOj9q JO BACGD “N'D 4O (SeYoU!) eDUDIS{P 1091320

—31-.

Ficurx 13. Displacement of body C. G, by caudad movements.

oe oS age epee cetera ——— ere



TABLE XI
Displacement of Body C. G. by Caudad Movernents

Horizontal &
eo Location of Vertical Range
Body Position Av. C.G. For Subjects
A. standing straight (5, + 5%) =e
B. Tey heed toon (7%, —%) + 3x”
flexion toward feet
C. Trunk, head and arms in maximum (10x, — 4%) & 1x”
position toward feet
. '
, t
.
é
‘
wf q
/ bites
7
od \
*
Ld .
. -30-

A



BES om saa aw wm Subject No.

SRBRBREBRBEREBRASREASSAB BE Age

se

Anthropometric Measurements of Subjects Used for Check Tests

2 stature
g £ #8 Sitting Ht.

72
705,
69.75
68.5
a5
70.75
T7475
70

70
67.75
675
675
66.25,
66.5,

T25
68.75

69.25
725

(Anthro,)

BEBREERY

pany

8

32.25

31.25

TABLE Ib-

Level
thro. )

8 gs Trunk Height
Ps
(

2
b
a
g BER RES puttocks knee
aa a

a

a
BSSBeee se

eenee

BE

235
19.75
23.95
225
21.75

2g
a
E
E
a

&
&

235
SiS 22
30.5 21.75
wW5 225
32.75 24
WS 235
3 24.25

a

e*EETREEEE

2425 32.75 215
23 (3175s ‘e335
215 30 2475

37 523 315 24.25
3079 24 © 31.75 23.25

Se Patelh
Ee ge Height
= Ge Abdominal
= BE iin

SERESS
aa
gaseees

215
13.5

8
B

8
a
3

195 315
18.75 32.75
195 28
22 05
20.25 27.75

20 + 37
200 (2475
20.25 31.75
210 385
225 2875
20 USS

Thigh
Circumference

185

185

Abdominal
Depth

BE

105
65

8
7
65


HERS SHE a5yapanaitan
i ttttE aera :
E : seal Set
= i ge fe
o +f 1 =
2 =
2 '° : et
2 BR EH
- Hy as
3s 4
o
~ 9
e Hi
~ Seth rite
= ;
e
3s
c =
= 6 j
Ss fe
¢
o
2
2
Zs
os 7
o
= st
5 me
6
T 8 9 10 in 12 13

y
Horizontal distance (inches) of C. G. from reference point

'

Ficune 8. Displacement of body C. C. of commercial airline passengers

-21-


0
3 +
3
ie
: 6 i
md 5
. 3
" E
° a
i = P
He ees faics rs E {
pea ow 8 z.
sae ae a a]
ene 3 a
Beretiisnineeeit > E f
pain - A
z Ls Ane -§ tg
eaieart deoapaetad aerated iret s. #2
Hae ane 4 at
sarees : 5
i 4 : Ht o.
tv ° 3
HE SHAH] | MEER OIRERTEE : fi 3
BSS Ertl a HES ereeeeer trea a H i
ES laatea Re . i
Hit sue reapieu tte feet i “ * Hy
| vet Maadnere cud ATTA HE .
a oo Lad © 0 t =
WNIYDS! Woy "9 °Q jo (RBYDUI) BOUDYSIP 1DD1JI0A : -

we



their c.g, to fall 1 inch above the established
range for the standing position. Their anthro-

pometric measurements are presented in
Table Ib.

SITTING

Studies were made on three different sitting
groups. The first group (Fig. 4) represents
man in the normal sitting position; that is, trunk
erect, thighs 90° to the trunk and legs 90° to
thighs, and presents data showing the effects
upon the center of gravity of moving one and

arms to various positions. In addition to
the arm movements, two tests were made to
show the shift of center of gravity when the
trunk was flexed forward from the sitting posi-
tion. The vertical height of the center of grav-
ity was measured either from the seat bottom or
from the ischium, as it was assumed that the
ischium was in ccatact with the seat bottom.
Horizontal distances to the c.g in these tests
were measured from the seat back.

The second group (Figs. 5, 6 and 7) con-
cerns itself with the <tudy of various pilot posi-
tions and shows the shift of center of gravity if
the arms are moved to various positions for
operation of controls with the legs at the com-
fort angle “”” where the knees are 110°, +5°,
and, in addition, two extreme positions for the
feet, one in which the feet are back under the
chair and one where the legs are fully extended.

The third group (Fig 8) represents the com-
mercial airline passenger in the full reclining
position and shows the displacement of the
center of gravity pf the bodyifor the passerer
when the arms are moved to various posit us
and when the feet are on the floor or on the
foot rest of the seat immediately in front. IA
this position the seat back makes an angle of
115° with the seat cushion. Hpbwever, since
both the trunk ahd pelvis are r¢clining at this
angle, these tests and measurertents were made
by dropping the legs to the 115° angle. It
must be noted here that vertical distances of
the center of gravity were measured ‘from the
ischium parallel to the plane of the subject's
back,gwhile horizontal distances of the c.g were
Perpendicular distances from this plane. In
F of Fig, 8 the passenger is not reclining but is
assuming one positior. in a current study to

determine the best position for passengers in
the event of a crash.

MAXIMUM DISPLACEMENT OF C.G.

In this study of shift of the center of gravity
with maximum movements of the body the
pelvis remains fixed and all movable body parts
were shifted on the pelvis in a given direction.
In the first group (Fig. 9) the shift of the cen-
ter of gravity accompanying various anterior
movements of body parts was studied and re-
corded. This included flexing the head for-
ward, extending both arms straight forward,
flexing the trunk forward (note th= small
amount of flexion of the trunk wnen the
pelvis is held rigid), extending the legs straight
forward and the final test in which all body
parts were moved in unison to the maximum
anterior position. The center of gravity was
measuied as the vertical height above the is-
chium and the horizontal distance from the
posterior body plane.

For the posterior motions (Fig. 10) tests
similar to those described in the anterior group
we-e made. These individual tests were made
to determine the effect on the center of gravity
for posterior motions of head, arms, trunk, legs
and all body parts moved in posterior direction.
Again the center of gravity was measured ver-
tically from the ischium and horizontally from
the anterior body plane.

In the study of lateral shifts of c.g. (Fig. 11)
individual tests were made for location of the
center of gravity with the head flexed to the
side. with the left arm -:ended laters "ly, + th
Sie rigut aim acrovs the Voest, with the head
and trunk flexed to one side, with the left leg
in maximum abduction, with the left leg ab-
ducted and the right leg adducted, and a final
test with all body parts moved laterally as far
as possible. In all tests the pelvis was not
moved and the center of gravity was measured
vertically from the ischium and horizontally
from the mid-sagittal plane.

In tests to move the center of gravity as far
as possible toward the head (cephalad)
(Fig. 12) ivciv. ual tests for both arms ex-
tended over the head and for both legs flexed
toward the head 1s well as one final test, with
both legs and L “+ arms in maximum cephalad

-3—


me

pn p>

he

Sitting Back Erect, Seat 90° to Back, Legs 50° to Thighs

Body Position
One hand on stick control,
‘one on control at side of seat
‘One hand on overhead control,
‘one on contiol at side of seat
Both hands on overhead control
‘Tron’ ‘2d on thighs,
arms ar -und knees

TABLE Il

Location of

Av. C. G.
(7%, 9%)

(8, 10%)

(8%, 10-9/16)
(13%, 4%)

-M4-



TABLE IV
Sitting Back Erect, Seat 90° to Back,
Legs 110° to Thighs
: Location of
. Body Position Av. CG.
~ A. One hand on stick control, (9-1/16, 9%)
one on control at side of seat
B. One hand on overhead ccntrol, (95/18, 10%)
"one on control at side of seat
C, Both hands on overhead control (3, 109/18)
y
i 4
i
‘ .
i
} ‘
5
, Sega
' / *

—-i6—

Vertical Range
For Subjects
co a

=a

=i



tay

comer of this four foot square platform. Each
of these contact points lights a tight in its cor-
ner if the platform is tilted in that direction.
Hence, the platform may be assumed to be in
balance when all four lights are out. A hori-
zontal scale with one-fourth inch increments
was mounted on the supporting structure of
the tilt chair with its zero in vertical alignment
with the reference point on the seat.

A vertical cable was stretched taut from the
ceiling to the base platform in front of the
horizontal scale and a camera sight set up ap-
proximately ten feet from the platform, The
camera sight, vertical cable and ball and socket
fulcrum were in alignment, A similar arrange-
ment was placed at the end of the platform for
reading lateral displacements of c.g. The sub-
ject was then placed in the supporting structure
with the seat back in the horizontal position
(Fig. la), the equipment balanced by means
of turning the jack screws and a reading taken
on the horizontal scale. This reuding repre-
sents the vertical height of the c.g. of the sub-
ject above the reference point when the subject
is‘in normal upright sitting posture. The seat
was then tilted approximately 20°, locked in
position (Fig. 1b) and rebalanced. The read-
ing from the horizontal scale obtained as de-
scribed above was then set on the base leg of a
special adjustable T-square and the base of this.
T-square placed upon the seat back with the
zero of the square at the line of intersection of
the seat back and seat bottom. A second read-
ing (the horizontal distance of the c.g. of the
subject from the reference point) was then
taken through the camera sight where the per-
pendicular member of the adjustable T-square

‘intersected the vertical dable. By this method

the location of the center of gravity of the -1-b-
ject was determined directly with referenx. co
the seat. qi )
Although the total weight of the uipment
and subject on the fulcrum niay hdve re-ched
800 pounds, the equipment was sensitive
enough that the weight of a silver half dollar
placed sn one comer would light the light in
that comer. The breaker-over distance the plat-
form had te be moved by turning the jack screw
to turn out one pair of lights and turn on the.op-
posite pair was about one-eighth inch. For
“bis reason, accuracy of reading is believed to

be within one-eighth of an inch with Tepeat
readings on the saing subject not varying more
than one-fourth inch. The latter variation was
probably caused ‘by slight differences in the
Position of thé subject as he remounted the
piatform.

During this study it became apparent that if
any point on the pelvic structure was chosen
as a reference point the centers of gravity of
all men fell in a very small area, For this
reason all vertical distances to the centers of
gravity are measured from the inferior spine of
the ischium. Horizonta? uicasurements are
either from the aucenor or posterior plane of
the body, depending upon the type of motion
involved. For convenience. of discussion the
sixty-seven different body positions studicd «7:
divided into three groups: sitting, maximum
displacement of c.g., and the effects on the
c.g. of adding various weights to the body.

THE SAMPLE

The number of subjects tested was limited
by the large number of positions being studied.
Only five men were tested in all s?:ty-seven
Positions, but they were carefully chosen to in-
clude a wide range of body sizes and weights.
Authropometric measurements of these sub-
jects are presented in Table Ia. In addition to
the five tested in all positions, an additional
twenty-seven men were check tested in one
sitting and one standing position. In the sit-
ting position (Fig. 4, B—sitting with hands in
lap) the centers of gravity of all but one sub-
ject (97%) were found to fall within the range
established for the original five subjects. In the
standing position, all but three (91%) fell with-
in the established range. An anal; -is of the
anthropometric measurements of these four
subjects (Table Ib, subjects number 12 sitting,
and -7, 10, amd’ 24 standing) shows the very
abnormal distribution cf weight between the
trunk and legs. Subject number 12 has the
major portion of his 202 pounds in his trunk
with very short, light legs. His center of grav-
ity falls 3/4 ‘inch above the established «range
for the sitting position. Subject number 7 has
extremely long, heavy legs and a short, light
trunk, causing his c.g. to fall 7/8 inch below the
established range for the standing position,
Body characteristics of subjects 10 and 24 cause

-2-


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in sitting and standing positions.

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Frours 10. Displacement of body C. G. by posterior movements,



DETERMINATION OF CENTERS OF GRAVITY OF MAN

JOHN J. SWEARINGEN

ABSTRACT

Dsta are presented concerning the location of che center of gravity of the adult male in
various body positions and the ability to shift the c.g. voluntarily with varices body, motions.

that of an erect standing posture were found to be

11% inches toward the head, 10 inches toward the feet, 8 inches anteriorly, 4% inches

posteriorly and 4% inches laterally.

INTRODUCTION

The data presented in this report conceming
the location of the center of gravity of the
adult male and the ability to shift the c.g. with
various body motions were originally published
as a Civil Aviation Medical Research Laboratory
Report in 1953 (CAA Project No. 53-203).
During the past nine years these data have
proved most useful in studies to’ determine
(1) effective restraint ;devices fot protection
against cresh férces, (2) flight and balance
characteristics of one-mas helicopters, (3) de-
iz of Rotation equipment, (4) orientation in

ute jumps, (5) capsule stabil-
ity, and (6) fying platform characteristics.

With the advent of tHe space age it is felt that
these data deserve wider distributin as they
will have obvious application ‘in the design of
artificial gravity fields, space work capsules for
assembling space stations, lunar and planetary
landing equipment, and locomotion devices on’
planets with gravitational fields greater or less
than one g*

For these reasons the author is taking the
liberty of republishing the data as a CARI
report. :

EQUIPMENT AND PROCEDURE

A number of different techniques for locating
and recording the c.g. were tested and the fol-
lowing chosen for use in this study. The equip-
ment consists essentially of five platforms
(Fig. la) mounted one above the other. The
top platform, which supports the subject, con-
sists of an adjustable seat with arm and foot
rests, The bottom of the seat, the foot rest
and the arm rests are adjustable to different
angles and ean be counterbalanced in each posi-
tion by a sliding weight on the back of the seat.
This adjustable chair can be rotated about a
horizontal axis from the horizontal through ap-
proximately 20° to a second position and locked
in position. The second and third platforms
slide horizontally at right angles to one another
by means of jack screws. Each of these plat-
forms also has its own counterbalance system,
keeping the ‘equipment as a whole in perfect
balance regardless of position with reference to
the bottom platform. Details of these counter-
balance systems are s!.own in Fig. 2. The fourth
platform is separated from the bottom platform
by means of a ball and socket joint in the center
and four electrical contact points, one at each

-1l-


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Vertical distance (inches) of C.G. from ischium

Displacement of body C. G. by abduction of and I
ie ” fixed in os position}, arms al

-3~

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Displacement of Body C. G. by Cephalad Movements

Body Position
Body standing straight
Both = extended over head
Bot in maximum position
toward ad head : pe

ly in maximum
Seopa

TABLE X

Location of
Av. CG.
(5, 5%)
(5%, 8%)
(10%, 15)

(11%, 17%)

Horizontal &
Vestical Range
For Subjects

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rn 6

TABLE II

Sitting With Seat 90° to Back, Legs 90° to Thighs

Body Position

Both arms down at sides

Both hands in lap

One arm forward, one hand in lap
Both arms straight forward

Both arms extended over head
One aim over head, one hand in lap
Both arms extented laterally

One arm extended laterally,
one hand in lap

Both arms extended posteriorly
Trank flexed on thighs,

arms extended forward

‘Trunk flexed on thighs, arms down

Location of
AV. c.g
(8%, 9%)
(8%, 9%)
(8%, 10%)
(9%, 10%)
(8%, 12)
(8%, 10%)
(8%, 10%)
(8%, 10%)

(8, 298)
(15K, 5-316)

(14-15/16, 5)

-R-



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Ficune 5. Position of body C. G.
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