409

PROCEEDINGS of the HUMAN FACTORS AND ERGONOMICS SOCIETY 39th ANNUAL MEETING-1995

AN ESTIMATION OF‘ LUMBAR HEIGHT AND DEPTH
FOR THE DESIGN OF SEATING
William R. Dowel1
Herman Miller, Inc.
Zeeland, Michigan USA
The horizontal and vertical position of the apex of the lumbar curve of 773 seated persons were measured,The position of the lumbar landmark is given. Three common seated anthropometric measurements werealso taken: popliteal height, buttock-popliteal length, and elbow rest height. The three commonmeasurements are compared with data from an existing anthropometric data base.

INTRODUCTION
The location of the apex of the lumbar curve in the seatedposture is regarded as an important piece of information forthe design of the back shape of the chair. Anthropometricsurveys do not include data for lumbar landmarks. Branton(1984) reports locations of spinal landmarks for 114 British
Railways employees. Without recent information for the U. S .
population, chair designers resort to using recommendations
from the standards literature or replicating past designs. For
this study specimen values were taken of a large sample
using an efficient measuring device to help understand thelumbar shape.

Buttockpopliteal
lengthMETHOD

This study included 773 subjects from seven sites throughout
the United States. Five measurements were taken:bElbow restII

PoplitealheightI) The depth of the lumbar region of the back at its
2)
3)
4)
5)

maximum curvature
The height at the deepest part of the lumbar curve
The popliteal height including heels
The buttock-popliteal length
The elbow rest heightThe sample was taken from attendees at six furnitureexhibitions and ergonomic conferences during 1993-1994,
and from one U S . corporation.
The five dimensions were measured using an apparatus thatcan quickly and unobtrusively estimate each dimension. Thedevice uses a series of sliding shelves that act as probes torelate a landmark to a datum plane that the subject is sitting
upon or leaning against (Figure 1). The distance from thedatum plane is listed on the shelf. The device is referred to as
the AnthropometricPercentile Estimator, or APE. d ldimensions except lumbar depth were made to the nearest
inch (2.54 cm), hence the term estimator. Lumbar depth wasmeasured to the nearest half inch (1.27 cm).

Figure 1. The Anthropometric Percentile Estimator
To measure the subjects, they sat upon the device in the90 degree upright posture. The thoracic region of their backs
and their buttocks touched the vertical plane. They sat upon
the horizontal plane.
Popliteal height is measured as the researcher selects theparticular shelf that satisfies the following three criteria:
1)the subject’s feet are flat on the shelf, 2) the subject’s
femur is approximately parallel with the floor, and3) there is little pressure under the thigh.

410

PROCEEDINGS of the HUMAN FACTORS A N D ERGONOMICS SOCIETY 39th A N N U A L MEETING-1995

Buttock-popliteal length is measured by extending theshelf directly under the seating plane out to the poplitealcrease.
Elbow rest height is measured on the right side byextending a small flat adjustable arm support up to theelbow which is bent at 90 degrees. The researcher took
special notice that the subjects shoulders were parallelwith the floor, and that their upper arms were notabducting.
The apex of the lumbar curve is determined by visualinspection of the profile of the lumbar region.

RESULTS
One method of evaluating the accuracy of the measuring
device (APE),is to compare the mean measures for popliteal
height, buttock-popliteal length, and elbow rest height withthe same dimensions obtained by traditional measuring
instruments. These dimensions were measured for theAnthropometric Survey of U.S. Army Personnel: Summary
Statistics, Gordon, et al(1988), Natick, Massachusetts, also
known as ANSUR.
Visual inspection indicates a tight consistency with theexisting data for these dimensions. For popliteal height inmales, the two samples are not statistically different at the0.05 level. For the five other comparisons, the two samples
are statisticallyWerent.

Lumbar height is measured as the researcher selects theparticular shelf at the height of the apex of the lumbarcurve.
Lumbar depth is measured by extending that shelf out tothe apex of the lumbar curve.

Table 1. Summary statistics forfemale subjects. The value for ANSUR popliteal height includes a 1.0 inch (2.54 cm) heel.
Dimensional values are in inches and (centimeters).

APE-popliteal height
ANSUR- popliteal height

354
2208

16.47 (41.83)
16.33 (41.48)

1.28 (3.25)
0.93 (2.37)

APE-buttock-popliteal length
ANSUR- buttock-popliteal length

354
2208

18.41 (46.76)
18.96 (48.17)

0.93 (2.36)
1.05 (2.66)

APE-elbow rest height
ANSUR- elbow rest height

354
2208

9.54 (24.2)
8.68 (22.1)

0.89 (2.26)
1.05 (2.68)

Table 2. Summary statistics for male subjects. The value for ANSUR popliteal height includes a 1.0 inch (2.54 cm) heel.
Dimensional values are in inches and (centimeters).

APE-popliteal height
ANSUR- popliteal height

419
1774

18.19 (46.20)
18.09 (45.95)

1.25 (3.18)
0.98 (2.49)

APE-buttock-popliteal length

419
1774

19.59 (49.76)
19.70 (50.04)

1.06 (2.69)
1.05 (2.66)

419
1774

9.92 (25.2)
9.08 (23.1)

1.00 (2.54)
1.07 (2.72)

ANSUR- buttock-popliteal length

APE-elbow rest height
ANSUR- elbow rest heightPROCEEDINGS of the HUMAN FACTORS A N D ERGONOMICS SOCIETY 39th ANNUAL MEETING-1995

411

Table 3. Summary statistics for the height and maximum depth of the lumbar curve. Dimensional values are in inches and(centimeters).

Female lumbar height
Female lumbar depth

353
352

0.98 (2.49)

9.75 (24.77)

1.09 (2.77)
0.43 (1.09)

14.0 (35.56)
2.5 (5.72)

7.0 (17.78)
0.0 (0.0)

Male lumbar height
Male lumbar depth

415
415

9.95 (25.27)
0.87 (2.21)

1.12 (2.84)
0.43 (1.09)

14.0 (35.56)
2.5 (5.72)

6.0 (15.24)
0.0 (0.0)

DISCUSSIONACKNOWLEDGMENTS

This study reports seated lumbar dimensions for a large U.S.
sample. When compared with the dimensions reported byBranton (1984), these results seem reasonable. The accepted
opinion that women are more lordotic than men is reinforcedby the data reported here.

I would like to thank Bruce Bradtmiller and theAnthropology Research Project, Inc., for the statisticalcomparison of the APE sample with the ANSUR data base.

The comparison between the U.S. Army data and those same
dimensions measured using the APE device is interesting.
Because both samples were large, significant statisticaldifferences are easily detected. It should also be noted thatANSUR does not claim to represent the U.S. civilian
population. There are anthropometric restriction criteria forentry and retention in the military, and the military sample isyounger than the civilian population. None the less, thenarrow dimensional differences between the two data bases
for the same measurements seem to validate the ability of theAPE device to accurately locate anthropometric landmarks.

Branton, P. (1984). Backshapes of seated persons-how close
can the interface be designed? Applied Ergonomics, Is,
105-102.

Finally, compared with more traditional anthropometricsurveys, it could be said that a limitation of this study is that
all of the subjects were fully clothed when they were
measured. This may be an acceptable limitation when
considering the approximate nature of seating back shapedesign. This limit can also be considered a strength as it istypical in the operation of most seating that the users remain
clothed.

REFERENCES

Gordon, C., Churchill, T., Clauser, C., Bradtmiller, B.,
McConville, J., Tebbetts, I., Walker, R. (1988).
Anthropometric Survey of U.S. Army Personnel: Summary
Statistics Interim Report, Natick, Massachusetts: U. S. Army
Natick Research, Development and Engineering Center.
Pheasant, S. (1986). Bodyspace-Anthropometry,Ergonomics
and Design. London: Taylor & Francis Ltd.