Because fall experiments with volunteers can be both challenging and risky, especially with older volunteers, we wished to develop computer simulations of falls to provide a theoretical framework for understanding and extending experimental results. To perform a preliminary validation of the articulated total body (ATB) model for passive falls, we compared the model predictions of fall direction, impact location, and impact velocity as a function of disturbance type (faint, slip, step down, trip) and gait speed (fast, normal, slow) to experimental results with young adult volunteers. The three-dimensional ATB model had 17 segments and 16 joints. Its physical characteristics, environment definitions, contact functions, and initial conditions were representative of our experiment. For each combination of disturbance and gait speed, the ATB model was left to fall passively under gravity once disturbed, i.e., no joint torques were applied, until impact with the floor occurred. Finally, we also determined the sensitivity of the model predictions to changes in the model’s parameters. Our model predictions of fall angles and impact angles were qualitatively in agreement with those observed experimentally for ten and seven of the 12 original simulations, respectively. Quantitatively, the model predictions of fall angles, impact angles, and impact velocities were within one experimental standard deviation for seven, three, and nine of the 12 original simulations, respectively, and within two experimental standard deviations for ten, nine, and 11 of the 12 original simulations, respectively. Finally, the fall angle and impact angle region did not change for 92% and 95% of the 74 input variation simulations, respectively, and the impact velocities were within the experimental standard deviations for 78% of the 74 input variation simulations. Based on our simulations and a sensitivity analysis, we conclude that our preliminary validation of the ATB model for passive falls was successful. In fact, these ATB model simulations represent a significant step forward in fall simulations. We believe that with additional work, the ATB model could be used to accurately simulate a variety of human falls and may be useful in further understanding the etiology and mechanisms of fall injuries such as hip fractures.

1.
Greenspan
,
S. L.
,
Myers
,
E. R.
,
Maitland
,
L. A.
,
Resnick
,
N. M.
, and
Hayes
,
W. C.
, 1994, “
Fall Severity and Bone Mineral Density as Risk Factors for Hip Fracture in Ambulatory Elderly
,”
J. Am. Med. Assoc.
0098-7484,
271
(
2
), pp.
128
133
.
2.
Greenspan
,
S. L.
,
Myers
,
E. R.
,
Kiel
,
D. P.
,
Parker
,
R. A.
,
Hayes
,
W. C.
, and
Resnick
,
N. M.
, 1998, “
Fall Direction, Bone Mineral Density, and Function: Risk Factors for Hip Fracture in Frail Nursing Home Elderly
,”
Am. J. Med.
0002-9343,
104
(
6
), pp.
539
545
.
3.
Hayes
,
W. C.
,
Myers
,
E. R.
,
Morris
,
J. N.
,
Gerhart
,
T. N.
,
Yett
,
H. S.
, and
Lipsitz
,
L. A.
, 1993, “
Impact Near the Hip Dominates Fracture Risk in Elderly Nursing Home Residents Who Fall
,”
Calcif. Tissue Int.
0171-967X,
52
(
3
), pp.
192
198
.
4.
Nevitt
,
M. C.
, and
Cummings
,
S. R.
, 1993, “
Type of Fall and Risk of Hip and Wrist Fractures: The Study of Osteoporotic Fractures
,”
J. Am. Geriatr. Soc.
0002-8614,
41
(
11
), pp.
1226
1234
.
5.
Schwartz
,
A. V.
,
Kelsey
,
J. L.
,
Sidney
,
S.
, and
Grisso
,
J. A.
, 1998, “
Characteristics of Falls and Risk of Hip Fracture in Elderly Men
,”
Osteoporosis Int.
0937-941X,
8
(
3
), pp.
240
246
.
6.
Smeesters
,
C.
,
Hayes
,
W. C.
, and
McMahon
,
T. A.
, 2001, “
Disturbance Type and Gait Speed Affect Fall Direction and Impact Location
,”
J. Biomech.
0021-9290,
34
(
3
), pp.
309
317
.
7.
Mochon
,
S.
, and
McMahon
,
T. A.
, 1980, “
Ballistic Walking
,”
J. Biomech.
0021-9290,
13
(
1
), pp.
49
57
.
8.
Cheng
,
H.
,
Rizer
,
A. L.
, and
Obergefell
,
L. A.
, 1998, “
Articular Total Body Model Version V: User’s Manual
,” Human Effectiveness Directorate, Crew Survivability and Logistics Division, Wright-Patterson AFB, Dayton, OH, Report No. AFRL-HE-WP-TR-1998-0015.
9.
ATB3I: The Intuitive, Intelligent Interface for ATB
” [computer program], 1998, Version 1.1.05, Veridian, Dayton, OH.
10.
van den Kroonenberg
,
A. J.
,
Hayes
,
W. C.
, and
McMahon
,
T. A.
, 1995, “
Dynamic Models for Sideways Falls From Standing Height
,”
ASME J. Biomech. Eng.
0148-0731,
117
(
3
), pp.
309
318
.
11.
Cheng
,
H.
,
Obergefell
,
L.
, and
Rizer
,
A.
, 1994, “
Generator of Body Data (GEBOD) Manual
,” Air Force Material Command, Wright-Patterson AFB, Dayton, OH, Report No. AL/CF-TR-1994-0051.
12.
Ma
,
D.
,
Obergefell
,
L. A.
, and
Rizer
,
A. L.
, 1995, “
Development of Human Articulating Joint Model Parameters for Crash Dynamics Simulations
,”
Proceedings of the 39th STAPP Car Crash Conference
,
San Diego, CA
, November 8-10, pp.
239
250
, SAE Technical Paper Series 952726.
13.
Robinovitch
,
S. N.
,
Hayes
,
W. C.
, and
McMahon
,
T. A.
, 1991, “
Prediction of Femoral Impact Forces in Falls on the Hip
,”
ASME J. Biomech. Eng.
0148-0731,
113
(
4
), pp.
366
374
.
14.
Courtney
,
A. C.
,
Wachtel
,
E. F.
,
Myers
,
E. R.
, and
Hayes
,
W. C.
, 1994, “
Effects of Loading Rate on Strength of the Proximal Femur
,”
Calcif. Tissue Int.
0171-967X,
55
(
1
), pp.
53
58
.
You do not currently have access to this content.