This paper presents a methodology that quantifies gait and fall characteristics from video of real-life fall events. The method consists in selecting on-screen the points on the ground where the feet are in contact with the ground. The essence of the method lies in establishing a transformation from the video frames to the “real world.” In projected images, geometric properties such as lengths, angles, and parallelism are not preserved; thus, concepts of projective geometry are applied, namely homography. Because the ground is an invariant plane, using this plane for homography results in a constant transformation. The homographic transformation relies on the accuracy in the selection of on-screen points. An optimization algorithm that minimizes the errors caused by inaccurate on-screen point selection improves the results of the homographic transformation. Experimental trials are conducted at three walking velocities (slow, preferred, and fast) using two video cameras and a GAITRite walkway system. Spatial parameters of two independent video analyses are compared with the GAITRite system, yielding a limit of agreement of step length from −2.12 cm to 2.03 cm. Temporal parameters are less confident due to the existence of dropped frames in the video footage. This method is then used to analyze two real fall events as demonstrative cases. First, the gait characteristics are analyzed before imbalance, and subsequently, the characteristics of stepping are analyzed during the fall. In particular, we propose the stepping/impact angle as the metric that quantifies how much stepping affected the direction of the fall.

References

References
1.
Liebowitz
,
D.
, and
Zisserman
,
A.
,
1998
, “
Metric Rectification for Perspective Images of Planes
,”
Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition
, Santa Barbara, CA, Jun. 23–25, IEEE, New York, pp.
482
488
.
2.
Szeliski
,
R.
, and
Shum
,
H.-Y.
,
1997
, “
Creating Full View Panoramic Image Mosaics and Environment Maps
,”
Proceedings of the 24th Annual Conference on Computer Graphics and Interactive Techniques
, Los Angeles, CA, Aug. 3–8, pp.
251
258
.
3.
Zhang
,
Z.
, and
Hanson
,
A. R.
,
1996
, “
3D Reconstruction Based on Homography Mapping
,”
Proceedings of the ARPA Image Understanding Workshop
, Palm Springs, CA, Feb. 13–15, pp.
1007
1012
.
4.
Dubrofsky
,
E.
, and
Woodham
,
R. J.
,
2008
, “
Combining Line and Point Correspondences for Homography Estimation
,”
Advances in Visual Computing
, pp.
202
213
.
5.
Criminisi
,
A.
,
2001
, “
Accurate Visual Metrology From Single and Multiple Uncalibrated Images
,” Distinguished Dissertation series (University of Oxford), Springer-Verlag, London.
6.
Spencer
,
N.
, and
Carter
,
J.
,
2005
, “
Towards Pose Invariant Gait Reconstruction
,”
Proceedings of the IEEE International Conference on Image Processing
, Genoa, Italy, Sep. 11–14, IEEE, New York, pp.
261
264
.
7.
Jean
,
F.
,
Branzan-Albu
,
A.
, and
Bergevin
,
R.
,
2009
, “
Towards View-Invariant Gait Modeling: Computing View-Normalized Body Part Trajectories
,”
Pattern Recog.
,
42
(
11
), pp.
2936
2949
.10.1016/j.patcog.2009.05.006
8.
Jean
,
F.
,
Bergevin
,
R.
, and
Branzan-Albu
,
A.
,
2011
, “
Human Gait Characteristics From Unconstrained Walks and Viewpoints
,”
Proceedings of the IEEE International Conference on Computer Vision Workshops (ICCV 2011)
, Barcelona, Spain, Nov. 6–13, IEEE, New York, pp
1883
1888
.
9.
Maki
,
B. E.
, and
McIlroy
,
W. E.
,
1997
, “
The Role of Limb Movements in Maintaining Upright Stance: The ‘Change-in-Support’ Strategy
,”
Phys. Ther.
,
77
(
5
), pp.
488
507
.
10.
Firmani
,
F.
, and
Park
,
E. J.
,
2013
, “
Theoretical Analysis of the State of Balance in Bipedal Walking
,”
ASME J. Biomech. Eng.
,
135
(
4
), p.
041003
.10.1115/1.4023698
11.
Maki
,
B. E.
,
McIlroy
,
W. E.
, and
Fernie
,
G. R.
,
2003
, “
Change-in-Support Reactions for Balance Recovery
,”
IEEE Eng. Med. Biol. Mag.
,
22
(
2
), pp.
20
26
.10.1109/MEMB.2003.1195691
12.
Hsiao
,
E. T.
, and
Robinovitch
,
S. N.
,
2007
, “
The Effect of Step Length on Young and Elderly Women's Ability to Recover Balance
,”
Clin. Biomech.
,
22
(
5
), pp.
574
580
.10.1016/j.clinbiomech.2007.01.013
13.
Maki
,
B. E.
,
Cheng
,
K.
,
Mansfield
,
A.
,
Scovil
,
C. Y.
,
Perry
,
S. D.
,
Peters
,
A. L.
,
McKay
,
S.
,
Lee
,
T.
,
Marquis
,
A.
,
Corbeil
,
P.
,
Fernie
,
G. R.
,
Liu
,
B.
, and
McIlroy
,
W. E.
,
2008
, “
Preventing Falls in Older Adults: New Interventions to Promote More Effective Change-in-Support Balance Reactions
,”
J. Electromyogr. Kinesiol.
,
18
(
2
), pp.
243
254
.10.1016/j.jelekin.2007.06.005
14.
Hsiao
,
E. T.
, and
Robinovitch
,
S. N.
,
1999
, “
Biomechanical Influences on Balance Recovery by Stepping
,”
J. Biomech.
,
32
(
10
), pp.
1099
1106
.10.1016/S0021-9290(99)00104-9
15.
Rogers
,
M. W.
,
Hedman
,
L. D.
,
Johnson
,
M. E.
,
Martinez
,
K. M.
, and
Mille
,
M. L.
,
2003
, “
Triggering of Protective Stepping for Control of Human Balance: Age and Contextual Dependence
,”
Cognit. Brain Res.
,
16
(
2
), pp.
192
198
.10.1016/S0926-6410(02)00273-2
16.
Schulz
,
B. W.
,
Ashton-Miller
,
J. A.
, and
Alexander
,
N. B.
,
2006
, “
Can Initial and Additional Compensatory Steps be Predicted in Young, Older, And Balance-Impaired Older Females in Response to Anterior and Posterior Waist Pulls While Standing?
,”
J. Biomech.
,
39
(
8
), pp.
1444
1453
.10.1016/j.jbiomech.2005.04.004
17.
Sturnieks
,
D. L.
,
Menant
,
J.
,
Vanrenterghem
,
J.
,
Delbaere
,
K.
,
Fitzpatrick
,
R. C.
, and
Lord
,
S. R.
,
2012
, “
Sensorimotor and Neuropsychological Correlates of Force Perturbations That Induce Stepping in Older Adults
,”
Gait Posture
,
36
(
3
), pp.
356
360
.10.1016/j.gaitpost.2012.03.007
18.
Pavol
,
M. J.
,
Owings
,
T. M.
,
Foley
,
K. T.
, and
Grabiner
,
M. D.
,
2001
, “
Mechanisms Leading to a Fall From an Induced Trip in Healthy Older Adults
,”
J. Gerontol.
,
56
(
7
), pp.
M428
M437
.10.1093/gerona/56.7.M428
19.
Mansfield
,
A.
, and
Maki
,
B. E.
,
2009
, “
Are Age-Related Impairments in Change-in-Support Balance Reactions Dependent on the Method of Balance Perturbation?
,”
J. Biomech.
,
42
(
8
), pp.
1023
1031
.10.1016/j.jbiomech.2009.02.007
20.
Ma
,
L.
,
Chen
,
Y.
, and
Moore
,
K. L.
,
2004
, “
Rational Radial Distortion Models of Camera Lenses With Analytical Solution for Distortion Correction
,”
Int. J. Inf. Acquis.
,
1
, pp.
135
147
.10.1142/S0219878904000173
21.
Fitzgibbon
,
A. W.
,
2001
, “
Simultaneous Linear Estimation of Multiple View Geometry and Lens Distortion
,”
Proceedings of the 2001 IEEE Computer Society Conference on Computer Vision and Pattern Recognition (CVPR 2001)
, Vol.
1
, Kauai, HI, Dec. 8–14, IEEE, New York, pp.
125
132
.
22.
Criminisi
,
A.
,
Reid
,
I.
, and
Zisserman
,
A.
,
1999
, “
A Plane Measuring Device
,”
Image Vis. Comput.
,
17
(
8
), pp.
625
634
.10.1016/S0262-8856(98)00183-8
23.
Negahdaripour
,
S.
,
Prados
,
R.
, and
Garcia
,
R.
,
2005
, “
Planar Homography: Accuracy Analysis and Applications
,”
Proceedings of the IEEE International Conference on Image Processing
, Genoa, Italy, Sep. 11–14, Vol. 1, IEEE, New York, pp.
1089
1092
.
24.
CIR Systems, Inc.,
2006
, The GAITRite Electronic Walkway: Measurements & Definitions, Revision A.2.
25.
Yang
,
Y.
,
Schonnop
,
R.
,
Feldman
,
F.
, and
Robinovitch
,
S. N.
,
2013
, “
Development and Validation of a Questionnaire for Analyzing Real-Life Falls in Long-Term Care Captured on Video
,”
BMC Geriatr.
,
13
, p.
40
.10.1186/1471-2318-13-40
26.
Maki
,
B. E.
, and
McIlroy
,
W. E.
,
1999
, “
The Control of Foot Placement During Compensatory Stepping Reactions: Does Speed of Response Take Precedence Over Stability?
,”
IEEE Trans. Rehabil. Eng.
,
7
(
1
), pp.
80
90
.10.1109/86.750556
You do not currently have access to this content.