Biomedical Engineering Reference
In-Depth Information
Fig. 5.70 a General ground force characteristics during walking adopted from (Perry 2003),
b measured ground reaction forces during walking and running, barefoot and with sports shoes
Müller and Dr. Peter Wolf), as well as at the gait analysis laboratory at the
University Clinic in Heidelberg/Germany (supervision by Dr. Sebastian Wolf).
Human Motion Capturing: The human motion capturing (HMC) method
provides 4D-data including spatial coordinates of material points of an object at
definite times. For optical HMC, reflecting markers are attached to selected points
of the body (skeleton related joint and reference points such as shoulders, hip,
upper leg, knee etc.), Figs.
5.68
and
5.69
. The marker reflections are captured by
not less than three and maximally 24 cameras from defined perspectives. The
motion of the single marker points is then digitalized. Based on the camera
positions, the single marker trajectories, or spatial position at any time, can be
derived, Fig.
5.67
b, (Wikipedia 2009).
Figure
5.68
depicts two video sequences of the leg of a 34 year old male
volunteer with position markers attached in the bi-pedal initial and the mono-pedal
stance phase in walking motion with sports shoes, Fig.
5.68
a and bare foot,
Fig.
5.68
b and the corresponding HMC- sequences, Fig.
5.68
c. In Fig.
5.69
the
sequences during running are captured. Here, a total of 55 markers captured four
gait cycles in 4.46 s of walking and 2.58 s of running with 12 video cameras at
100 Hz, producing approximately 83,000 spatial coordinates.
Ground Reaction Force and Kinematics: Generation of FE-models of the human
musculoskeletal system, employed for simulating the rolling motion of the foot,
require kinetic information besides kinematic data. Kinematic information is com-
monly gathered via measurements of ground reaction forces during a gait cycle.
Walking and running exhibit the following kinetic and kinematic differences:
according to Fig.
5.70
a, the vertical force pattern during walking (at normal speed)
exhibits two maxima during the stance phase of approximately the same magnitude (F1
and F3) and one minimum (F2). The first maximum is caused by body weight shifting
onto one foot at heel contact (BA phase). Simultaneously, the body's centre of mass
(BCM) is lowered, resulting in upward directed acceleration. The BCM is lifted and in
the mid stance phase (MSt) is moved forward. During this process, the BCM is quickly
