Biomedical Engineering Reference
In-Depth Information
11.1.1 Relationship between
M
s
and the Vertical Ground
Reaction Force
As the support moment represents a summation of the extensor moments
at al three joints, it quantifies how much the total limb is pushing away
from the ground. The profile of
M
s
has the characteristic “double-hump”
shape seen in the vertical ground reaction force,
F
y
. To check this out,
a linear correlation was done between the averaged
M
s
and
F
y
profiles
for three groups of walking adults (Winter, 1991): those walking their nat-
ural cadence, fast cadence (natural
+
20), and slow cadence (natural -
20). Figure 11.3 is a plot of
M
s
and
F
y
averaged profiles for the 19 sub-
jects walking with their natural cadence. Here, we see an almost perfect
match between the two profiles, and this is reinforced by the correlation
r
0
.
90.
Even the atypical moment patterns seen in pathological gait yielded
r
=
0
.
97. For 19 fast walkers,
r
=
0
.
95 and for 17 slow walkers,
r
=
=
0
.
96 for two walking trials for a 69-year-old female total knee replacement
patient and
r
=
0
.
92 for two trials for a 69-year-old male knee replacement
patient.
Ms and Fy for Natural Cadence (N
=
19)
12
1.2
10
1
8
0.8
6
0.6
4
0.4
Fy(nat, N/kg)
2
0.2
R
=
0.97
Ms(nat, Nm/kg)
0
0
−
2
−
0.2
0
10
20
30
40
50
60
% Stride
Figure 11.3
Average vertical ground reaction force,
F
y
, and the average support
moment,
M
s
, for 19 adult subjects walking with their natural cadence. The close sim-
ilarity in these two profiles yielded
r
0
.
97 from a linear regression. (Reproduced
with permission from Winter, D. A.
Biomechanics and Motor Control of Human Gait:
Normal, Elderly and Pathological
, 2nd Edition, Waterloo Biomechanics, 1991.)
=
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