Biomedical Engineering Reference
In-Depth Information
from 30
to 70
. In this case, the decrease presents a small dependence on the
mass that is lifted. The greater decrease (2.0 and 1.9) occurs for the greater lifted
mass (50 kg).
Thus, we have quantitatively verified how important it is to protect our spinal
column and, to not damage the intervertebral discs, assume a correct posture that
can reduce by 2.5 times the muscle force and by 1.9 times the contact force by
changing the inclination of the spinal column with the horizontal from 30
to 70
.
6.7 Answers to Exercises
Exercise 6.1
(a)
d
¼
21.4 cm; (b)
N
¼
500 N.
Exercise 6.2
(a) on both hands,
N
hand
¼
375 N; (b) on both feet,
N
feet
¼
225 N.
Exercise 6.3
(a)
C
¼
1,358 N and the angle of the contact force with the horizontal
is 54
; (b)
F
¼
997 N.
Exercise 6.4
(a)
F
¼
1,913 N; (b)
C
¼
2,869 N and the angle of the contact force
76.8
. Note that doubling the body mass, the contact
C
with the horizontal
¼
force
C
also has doubled.
Exercise 6.5
(a)
F
¼
4,998 N;
C
¼
5,367 N and the angle of
C
with the
2.3
.
horizontal
¼
Exercise 6.6
With the correct posture, what changes is the angle of the spinal
column with the horizontal. The less inclined is the column, i.e., the more erect is
the column, the smaller are the involved forces.
