KINEMATICS - Biomechanics and Motor Control of Human Movement - page 79

3.6 PROBLEMS BASED ON KINEMATIC DATA

1. Tables A.1 and A.2 in Appendix A, plot the vertical displacement of
the raw and filtered data (in centimeters) for the greater trochanter (hip)
marker for frames 1 to 30. Use a vertical scale as large as possible so as
to identify the noise content of the raw data. In a few lines, describe the
results of the smoothing by the digital filter.
2. Using filtered coordinate data (see Table A.2), plot the vertical dis-
placement of the heel marker from TOR (frame 1) to the next TOR
(frame 70).
(a) Estimate the instant of heel-off during midstance. ( Hint: Consider the
elastic compression and release of the shoe material when arriving
at your answer.)
(b) Determine the maximum height of the heel above ground level dur-
ing swing. When does this occur during the swing phase? ( Hint:
Consider the lowest displacement of the heel marker during stance
as an indication of ground level.)
(c) Describe the vertical heel trajectory during the latter half of swing
(frames 14 - 27), especially the four frames immediately prior to
HRC.
(d) Calculate the vertical heel velocity at HRC.
(e) Calculate from the horizontal displacement data the horizontal heel
velocity at HCR.
(f) From the horizontal coordinate data of the heel during the first foot
flat period (frames 35 - 40) and the second foot flat period (frames
102 - 106), estimate the stride length.
(g) If one stride period is 69 frames, estimate the forward velocity of
this subject.
3. Plot the trajectory of the trunk marker (rib cage) over one stride (frames
28 - 97).
(a) Is the shape of this trajectory what you would expect in walking?
(b) Is there any evidence of conservation of mechanical energy over the
stride period? (That is, is potential energy being converted to kinetic
energy and vice versa?)
4. Determine the vertical displacement of the toe marker when it reaches
its lowest point in late stance and compare that with the lowest point
during swing, and thereby determine how much toe clearance took place.
Answer: y toe ( fr . 13 ) = 0 . 0485 m, y toe ( fr . 66 ) = 0 . 0333 m,

=

clearance

0.0152 m = 1.52 cm.
5. From the filtered coordinate data (see Table A.2), calculate the following
and check your answer with that listed in the appropriate listings (see
Tables A.2, A.3, and A.4).
(a) The velocity of the knee in the X direction for frame 10.