Download Brandon Smith Gait Analysis Lab Biomechanics Monroe Due 3/27

Brandon Smith
Gait Analysis Lab
Biomechanics
Monroe
Due 3/27/13
Introduction:
The way that people walk can be described as their Gait in a mathematical sense. As
people walk, they create Ground Reaction Forces (GRFs) in all three directions, which can be
measured by foot force plates. This information can be analyzed to help determine how the
forces work within a certain section of the body during movement. It has become useful to
surgeons and other researchers who are trying to develop methods to help correct gait issues
caused by different forms of physical handicaps. Two types of medical conditions that can be
evaluated using gait analysis are osteoarthritis and multiple sclerosis. In Osteoarthritis, the
cartilage between joints breaks down as a result of simple wear and tear over the years. Gait
analysis has showed more correlative effects to help determine the success of a certain surgery.
In “Methods for Evaluating the Progression of Osteoarthritis”, the researchers show that there
adduction moment of the knee in patients was lowered following a certain surgery (1). In
multiple sclerosis, the immune system degrades the myelin sheath around axons within nerves.
The result is disruption or loss of the normal communication within the nervous system between
the brain and the rest of the body. Some MS patients will lose the ability to walk. Gait analysis
can be used to based on the relationship that increased gait imparity is related to the severity of
miscommunication within the nervous system (2).
The foot force plates are able to gather data in the x, y, and z directions. Fz represents the
force from above that is being placed on the plates. Fx and Fy peaks show the push back on the
foot and then the push off of the foot based on the coordinate system set up on the plates. The
plates also show the acceleration in the x and y direction on the plate, Ax and Ay. Fx, Fy, Ax,
and Ay are important in helping to determine the center of pressure during gait.
Materials and Methods:
The materials used in this lab consisted of the force foot plates, the BioWare software
package, and the AD hardware and computer. The force foot plates used were Kistrel
Piezoelectric Force Plates, which use a piezoelectric transducer to take the load forces placed on
them by the person walking on it, into electrical data that can be converted into relevant data by
the BioWare software, the AD hardware and the computer. The AD hardware was set at 100 Hz
during this experiment.
In this lab, the gait of each student was recorded under two scenarios. The first was just
walking normal, while the second was walking with some other kind of condition, in this case,
wearing an ankle boot as if the subject had damaged his foot. The collection of data included
walking across the foot force plates while the BioWare Software package was running. It was set
to record for ten seconds, allowing the subject to start from a distance which resulted in a normal
gait when he walked on the plates. Based on the data collected by the plate, the BioWare
Software produced a graph similar to the graphs found in the results that included the GRFs in
the X, Y, and Z directions. It also produced information about the acceleration in the X and Y
directions. We took the data from the software and recreated the graphs in excel and analyzed
certain aspects of the information, reported below in the results.
Results:
The following graphs depict the data collected by the BioWare software. The first peak of
the Fz and also resultant force shows the Heel-strike of the foot as the subject walked across the
plate. The dip shows the knee bend, and the following peak depicts the Toe-off of the step.
Figure 1:
Ground Reaction Force Components for Normal
Gait
250
200
Force (lbf)
150
Fx Right
Fy Right
Fz Right
100
Fx Left
Fy Left
50
Fz Left
0
3
-50
3.2
3.4
3.6
3.8
4
4.2
4.4
Time (seconds)
In figure one, we see the three components of the GRF for the normal gait scenario. We
see that for the right foot, the Fz is greatest during Toe-off, while for the left foot, the Fz is
greatest during Heel-strike. For the right foot, the Heel Strike peak of Fz is 177.5 lbf, the Toe Off
peak of Fz is 183.9 lbf. The peaks of the Fx and Fy forces are 11.8 lbf and 43.9 lbf respectively.
For the left foot, the Heel Strike peak of Fz is 200.8 lbf, and the Toe Off peak is 195.0 lbf. The
peaks of the Fx and Fy forces are 11.8 lbf and 35.7 lbf respectively.
Figure 2:
Ground Reaction Force Resultants for Normal
Gait
250
Force (lbf)
200
150
Resultant Right
100
Resultant Left
50
0
3
3.2
3.4
3.6
3.8
4
4.2
4.4
Time (seconds)
In figure 2, we see the resultant GRFs of the left and right foot during normal gait. In the
right foot resultant, the peak of the Heel Strike was 179.3 lbf and the Toe Off was 186.8 lbf. The
Heel Strike peak of the Left foot resultant was 200.8 lbf, while the Toe Off peak was 196.9 lbf.
Figure 3:
Ground Reaction Force Components of Gait with
Ankle Brace
250
200
Force (lbf)
150
Fx Right
Fy Right
Fz Right
100
Fx Left
Fy Left
50
Fz Left
0
0.5
-50
1
1.5
2
2.5
Time (seconds)
Figure 3 depicts the data recorded by the BioWare software for the gait of the subject
walking in a boot (ankle brace). Unlike in figure 1, the greatest GRF (Fz) for both feet was found
in the Heel Strike. The peak Fz force during Heel Strike for the right foot was 181.2 lbf and was
164.2 lbf during Toe Off. The peak Fx and Fy forces were 12.324 lbf and 25.3 lbf. The peak Fz
force during Heel Strike of the left foot was 194.4 lbf and 168.7 lbf during Toe Off.
Figure 4:
Ground Reaction Force Resultant of Gait with
Ankle Brace
250
Force (lbf)
200
150
Resultant Right
100
Resultant Left
50
0
0.5
1
1.5
2
2.5
Time (seconds)
Figure 4 shows the resultant GRF formed by the three components. The Peak GRF of the
Heel Strike was 182.4 lbf and the peak of the Toe Off was 164.9 lbf. The peak GRF resultant of
the left foot during Heel Strike was 197.0 lbf. The peak GRF resultant during Toe-Off was 170.3
lbf.
Discussion:
In order to determine the way in which the subject’s gait changed after putting the boot
on his right foot, we calculated the different peak GRFs, seen above in the results section, along
with the loading and decay rates of the Fz of both feet for both scenarios, the impact duration,
and the impulse caused by the feet while on the foot force plates. In terms of the peak GRFs, we
see higher ground reaction forces in during normal gait. The loading rate of the right foot during
normal gait was 1183.1 lbf/s and 904.5 lbf/s as the subject walked around in the boot. The
loading rates of the left foot were 1332.6 lbf/s and 1386.4 lbf/s. These loading rates make sense
because the boot is supposed to help relieve pressure on the foot it is on, the right foot, and as a
result, the left foot has to compensate by increasing its load rate. The decay rates for the right and
left feet during normal gait were -1586.6 lbf/s and -1666.1 lbf/s, while they were only -911.1
lbf/s and -1077.0 lbf/s for the second scenario. The impact duration increased from .65 seconds
in both feet to .72 seconds in the right foot and .74 seconds in the left foot after putting the boot
on. This increase makes sense because the body has adjust its gait more to accommodate for
moving the boot which changes the walking levels of each foot. The impulse, calculated by
integrating the GRF (resultant force) with respect to the impact duration, also increased as the
subject put on the boot, most likely due to the fact that the impact time increased. It went from
2645.7 lbf*s to 3506.59 lbf*s in the right foot and from 2463.0 lbf*s to 3200.4 lbf*s in the left
foot.
The largest differences in parameters between the two movements were found in the
loading rate and impulse for the right foot. The loading rate decreased by 278.6 lbf/s after putting
the boot on and the impulse increased by 860.89 lbf*s. The boot helped to relieve some of the
load on the foot, especially in terms of the loading rate, while increasing the impact time, which
increased the impulse.
I don’t really have any recommendations that could have made this lab more meaningful
to me. Hearing about this lab was one of the things that got me excited about the course. Plus I
chose the boot because my sister just recently had to have a boot put on her foot and I wanted to
be able to quantify how it changed the way she walked. I would say have each person participate,
unlike last lab, but everyone had their own set of data for this lab.
References:
1. Andriacchi, Thomas P., et al. "Methods for evaluating the progression of osteoarthritis."
Journal of rehabilitation research and development 37.2 (2000): 163-170.
2. Givon, Uri, Gabriel Zeilig, and Anat Achiron. "Gait analysis in multiple sclerosis:
Characterization of temporal–spatial parameters using GAITRite functional ambulation
system." Gait and Posture 29.1 (2009): 138.