There are several methods for analyzing human gait, ranging from simple visual analysis to complex 3D motion capture systems. The document compares visual analysis, the Vicon Nexus system, CODA system, and Kistler force plate. Visual analysis is the most common due to low cost but has limitations. The Vicon and CODA systems use multiple cameras to create 3D models of subjects walking but are expensive. The Kistler force plate measures ground reaction forces. Both Vicon and CODA provide highly accurate data, though Vicon's wider camera view offers better 3D images. Overall, visual analysis remains standard due to cost constraints of advanced systems.

1. Gait analysis, A Comparative
Report:
By
Conor Sheehan
University of Strathclyde
There are several different methods in commonly used, is observational analysis
examining gait and different ways in by a trained professional. This is where
which they are graded or assessed, from the examiner will look for any
standard viewing with use of a gait score discrepancies with the person in questions
card, right up to 3D computerised gait, in comparison to that of a normal
instruments. Using the IMRAD report one, some areas that are checked include
model the following evidence and facts the foot position, which muscles are firing
describe, some of main methods used in (are active), time of stance and swing
practice for the analysis of gait: phase, etc. This technique is also
sometimes combined with the use of a
The key areas that will be focused on in
digital camera system that is used for
this report include: visual gait analysis, the
recording and playback, for further study
Vicon Nexus system and the CODA system
of a subject’s gait. Also as previously
as well as the Kistler force plate which can
mentioned a score card is sometimes
be used in conjunction with any of the
used, such an example is the Edinburgh
above systems. Discussed will be how
visual gait scoring chart that helps to focus
some of the named systems work or how
in on the different areas of the gait cycle.
they analyse gait, along with the
The main reason this is the most
advantages and disadvantages
frequently used practice is the fact that it
respectively. Each method will first be
is low cost and a relatively quick way of
described as an individual area before
assessing someone. There do remain
being compared against one another.
some drawbacks to this though, such as:
The first method that will be described,
which is also the simplest and most
Conor Sheehan
University of Strathclyde, 2010

2. In real time the human eye is not landmarks on the subject, such an
fast enough to pick up on some example is the Vicon Nexus system. It
problem areas works by having a number of the specially
Observations may not be designed cameras (usually between 6 and
quantitative or objective 12) placed round a walkway or treadmill,
Subjects may fatigue if having to where a patient will walk and data is
walk for long lengths of time, this picked up from each camera, feeding back
could then change their walking information to a main computer. The
pattern cameras used are part of the Vicon
companies T-series range which states the
The use of a camera can help in reducing
cameras to be high resolution, high speed
these errors, allowing multiple viewing of
and highly accurate. The cameras work by
the same person’s gait an unlimited
shining an infrared (IR) beam that pick up
amount of times, the video can also be
on markers that have been placed on
slowed to frame by frame steps for very
anatomical landmarks of the subject, such
clear and precise viewing. However they
as profound bony landmarks (iliac spines,
do bring some of their own problems, like,
the malleoli of the ankle, the knee etc.)
the true angles made by the subject’s limb
the IR light then reflects back off the
or the position of the ground reaction
markers back into the camera. At any one
force (GRF) may not be seen as they truly
time there are at least two cameras
are. The cameras must also be positioned
locked on to any one marker, this is for a
correctly and images recorded from both
greater information consistency, the data
the coronal and sagittal planes. Finally the
is then fed back to a computer where
camera usually only remains stationary
software, “Nexus” in the case in of the
and so can only capture the person
Vicon Corporation, can produce a 3D
walking within a certain area of the
image of the sighted object. The program
situated camera.
can similarly calculate the velocity and
There are also more complex digital acceleration of a moving limb/prosthesis
systems that use several cameras to give a being worn; it can then display this
3-D shape of the subject and they can be information in a variety of ways. From a
used to pick up and located positioned 2D or 3D animation that itself can be
Conor Sheehan
University of Strathclyde, 2010

3. moved and viewed from any angle or extremely expensive to install and
plane as well as being slowed or sped up. upkeep, it needs a skilled operator and
The rest of the output information can although fast at processing it is still more
display information on body angle time consuming than observational gait
movements, where they peak and fall analysis and may not necessarily be able
throughout the different phases of gait, to provide any extra information that
how long these peaks last for etc. would be of significance to the patient,
than that of a trained professionals eye
The Vicon Nexus system is probably the
could. Finally a lot more space is needed
most advanced systems for use in the
for both the hard and software to be set
study of gait, in comparison to the other
up and used.
named methods. As stated it is extremely
accurate and fast at processing Moving on to the CODA (Cartesian
information. Furthermore, according to Optoelectronic Dynamic Anthropometer)
Vicon, the set up and use of the software system, which is another type of video
is easier to use than previous generation vector system with much of the same
of the equipment, “Unlike other Gait functions as the Vicon system. It differs in
Analysis systems, working with Vicon’s T- a number of ways though, primarily this
Series system doesn’t require an being, as stated by Codamotion its
engineering degree.”(2011, web) producer, it is a portable device. Although
However, this may be slight bias of the this may be the case, most clinics where it
company as this still only applies to a is used keep it remaining in a stationary,
skilled person/technician who knows and fixed position. Also unlike Vicon needing
understands the usage of the equipment. several cameras positioned round the
The markers are also considered to be walking area of the subject, the CODA
more confortable to wear for the patient, only need one cx1 unit, which is the base
by Vicon, as the indicators are designed to system containing the cameras. From this
be light and as they are only required to alone it can “create 3D measurements
reflect the infrared light, not have to without the reference of other cameras
produce it themselves like other video units” (Codamotion, 2011); however
systems, described later. The systems multiple units can be combined to give a
main disadvantage is the product is more accurate image. Also to compensate
Conor Sheehan
University of Strathclyde, 2010

4. for the lack of surrounding cameras, the lot fewer parts that need to be assembled
sensors have a wider viewing lens, and positioned with all the main
approximately 80 degrees. The markers components remaining in the single base
that are attached to the patient also unit. While the use of the software
differ; first they are known as active equipment still requires some
markers as they produce their own light understanding before use. According to a
source, rather than reflecting one Dr Barry Meadows, head of
produced by the camera. Due to this Neurobiomechanics at WESTMARK, SGH,
though the active markers need an the CODA analytical software can be
attached power source known as a taught to someone usually within a day.
DriveBox this does make for a more bulky This being in contrast to the “Nexus”, that
and heavier wear for the user as well as he said could take up to a week to learn.
the fact that wires are needed to attach
Continuing on to the Kistler force plate,
the markers and DriveBox. The advantage
which is a flat moving plate usually built
of this method though is the marker can
into the ground of a gait lab and usually
be programed to know what landmark it is
designed to match the flooring as not to
and so cannot shift or be confused by the
influence the walkers gait or foot position.
camera as another anatomical region,
The plate can be made in a number of
furthermore if the marker is somehow
sizes and in the shape of a single slab, but
hidden from the sensor by another part of
more often it is divided into two, four or
the body, the system and software can
more segments. The reason for this is,
calculate to an highly accurate point the
allowing a greater area to place the foot
position of where the marker is in relation
and the potential ability to get the GRF on
to the other selected points.
both feet without having the subject have
Much like its competitor, Vicon, the to walk twice and hit the plate with the
output traits are much the same. It claims opposite side. It is probably the most
the software and setup are easier to use, important component in measuring gait.
“Working with the Codamotion System Though independently it doesn’t serve
doesn't require an engineering degree” much of a purpose, it can be used in
(Codamotion, 2011). This may well be true conjunction with the above to calculate
to an extent for the setup, as there are a the ground reaction force applied by the
Conor Sheehan
University of Strathclyde, 2010

5. person and position of the foot, what part correctly stated by Dr Barry Meadows it is
of the foot is being used during initial a quicker and less perplexing system to
contact and through stance to toe off of learn.
that foot. With the aid of a specifically set
Although both the above methods are
up camera it can also show the direction
proven to be better than the conventional
and/or magnitude of where the GRF is in
visual gait examination and even with the
relation to the person on the force plate,
allowance of the extra time taken into
sometimes this is only done visually with
consideration to use either system, it still
the length of an indicated arrow on a
seems that they would be the more logical
computer screen, others it will give the
practice used. This remains not the case
actual force applied as a number, or
due to their high cost which currently at
sometimes both ways.
the moment cannot be afforded by most
From the above finding it is clear that the institutes and clinics, also as the more
evidence shows either the Vicon Nexus or advanced methods take longer to run for
CODA systems with the aid of the Kistler each patient this is seen as not an efficient
force plate are both very equally matched use of time and so is another reason used
in use of gait analysis and have a very high against the use of them. Finally at the
degree of accuracy if used correctly. The moment as a skilled clinician can usually
fact the Vicon system has the greater give just as good a result in determining
number of cameras with a wider viewing the main problematic areas and gait
sight due to the positioning of the deviations. So it seems unlikely that
cameras it is overall the more superior of anything will change until there is a
the two giving a better three-dimensional drastic diminishing in the cost of these
image. It does appear though, that the innovative systems, the time spent to
CODA technology has a few extra added assess a patient is reduced or there are
benefits over its counterpart, with it extreme advances in the technology that
“technically” being mobile, only needing makes gauging gait significantly better
the one base cx1 unit to function thus than the eye of a professional.
resulting in less space consumption and if
Conor Sheehan
University of Strathclyde, 2010

6. Reference List:
Figgins, E. 2010, Human Locomotion 6, Observing Gait, National Centre For
Prosthetics and Orthotics
Meadows, B. 2011, Slide 7, Gait analysis comes in many forms, WESTMARC, SGH
Codamotion. 2010a, Advantages & Capabilities [online]. Charnwood Dynamics Ltd,
Available at: http://www.codamotion.com/clinical-advantages-capabilities.html [6th
March 2011].
Codamotion. 2010b, Movement Analysis With CODA – Overview [online]. Charnwood
Dynamics Ltd, Available at:
http://www.codamotion.com/engineering-systems-overview.html [6th March 2011].
Kistler. 2011a, Motion and gait analysis [online]. Kistler Holding AG, Available at:
http://www.kistler.com/us_en-us/62_Biomechanics_Analysis/Motion-and-gait-
analysis.html [7th March 2011].
Kistler. 2011b, Why Kistler force plates? [online]. Kistler Holding AG, Available at:
http://www.kistler.com/us_en-us/64_Biomechanics_Kistler/Why-Kistler-force-
plates.html [7th March 2011].
Vicon. 2011a, Gait Analysis+Rehabilitation[online]. OMG plc, Available at:
http://www.vicon.com/applications/gait_analysis.html [6th March 2011].
Vicon. 2011b, Vicon Nexus [online]. OMG plc, Available at:
http://www.vicon.com/products/nexus.html [5th March 2011].
Vicon. 2011c, Vicon T-Series and T-Series S Edition[online]. OMG plc, Available at:
http://www.vicon.com/products/tseries.html [5th March 2011].
Wikipedia. 2011, Gait analysis [online]. Available at:
http://en.wikipedia.org/wiki/Gait_analysis [9th March 2011].
Wikipedia. 2011, IMRAD [online]. Available at: http://en.wikipedia.org/wiki/IMRAD
[8th March 2011].
Conor Sheehan
University of Strathclyde, 2010