View Full Version : Motion Analysis Systems

Earl F. Hoerner, M.d.
12-03-1998, 03:01 AM
Dear Subscribers,
The following is a summary of responses received to my posting regarding
motion analysis systems and, in particular, the APAS system:

Dear Dr. Hoerner,
I saw your posting on Biomech-L requesting feedback about the APAS
system and I would like to share my experiences with the Ariel APAS.
I bought my first Ariel APAS 386 collection system in 1990. I have
used the APAS for 3- D video analysis (kinematic & kinetic), force
platform analysis with a Kistler plate (gait & jump analyses) and 16
channel EMG analysis in a Physical Education undergraduate and
graduate environment. Also, I have used the EMG system to teach real
time EMG responses during different neuromuscular conditions at the
medical school. We regularly perform simultaneous video analysis,
force platform and EMG analyses on research & design evaluation of an
active traction rehabilitation prototype and master's
thesis projects. I have used up to 4 video cameras (60 HZ) and a
LoCam cinematographical camera (500 fps) for video analysis and I
have verified the accuracy of the system with known measures. The
accuracy I found to be similar to those reported in this year's 3D
conference at Tennesee. Also, I have used theDynamic Lift Task
Analysis (DELTA) software, Jump software, and GAIT software on
various research projects. Presently, I am working with the panning
module on a track & field project and last summer at the ISBS at
Konstanz, I used the APASview software to present the results from
the Track & Field competition at the 1996 Olympic Games. Since
purchasing my original system I have acquired another full APAS
desktop analog collection unit and an APAS laptop with A/D
capabilities and an Computerized Exercise Strength unit (CES). Also,
I have personally acquired an APAS laptop with A/D and I just
downloaded the new APAS light software for my home desktop computer
for my consulting business. All the systems have worked
exceptionally well and each machine generation has gotten better with
improvements in the software and hardware while decreasing in cost.
New versions of the software can be downloaded from the server and
the open architecture has made it a very powerful and versatile
analysis tool, that is a great bargain. My undergraduate and
graduate students finds the software easy to learn and well
documented with good help screens. Furthermore, if any technical
problems arise, John Probe, head of technical support will promptly
and accurately resolve the difficulty. The international APAS users
group is very helpful in sharing ideas, information on current and
new analysis applications. Your concern about the potential catch
about the low price is unfounded because Ariel does not believe in
using expensive proprietary hardware when comparable hardware is
available at a fraction of the cost. The only thing you are missing
is the time you will save completing your research projects using
these great systems.
I am so confident about these systems that I plan on personally
acquiring a new APAS notebook, hopefully in the next year.
If you have any further questions concerning the systems please
free to contact me at
or if you want to see some of the projects completed using an APAS
check out the Magin Putter project or the Olympic Discus project @

Alfred Finch,Ph.D.
Professor Biomechanics
Physical Education Department
Indiana State University

Dr. Hoerner,
I utilized the system during my year of study in USA at the United States
Sports Acdemy. I used it also for my thesis project. I am using it here in
Italy with Technogym for perfoming biomech. analyses.
I found it extremely good. It is very easy to use once the procedure has
been properly memorized and the new software for win98 is much more
user-friendly than the old versions.
My rating of APAS is very high. I think the ratio costs-benefits determine
APAS to be the best currently available on the market.

If you need further and more detailed info,
feel free of contacting me via email.

Marco Cardinale

Dear Dr. Hoerner,

I do not believe you miss anything if you choose to use an APAS system for
movement analysis. Here at the university of Copenhagen we have used the
APAS for about 4 years now and we have been very satisfied all the way.

We use the system on a daily basis for gait analysis. We use 5 video
(50 Hz) and 2 AMTI platforms, which we had before we bought APAS. We use
also EMG recordings from various EMG-systems. For digitizing we use the
system semi-automatically, which means that it takes a little less than 60
min to digitize 5 camera views (there are about 80 frames per view meaning
total of 400 frames). However, we run the APAS system on several computers,
so often several staff members work on the same project at the same time,
which may further cut down time consumption for the total offline analysis.

Normally, we calculate 3-D inverse dynamics by importing the 3D coordinates
and the force plate signals from APAS to Matlab.

An interesting alternative is to invest in an online system. I haven't any
experience with such a system, but it is my impression that you often run
into technical problems during experiments, so you may end up spending more
time in the lab. Also after experiments you may spent some time with the
data from online systems because these systems often mix the markers (see
the Chattanooga presentation about marker confusion).

I hope you can use our experience and you are welcome to return with
specific questions.

Erik B. Simonsen, associate professor, Ph.D.

++++++++++++++++++++++++++++++++++++++++++++++++++ ++++++++++++
Erik B. Simonsen, Associate Professor, M.Sc. Ph.D.
Institute of Medical Anatomy section C.
Panum Institute. University of Copenhagen
Blegdamsvej 3., DK-2200 Copenhagen N
Phone: +45 35 32 72 30 (work) Fax: +45 35 32 72 17
Phone: +45 45 80 93 04 (home)
E-mail: E.Simonsen@mai.ku.dk

Dear Dr. Hoerner:

Yes, you are missing something very important.
You are missing negative balance due to so much money for sales,
maintenance fee and some bubbles.:-)

If you are so busy and have no time, you may stop here just after knowing
to miss.
Somewhat long phrase are here.

I am an M.D.(physiatrist) and used APAS since 1994 in Korea. I analyzed the
motions of baseball
players and abnormal gait patients with APAS since it was DOS version. As
experience, it
works so fine, is accurate and has user friendly interface. Most of all,
the APAS
is very
powerful. The more know you about the APAS, the greater power may you feel.
think the power
of the system may come from the opened nature. No black box there.

What would be left to be desired for the system? Dynamic EMG?, Forceplate?
Do you
know the
analog module of APAS with AD converter can be used as an polygraph
equipped with
signal processing ability? You may know some kind of commercialized digital
polygraph system is
sold at the price of more than $10,000.

If you think that I may have some relation with the APAS company, the
would be
maintained by only below idea.

How much, do you think, would be appropriate for a motion analysis system?
$200,000, $300,000
.. ...
Why do you think that it would be?

I have two simple estimation - forward and inverse.

Forward : The price for making the motion analysis system per se.
1. It should depend on the hardwares. The price of hardwares will
correlate to
the number of consumer. Which consumer group would be larger, the consumer
of common
camcorder or that of specialized CCD camera? If a motion system try to have
own hardware,
the price may go up steeply. The black box may give some convenience but
it provokes
many troubles and prevents extensibility and power.

2. It should depend on the technology. How much should the company pay
adopting the
DLT, various smoothing algorithm, Euler/Cardan angles, inverse dynamics and
processing algorithm? None!! Except for several hundred dollars for the
books and

3. It should depend on the software to assemble all the calculation,
processing and driving
the hardware. They may pay far more money to build user friendly interface
than to
assemble the
modules and hardware. You can compare the system by system about the

4. There remains may be what you are missing.

Inverse : The price for the patient or client to pay for the

In Korea, Magnetic Resonance Imaging on a body segment as brain,
costs about
$500, provided that the exchange rate is 1:1000(really 1: 1300-1400). The
analysis by the
motion analysis system that you think nothing to miss, costs about $500 -
This price can
be accepted if the information is so critical for clinical decision with
But, far more often, we meet the situation that the gait analysis data is
not so
critical as
for following up the treatment course, for minor orthotic change, dosage
change of
drugs etc. Few patients can afford that price for their weekly or monthly
follow-up or for the
minor clinical decision. Of course, I think, as a rehabilitation doctor, we
work and
study harder to make the information from gait analysis more valuable than
But the price
should be down and cheaper information could be supplied. Why not?

This "inverse estimation" is not exactly applicable to the research
institute or
other rich
country as the "inverse dynamics" cannot show the real joint kinetics
bone on bone
force. :-)

My idea is that more patients, clients or sports men should be helped with
knowledge which is build up of so many scientists' sincere and brilliant
Maybe I meet
with the APAS company at this point.

Thank you for reading my clumsy words.


================================================== =
Sun G. Chung M.D., Ph.D.
Dept Rehab Med
Seoul National University College of Medicine
Chong Ro Ku YeonGeon Dong Seoul
South Korea
(TEL)82-2-760-2619 (FAX)82-2-743-7473

Dear Earl,

Our department is also planning to purchase a motion analysis system. We
have looked into the APAS and I agree that the price does seem extremely
reasonable. However, we have been looking into the specifics of the system
and are yet to find anything to put us off. I don't have the knowledge to
completely answer your query. However, I would recommend that you check
the sampling frequency as some systems sample at an insuffiecent rate to
analyse very fast movements (particularly in sporting situations).
Obviously this depends on what you will analyse.

Would you please send me a summary of your replies as I would appreciate
reading these before we purchase the APAS.

Kind regards,

Daina Sturnieks.

Daina Sturnieks, B.App.Sc. (Hons)
Department of Human Biology and Movement Science
RMIT University
PO Box 71
Victoria, 3083
Ph. +61 3 9925 7682
Fax +61 3 9467 8181

I am a long time user of the apas system, and would be happy to discuss it
further with you. Basically, it is what it is, quite robust and accurate,
and will probably serve you quite well..

best wishes with your venture.

Leonard Elbaum
Associate Professor
Department or Physical Therapy
FIU / Miami, FL

Hello Earl Hoerner,

We have been using APAS for a few years now and we have been
very satisfied. Once we sorted out our data collection space (i.e.,
painting walls black and adding dark flour tiles) APAS was extremely
capable of detecting marker positions. Support from Ariel Dynamics has
also been fine. We are still using the old DOS system but are planning to
move to the new software. Interfacing the APAS system with our other
hardware has been relatively easy (EMG, force plate, bioamps, etc.).

While we will always have a need for the APAS system (we can video
away from our gait lab and process later), we would also like to have an
automatic digitizing system (Vicon, etc.) to speed up our data processing
time. APAS is great for our clinical and R&D efforts; however, the
digitizing time for 3 cameras at 150-300 frames limits the volume of
clinical referrals that we can handle (since we deal with physical
disabilities, our client's walk very slowly). In Canadian $ the automatic
digitizing setup we need would cost around $200,000.00. This is purely
a speed of data processing concern - not a comment on data

In conclusion, I think that any new lab should have an APAS installation.
This is a very flexible system with a very reasonable price. I would
suggest that you get three cameras, instead of two. In addition to being
able to pickup most marker positions, we have been saved by having
some video-taping redundancy (i.e., when one camera did not record).
Also, factor in the cost of setting up the lab so that all cameras can be
turned on at one location - preferably beside main the data collection
computer (we are still working on this one!).

Please let me know how thing are progressing with your lab - our group
is always interested in sharing/learning with other physical rehab

Edward Lemaire, PhD
Clinical Researcher
The Rehabilitation Centre
(613) 737-7350 x5592

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