View Full Version : Foot Contact Summary

Kathy D. Browder
02-17-1995, 12:59 AM
Thanks to all of you that replied to my request about foot switches. Below
is my original question, followed by a summary of responses. Have a great


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We are looking for information about devices that would allow us to detect
foot contact with the ground in overground and treadmill locomotion. We
want to be able to identify foot strike and toe off, as well as determine
time of contact with the ground. Any information that anyone has about
methodology and technology for obtaining this information would be greatly
appreciated. I will post a summary of replies to the list.



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try the March, 1995 issue of the Journal of Biomechanics pp. 347-...

Rodger Kram
Univ.of California, Berkeley


Check out the March Journal of Biomechanics. I believe there is a
technical note on exactly what you are searching for.

Good luck,

Dan Ferris
Biomechanics Laboratory
University of California at Berkeley



I do not know if this will fit your needs but Langer Biomechanics of
Ronkonkoma (Long Island), NY make a product called an EDG
(eletrodynograph). The EDG measures timing and forces at sensors (5 or 6 I
think) placed on the sole of the foot. The device is used most often by

Sorry I do not have their phone number but I know they have an 800 number
and if not the area code is 516.



Dear Kathy,
We are using a simple custom-built device, which works well. It consists
of a pressure sensitive transducer attached to one end of a flexible
rubber tube, which, in turn, is glued to the outer perimeter of the sole
of a shoe. You will find a more detailed description in:
Nilsson, J., Stokes, V.P. and Thorstensson, A. A new method to measure
foot contact. J. Biomechanics 18 (8): 625-627, 1985.
Best regards,
Alf T.



May be an old note could be useful. The foot switches described are still used
here with a very similar encoding circuit. A software allows us to extract
17 parameters to caracterize gait, running and jumping.
BLANC Y., VADI P.: An inexpensive but durable foot-switch for telemetred
locomotion studies Biotelemetry Patient Monitg 8: 240-245, 1981
Good Luck
Blanc yves
Kinesiology laboratory
Hopital Cantonal Universitaire Geneve Switzerland


Dear Kathy

Novel GmbH "emed" system can be used to measure and record the dynamic
pressure distribution under the foot, thus identifying foot strike and
toe off. They also produce their "pedar" system, a soft insole which can
be placed inside the shoe in order to measure the dynamic pressure

Maybe you could contact Peter Seitz at Novel GmbH, Beichstr. 8, 80802
Munchen, Germany. Tel: 089/390102 Fax: 089/337432.

Dr. Anna Hayes
School of Mechanical Engineering
University of Bath
Claverton Down
Bath, BA2 7AY
Tel: 01225 826826 x5375
Fax: 01125 826928


Dear Kathy,

The Langer Biomechanics Group makes a system called the Electrodynogram which
uses a portable waist pack and sensors attacted to the foot. While pressure
levels may be less then perfectly accurate, the timing is quite good. The
advantage is the portability and ease of use in remote locations. There
number is 800-645-5520.

The F-Scan system made by Tekscan of Boston (617- 464-4500) can also be used
for this purpose. While far more accurate than the EDG, it uses a teathered
system to the computer which will store the information. This may limit
outdoor use, however, there system can be used with a laptop, which may
permit use in any location. Good luck.

Howard J. Dananberg,DPM



We have developed (are developing) a unit to do just this which ties
into one or two channels on the Penny and Giles electrogoniometer
data logger. You can have either forefoot and hindfoot info
separately (two channels) or just whole foot ground contact (one

It does not stand alone though you need to have the P&G elgon setup
plus data logger.

Let me know if you want further info



I have built several foot switch systems in the past and have always found the
switch to be the most difficult component. What I have found to work the best
are homemade switches where I embed a small piece of a staple in a slightly thi
cker piece of pencil eraser. This is then placed between two small copper plate
s. The entire package can be made to be not much thicker than a foot pad insert
In some cases I have used a paper punch to put hole in the foot pad and built
the switch into the hole. The foot pads can be placed into a shoe or taped to
the foot. The wires used to connect the copper plates to a voltage source are s
mall and I have not had any subject complaints about the additional hardware. W
ith some additional circuitry, you can give each switch a different voltage suc
h that any combination of switches in contact produces a unique output voltage.
If you would like further information on circuit design or a sketch of the hom
eade switches, please feel free to contact me.

Peter Pidcoe, PhD


Hello Kathy,

B & L Engineering has an excellent stride analyzer system that does what
your looking for. There phone # is 310-903-1219 Hope this helps.

Micah Forstein
Motion Lab Engineer
Childrens Hospital Los Angeles


We have foot switches which we combine with an EMG
analysis system. We could sell them to you separately,
however. Contact Dewayne Rice or Jay Beakstead at
the Noraxon USA headquarters, 1-800-364-8985.

Jonathan Teets
Noraxon USA


Hi Kathy-

Check out the March 95 issue of Journal of Biomechanics. There's a Technical
Note, "Footswitch system for measurement of the temporal parameters of gait"
(Hausdorff, Ladin, and Wei, Vol. 28, No. 3, pp. 347-351). They describe a
simple inexpensive footswitch system that can apparently be built for under
fifty bucks. It outputs a voltage of 0-3.5v, so just make sure it has a BNC
output connector, and you can run it into your ADIU, use it to trigger, collect
the data with your ASM and sync it with your kinematic data. Pretty slick.
(Assuming that's what you want to use it for.)

Talk to you later.

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George Miller
Peak Performance Technologies, Inc.
7388 S. Revere Parkway, Suite 601
Englewood, Colorado 80112 USA
Ph: 303-799-8686 Fax: 303-799-8690
E-Mail: 76244.3047@CompuServe.com
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Kathy --

B & L Engineering manufactures footswitches that are used in conjunction
with their Stride Analyzer and EMG Analyzer Systems. Each footswitch has
four switches (large areas of contact): heel, 1st and 5th metatarsals,
and great toe. These footswitches are used to identify which areas of the
foot are in contact with the floor during gait. The forefoot section and
heel section can be separated to make small adjustments when inserting them
into the subject's shoe or taping them to the bare foot. Initial contact,
toe off, and the stance phase can be easily determined.

These footswitches are made in standard adult sizes. Smaller children's
sizes can be provided by sending B & L an outline of the foot.

For more information contact:

B & L Engineering
P.O. Box 3905
12309 E. Florence Ave.
Santa Fe Springs, CA 90670
TEL: (310) 903-1219
FAX: (310) 903-1221

I hope this information is useful to you.



We have used the PEDAR system when we are interested in plantar pressure data
as well as HS, TO times. B&L Engineering in Los Anglees has some foot
switches.These have been used extensively by Rancho Los Amigos' Gait lab.
Check it out.
Mark W. Cornwall, PhD, PT
Dept. of Physical Therpay
Northern Arizona UNiversity


Hi Kathy,

please read the technical note in the last issue of the J Biomechanics (march95)
from Hausdorf et al. (p347-3510 " Footswitch system for measurement of the
temporal parametrs of gait"
We use the same type of sensors (FSR's) and are quite happy with it.

Jaap Harlaar

email; jharlaar@cca.vu.nl


We are currently using Force Sensing Resistors (FSRs by Interlink
Electronics, Carpinteria, CA, phone: 805-484-1331, fax: 805-484-8989) as
footswitches. Our system was constructed in-house and uses four FSRs
(model 304C, 0.875" circular sensor with female connector, about $5 per
sensor) - one for each heel and one for each toe - linked to a simple
circuit that converts the resistance measure provided by the sensor to a
voltage signal that we sample with our A/D. The sensors are reasonably
durable, flexible, quite unobtrusive (thickness is about 0.010"), and
easy to apply with tape. I'm sure Interlink would be happy to send you
product information.

Phil Martin (atpem@asuvm.inre.asu.edu)
Dept. of ESPE, Arizona State Univ., Tempe
(602) 965-1023



I think you can use the F-scan system. You can contact them in:
307 West First Street
South Boston, MA 02127-1342
(617) 464-4500

Or trying to build a device using little strain gauges or piezoelectrics
attached on the shoe sole.

Luis Mochizuki
Lab. Biomechanics
School of Physical Education - Univ. of Sao Paulo


Hi Kathy,

We currently use the Motion Analysis footswitch system for this
purpose. The system actually is intended for use with their FootTrak software,
but we have adapted it for many other applications. Basically, it involves
four small footswitches that can be placed either in the shoe or on the sole of
the barefoot or the sole of the shoe. These switches drive four leds, mounted
in a housing, that can be viewed by a camera. For applications where we wish
to sync the data with video data, we simply digitize the four leds along with
the other markers. Thus, by looking at the video data for the leds, we can
determine when the gait events occured. For application when video may not be
involved, we can output the signal from the footswitches through a custom made
box that produces a specific output voltage, depending on which switches are
closed. This is typically input as an A/D input channel, along with other
analog inuts, to the computer. This data can then be searched by the software
to determine the on/off phases for the switches. It may be possible to
purchasee the footswitch hardware, independent of the FootTrak software, from
Motion Analysis.


* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* Charles W. Armstrong, Ph.D. Phone: 419-537-2753 *
* Applied Biomechanics Lab Fax: 419-537-4759 *
* Health Education Center *
* University of Toledo *
* Toledo, Ohio 43606 email: carmstr@uoft02.utoledo.edu *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *


Contact Joe Hamill (his email is JHamill@excsci.umass.edu). He
has some switches he has been using for the past several years and seems
very satisfied with them.

Robert Hintermeister
Steadman Hawkins Sports Medicine Foundation
Vail, CO


At the AAOS meeting (currently in progress), a company called Novel
electronics, Inc is displaying a commercial device that might do what
you want. They are a German compnay, but they have a USA contact:

Susan Diekrager, Vice President
(612) 332-8605
(612) 332-8606 FAX

Good Luck!

John A. Hipp, Ph.D. voice: (617) 667-4564
Orthopaedic Biomechanics Laboratory FAX: (617) 667-4561
Beth Israel Hospital and page: (617) 667-5555 ID 1657
Harvard Medical School email: jah@bihobl2.bih.harvard.edu
330 Brookline Ave
Boston MA 02215

Kathy D. Browder, Ph.D.
Director, Biomechanics / Motor Behavior Laboratory
School of HPER
Bowling Green State University
Bowling Green, Ohio 43403
Phone: (419) 372-6912
Fax: (419) 372-2877
e-mail: kbrowde@bgnet.bgsu.edu