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  • Foot Contact Summary

    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


    ************************************************** ******************************


    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.



    ************************************************** ******************************

    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
    UIC - PT


    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.

    ************************************************** **************************
    George Miller
    Peak Performance Technologies, Inc.
    7388 S. Revere Parkway, Suite 601
    Englewood, Colorado 80112 USA
    Ph: 303-799-8686 Fax: 303-799-8690
    ************************************************** **************************


    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



    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 (
    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: *
    * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *


    Contact Joe Hamill (his email is 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:
    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