View Full Version : -no subject-

05-11-2005, 04:26 PM
Dear Subscribers,

I couple of months ago I posted a question about the Hammer throw. Below
is a copy of the original email as well as the responses that I
received. Many thanks to all who replied.
Sara Jaycock
AIS Biomechanics
Post-Graduate Scholar
Phone: +61 2 6214 7898
Mobile: 0421 188 555
Email: sara.jaycock@ausport.gov.au

Dear Subscribers,

I'm carrying out a study on hammer throwing and have obtained many
articles about the kinematics of the throw, and whilst some of these
papers have derived applied forces, there does not appear to be much in
the way of kinetic analysis. The forces derived from kinematic data
depend upon the models used and it is doubtful how well these models
represent the actual movement. I am interested in the development of the
force applied to the hammer prior to release, the impulse produced and
the time between maximum force developed and release.

If anyone has any suggestions or information I would greatly appreciate
your response.

__________________________________________________ ______________________

There is no research regarding the kinematics of the hammer throw. We
attempted mounting multiple force plates in the ring this past fall.
USOC Olympic training center has the capablity to mount them this way.
We were unable to acquire data due to software problems. We are hoping
to attempt again this summer.

The problem I foresee is the length of the movement, direction of the
movement, time of movement, and rotational motions. The direction is
not linear across the ring making it hard to place force plates. The
length and the time of movement are long in terms of collecting data off
forces plates.

In my opinion, maximum force will occur at the transition into turn 1
due to increased friction and inertia on the system, especially in male
throwers. As the athlete increases velocity in the turns the force they
are able to apply is lessening.
Even the block after return to DS would probably not have as much force
due to momentum of the system.

The studies done by Dapena are the best kinematic data you will find.
The deriving of applied forces based upon this information will be as
accurate as the calibration. My suggestion would be to utilize that
approach. Or, the use of accelerometers or strain gauges attached to
the athlete or mounted within the ball. This may prove to be costly
however due to the units being possible broken with every throw.

I hope something I have written is of help to you.

Suzie Konz, MS ATC CSCS
Doctoral Student
Brigham Young University
Physical Education Department
__________________________________________________ ______________________

I don't know how much help it will be to you, but I recommend that you
check some of the past issues of the Soviet sports Review (Table of
Contents is available at www.dryessis.com and in some libraries.

the Russians did extensive research on the hammer throw and much of it
is available in Russian. The only English sources that I know of are in
the above journal.

Michael Yessis, Ph.D
President, Sports Training, Inc.
__________________________________________________ ______________________

Here's an article with some references you might look into, though it
looks like there's just not much out there:


Try to look in the Russian literature, though it's tough
because a lot of it is untranslated.

Also, check out this guy:

Jesus Depena


Here's a link to one of his publications:

Alexander "Sandy" Chase
__________________________________________________ ______________________

If the kinematic data for the hammer is accurate, then it is a simple
matter to derive the forces between the hammer and the human body. The
hammer is with good approximation a particle, so you only have to
differentiate the positional vectors twice and multiply them by the mass
of the hammer.

However, differentiating twice will increase the error in the positional
data by two orders of magnitude, so the kinematic data must be really
good or at least subjected to a reliable filtering.

I cannot resist mentioning that if you have the kinematics of the hammer
AND the athlete then you can perform an inverse dynamics simulation of
the forces using the kind of technology we develop in our project, i.e.
the AnyBody Modeling System. Please refer to www.anybody.aau.dk
www.anybodytech.com for more information or write to me personally if
you have specific questions about this.


John Rasmussen,
Associate Prof., PhD, The AnyBody Group, Institute of Mech. Eng. Aalborg
University www.ime.aau.dk/~jr, jr@ime.aau.dk

__________________________________________________ ______________________

__________________________________________________ _________________This message is intended for the addressee named and may contain confidentialand privileged information. If you are not the intended recipient please note thatany form of distribution, copying or use of this communication or the information in it is strictly prohibited and may be unlawful. If you receive this message in error,please delete it and notify the sender.Keep up to date with what's happening in Australian sport. Visit www.ausport.gov.au________________________________ ___________________________________