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Thanks to all who replied to my problem about balance and feet position.
Special thanks to Ambarish Goswami. I found his work most applicable to the
problem at hand.
Regards
Rene Ferdinands
Department of Physics and Electronic Engineering
University of Waikato
Hamilton 2001
New Zealand
--------------------------------
ORIGINAL EMAIL
--------------------------
Hello, I am a biomechanist specialising in the biomechanics of cricket. At
the moment I am studying the role of footwork in batting. Of particular
importance to a good batsman is the ability to use his footwork in order to
optimise balance. The question of balance and footwork in cricket has not
been objectively dealt with in the past - current theories are mostly
subjective, and not based on sound biomechanical principles. I am not sure
whether this is the case in other ball sports.
So my problem is the following:
"How can one quantify balance? Obviously, the area of the base of support
and the position of the centre of gravity in relation to it is a
fundamental concept. But how can this be quantified? Also what about the
types of base of support and their stability in relation to perturbations
from various angles?
For example, if one adopts a stationary posture with splayed feet, what
kind of perturbation forces is he more able to withstand than if he stood
with the feet straight or even pigeon-toed? Or what if one foot is straight
and the other splayed? (This can be the case in batting postures.) In other
words, how does the postion of the feet in relation to the direction of a
perturbation force effect balance. For example, if one considers the type
of posture that is best to withstand a front-on tackle in rugby, then what
about the angles of the feet in relation to the direction of the impact
force - which way should they point? - e.g. perpendicular/parallel etc to
the line of impact force ? What kind of calculations can quantify this? Is
there current biomechanical research that can deal with this problem? "
If you believe you can help me in this area, then a detailed reply would be
most appreciated.
Thank you.
Rene Ferdinands
Department of Physics & Electronic Engineering
University of Waikato
Hamilton 2001
New Zealand
---------------------------------------
SUMMARY OF REPLIES:
************************************************** **********************
It might be worth sking my French friend , D. P-M Gagez at
pmgagey@club-internet.fr
He is president of the posturological society (but not much cricket is
played in Paris !)
--
Geoffrey.Walsh@ed.ac.uk
http://www.ed.ac.uk/~gwalsh
Phone (0)131.664.3046
64, Liberton Drive,
Edinburgh
EH16 6NW
UK
************************************************** ***********************
Hi Rene,
You can use a pressure mat and collect foot pressure distribubtion. From
the mat, you can then obtain center of pressure trajectory and calculate its
length and area of travel, and this with respect to time.
If you wish more information, email or call me at 1-800-248-3669 ext 263.
You can also visit the following web site:
http://www.tekscan.com/medical/system_matscan.html
There is much research done in Europe (mostly in french) that deals with
posture and balance.
The research does indicate a relationship between normal able-bodies vs
pathological conditions with respect to center of pressure trajectory,
length and area of travel.
Hope this helps,
norman
Norman Murphy, Ph.D.
************************************************** **********************
Dear Rene,
G'day. I just had a teach-in on this topic on the Clinical Gait Analysis
list/website:
http://guardian.curtin.edu.au/cga/teach-in/bos
I have developed a BodyBuilder model which calculates the discrepancy
between the base of support and the centre of mass. Of course, most of
the time the latter is contained by the former, but not always - e.g. in
gait there are two periods each gait cycle when the CoM goes outside the
BoS, as you can see on the page.
Hope this helps!
Best wishes,
Chris
--
Dr. Chris Kirtley MD, PhD
Assistant Professor
Department of Rehabilitation Sciences
The Hong Kong Polytechnic University
Hung Hom
Hong Kong Special Administrative Region of the People's Republic of
China
Tel.: +852 2766 6755 Fax +852 2330 8656
************************************************** **********************
Hello Rene:
Please see my recent paper on postural stability of biped
robots (the concepts are quite relevant to the human). You
can download the paper from:
http://www.cis.upenn.edu/~goswami/papers/paper.html
The paper is:
Postural stability of biped robots and the foot rotation
indicator (FRI) point
A. Goswami
International Journal of Robotics Research, Vol. 18, No. 6, 1999.
If you have any question, I will be happy to answer. My work
in this area continues.
Ambarish Goswami
************************************************** *******************
>So my problem is the following:
>
>"How can one quantify balance? Obviously, the area of the base of support
>and the position of the centre of gravity in relation to it is a
>fundamental concept. But how can this be quantified? Also what about the
>types of base of support and their stability in relation to perturbations
>from various angles?
>From an instrumental approach, we have looked at several ways to assess
balance and postural sway. We have used three methods; force plate,
accellerometers, and motion analysis.
Motion analysis turned out to be the least sensitive of the three.
Force plates are the most conventional method of balance. A force plate is
a large plate (aluminum), that has force sensors in the four corners. The
subject stands in the center of the force plate, and any change in balance
(sway) is picked up by the sensors. When the subject is in balance (no
sway), the forces on the sensors will be equal (or will have reached a
static steady state).
Another way to measure balance is by attaching accelerometers to either the
subjects head or in the region of the C7 vertibra. The accelerometer picks
up motions of the head as the subject tries to maintain an upright
position. I've got some pictures on my web page at
http://www.ecn.ou.edu/~major/www/accel.html .
With either the force plate or the accelerometer method, one can easily
reduce the data (say for a 10 second trial) to a single number. There are
a number of statistical methods to do this, but the easiest (for us) was to
calculate the RMS (root-mean-squared) value for the entire 10 second trial.
The voltage produced by the accelerometer (or force platform) was recorded
via a digital-to-analog board every 1/100 of a second, and stored on the
hard drive as an ascii file (10,000 entries for a 10 second trial).
To calculate the RMS number, the values in the ascii file were all squared.
These numbers were all added up and divided by 10,000 (to calculate the
mean), and the square-root of this number was taken. This gives a single
number corresponding to the total amount of postural sway for the interval
of the trial.
Trying to condense everything down to a single e-mail message, I may have
overlooked or not explained something very well. If you have any
questions, please feel free to post back and I will do my best to help out.
Dan Major
Univ. of Okla. School of Industrial Engineering
major@ou.edu htp://www.ecn.ou.edu/~major
************************************************** ***********************
---------------------------------------------------------------
To unsubscribe send SIGNOFF BIOMCH-L to LISTSERV@nic.surfnet.nl
For information and archives: http://isb.ri.ccf.org/biomch-l
---------------------------------------------------------------
Special thanks to Ambarish Goswami. I found his work most applicable to the
problem at hand.
Regards
Rene Ferdinands
Department of Physics and Electronic Engineering
University of Waikato
Hamilton 2001
New Zealand
--------------------------------
ORIGINAL EMAIL
--------------------------
Hello, I am a biomechanist specialising in the biomechanics of cricket. At
the moment I am studying the role of footwork in batting. Of particular
importance to a good batsman is the ability to use his footwork in order to
optimise balance. The question of balance and footwork in cricket has not
been objectively dealt with in the past - current theories are mostly
subjective, and not based on sound biomechanical principles. I am not sure
whether this is the case in other ball sports.
So my problem is the following:
"How can one quantify balance? Obviously, the area of the base of support
and the position of the centre of gravity in relation to it is a
fundamental concept. But how can this be quantified? Also what about the
types of base of support and their stability in relation to perturbations
from various angles?
For example, if one adopts a stationary posture with splayed feet, what
kind of perturbation forces is he more able to withstand than if he stood
with the feet straight or even pigeon-toed? Or what if one foot is straight
and the other splayed? (This can be the case in batting postures.) In other
words, how does the postion of the feet in relation to the direction of a
perturbation force effect balance. For example, if one considers the type
of posture that is best to withstand a front-on tackle in rugby, then what
about the angles of the feet in relation to the direction of the impact
force - which way should they point? - e.g. perpendicular/parallel etc to
the line of impact force ? What kind of calculations can quantify this? Is
there current biomechanical research that can deal with this problem? "
If you believe you can help me in this area, then a detailed reply would be
most appreciated.
Thank you.
Rene Ferdinands
Department of Physics & Electronic Engineering
University of Waikato
Hamilton 2001
New Zealand
---------------------------------------
SUMMARY OF REPLIES:
************************************************** **********************
It might be worth sking my French friend , D. P-M Gagez at
pmgagey@club-internet.fr
He is president of the posturological society (but not much cricket is
played in Paris !)
--
Geoffrey.Walsh@ed.ac.uk
http://www.ed.ac.uk/~gwalsh
Phone (0)131.664.3046
64, Liberton Drive,
Edinburgh
EH16 6NW
UK
************************************************** ***********************
Hi Rene,
You can use a pressure mat and collect foot pressure distribubtion. From
the mat, you can then obtain center of pressure trajectory and calculate its
length and area of travel, and this with respect to time.
If you wish more information, email or call me at 1-800-248-3669 ext 263.
You can also visit the following web site:
http://www.tekscan.com/medical/system_matscan.html
There is much research done in Europe (mostly in french) that deals with
posture and balance.
The research does indicate a relationship between normal able-bodies vs
pathological conditions with respect to center of pressure trajectory,
length and area of travel.
Hope this helps,
norman
Norman Murphy, Ph.D.
************************************************** **********************
Dear Rene,
G'day. I just had a teach-in on this topic on the Clinical Gait Analysis
list/website:
http://guardian.curtin.edu.au/cga/teach-in/bos
I have developed a BodyBuilder model which calculates the discrepancy
between the base of support and the centre of mass. Of course, most of
the time the latter is contained by the former, but not always - e.g. in
gait there are two periods each gait cycle when the CoM goes outside the
BoS, as you can see on the page.
Hope this helps!
Best wishes,
Chris
--
Dr. Chris Kirtley MD, PhD
Assistant Professor
Department of Rehabilitation Sciences
The Hong Kong Polytechnic University
Hung Hom
Hong Kong Special Administrative Region of the People's Republic of
China
Tel.: +852 2766 6755 Fax +852 2330 8656
************************************************** **********************
Hello Rene:
Please see my recent paper on postural stability of biped
robots (the concepts are quite relevant to the human). You
can download the paper from:
http://www.cis.upenn.edu/~goswami/papers/paper.html
The paper is:
Postural stability of biped robots and the foot rotation
indicator (FRI) point
A. Goswami
International Journal of Robotics Research, Vol. 18, No. 6, 1999.
If you have any question, I will be happy to answer. My work
in this area continues.
Ambarish Goswami
************************************************** *******************
>So my problem is the following:
>
>"How can one quantify balance? Obviously, the area of the base of support
>and the position of the centre of gravity in relation to it is a
>fundamental concept. But how can this be quantified? Also what about the
>types of base of support and their stability in relation to perturbations
>from various angles?
>From an instrumental approach, we have looked at several ways to assess
balance and postural sway. We have used three methods; force plate,
accellerometers, and motion analysis.
Motion analysis turned out to be the least sensitive of the three.
Force plates are the most conventional method of balance. A force plate is
a large plate (aluminum), that has force sensors in the four corners. The
subject stands in the center of the force plate, and any change in balance
(sway) is picked up by the sensors. When the subject is in balance (no
sway), the forces on the sensors will be equal (or will have reached a
static steady state).
Another way to measure balance is by attaching accelerometers to either the
subjects head or in the region of the C7 vertibra. The accelerometer picks
up motions of the head as the subject tries to maintain an upright
position. I've got some pictures on my web page at
http://www.ecn.ou.edu/~major/www/accel.html .
With either the force plate or the accelerometer method, one can easily
reduce the data (say for a 10 second trial) to a single number. There are
a number of statistical methods to do this, but the easiest (for us) was to
calculate the RMS (root-mean-squared) value for the entire 10 second trial.
The voltage produced by the accelerometer (or force platform) was recorded
via a digital-to-analog board every 1/100 of a second, and stored on the
hard drive as an ascii file (10,000 entries for a 10 second trial).
To calculate the RMS number, the values in the ascii file were all squared.
These numbers were all added up and divided by 10,000 (to calculate the
mean), and the square-root of this number was taken. This gives a single
number corresponding to the total amount of postural sway for the interval
of the trial.
Trying to condense everything down to a single e-mail message, I may have
overlooked or not explained something very well. If you have any
questions, please feel free to post back and I will do my best to help out.
Dan Major
Univ. of Okla. School of Industrial Engineering
major@ou.edu htp://www.ecn.ou.edu/~major
************************************************** ***********************
---------------------------------------------------------------
To unsubscribe send SIGNOFF BIOMCH-L to LISTSERV@nic.surfnet.nl
For information and archives: http://isb.ri.ccf.org/biomch-l
---------------------------------------------------------------