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Dear BIOMCH-L subscribers:
Here are the responses I received to my request of Oct. 27th on the
Peak 2D system. I hope this information will be of some benefit to
others and I thank everyone who took the time to share their opinions
with me. My original request was as follows:
Dear BIOMCH-L'ers,
My request is directed at those of you who have a Peak 2D system in
your labs. I have a few questions about the system. I hope this posting
does not qualify as "commercial" in nature. I have already spoken to
Peak, and I simply wish to get some information from those of you who
use the system (for the purpose of objectivity). My questions are:
1. Will the Peak system (2D) compute linear and angular kinematics of the
"segment" (i.e., at the segment centre of mass)? If so, do you know whose
centre of mass proportions are used (Dempster, Clauser, etc.).
2. Is there a limit to the number of markers that can be digitized?
3. When digitizing a grid for scaling purposes, are there limits to the
number of points that can be used?
4. Kinematically speaking, are there any limits to Peak's analysis capab-
ilities?
5. How well do the system's filtering options work (e.g., can you change
the cutoff frequency of the digital filter to any value, is the filter
a zero-lag filter, etc.)?
Any other information and/or helpful comments you may wish to add
would be most appreciated. Again, I hope that this is an "acceptable"
request, and offer my sincere apologies if it is not. Those of you who
have the system can be of great help to me. Thank you in advance for
your time and your help. If there are enough, I will post a summary of
the replies.
Sincerely,
John Barden
E-mail: barden@max.cc.uregina.ca
Phone: (306) 585-4698
Fax: (306) 585-4854
Address: Faculty of Physical Activity Studies
University of Regina
Regina, Saskatchewan
Canada S4S 0A2
-------------------------------------------------------------------------
From: Rodger Kram, Berkeley (rkram@garnet.berkeley.edu)
1. Will the Peak system (2D) compute linear and angular kinematics of the
"segment" (i.e., at the segment centre of mass)? If so, do you know whose
centre of mass proportions are used (Dempster, Clauser, etc.).
it will do this but you have to input the mass or % of total
2. Is there a limit to the number of markers that can be digitized?
yes, it is 34 or 35 i think
3. When digitizing a grid for scaling purposes, are there limits to the
number of points that can be used?
i think it only uses 2 points
4. Kinematically speaking, are there any limits to Peak's analysis capab-
ilities?
too vague to answer
5. How well do the system's filtering options work (e.g., can you change
the cutoff frequency of the digital filter to any value, is the filter
a zero-lag filter, etc.)?
you can change cut-off frequency within some bounds. i think the max
cutoff is 100Hz. should be fine for humans but we study lots of much
faster invertebrates in our lab and this is a limitation.
peak should certainly be able to answer these questions for you.
try calling jeff pinkerton at 1 800 775-7325 and please tell him i directed
you his way.
rodger kram
------------------------------------------------------------------------
From: Gary D. Heise, LSU (kiheise@lsuvm.sncc.lsu.edu)
Some points about Peak Performance System (I have used it for about 5 years).
1. Yes you can get segment info (i.e., kinematics of segment center of mass)
based on Dempster's data I believe.
2. Number of markers: the max used to be 35 points per picture. This may
have been updated.
3. The "grid" you refer to is simply a 2 point scaling factor which can now
be digitized several times for purposes of averaging a conversion factor.
I didn't think that Peak offers a grid or a 2-D DLT calibration approach.
4. Concerning filtering: It is quite good. The user now has the choice of 3
different schemes (Butterworth zero-lag, Fast Fourier Tran, Cubic Spline)
5. A limitation concerns the graphics area-you can't normalize multiple sets
of data. For example you can't graph subject A, B, and C with respect to
percent of gait cycle.
I would be happy to discuss any more concerns you may have about this system.
I have found it useful and pretty user-friendly. I have also written several
support programs to calculate kinetics and other things that Peak doesn't
offer.
Sincerely,
Gary D. Heise, Asst. Prof., Kinesiology, LSU
(504) 388-3552
Here are the responses I received to my request of Oct. 27th on the
Peak 2D system. I hope this information will be of some benefit to
others and I thank everyone who took the time to share their opinions
with me. My original request was as follows:
Dear BIOMCH-L'ers,
My request is directed at those of you who have a Peak 2D system in
your labs. I have a few questions about the system. I hope this posting
does not qualify as "commercial" in nature. I have already spoken to
Peak, and I simply wish to get some information from those of you who
use the system (for the purpose of objectivity). My questions are:
1. Will the Peak system (2D) compute linear and angular kinematics of the
"segment" (i.e., at the segment centre of mass)? If so, do you know whose
centre of mass proportions are used (Dempster, Clauser, etc.).
2. Is there a limit to the number of markers that can be digitized?
3. When digitizing a grid for scaling purposes, are there limits to the
number of points that can be used?
4. Kinematically speaking, are there any limits to Peak's analysis capab-
ilities?
5. How well do the system's filtering options work (e.g., can you change
the cutoff frequency of the digital filter to any value, is the filter
a zero-lag filter, etc.)?
Any other information and/or helpful comments you may wish to add
would be most appreciated. Again, I hope that this is an "acceptable"
request, and offer my sincere apologies if it is not. Those of you who
have the system can be of great help to me. Thank you in advance for
your time and your help. If there are enough, I will post a summary of
the replies.
Sincerely,
John Barden
E-mail: barden@max.cc.uregina.ca
Phone: (306) 585-4698
Fax: (306) 585-4854
Address: Faculty of Physical Activity Studies
University of Regina
Regina, Saskatchewan
Canada S4S 0A2
-------------------------------------------------------------------------
From: Rodger Kram, Berkeley (rkram@garnet.berkeley.edu)
1. Will the Peak system (2D) compute linear and angular kinematics of the
"segment" (i.e., at the segment centre of mass)? If so, do you know whose
centre of mass proportions are used (Dempster, Clauser, etc.).
it will do this but you have to input the mass or % of total
2. Is there a limit to the number of markers that can be digitized?
yes, it is 34 or 35 i think
3. When digitizing a grid for scaling purposes, are there limits to the
number of points that can be used?
i think it only uses 2 points
4. Kinematically speaking, are there any limits to Peak's analysis capab-
ilities?
too vague to answer
5. How well do the system's filtering options work (e.g., can you change
the cutoff frequency of the digital filter to any value, is the filter
a zero-lag filter, etc.)?
you can change cut-off frequency within some bounds. i think the max
cutoff is 100Hz. should be fine for humans but we study lots of much
faster invertebrates in our lab and this is a limitation.
peak should certainly be able to answer these questions for you.
try calling jeff pinkerton at 1 800 775-7325 and please tell him i directed
you his way.
rodger kram
------------------------------------------------------------------------
From: Gary D. Heise, LSU (kiheise@lsuvm.sncc.lsu.edu)
Some points about Peak Performance System (I have used it for about 5 years).
1. Yes you can get segment info (i.e., kinematics of segment center of mass)
based on Dempster's data I believe.
2. Number of markers: the max used to be 35 points per picture. This may
have been updated.
3. The "grid" you refer to is simply a 2 point scaling factor which can now
be digitized several times for purposes of averaging a conversion factor.
I didn't think that Peak offers a grid or a 2-D DLT calibration approach.
4. Concerning filtering: It is quite good. The user now has the choice of 3
different schemes (Butterworth zero-lag, Fast Fourier Tran, Cubic Spline)
5. A limitation concerns the graphics area-you can't normalize multiple sets
of data. For example you can't graph subject A, B, and C with respect to
percent of gait cycle.
I would be happy to discuss any more concerns you may have about this system.
I have found it useful and pretty user-friendly. I have also written several
support programs to calculate kinetics and other things that Peak doesn't
offer.
Sincerely,
Gary D. Heise, Asst. Prof., Kinesiology, LSU
(504) 388-3552