Dick Dreissigaker versus Mark Campbell
boatie
Fight in the Dog is a US blogger on rowing stuff (read him - generally
interesting stuff)
he has had the balls to call out the two majors to justify their
corners after an article written by Ivan Hooper about injury
prevention.
http://www.rowperfect.co.uk/news/?attachment_id=46
Here is the link to FITD site
http://fightindog.blogspot.com/index.html
Some very well-considered words from two masters.
Add you comments here and also on the FITD site - it deserves as much
publicity as possible.
Rebecca
Charles Carroll
Did you see the post from Xeno on fightinthedog.blogspot.com? Wow! Is this
ever going to make Rowperfect fans happy!
Cordially,
Charles
liz
blog makes interesting reading.
"boatie" <reb...@caroe.com> wrote in message
news:1170183730....@k78g2000cwa.googlegroups.com...
paul_v...@hotmail.com
> This has to be THE most authoritative ergo discussion ever.
>
> Fight in the Dog is a US blogger on rowing stuff (read him - generally
> interesting stuff)
> he has had the balls to call out the two majors to justify their
> corners after an article written by Ivan Hooper about injury
> prevention.
>
> http://www.rowperfect.co.uk/news/?attachment_id=46
>
>
> Some very well-considered words from two masters.
>
> Add you comments here and also on the FITD site - it deserves as much
> publicity as possible.
> Rebecca
Here we go again!
The comparison without holding the handle, while it makes the point
that the person wants to make, it's just not what we do.
For example: If the dynamic Ergo (yes, I'm using the term in spite of
my better judgement) can be shown to allow an athlete to produce more
handle force than the grounded Ergo, then their may be some support
for this "difference in energy requirements" that continually gets
claimed to exist. Unless someone has found a way to accelerate the
Rower/Boat system other than application of handle force. (even the
"thumbing along" would cound as handle force!) [;o)
Where the Sliding Ergo is definitely more boatlike is in regards to
the ability of the rower to generally rate higher. Why this is not a
good thing, is that the sliding Ergo doesn't penalize the rower for
doing the bad things they do when rating up, namely rushing the
recovery. The grounded Erg does penalize a rushed recovery by making
the rower expend a certain amount of energy in either stopping or
absorbing the additional momentum involved. The Boat penalizes the
same motions with faster system deceleration and greater hull speed
migration about the system speed (pretty hard on efficiency).
As for the discussion regarding how the foot stretcher loads up on the
grounded Erg differently than in a boat. Let's just give that a
little thought. In a boat it's our body that's floating along and
dragging the hull with it, there should be a pulling force against the
stretcher until the catch it made, though we could "thumb" ourselves
onto it a bit before the catch. On a grounded Ergo, once the hands
have gone away and the body pivoted forward we basically have to
resist flying into the catch too quickly, especially along with the
bungee pulling us down the sloped rail (Is it really a surprise now
that there might be a build up of foot pressure prior to the catch in
that situation?). On the sliding Ergo ther will be a smaller build up
due to the friction that must be overcome in relation to the mass that
is being moved, namely the Erg&Slide carriages (C2) or Flywheel Head
(RP).
While they mention that "for the same rower a different force profile
is accomplished between either the Sliding or Grounded Erg. And that
the profile on the sliding Ergo is more like what was measured in a
boat.", I think that the understanding/explanation of that is not very
complete, and self-serving for the promoters of the RP. It's like
finding a correlational relationship and claiming that it is causal.
(A big "no-no" in the real world of science.)
Don't get me wrong, I have nothing against RP, C2, or Slides, but the
key to using any of the systems to train us how to move boats better
is the evaluation of all the input that is happening while using
them. The most simple way to determine if the rower has consistent
technique would be to evaluate how closely their force profiles align
between the Sliding and Grounded situations.
Finally, the suggestion of lowering the DF is very good, of course
I've been arguing against high DF's for a long time but it seems that
everyone wants to argue rather than listen. The argument I use was
not touched on in these discussions, and it was even suggested that
the lowest DF's were likely best for lightweight women. This attitude
demonstrates that even though they are suggesting the correct thing
they don't know why they are doing so. The DF should really be
suggested by the Target Boat speed, the faster the boat the lower the
DF, as that is going to determine the speed of the flywheel and the
time of the drive (along with drive length and even the athletes
bladework and timing). Lwt women can't generate the force of a Hwt
man (not usually anyhow), and are not generally going to be in boats
travelling as fast (but even that is closer than one might suspect).
Another difference is that as a boat goes faster the drive time does
not necessarily go down, this is due to the change in hydrodynamic
lift as it applies to the blade, along with the flexible coupling
(shaft) of that blade to the boat. Note that this has been discussed
before in relation to why the majority of the time taken from a given
stroke when the rate is increased comes from the recovery and not the
drive, something that can simply not be replicated on the Erg unless
one does extensive testing and selects the DF that will give them the
Drive time desired at the planned pace target for the specific piece.
Well, enough for now. I really should do this when it's the only
thing to concentrate on, but I've no doubt the usual suspects will be
along to nit and pick if I have gone too far astray, giving me a
chance to clarify or elaborate if needed. [;o)
Cheers,
Paul Smith
www.ps-sport.net
Charles Carroll
> my better judgement) can be shown to allow an athlete to produce more
> handle force than the grounded Ergo, then their may be some support
> for this "difference in energy requirements" that continually gets
> claimed to exist.
Paul,
I am just going to take a shot at this one part of your post. My experience
has been that it is much easier to lift the body up and off the seat of an
erg on slides than it is to get it off the seat of an erg that is not on
slides.
Cordially,
Charles
KC
Here's what I wrote in a "comment" on the blog post titled, "More From
Concept II"
I'm amazed that Dr. Dudhia, Dr. Kleshnev, Ivan Hooper, Dick
Dreissigacker, Mark Campbell, and even Xeno all forgot to account for
the effects that hydrodynamic drag has on the hull of a boat when it is
moving. The suggested example (from Anu Dudhia's rowing FAQ and Ivan
Hooper's paper) of sitting on a static erg at the catch and watching how
much your body moves when you extend your legs, versus sitting in a boat
and doing the same (blades out of the water) totally neglects the fact
that when the water is MOVING under the hull, there is a significant
amount of resistance to the hull's bow-ward motion.
One of the main claims to fame by Row Perfect is that the moving head of
their erg is roughly the same mass as a single scull. Simply matching
the mass of a boat does not come near a full simulation of the complex
dynamic system that is on-water-rowing.
Let's consider two situations where a dynamic erg is supposedly better
than a static erg: First the release/recovery, then the catch/drive:
At the release, on a dynamic erg like the RP, as the rower comes up the
slide during the recovery, their body remains almost stationary, while
the erg head moves toward them. The RP erg head has very little
resistance as it slides along its track toward the rower. In a *moving*
boat, the hull has a very significant amount of force acting across its
entire hull: hydrodynamic drag from the flow of water. So, the hull is
not going to travel "toward the rower" the same amount that the RP erg
head did, even though it is roughly the same mass as the RP erg head.
So, the rower has to do more work during the recovery while rowing on
water, than they do while on an RP ergometer (but definitely MUCH less
work than they must do on a static erg). Making the mass of the moving
head of the RP erg more or less wouldn’t fix this problem, either, since
the resistance to the hull’s motion is not affected (much) by its mass;
it is affected by it’s speed through the water, and the surface area of
the hull that is underwater. So, a C2 on slides is probably just as
good as an RP in this regard.
Next, the catch:
On an RP erg, again there is virtually no resistance for the RP erg head
to slide on its track. So, as the rower drives his/her legs down, the
rower’s center of gravity remains virtually stationary, while the RP erg
head moves away from the rower easily. In a *moving* boat, hopefully
the rower has adeptly placed the oar in the water, and is pulling on it
with good "connection" to the water (I'll not go into the hydrodynamics
of the blade here). Since the blade is "locked on" so to speak, then as
the rower drives his/her legs, the hull will have to accelerate through
the water, increasing its bow-ward velocity. The rower must travel with
the boat, so the rower has to accelerate his/her mass in the bow-ward
direction too, but even more so than the boat, which is not simulated AT
ALL by an RP erg (or C2/slides). In this case, a static erg would
actually be a better simulation of what happens during the drive of an
on-water stroke.
So, what it comes down to, is that the recovery on a dynamic erg is a
*better* simulation of on-water rowing than a static erg, but by no
means is it perfect, and the fact that an RP’s moving mass is similar to
that of a single scull doesn’t really matter. On the other hand, a
dynamic erg is actually a WORSE simulation of the drive of real on-water
rowing, than is a static erg, since in real rowing, the rower must
accelerate their own body away from an also accelerating boat, whereas
on a dynamic erg, the rower need not accelerate their body much at all.
So, which is better? I prefer training on the dynamic erg, mostly for
the reasons that Dick Dreissigacker outlined: the recovery is much
easier on a dynamic erg, thus a higher stroke rate can be maintained.
With a higher stroke rate, you can keep the wheel spinning faster, thus
the load at the catch is lighter, and feels more like real rowing, even
though the rower's body is not accelerated during the drive like it is
on the water. Dreissigacker suggested using a lower damper setting on a
static erg to get the lighter feel at the catch that a higher rate would
otherwise allow. This only solves half the problem: the static erg
still has the significant work requirement of hauling one's body from
release to catch during the recovery. But I'm fairly certain that the
lower incidences of back problems with dynamic ergs is largely due to
the lower loading thanks to the higher stroke rates. Also the fact that
you don't have to accelerate your torso during the drive as much on a
dynamic erg helps reduce the loads on the back.
Furthermore, the higher rates achievable on a dynamic erg better
simulate the muscle requirements (speed of contraction) of real rowing.
And, since the rower does not have to really slow his/her body down as
they approach the catch on a dynamic erg, the position a rower takes at
the catch on a dynamic erg is probably more like that which he/she takes
in a boat, than that done on a static erg.
-Kieran
paul_v...@hotmail.com
wrote:
It's even easier if someone keeps the flywheel from moving (or boat
advancing, as the case may be). [:o)
Vertical displacement of your COG whether in a boat or on an Erg does
nothing at all to put useful energy into the system, as it will be
reflected in the objective indicators of power production, namely PM
or Speed Coach Paces.
The main point of that sentence was to point out that all advantage
assumed on the sliding Ergo is to do with the increase in rate, thus
the reason it is short lived, I doubt beyond a 2 minute trial, though
they suggest as much as 2k, which I think is extremely optimistic.
- Paul Smith
KC
What about "specificity of training?" The muscle contractions at the
catch on a dynamic erg are much more similar (in a speed & time of
contraction sense) to on-water rowing than on a static erg. The point
they made about the legs firing sooner on a static erg are important:
the contractions are then spread out over a longer period of time.
Also, rates similar to that of on-water racing pace are sustainable on a
dynamic erg for virtually as long as they are on the water. On-water
race pace rates are not sustainable on a static erg for very long at
all. This is important first because again: specificity of training...
but also because the higher the rate, the shorter the recovery time.
That means that you can sustain the same overall work output rate with a
lower force level during the drive, and that means muscles fatigue more
slowly.
On another note, does anyone have a reference for the specific Hagerman
paper everyone keeps referencing here? I've read a lot of his work, but
I'd like to re-read this one. I still suspect that he may not have
accounted for the decreased cooling on a dynamic erg due to the decrease
in air movement over the skin.
-Kieran
Lauren G
only important in your ability to get it into the water, once it's in
the water your ability to move the boat (as far as the boat's part in
it is concerned) has more to do with how it's constructed - that's why
they're long and skinny, right? So, why are we comparing the weight
of an Erg to the weight of a shell?
Not that it matters much to me, I don't have access to dynamic ergs
and I'm not in the market to buy any erg and I generally avoid ergs if
at all possible anyway, it just seems like quite a leap in logic.
-Lauren
paul_v...@hotmail.com
>
> - Show quoted text -
It seems to be a big mystery. I'm quite sure I read the paper and I
think you are correct that there was no control for cooling effect,
however the distances were not that great and the efforts involved not
that severe. I asked C2, who I believe commissioned the particular
study as part of deciding if times on Slides could be included in the
Online World Rankings for all distances (which they were not in the
early days of the slides because of the preconception that there would
have been an advantage), for the link to the document, but the
response was that it was not available at the time. There is a
Swedish (I think) study replicating the the results of Hagerman.
I still do not understand how at the same stroke rate and pace that
the drive can be quicker on a sliding Erg, every time I reduce drive
time and maintain stroke length the pace increases as does the rate,
along with getting more difficult. Perhaps others row boats quickly
without additional effort, I've never found that to be the case.
- Paul Smith
KC
snip
Well if you come across it ever, let me know, please. Thanks.
> I still do not understand how at the same stroke rate and pace that
> the drive can be quicker on a sliding Erg, every time I reduce drive
I don't think I said it would be quicker. In fact with the same pace,
same SR, I would imagine that in going to a dynamic erg from a static
erg, the drive time would increase (since the recovery time would likely
decrease).
For example....
Constraints = pace (time/500m) and stroke rate (s/m).
That leaves recovery time and drive time as variables. If you reduce
the recovery time, then you can lengthen the drive time, while
maintaining the same rate. If you do this while maintaining the same
pace, you're doing the same overall work/time, but the work is a smaller
"F" times a longer "d". That smaller F means your muscles don't fatigue
as quickly. (lots of reasons for that, but right off the top of my
head: lower force of contraction means better blood flow, which means
better delivery of O2/glucose/etc., and better removal of waste, less
cardiovascular afterload, better preload/venous return.)
What *is* "quicker" is the initial contraction of the knee and hip
extensors at the catch. Since the legs don't have to slow the body down
(much) the initial extension contraction of the lower limbs can come on
much more quickly. Also, there is some slack to be taken up on both the
c2 and the RP... an initial aerodynamic loading up to a significant
level, as well as actual slack in the chain & cog. Since the mass to be
moved to take up that slack is much less with a dynamic erg (just the
erg) and much more with the static erg (most of the mass of the rower)
that means that again, the initial application of force by the hips/legs
happens much more quickly. (I'm talking about just the first few cm of
handle travel).
To me, this is possibly the most significant difference in "feel" from
dynamic to static "mode".
-Kieran
Charles Carroll
> nothing at all to put useful energy into the system
Paul,
I am not sure I understand. But I want to agree. It is really how to see how
moving ninety degrees up from the horizontal direction in which you want to
move is going to help you go faster. Except I have one problem: when I lift
my weight off the seat and put it on to the erg handle I usually observe six
to ten seconds off my splits for a given heart rate.
Another other thing to think about: to lift off the seat I have to draw in
my belly and brace myself. I simply can't do it if I lose "the connection,"
that is, if the seat moves faster than the handle, or the handle moves
faster than the seat. Before I started using the Rowers Shadow I was never
able to lift my weight off the seat (unless, of course, I had the help of a
friend who would keep the flywheel from moving. [:o) So in this sense
lifting off the seat means that I am braced. Another way of saying this is
it means the spine has been stabilized. Doesn't this significantly reduce
the risk of back injury?
But, as usual, I've probably said too much ...
Cordially,
Charles
paul_v...@hotmail.com
Sorry, poor choice of words in my haste. Quicker as in higher
velocity, which would sill result in a shorter time, but does tighten
the terms a bit.
Unless you have altered the DF for your switch to higher rate rowing
on the Slides, there is no alternative but for the flywheel to be
working within a narrower range of RPM's for the same overall Avg RPM
(once DF has been calculated the electronic PM is no different than
the Analog Speedometer of the Model A > Same avg RPM, same speed.) so
the Drive will necessarily be over more quickly unless it is altered
in some other way, minding that it can not be by reducing force too
much or the Pace will slow. i.e. "Trading rate for pace" is a fall
toward diminishing returns. Frankly, compressing the ratio, and
maintaining the same pace is very difficult to do, it's more likely
that the pace will speed up, even with a less forceful drive, but now
the muscle recovery period is reduced and once again we run into the
problem of sustainable energy production that is required for Time
Trial efforts over about 2 minutes.
> For example....
>
> Constraints = pace (time/500m) and stroke rate (s/m).
>
> That leaves recovery time and drive time as variables. If you reduce
> the recovery time, then you can lengthen the drive time, while
> maintaining the same rate. If you do this while maintaining the same
> pace, you're doing the same overall work/time, but the work is a smaller
> "F" times a longer "d". That smaller F means your muscles don't fatigue
> as quickly. (lots of reasons for that, but right off the top of my
> head: lower force of contraction means better blood flow, which means
> better delivery of O2/glucose/etc., and better removal of waste, less
> cardiovascular afterload, better preload/venous return.)
Lower force of contraction, but at a higher speed to catch and
accelerate the flywheel, I'm not sure that is going to be so tidy.
> What *is* "quicker" is the initial contraction of the knee and hip
> extensors at the catch. Since the legs don't have to slow the body down
> (much) the initial extension contraction of the lower limbs can come on
> much more quickly. Also, there is some slack to be taken up on both the
> c2 and the RP... an initial aerodynamic loading up to a significant
> level, as well as actual slack in the chain & cog. Since the mass to be
> moved to take up that slack is much less with a dynamic erg (just the
> erg) and much more with the static erg (most of the mass of the rower)
> that means that again, the initial application of force by the hips/legs
> happens much more quickly. (I'm talking about just the first few cm of
> handle travel).
"Initial aerodynamic loading"? No, that's already been done. That
would be like saying 'initial drag loading' at the catch in a boat,
but it's already there too.
If there is slack in the chain, adjust the bungee, and the clutch is
engaged in a small enough distance as to be difficult to measure.
There is a short period of time where we have not yet caught the
flywheel, and if driving with the feet so that the seat and handle are
moving exactly together the Erg will be driven backwards a slight but
discreet distance during that instant (on something like a hardwood
or concrete floor) Using an example of a beginning handle speed of
200cm/sec, a mere 0.01sec would result in 2cm being used for this
initial catching of the flywheel. Strangely enough the more slowly
the catch is approached the more quickly the drive can be meaningfully
initiated. Meaning work being done to accelerate the flywheel and not
stop our bodies movement toward the feet. I think you will hate
hearing this again, but the difference you feel is exactly what causes
the difference in force profiles, and is the result of flawed
technique (WRT what would benefit you in a boat). Work to minimize
the difference in "feel" and profile in the two situations and you
will be learning how to move your body much better.
> To me, this is possibly the most significant difference in "feel" from
> dynamic to static "mode".
>
> -Kieran
I liked most of your comments for the "fightinthedog" blog, as they
are incomplete agreement with things I have argued in the past (I
thought with you, so maybe there was some progress made in spite of
appearances otherwise.), however there were a couple things that I'm
going to have to address to see where the misunderstanding is. [;o)
Cheers,
Paul Smith
PS - Whatever it was you had sent me recently, perhaps you could send
it again, I imagine that it was going to allow me to learn something
new, or at least more completely.
KC
Okay, so, I'm not sure if you are disagreeing with me or agreeing with
me here. First you say that the drive will necessarily be over more
quickly... then you say that the pace will speed up even with a less
forceful drive (which I take to imply that it would be *possible* to
maintain pace with a less forceful (& longer) drive, just difficult).
>> For example....
>>
>> Constraints = pace (time/500m) and stroke rate (s/m).
>>
>> That leaves recovery time and drive time as variables. If you reduce
>> the recovery time, then you can lengthen the drive time, while
>> maintaining the same rate. If you do this while maintaining the same
>> pace, you're doing the same overall work/time, but the work is a smaller
>> "F" times a longer "d". That smaller F means your muscles don't fatigue
>> as quickly. (lots of reasons for that, but right off the top of my
>> head: lower force of contraction means better blood flow, which means
>> better delivery of O2/glucose/etc., and better removal of waste, less
>> cardiovascular afterload, better preload/venous return.)
>
> Lower force of contraction, but at a higher speed to catch and
> accelerate the flywheel, I'm not sure that is going to be so tidy.
The rate at which a contraction occurs is not necessarily connected to
the maximum force applied. The benefits of a lower max force of
contraction remain, regardless of how quickly that force level was attained.
>
>> What *is* "quicker" is the initial contraction of the knee and hip
>> extensors at the catch. Since the legs don't have to slow the body down
>> (much) the initial extension contraction of the lower limbs can come on
>> much more quickly. Also, there is some slack to be taken up on both the
>> c2 and the RP... an initial aerodynamic loading up to a significant
>> level, as well as actual slack in the chain & cog. Since the mass to be
>> moved to take up that slack is much less with a dynamic erg (just the
>> erg) and much more with the static erg (most of the mass of the rower)
>> that means that again, the initial application of force by the hips/legs
>> happens much more quickly. (I'm talking about just the first few cm of
>> handle travel).
>
> "Initial aerodynamic loading"? No, that's already been done. That
> would be like saying 'initial drag loading' at the catch in a boat,
> but it's already there too.
>
> If there is slack in the chain, adjust the bungee, and the clutch is
> engaged in a small enough distance as to be difficult to measure.
FYI, It's not a clutch, or I doubt it's a clutch anyway. I'm sure it's
a ratchet, same as in a bicycle freewheel, and in ratcheting hand tools.
Whether it's due to some very small amount of mechanical slack in the
system, or just due to the extra mass that must have it's momentum
reversed, or some combination of both (most likely), I find, and
everyone I've asked and observed on slides agrees, that on a static erg
the inclination is to use the arms and torso more to initiate the drive,
whereas on a dynamic erg, it is much easier to hammer the legs quickly.
> There is a short period of time where we have not yet caught the
> flywheel, and if driving with the feet so that the seat and handle are
So you agree that there is some amount of "slack" to be taken up at the
catch? What causes it then, in your opinion?
> moving exactly together the Erg will be driven backwards a slight but
> discreet distance during that instant (on something like a hardwood
I have fixed stops around the feet of the erg to prevent this.
> or concrete floor) Using an example of a beginning handle speed of
> 200cm/sec, a mere 0.01sec would result in 2cm being used for this
> initial catching of the flywheel. Strangely enough the more slowly
> the catch is approached the more quickly the drive can be meaningfully
This is likely (at least in part) due to the fact that the rower's body
has less momentum as it approaches the catch, so the turn-around is
easier & quicker.
> initiated. Meaning work being done to accelerate the flywheel and not
> stop our bodies movement toward the feet. I think you will hate
(obviously I'm typing as I read your post...)
> hearing this again, but the difference you feel is exactly what causes
> the difference in force profiles, and is the result of flawed
> technique (WRT what would benefit you in a boat). Work to minimize
I don't hate to hear it, I just don't entirely agree with it.
Regardless of how "slowly" and/or carefully one approaches the catch,
the change in momentum is still significantly different on a sliding erg
versus a static erg. No matter how skillful one is just before, during
and just after the catch, it is still going to feel quite different when
only 1/5th the mass needs to change direction.
> the difference in "feel" and profile in the two situations and you
> will be learning how to move your body much better.
Well, IMO, this defeats much of the point of using a dynamic erg - that
being specificity of training. One can not sustain high rates on a
static erg as long as on the water, but it is possible on a dynamic erg.
If you slow down / control the recovery so that it "feels" more like
the static erg, then you may as well just row on a static erg, because
you won't be at the high rates.
>> To me, this is possibly the most significant difference in "feel" from
>> dynamic to static "mode".
>>
>> -Kieran
>
> I liked most of your comments for the "fightinthedog" blog, as they
> are incomplete agreement with things I have argued in the past (I
> thought with you, so maybe there was some progress made in spite of
> appearances otherwise.), however there were a couple things that I'm
> going to have to address to see where the misunderstanding is. [;o)
I'll be interested to read your remarks. I don't think anything I said
in that post contradicts anything I've said or argued in the past. If
you see otherwise, let me know.
There are a few points about the catch & drive phase that I didn't go
into there, that I feel slightly help the argument toward the dynamic erg.
> Cheers,
> Paul Smith
>
> PS - Whatever it was you had sent me recently, perhaps you could send
> it again, I imagine that it was going to allow me to learn something
> new, or at least more completely.
No, it was nothing new... just a chapter from a book that I happened to
have in pdf form (ran across it while doing some HDD cleaning), and
thought some people would like. I cc'd you on the list using the addy
you use here on RSR. I haven't even read the whole chapter myself, but
it looks like it may have some interesting stuff in it. Unfortunately
much of the fine detail from the graphs are blurred in the scanning of
the document. I'll see if I can find it again. It may be in my "sent"
box in my email.
-Kieran
Charles Carroll
how
That should read: It is really difficult to see how ...
Sorry.
Neil Wallace
(snip)
> I'm amazed that Dr. Dudhia, Dr. Kleshnev, Ivan Hooper, Dick Dreissigacker,
> Mark Campbell, and even Xeno all forgot to account for the effects that
> hydrodynamic drag has on the hull of a boat when it is moving. The
> suggested example (from Anu Dudhia's rowing FAQ and Ivan Hooper's paper)
> of sitting on a static erg at the catch and watching how much your body
> moves when you extend your legs, versus sitting in a boat and doing the
> same (blades out of the water) totally neglects the fact that when the
> water is MOVING under the hull, there is a significant amount of
> resistance to the hull's bow-ward motion.
>
> One of the main claims to fame by Row Perfect is that the moving head of
> their erg is roughly the same mass as a single scull. Simply matching the
> mass of a boat does not come near a full simulation of the complex dynamic
> system that is on-water-rowing.
I couldn't agree more.
On the water we do a considerable amount of work _during the recovery_.
And the heavier one is, the faster one's shell is moving across the water
and the higher one is rating the more relevant this is.
n'est pas?
I think shell speed is the most important.
I've often wondered about the feasibility of a resistance mechanism between
seat and flywheel components, which alters as flywheel speed increases.
that way erging would include training the muscles involved in drawing the
"boat" underneath oneself.
but this thread isn't about how well these ergs emulate a boat situation is
it?
Aren't we supposed to be discussing back injuries?
KC
> "KC" wrote in message
> (snip)
>> I'm amazed that Dr. Dudhia, Dr. Kleshnev, Ivan Hooper, Dick Dreissigacker,
>> Mark Campbell, and even Xeno all forgot to account for the effects that
>> hydrodynamic drag has on the hull of a boat when it is moving. The
>> suggested example (from Anu Dudhia's rowing FAQ and Ivan Hooper's paper)
>> of sitting on a static erg at the catch and watching how much your body
>> moves when you extend your legs, versus sitting in a boat and doing the
>> same (blades out of the water) totally neglects the fact that when the
>> water is MOVING under the hull, there is a significant amount of
>> resistance to the hull's bow-ward motion.
>>
>> One of the main claims to fame by Row Perfect is that the moving head of
>> their erg is roughly the same mass as a single scull. Simply matching the
>> mass of a boat does not come near a full simulation of the complex dynamic
>> system that is on-water-rowing.
>
>
> I couldn't agree more.
> On the water we do a considerable amount of work _during the recovery_.
I don't agree with that statement. Granted some work is done, but it is
much less than what is done during the recovery on a static erg.
> And the heavier one is, the faster one's shell is moving across the water
Oh, I don't know about that! I'd say it's more dependent on one's
rowing skills and fitness than their weight. Put William Perry in a 1x
against Greg Ruckman, and I think Greg will go faster, despite that he
would weigh less than 1/2 of his "competition". ;^)
-Kieran
paul_v...@hotmail.com
If you left out the "& longer" (I thought drive length was not being
changed), the last bet would be fine. The Drive time (w/unchanged
length) will have to be shorter as the rate increases as will the
recovery. The input energy must remain the same, in equilibrium with
whatever the flywheel is absorbing for a given displayed pace. Let's
take an example of 300watts ~1:45 R30 and R20. The drive time will be
considerably longer at R20 (slower starting flywheel speed) but the
ratio will be far higher than at the R30 for a given DF. This is
probably a reasonable range that you can answer based on experience,
which could be sustained longer? Would it matter if you were on
Slides or the Ground?
While on the ground we get to use our bodies momentum against the
flywheel, but we don't get to do the same when on slides. That is to
say, a finish on the ground involves stopping our bodies rearward
travel, but on the slides we are having to hold the Erg away from our
body while drawing the handle in. So while you have liked to point
out that the body mass must be moved more on the grounded Erg, we also
get more for moving it. Self cancelling in the overall scheme of
things. The matter of being able to recover the body well is much
more difficult. The Slides offer visual feedback on how well it's
being accomplished but little in the way of anything else. i.e. Sit
directly down on an Erg on Slides and the whole machine moves through
the recovery quite quickly, now with the addition of the bungee return
mechanism the need to do much of anything is pretty well eliminated if
you are willing to turn control over to the Erg and slides. On the
grounded Erg once we use muscular effort to recover the body we will
fly up to the catch with no additional effort, but that is the
difficult part for many people to grasp and they continue to "draw"
themselves 'downhill with bungee assistance' culminating in crashing
the frontstops one way or another and suffering the consequences.
So my use of "difficult" should perhaps have been emphasized a bit...
very very difficult! (I'd like to say impossible, but clearly that
would be wrong in the absolute sense.)
> >> For example....
>
> >> Constraints = pace (time/500m) and stroke rate (s/m).
>
> >> That leaves recovery time and drive time as variables. If you reduce
> >> the recovery time, then you can lengthen the drive time, while
> >> maintaining the same rate. If you do this while maintaining the same
> >> pace, you're doing the same overall work/time, but the work is a smaller
> >> "F" times a longer "d". That smaller F means your muscles don't fatigue
> >> as quickly. (lots of reasons for that, but right off the top of my
> >> head: lower force of contraction means better blood flow, which means
> >> better delivery of O2/glucose/etc., and better removal of waste, less
> >> cardiovascular afterload, better preload/venous return.)
>
> > Lower force of contraction, but at a higher speed to catch and
> > accelerate the flywheel, I'm not sure that is going to be so tidy.
>
> The rate at which a contraction occurs is not necessarily connected to
> the maximum force applied. The benefits of a lower max force of
> contraction remain, regardless of how quickly that force level was attained.
Well, I think what has to be recognized is that the speed of
contraction will be dependent on the Flywheel RPM (boat speed), for a
given pace, the amount of force that can be applied at the contraction
speed is what will make the difference in the end. i.e. you have 2
6:00 2kers of equal skill, technique and style, and need to pick one
of them to go into a boat with 7 other sub 6 2kers all with equal
skills. The only thing that is different between the 2 being selected
from is that one rated 34 and the other rated 40 for their 2k (BTW at
the recent danish IRC the top 3 lwts all averaged over R40 for the 2k
on grounded Ergos), so who do you choose? The 7 in the boat all rated
between 30 and 36 for their 2k trials.
> >> What *is* "quicker" is the initial contraction of the knee and hip
> >> extensors at the catch. Since the legs don't have to slow the body down
> >> (much) the initial extension contraction of the lower limbs can come on
> >> much more quickly. Also, there is some slack to be taken up on both the
> >> c2 and the RP... an initial aerodynamic loading up to a significant
> >> level, as well as actual slack in the chain & cog. Since the mass to be
> >> moved to take up that slack is much less with a dynamic erg (just the
> >> erg) and much more with the static erg (most of the mass of the rower)
> >> that means that again, the initial application of force by the hips/legs
> >> happens much more quickly. (I'm talking about just the first few cm of
> >> handle travel).
>
> > "Initial aerodynamic loading"? No, that's already been done. That
> > would be like saying 'initial drag loading' at the catch in a boat,
> > but it's already there too.
>
> > If there is slack in the chain, adjust the bungee, and the clutch is
> > engaged in a small enough distance as to be difficult to measure.
>
> FYI, It's not a clutch, or I doubt it's a clutch anyway. I'm sure it's
> a ratchet, same as in a bicycle freewheel, and in ratcheting hand tools.
I think it is called a "roller clutch", though I don't know what that
is.
> Whether it's due to some very small amount of mechanical slack in the
> system, or just due to the extra mass that must have it's momentum
> reversed, or some combination of both (most likely), I find, and
> everyone I've asked and observed on slides agrees, that on a static erg
> the inclination is to use the arms and torso more to initiate the drive,
> whereas on a dynamic erg, it is much easier to hammer the legs quickly.
And making it easier to "hammer the legs quickly" is desireable?
I think that making that more difficult (grounded Ergo) was one of
your better points in the FITD response. Since in the boat we are
truly trying to advance our body across the Earth, not just across the
hull.
> > There is a short period of time where we have not yet caught the
> > flywheel, and if driving with the feet so that the seat and handle are
>
> So you agree that there is some amount of "slack" to be taken up at the
> catch? What causes it then, in your opinion?
>
> > moving exactly together the Erg will be driven backwards a slight but
> > discreet distance during that instant (on something like a hardwood
>
> I have fixed stops around the feet of the erg to prevent this.
Hopefully you only need them off one end. i.e. to prevent running the
flywheel into the wall. (if going the other direction that's a whole
nuther discussion about "tugging" at the footstretcher.) [;o)
> > or concrete floor) Using an example of a beginning handle speed of
> > 200cm/sec, a mere 0.01sec would result in 2cm being used for this
> > initial catching of the flywheel. Strangely enough the more slowly
> > the catch is approached the more quickly the drive can be meaningfully
>
> This is likely (at least in part) due to the fact that the rower's body
> has less momentum as it approaches the catch, so the turn-around is
> easier & quicker.
>
> > initiated. Meaning work being done to accelerate the flywheel and not
> > stop our bodies movement toward the feet. I think you will hate
>
> (obviously I'm typing as I read your post...)
>
> > hearing this again, but the difference you feel is exactly what causes
> > the difference in force profiles, and is the result of flawed
> > technique (WRT what would benefit you in a boat). Work to minimize
>
> I don't hate to hear it, I just don't entirely agree with it.
> Regardless of how "slowly" and/or carefully one approaches the catch,
> the change in momentum is still significantly different on a sliding erg
> versus a static erg. No matter how skillful one is just before, during
> and just after the catch, it is still going to feel quite different when
> only 1/5th the mass needs to change direction.
All mass at the catch should, for an instant, be at rest (WRT the
Earth - Ergos only); the overwhelming resistance to moving at that
point is coming from the flywheel. Execute a drive without the handle
sometime just to see how little it takes to move the body along the
rail if you like. Make sure to put some pillows off the back side to
land on. Now that was far too quick for a normal drive, so try it
again with the same leg speed that happens under flywheel resistance,
it takes little more than letting the knees fall under the influence
of gravity.
The point being that body momentum problems are caused by the athlete
and occur during the recovery on a grounded Erg. Those same problems
are masked when on slides, which, IMO, is not a good thing.
> > the difference in "feel" and profile in the two situations and you
> > will be learning how to move your body much better.
>
> Well, IMO, this defeats much of the point of using a dynamic erg - that
> being specificity of training. One can not sustain high rates on a
> static erg as long as on the water, but it is possible on a dynamic erg.
> If you slow down / control the recovery so that it "feels" more like
> the static erg, then you may as well just row on a static erg, because
> you won't be at the high rates.
Yes, you may as well... If you do not learn the right things on the
Erg it's unlikely that you will execute them correctly in a boat.
> >> To me, this is possibly the most significant difference in "feel" from
> >> dynamic to static "mode".
>
> >> -Kieran
>
> > I liked most of your comments for the "fightinthedog" blog, as they
> > are incomplete agreement with things I have argued in the past (I
> > thought with you, so maybe there was some progress made in spite of
> > appearances otherwise.), however there were a couple things that I'm
> > going to have to address to see where the misunderstanding is. [;o)
>
> I'll be interested to read your remarks. I don't think anything I said
> in that post contradicts anything I've said or argued in the past. If
> you see otherwise, let me know.
Ok. But I'll try to stay away from whether or not you are
contradicting yourself, as that has never gone over well. (not
bringing it up but the evidence is "the thread that shall not be
named".)
- Paul Smith
paul_v...@hotmail.com
wrote:
> > Vertical displacement of your COG whether in a boat or on an Erg does
> > nothing at all to put useful energy into the system
>
> Paul,
>
> I am not sure I understand. But I want to agree. It is really how to see how
> moving ninety degrees up from the horizontal direction in which you want to
> move is going to help you go faster. Except I have one problem: when I lift
> my weight off the seat and put it on to the erg handle I usually observe six
> to ten seconds off my splits for a given heart rate.
Then do it all the time, especially if you are getting 6-10 seconds
off your split for what appears to be no additional effort.
> Another other thing to think about: to lift off the seat I have to draw in
> my belly and brace myself. I simply can't do it if I lose "the connection,"
> that is, if the seat moves faster than the handle, or the handle moves
> faster than the seat. Before I started using the Rowers Shadow I was never
> able to lift my weight off the seat (unless, of course, I had the help of a
> friend who would keep the flywheel from moving. [:o) So in this sense
> lifting off the seat means that I am braced. Another way of saying this is
> it means the spine has been stabilized. Doesn't this significantly reduce
> the risk of back injury?
IMO, yes.
I was also an early adopter of the Rowers Shadow, and though I've used
it with students to help eliminate bum shove (one was taking skin off
their knuckles because the bar was hitting them so hard, and
repeatedly. Unfortunately unless the athlete wants to maintain focus
and not get lazy the effects are as short lived as longer drives from
the latest Driver added to the golf bag. Perhaps we need a Rowers
Shadow for the boat. [;o)
- Paul Smith
paul_v...@hotmail.com
> Neil Wallace wrote:
> > "KC" wrote in message
> > (snip)
> >> I'm amazed that Dr. Dudhia, Dr. Kleshnev, Ivan Hooper, Dick Dreissigacker,
> >> Mark Campbell, and even Xeno all forgot to account for the effects that
> >> hydrodynamic drag has on the hull of a boat when it is moving. The
> >> suggested example (from Anu Dudhia's rowing FAQ and Ivan Hooper's paper)
> >> of sitting on a static erg at the catch and watching how much your body
> >> moves when you extend your legs, versus sitting in a boat and doing the
> >> same (blades out of the water) totally neglects the fact that when the
> >> water is MOVING under the hull, there is a significant amount of
> >> resistance to the hull's bow-ward motion.
>
> >> One of the main claims to fame by Row Perfect is that the moving head of
> >> their erg is roughly the same mass as a single scull. Simply matching the
> >> mass of a boat does not come near a full simulation of the complex dynamic
> >> system that is on-water-rowing.
>
> > I couldn't agree more.
> > On the water we do a considerable amount of work _during the recovery_.
>
> I don't agree with that statement. Granted some work is done, but it is
> much less than what is done during the recovery on a static erg.
This is excellent we have Neil and KC in small disagreement but it
seems to lead in the direction that the "static Erg" is the way to
go! Shocking, I say, shocking! [:o)
> > And the heavier one is, the faster one's shell is moving across the water
>
> Oh, I don't know about that! I'd say it's more dependent on one's
> rowing skills and fitness than their weight. Put William Perry in a 1x
> against Greg Ruckman, and I think Greg will go faster, despite that he
> would weigh less than 1/2 of his "competition". ;^)
>
> -Kieran- Hide quoted text -
>
> - Show quoted text -
In fairness to Neil, I think he meant as a cummulative effect, heavier
+ faster = more effect.
It's obvious that just being heavier is of not great benefit in a boat
(though there could be a small benefit of the system being heavier.)
since the heavier rower will sink the boat more, likely increasing the
wetted surface and hull drag. The boats really are quite self
adjusting for weight, so much so that it makes one wonder why the lwt
classes exist. But since the introduction of the DBA (Dwarf Basketball
Association) the spirit of inclusion has run rampant. [;o)
Oh yes, back injury bad! Limit longer workouts to 25 consecutive
minutes at a go followed by a minute or two break, stringing together
as many as you like.
- Paul Smith
KC
I don't see anything I've said as leading in the direction that the
static erg is the way to go. I much prefer the dynamic erg.
-Kieran
KC
> On Jan 31, 9:08 am, KC <kc_n...@sonic.net> wrote:
>> paul_v_sm...@hotmail.com wrote:
>>> On Jan 30, 6:24 pm, KC <kc_n...@sonic.net> wrote:
snip
I thought you said to keep the SR constant! Regardless, I think I may
have mis-typed at some point. Drive length I don't think would
necessarily change. But if you keep the *same stroke rate*, and shorten
the recovery time, then the drive TIME must be longer. If the drive
time increases, and the drive distance is constant, then the force
applied must decrease. This is not to say that you couldn't lengthen
the drive distance, too (every rower can row a bit shorter or longer,
usually than their nominal stroke length), but as you've said, we'll
keep the stroke dist. constant for this discussion.
> recovery. The input energy must remain the same, in equilibrium with
> whatever the flywheel is absorbing for a given displayed pace. Let's
> take an example of 300watts ~1:45 R30 and R20. The drive time will be
> considerably longer at R20 (slower starting flywheel speed) but the
> ratio will be far higher than at the R30 for a given DF. This is
> probably a reasonable range that you can answer based on experience,
> which could be sustained longer? Would it matter if you were on
> Slides or the Ground?
Hmmm... well, this is just a guess, but I'll give it a shot.
Duration I could sustain:
SR20/1:45 > SR30/1:45 grounded
SR30/1:45 > SR20/1:45 sliding
SR30/1:45 sliding > SR30/1:45 grounded
SR20/1:45 sliding = SR20/1:45 grounded
Again, just a guess. I haven't even been on an erg of any kind (for a
real workout anyway) in MONTHS.
>
> While on the ground we get to use our bodies momentum against the
> flywheel, but we don't get to do the same when on slides. That is to
> say, a finish on the ground involves stopping our bodies rearward
> travel, but on the slides we are having to hold the Erg away from our
> body while drawing the handle in. So while you have liked to point
> out that the body mass must be moved more on the grounded Erg, we also
> get more for moving it. Self cancelling in the overall scheme of
> things. The matter of being able to recover the body well is much
> more difficult. The Slides offer visual feedback on how well it's
> being accomplished but little in the way of anything else. i.e. Sit
> directly down on an Erg on Slides and the whole machine moves through
> the recovery quite quickly, now with the addition of the bungee return
> mechanism the need to do much of anything is pretty well eliminated if
> you are willing to turn control over to the Erg and slides. On the
> grounded Erg once we use muscular effort to recover the body we will
> fly up to the catch with no additional effort, but that is the
> difficult part for many people to grasp and they continue to "draw"
> themselves 'downhill with bungee assistance' culminating in crashing
> the frontstops one way or another and suffering the consequences.
The amount of "effort" required to move toward the catch changes
gradually as you move through the recovery. At first, as you said,
there is a significant amount of effort required to stop and change
direction of the body. But also, even after you get moving, the bungee
and track slope is not enough to keep you moving; not at least, for the
first 1/3 to 1/2 of the recovery anyway. The mass of the legs have the
advantage here, and if relaxed, they will push you and bungee/handle
back to the finish position. Once the legs are compressed somewhat (say
somewhere around 1/2 slide) then the effective moment arms of the c.g's
of the thigh and shank are small enough that they can not produce enough
torque due to gravity to overcome the bungee and slide-slope effects.
>
> So my use of "difficult" should perhaps have been emphasized a bit...
> very very difficult! (I'd like to say impossible, but clearly that
> would be wrong in the absolute sense.)
Hmmm... I just don't agree. I think it is very possible to modify ratio
while maintaining pace (split) and rate. I think it's harder to do on a
grounded erg than on a sliding one though.
>>>> For example....
>>>> Constraints = pace (time/500m) and stroke rate (s/m).
>>>> That leaves recovery time and drive time as variables. If you reduce
>>>> the recovery time, then you can lengthen the drive time, while
>>>> maintaining the same rate. If you do this while maintaining the same
>>>> pace, you're doing the same overall work/time, but the work is a smaller
>>>> "F" times a longer "d". That smaller F means your muscles don't fatigue
>>>> as quickly. (lots of reasons for that, but right off the top of my
>>>> head: lower force of contraction means better blood flow, which means
>>>> better delivery of O2/glucose/etc., and better removal of waste, less
>>>> cardiovascular afterload, better preload/venous return.)
>>> Lower force of contraction, but at a higher speed to catch and
>>> accelerate the flywheel, I'm not sure that is going to be so tidy.
>> The rate at which a contraction occurs is not necessarily connected to
>> the maximum force applied. The benefits of a lower max force of
>> contraction remain, regardless of how quickly that force level was attained.
>
> Well, I think what has to be recognized is that the speed of
> contraction will be dependent on the Flywheel RPM (boat speed), for a
Why do you think that? Maybe you're talking about the overall velocity
of muscle contraction. I was talking about the rate at which
contraction force is achieved. It's called "time to peak tension" or
TPT. So, for a given muscle, the velocity of contraction defines the
peak available force. But how *quickly* you get to that peak force,
from a relaxed state is the TPT. This is not dependent on the
flywheel's rpm.
> given pace, the amount of force that can be applied at the contraction
> speed is what will make the difference in the end. i.e. you have 2
> 6:00 2kers of equal skill, technique and style, and need to pick one
> of them to go into a boat with 7 other sub 6 2kers all with equal
> skills. The only thing that is different between the 2 being selected
> from is that one rated 34 and the other rated 40 for their 2k (BTW at
> the recent danish IRC the top 3 lwts all averaged over R40 for the 2k
> on grounded Ergos), so who do you choose? The 7 in the boat all rated
> between 30 and 36 for their 2k trials.
I don't see how this applies to the current discussion, but I guess if I
couldn't use any other means to choose, I'd choose the guy who rated 30,
since some of the other 7 rated 30, too (between 30 and 36) thus they
might be better matched in that regard. Besides, if the guy who rated
40 needed to rate 40 to get that score, then he's probably a lot smaller
than the r30 guy, as well as the rest of the 7 crew members, and a
longer stroke is almost always better.
Yes, because the initial rotational velocity of the thighs and shanks in
on-water rowing is faster than on a grounded erg, and the dynamic erg
allows this faster rotation of the limbs, again providing training
specificity.
> I think that making that more difficult (grounded Ergo) was one of
> your better points in the FITD response. Since in the boat we are
> truly trying to advance our body across the Earth, not just across the
> hull.
This is true on a gross scale, but in the first few microphases of the
on-water stroke (to use Kleshnev's terminology) the dynamics are more
similar to the sliding erg than the grounded one. This is the part I
left out of the blog post. Due to slippage at the catch, inperfect
catch timing (missed water) flexing of the oar shaft, and a few other
factors, the initial loading of the catch on water is quite similar to
the sliding erg case. Once the blade is fully submerged and with good
lift-producing flow, and the oar is flexed, then the situation becomes
more like the grounded erg (as I described in the blog post).
>>> There is a short period of time where we have not yet caught the
>>> flywheel, and if driving with the feet so that the seat and handle are
>> So you agree that there is some amount of "slack" to be taken up at the
>> catch? What causes it then, in your opinion?
>>
>>> moving exactly together the Erg will be driven backwards a slight but
>>> discreet distance during that instant (on something like a hardwood
>> I have fixed stops around the feet of the erg to prevent this.
>
> Hopefully you only need them off one end. i.e. to prevent running the
> flywheel into the wall. (if going the other direction that's a whole
> nuther discussion about "tugging" at the footstretcher.) [;o)
Actually, in the lab I use double sided tape on the floor, and this
seems to be enough (usually) to keep the erg still.
>
>>> or concrete floor) Using an example of a beginning handle speed of
>>> 200cm/sec, a mere 0.01sec would result in 2cm being used for this
>>> initial catching of the flywheel. Strangely enough the more slowly
>>> the catch is approached the more quickly the drive can be meaningfully
>> This is likely (at least in part) due to the fact that the rower's body
>> has less momentum as it approaches the catch, so the turn-around is
>> easier & quicker.
>>
>>> initiated. Meaning work being done to accelerate the flywheel and not
>>> stop our bodies movement toward the feet. I think you will hate
>> (obviously I'm typing as I read your post...)
>>
>>> hearing this again, but the difference you feel is exactly what causes
>>> the difference in force profiles, and is the result of flawed
>>> technique (WRT what would benefit you in a boat). Work to minimize
>> I don't hate to hear it, I just don't entirely agree with it.
>> Regardless of how "slowly" and/or carefully one approaches the catch,
>> the change in momentum is still significantly different on a sliding erg
>> versus a static erg. No matter how skillful one is just before, during
>> and just after the catch, it is still going to feel quite different when
>> only 1/5th the mass needs to change direction.
>
> All mass at the catch should, for an instant, be at rest (WRT the
> Earth - Ergos only); the overwhelming resistance to moving at that
> point is coming from the flywheel. Execute a drive without the handle
> sometime just to see how little it takes to move the body along the
> rail if you like. Make sure to put some pillows off the back side to
Funny anecdote: while designing my experimental setup, I had used a
carabiner to attach the load cell to the handle. I thought it was one
of my climbing certified carabiners, but apparently it was just a
novelty one that you get at the checkout line at the hardware store. I
got on and rowed a bit with it. About 10 strokes in, it broke and I
went flying off the handle -literally- and fell on my kiester behind the
erg. OUCH. I now use a different setup that I've tested to 2.5X my
body weight, but I still place exercise mats behind the test subjects
while they row, since it is technically a "modified" erg. :-)
> land on. Now that was far too quick for a normal drive, so try it
> again with the same leg speed that happens under flywheel resistance,
> it takes little more than letting the knees fall under the influence
> of gravity.
I don't have to try that, as I agree 100% with it. Instead, try this:
erg without the handle (this is sounding familiar!) at a typical stroke
rate. First, on a grounded erg, then same stroke rate/ratio/etc on a
sliding erg. It takes much more effort to stop your body and change
direction at the catch on the grounded erg than it does on the sliding
erg. Granted the effort seems minimal compared to the effort required
to spin the flywheel, but it is not insignificant.
> The point being that body momentum problems are caused by the athlete
> and occur during the recovery on a grounded Erg. Those same problems
> are masked when on slides, which, IMO, is not a good thing.
I don't agree. I don't think that the sliding erg masks certain
problems. If anything I think it reveals some problems if the person
erging is migrating back and forth and hitting the front or rear stops
of the slide(s). Also, I don't agree that the "control" learned on a
grounded erg is necessarily a good thing. Again, the speed of the
recovery and the catch is going to be more boat-like on a sliding erg,
so again it is more specific to the end goal for which we train. The
"control" learned on the grounded erg is like the example of a baseball
batter using a weighted bat for practice. If that's all he uses, he'll
never have a swing fast enough. The weighted bat has its purpose, but
he also needs to develop the speed with a light bat. Just as we learn
slide control by doing low rate ratio drills on the water by sixes in an
eight, the grounded erg can be useful. But I think that the sliding erg
better simulates some (not all) of the important dynamics of on-water
rowing.
>>> the difference in "feel" and profile in the two situations and you
>>> will be learning how to move your body much better.
>> Well, IMO, this defeats much of the point of using a dynamic erg - that
>> being specificity of training. One can not sustain high rates on a
>> static erg as long as on the water, but it is possible on a dynamic erg.
>> If you slow down / control the recovery so that it "feels" more like
>> the static erg, then you may as well just row on a static erg, because
>> you won't be at the high rates.
>
> Yes, you may as well... If you do not learn the right things on the
> Erg it's unlikely that you will execute them correctly in a boat.
Well, I think it's unlikely you'll learn the right things on a grounded
erg any better than on a sliding one. Both should be used at certain
times, but for volume training, the sliding erg is going to be better
IMO, both from a technical aspect, and from an injury aspect.
-Kieran
Charles Carroll
Paul,
I know you were. I read your posts on the C2 Training Forum. I acquired mine
because Gordon was astonishingly enthusiastic about it. But your posts
figured heavily in my decision.
I have a question. Gordon told me that once I got used to using the Rowers
Shadow it would really change my force curve. But he refused to tell me how.
The other day I was playing with an erg at the Club just for a minute or two
before going out. The Club's erg of course didn't have a Rowers Shadow
attached, but I was trying as hard as I knew how to pretend that it did, in
other words, to keep the connection. Afterwards I remembered to look at my
force curve. It was almost rectangular -- a flat line straight across except
for right at the beginning and at the end.
I assume this means an even application of power all the way through the
stroke. Is this good? Bad? Any comments?
Cordially,
Charles
paul_v...@hotmail.com
wrote:
Well, it actually means a fairly uniform Force is being maintained,
but as the handle speeds up it would lead to increasing Power input
(and consequential Energy output).
IMO, what is desireable is a Front loaded Force profile, allowing the
largest and strongest muscles to take the majority of the load, then
to sustain the pressure as best one can through the transition and
finish, which will necessarily lead to a tailing off of the force, but
more continual power input. As it happens, the blade/water interface
appreciates that sort of application also.
This is somewhat described here:
http://www.biorow.com/RBN_en_2006_files/2006RowBiomNews06.pdf
The shape of the Force profile that I prefer to see would be somwhere
between the Black lines plotted for the Adam and Grinko styles here:
http://www.biorow.com/RBN_en_2006_files/2006RowBiomNews05.pdf
Note: Those are not Force plots (what is seen on the PM3, PM4, RP),
but Power. Still, they are fine for the illustrative purpose.
As far as the body components in the various "styles", I would
advocate something quite close to "Grinko", but with a bit more trunk
emphasis to extend the Power a bit longer through the drive, Similar
to what happens in the "Adam" style, but with a quicker use of the
legs.
- Paul Smith
Charles Carroll
> largest and strongest muscles to take the majority of the load, then
> to sustain the pressure as best one can through the transition and
> finish, which will necessarily lead to a tailing off of the force, but
> more continual power input. As it happens, the blade/water interface
> appreciates that sort of application also.
Paul,
Many thanks. I obviously have something to read and think about. When we
were in school didn't we used to call this "study?"
> Note: Those are not Force plots (what is seen on the PM3, PM4, RP),
> but Power. Still, they are fine for the illustrative purpose.
In spite of many rsr posts pointing out the difference between Force and
Power, I still find myself unclear about it and its relevance to how to pull
on an inboard lever. The Japanese have a maxum: read a book a hundred times
and you will understand it. Sigh! More reading! More study!
One thing I do know is that whatever the explanation, I am getting slightly
faster on the water. The last time I went out I rowed in forty-five minutes
a distance that has always taken me sixty to sixty-five minutes to row.
Forty-five minutes for this distance is not a bad time. I rowed at a steady
rate, but kept my usual comfortable, leisurely pace. I concede that a lot of
this has to do with knowing a little more about how to move a boat better.
But I also think some of it has to do with the Rowers Shadow, which is
really teaching me a out "the connection."
Cordially,
Charles
paul_v...@hotmail.com
wrote:
> > IMO, what is desirable is a Front loaded Force profile, allowing the
> > largest and strongest muscles to take the majority of the load, then
> > to sustain the pressure as best one can through the transition and
> > finish, which will necessarily lead to a tailing off of the force, but
> > more continual power input. As it happens, the blade/water interface
> > appreciates that sort of application also.
>
> Paul,
>
> Many thanks. I obviously have something to read and think about. When we
> were in school didn't we used to call this "study?"
>
> > Note: Those are not Force plots (what is seen on the PM3, PM4, RP),
> > but Power. Still, they are fine for the illustrative purpose.
>
> In spite of many rsr posts pointing out the difference between Force and
> Power, I still find myself unclear about it and its relevance to how to pull
> on an inboard lever. The Japanese have a maxum: read a book a hundred times
> and you will understand it. Sigh! More reading! More study!
Well, maybe one of our intrepid engineering types will be along to
clear it up. If I try, there will no doubt be much wailing and
gnashing of teeth over my improper use of terms with precise
definitions.
I really don't know how Power (W) [presumably Watts, which is Joules/
sec] was arrived at in the RBN2006#5. With ErgMonitor we can express
something similar with a Unit called "TorqueJoule" (axel torque *
watts * time, time cancels to yield energy multiplied by torque),
which may or may not parallel the character of the concurrent Handle
force plot. It does seem to have the character of the RBN "power"
plots when the specific styles are implemented as described.
Hopefully Kleshnev will illustrate the two distinct plots in an
upcoming newsletter. I did get the impression he was going to do so
after an email exchange we had last year.
> One thing I do know is that whatever the explanation, I am getting slightly
> faster on the water. The last time I went out I rowed in forty-five minutes
> a distance that has always taken me sixty to sixty-five minutes to row.
> Forty-five minutes for this distance is not a bad time. I rowed at a steady
> rate, but kept my usual comfortable, leisurely pace. I concede that a lot of
> this has to do with knowing a little more about how to move a boat better.
> But I also think some of it has to do with the Rowers Shadow, which is
> really teaching me a out "the connection."
>
> Cordially,
>
> Charles
Reducing your time to cover a distance by 30% is quite significant,
and illustrates that knowing the difference between Force and Power is
certainly not required to improve boat moving, or more accurately
"advancing your body over the course while dragging your support tools
along with you". [:o)
Cheers,
Paul Smith
KC
> On Feb 3, 12:46 pm, "Charles Carroll" <charles_carr...@comcast.net>
> wrote:
>>> IMO, what is desirable is a Front loaded Force profile, allowing the
>>> largest and strongest muscles to take the majority of the load, then
>>> to sustain the pressure as best one can through the transition and
>>> finish, which will necessarily lead to a tailing off of the force, but
>>> more continual power input. As it happens, the blade/water interface
>>> appreciates that sort of application also.
>> Paul,
>>
>> Many thanks. I obviously have something to read and think about. When we
>> were in school didn't we used to call this "study?"
>>
>>> Note: Those are not Force plots (what is seen on the PM3, PM4, RP),
>>> but Power. Still, they are fine for the illustrative purpose.
>> In spite of many rsr posts pointing out the difference between Force and
>> Power, I still find myself unclear about it and its relevance to how to pull
>> on an inboard lever. The Japanese have a maxum: read a book a hundred times
>> and you will understand it. Sigh! More reading! More study!
>
> Well, maybe one of our intrepid engineering types will be along to
> clear it up. If I try, there will no doubt be much wailing and
> gnashing of teeth over my improper use of terms with precise
> definitions.
>
> I really don't know how Power (W) [presumably Watts, which is Joules/
> sec] was arrived at in the RBN2006#5. With ErgMonitor we can express
I asked Valery the same question a while ago, and he sent me an
unpublished paper he wrote on his methods for determining segmental
power. I don't particularly like or agree with these methods, and the
paper as a few (minor) errors, but I'll send it to you if you like.
However Paul, I've tried emailing you twice in the past 10 days or so,
with no response, so I think either I'm in your kill file, or your spam
filter thinks my domain is bogus, or both. Or you're just ignoring me
:-) Check your spam/junk folders and/or give me another address to
email you.
> something similar with a Unit called "TorqueJoule" (axel torque *
> watts * time, time cancels to yield energy multiplied by torque),
> which may or may not parallel the character of the concurrent Handle
> force plot. It does seem to have the character of the RBN "power"
> plots when the specific styles are implemented as described.
As you know, this is my *only* gripe about ErgMonitor. Multiplying
torque and work (Joules) is pretty meaningless, AFAIK. And IMO,
"TorqueJoule" should be removed from the available outputs in EM.
Power must always be expressed as some form of a force times a distance
divided by a time. This can be force times velocity, or work divided by
time, or impulse times acceleration, or any other combination that gives
F*d/t. EM also can display something called Power, with units of Watts,
but it's not clear how it's derived, as it doesn't seem to equal F*d/t
in any combination of the available output data. I'd love it if you
could (or maybe Mike M. could) explain how the power is calculated and
how it relates to some force (average?), distance and time.
Also, I've been meaning to ask how EM determines the beginning of a
stroke. It seems like force always rises from time=0. In my data, I
determine t=0 as the instant when the handle changes direction (actually
when handle velocity crosses zero with an increasing slope). Using this
method, there is a significant time lag between the handle changing
direction, and the onset of force as measured from the transducer in the
chain (which is sensitive to .01 N) This time lag that is in my data,
is where I based my comments on the "slack" in the system at the catch.
There is some slack... what causes it I'm not sure, but it's
irrefutable... so far every trial (45 so far) shows it.
This is another difference in EM vs. using a transducer and tracking the
physical handle position: (not a criticism, just an observation) Since
each stroke's force curve starts at t=0 on the graph, you can't see any
time-shifts in the force curve. With my setup, if you take the catch
really quickly with the arms, you see the force curve move dramatically
earlier in time compared to the previous stroke. Not only is the rise
of the force curve steeper, but it actually shifts to the left. Again,
this isn't a criticism, as my setup is hardly marketable! :-)
-Kieran
paul_v...@hotmail.com
I would like. Yes, the differential potentiometer method does leave a
bit to be desired, though it seems quite novel for the situation in
which it is being used.
> However Paul, I've tried emailing you twice in the past 10 days or so,
> with no response, so I think either I'm in your kill file, or your spam
> filter thinks my domain is bogus, or both. Or you're just ignoring me
> :-) Check your spam/junk folders and/or give me another address to
> email you.
Sent a test email to you, and got you onto my contacts. If only spam
filters could be so good with things we WANT to not be bothered with.
[;o)
> > something similar with a Unit called "TorqueJoule" (axel torque *
> > watts * time, time cancels to yield energy multiplied by torque),
> > which may or may not parallel the character of the concurrent Handle
> > force plot. It does seem to have the character of the RBN "power"
> > plots when the specific styles are implemented as described.
>
> As you know, this is my *only* gripe about ErgMonitor. Multiplying
> torque and work (Joules) is pretty meaningless, AFAIK. And IMO,
> "TorqueJoule" should be removed from the available outputs in EM.
Any of the units that ErgMonitor plots is easy to ignore, simply do
not add it to what you want to view.
As far as being "meaningless", opinions vary. I've got a very good
use for it, that seems to be supported quite well, but we've talked
about it before, so no need to belabor the point.
> Power must always be expressed as some form of a force times a distance
> divided by a time. This can be force times velocity, or work divided by
> time, or impulse times acceleration, or any other combination that gives
> F*d/t. EM also can display something called Power, with units of Watts,
> but it's not clear how it's derived, as it doesn't seem to equal F*d/t
> in any combination of the available output data. I'd love it if you
> could (or maybe Mike M. could) explain how the power is calculated and
> how it relates to some force (average?), distance and time.
The "Watt" plot is simply the power absorbtion of the flywheel for a
given time between sensor pulses. See Anu's Physics of ergometers
page if you want all the maths involved.
> Also, I've been meaning to ask how EM determines the beginning of a
> stroke. It seems like force always rises from time=0. In my data, I
> determine t=0 as the instant when the handle changes direction (actually
> when handle velocity crosses zero with an increasing slope). Using this
> method, there is a significant time lag between the handle changing
> direction, and the onset of force as measured from the transducer in the
> chain (which is sensitive to .01 N) This time lag that is in my data,
> is where I based my comments on the "slack" in the system at the catch.
> There is some slack... what causes it I'm not sure, but it's
> irrefutable... so far every trial (45 so far) shows it.
Basically, it's determined by the change from a decellerating flywheel
to a not-decellerating flywheel. For example, in your setup, if the
handle were moved from catch to finish precisely matching the speed at
which the chain is being fed by the cog (decelerating all the way),
you might call that a DRIVE with zero force, EM would not recognize it
had even happened, and include it in the previous recovery. This is
parallel to the situation in a boat where we might say something like
"You must catch up to the speed of the system before you can
accelerate it." And one of the reasons that I define "Drive" time, as
all non-negative system acceleration when in a boat for the purpose of
determining ratio, on the Erg it's a bit easier, "all non-negative
flywheel (which is the 'system' in that case) acceleration is DRIVE.
Handle Travel with no force can hardley be considered "Drive" can it?
Whether that occurs nearer the catch or release, it really is part of
the recovery (def. the entire time when the system is suffering
negative acceleration).
Due to the limit of resolution, by having only 1 sensor pulse every
3.5/3" of horizontal handle travel, EM will show a bit of left to
right shifting of the profile. Though the slope of the rise will
remain quite consistent for a given individual.
> This is another difference in EM vs. using a transducer and tracking the
> physical handle position: (not a criticism, just an observation) Since
> each stroke's force curve starts at t=0 on the graph, you can't see any
> time-shifts in the force curve. With my setup, if you take the catch
> really quickly with the arms, you see the force curve move dramatically
> earlier in time compared to the previous stroke. Not only is the rise
> of the force curve steeper, but it actually shifts to the left. Again,
> this isn't a criticism, as my setup is hardly marketable! :-)
>
> -Kieran
As said above, unless there is positive handle force (axel torque) EM
will not recognize the DRIVE as having started. IMO anyone who wants
to say the drive has begun prior to any handle force being generated
should let the others in their boat know, so expectations of
performance can be lowered accordingly. You know who you are, the
"Catch, connect, drive" folks. If you "connect" for 0.1sec in a boat
moving 5m/s you were a heavy passenger for more than 10% of the
distance that will be covered during that drive, and can be
appropriately nicknamed "the anchor". Of course the "rowing in" group
isn't any better, but will be a bit worse since they will never truly
get connected at all (but their puddles look more impressive, so the
coach, and even other rowers might not think of them so negatively).
[;o)
- Paul Smith
>
>
> > Hopefully Kleshnev will illustrate the two distinct plots in an
> > upcoming newsletter. I did get the impression he was going to do so
> > after an email exchange we had last year.
>
> >> One thing I do know is that whatever the explanation, I am getting slightly
> >> faster on the water. The last time I went out I rowed in forty-five minutes
> >> a distance that has always taken me sixty to sixty-five minutes to row.
> >> Forty-five minutes for this distance is not a bad time. I rowed at a steady
> >> rate, but kept my usual comfortable, leisurely pace. I concede that a lot of
> >> this has to do with knowing a little more about how to move a boat better.
> >> But I also think some of it has to do with the Rowers Shadow, which is
> >> really teaching me a out "the connection."
>
> >> Cordially,
>
> >> Charles
>
> > Reducing your time to cover a distance by 30% is quite significant,
> > and illustrates that knowing the difference between Force and Power is
> > certainly not required to improve boat moving, or more accurately
> > "advancing your body over the course while dragging your support tools
> > along with you". [:o)
>
> > Cheers,
> > Paul Smith- Hide quoted text -
>
> - Show quoted text -- Hide quoted text -
Peter Ford
What are the times, and distances moved, before the force starts being
applied? this is what I've always thought was the biggest difference
between different age and standard of upkeep ergos; and is most of the
reason that, from our 8 ergos at school, most people are only willing
to use two of the ergos, as the others seem substantially slacker at
the catch.
KC
I don't recall off the top of my head. It's all on my laptop at home.
I'll look it up and post when I get a chance.
My erg is old, but well maintained and not used *too* much over the
years (heavily for brief periods of several months, then not much at all
for longer periods, etc.) But the bungee, chain, etc., are all in good
shape. It's a model C, btw, bought in... hmmm... 1997 I think, from
Long Beach Rowing Assn, after their winter erg sprints (it was new
except for the erg competition).
-Kieran
paul_v...@hotmail.com
>
> - Show quoted text -
I don't believe that the "slack" is caused by the flywheel Clutch, or
if it is, then it would either be working or not, and not to a varying
degree as Peter seems to be observing/suggesting.
C2 discusses the Clutch repair here:
http://www.concept2.com/05/rower/service/cparts.asp
Short version, just order a new flywheel assembly. [;o)
The Slack around the catch probably has more to do with the Drag
Factor and subsequent speed of the flywheel at the catch. A Model C
or newer with a DF below 140 would see an RPM at the catch in the area
of 1200 at race pace/rates. With 3.5" of chain for each revolution
one would have to be moving at 70"/sec before engaging the clutch, If
this is to be accomplished in the "classical" manner (seat and handle
moving together, without a grab of the arms), then most of the rowers
mass will need to be accelerated up to 70"/sec in a short, but
measurable, time; at which point the flywheel will provide increasing
resistance to further acceleration of the rowers mass. The faster one
rushes into the catch the longer the "turn around" will last due to
first absorbing the momentum and then reversing it. It's easy to
imagine how one could even be still engaged in slowing the majority of
their mass for a time after the handle had changed direction, making
the time to catch the flywheel even longer.
- Paul Smith
KC
Paul, congratulations. You just made me think of something I need to do
differently with my data collection! (actually, it was a combination of
this post you just made, and my re-reading Kleshnev's paper that I just
sent to you.) I'm not currently directly tracking seat velocity or
position, and I should. Easy to fix, and fortunately, I only have half
of my data collected, so I can still get some significant statistics
from the remainder. And, if I really wanted to track it in my current
data, I could but I'd have to manually click on a physical feature (e.g.
corner) of the seat in EVERY frame of my video data... 60Hz video x 25
seconds per trial, x 3 cameras per trial x 3 trials per session x 3
sessions per rower, x 5 rowers collected w/o seat data. That's way too
many mouse clicks! :^P Actually, I do have a tracking marker on the
hip, which is ALMOST as good as the seat in most cases, so I'll add the
seat marker for future trials, and use the hip marker for past trials,
*IF* I decide I need seat data (might be useful though).
Anyway... back on topic:
>
> I don't believe that the "slack" is caused by the flywheel Clutch, or
> if it is, then it would either be working or not, and not to a varying
> degree as Peter seems to be observing/suggesting.
> C2 discusses the Clutch repair here:
> http://www.concept2.com/05/rower/service/cparts.asp
> Short version, just order a new flywheel assembly. [;o)
>
> The Slack around the catch probably has more to do with the Drag
> Factor and subsequent speed of the flywheel at the catch. A Model C
> or newer with a DF below 140 would see an RPM at the catch in the area
> of 1200 at race pace/rates. With 3.5" of chain for each revolution
> one would have to be moving at 70"/sec before engaging the clutch, If
> this is to be accomplished in the "classical" manner (seat and handle
> moving together, without a grab of the arms), then most of the rowers
> mass will need to be accelerated up to 70"/sec in a short, but
> measurable, time; at which point the flywheel will provide increasing
> resistance to further acceleration of the rowers mass.
Which is why a sliding erg provides a more boat-like feel to the leg
drive at the catch: all that needs to be accelerated up to that 70"/sec
is the mass of the erg. This happens much more quickly on a sliding
erg, thus a quicker connection, and less chain pull distance before
force/resistance from the flywheel is felt.
> The faster one
> rushes into the catch the longer the "turn around" will last due to
> first absorbing the momentum and then reversing it.
This is not really the case. We can not make the assumption that human
tissue behaves like standard mechanical materials (simple springs and
dampers). I know I recently said that human muscle is often modeled
this way, but it's only part of the equation. Tendon and muscle have
what's called visco-elastic characteristics, they can store and release
energy in ways that are not similar to metal springs or carbon fiber oar
shafts. There is a time-based aspect of energy storage and release for
human tissue: If stretched slowly, very little energy is stored. If
stretched quickly, the tissues can act like a steel spring with
excellent elasticity. Likewise the release of the energy must come
quickly: if you stretch quickly but then sit there, the tissue elements
relax and release the energy in heat. If you immediately bounce back
from the stretch, most of the energy is recovered. So, there can be a
benefit to approaching the catch fairly quickly, and quickly "bouncing"
(for lack of a better word) into and out of the compressed catch
position. There is a TON of research in this area for OTHER sports, if
you're interested search for info on plyometrics.
A very simple example of this phenomenon is done in every one of our
undergraduate biomechanics courses. The student stands on a force plate
(really expensive glorified scale that measures force and torque in and
about all three axes). Student then is asked to squat and jump as high
as they can. Height and force of squat/jump are recorded. Next, the
student is asked to slow down their squat, but still jump as high as
they can. The depth of the squat is the same each time, only the
velocity changes. Height and force of squat/jump are recorded again.
WITH OUT FAIL, every time, the first jump is higher, and the force is
higher (obviously). But also, the time of the force application is
shorter. So, even though they have more momentum going into the ground
on their squat (same mass * higher velocity) they are able to get off
the ground more quickly, and jump higher. This is due to the fact that
with the increased velocity, they are actually able to store and release
their body's momentum and use it to their advantage.
> It's easy to
> imagine how one could even be still engaged in slowing the majority of
> their mass for a time after the handle had changed direction, making
> the time to catch the flywheel even longer.
Yes, I suppose if you were to pull with the hands while still
compressing into the catch this would happen. Although in my
experiments, rowers either don't or can't really do this. When I ask
them to "grab the catch with the arms" the arms and legs come on
virtually simultaneously. They can feel/tell if/when they are still
compressing into the catch, and they don't pull until they can/are
extending the legs too.
-Kieran