High Rate? Or Slower Rate?
Charles Carroll
Let's say that you can sustain a speed, we'll call it X, for an entire 2k.
Furthermore let's say that you can sustain X at a rate of 26 spm and at a
rate of 30 spm.
Which rate would be the more advantageous, the slower or the higher?
Is the answer merely a matter of personal preference?
Or can science provide theory and evidence that will tell us which of the
two rates is the more advantageous?
Speaking only for myself I can say that my sculling is more enjoyable when I
do three things:
1) Get as long as I can;
2) Reproduce the same net velocity for each stroke;
3) And in any given stroke keep the amplitude between the highest velocity
and the lowest velocity as small as possible.
But I am not fast ...
Cordially,
Charles
James HS
wrote:
I think there are several arguments and it depends on whether you are
a Lighweight or not.
But here goes with my understanding
lower rate is more power intensive, higher rate more CV intensive
depending on your stroke and skill at the recovery your body mass is
shifting more often at higher rate and may therefore tempt you to pull
yourself up the slide rather than letting the boat come to you.
intuitively I would think that maintaining the split at the lower rate
would be easier - except they both require the same 'wattage' but I
would think that delivering that wattage is less efficient at higher
rates.
When I have worn myselef out at the higher rates I often calm down and
then delier the same splits at lower rates in more comfort.
When being coached on rate climbs I often see the rate climb and the
split drop - but that is skill and my coach says "don't swap split for
rate".
James
Stamps
wrote:
> Dear all,
>
> Let's say that you can sustain a speed, we'll call it X, for an entire 2k.
> Furthermore let's say that you can sustain X at a rate of 26 spm and at a
> rate of 30 spm.
>
> Which rate would be the more advantageous, the slower or the higher?
>
Ummm, this baffles me a bit. You are going the same speed, so they are
the same, aren't they? What do you mean by more advantageous, do you
win medals for some reason other than how fast you can go?!
Walter Martindale
wrote:
Well...
A higher stroke rate will offer more opportunities to propel the boat,
have a larger proportion of the time spent applying force to the pins,
and should provide more velocity in the long run. This assumes, of
course, that the forces being applied each stroke are approximately
the same each time.
A study published in (was it around 1970?) in Journal of Applied
Physiology found that as the stroke rate went up, the force per stroke
went down slightly, the duration of the stroke drive phase was a
little shorter, and that the impulse per minute increased. The
recovery duration went down, and the boat went faster - it doesn't
matter that they were in an 8+ for the study and you're in a Carl
Douglas 1X...
At a higher rate there is also more opportunity for a poorly timed
blade entry (pushing the footstretcher too early and missing water) to
show itself as a "check" in the run of the boat.
That's all I have time for..
W
IPS
Dave Sill
>
> Well...
> A higher stroke rate will offer more opportunities to propel the boat,
More opportunities, yes, but that isn't necessarily more efficient.
> have a larger proportion of the time spent applying force to the pins,
How's that? If the drive/recovery ratio is the same, I think time spent
applying force to pins is the same. Rushing the recovery, on the other
hand, would result in more time applying force to pins.
> A study published in (was it around 1970?) in Journal of Applied
> Physiology found that as the stroke rate went up, the force per stroke
> went down slightly, the duration of the stroke drive phase was a
> little shorter, and that the impulse per minute increased. The
> recovery duration went down, and the boat went faster - it doesn't
> matter that they were in an 8+ for the study and you're in a Carl
> Douglas 1X...
I think that's key: higher rates make for a more constant velocity,
which is more efficient.
-Dave
PaulS
wrote:
I think you have answered your own question. Same speed is same
speed, regardless of rate, so "no advantage".
To go faster, one must be stronger (all other things being equal).
Of course this reminds me of an analogous riddle:
Why do Harley Davidson Riders always go so slow?
.... Because they are already where they want to be.
Cheers,
Paul V. Smith
tony....@gmail.com
The question as posed does not make sense.The answer might be that if
speed X is truly the same at the two different rates then whichever
rate "feels" more comfortable is the right one. However if a rower is
giving truly maximum effort, human biomechanics states that there will
be an optimum speed, above or below which efficiency diminishes.
Human efficiency of exercise can be affected by speed of movement,
work rate and fiber type recruitment.
See for example
http://jan.ucc.nau.edu/pe/exs336web/336workpower.htm
Cheers
Tony Tarlo
Dave Sill
> Dave Sill wrote:
>> I think that's key: higher rates make for a more constant velocity,
>
Well, I don't have proof, but I believe so. Remember Charles' premise
was that the average speed of the boat is the same and stroke rate is
varying. So at a lower stroke rate, with a longer recovery, the boat
will slow more, requiring a higher peak velocity in order to maintain
the same average speak.
-Dave
Walter Martindale
The "ratio" does not remain the same as the stroke rate goes up. It
takes elite rowers somewhere around 0.7 and 0.8 second to do the drive
phase, no matter what the stroke rate. The only place that sufficient
time can be pared away to cause an increase in stroke rate is during
the recovery, spending less time with the blades in the air, and more
time with the blades in the water.
Please prove me wrong.
Take a video of any competent crew rowing at (say) 18, and then again
at (say) 38 (or 40, or 50 during a racing start). Count frames with
the blades in the water, count frames with the blades in the air.
Calculate the "ratio" - it's very rarely "2:1"
The determination of whether the recovery is rushed or not is usually
made by judging how effective the crew is at getting themselves ready
for the next drive, and at controlling the transition from recovery to
drive.
Walter
Dave Sill
>
> The "ratio" does not remain the same as the stroke rate goes up.
Remember that the premise of this thread is that you assume the
rower/crew can row a race in the same time at either a high rate or a
low rate, and, given that, which rate is "better".
> It
> takes elite rowers somewhere around 0.7 and 0.8 second to do the drive
> phase, no matter what the stroke rate. The only place that sufficient
> time can be pared away to cause an increase in stroke rate is during
> the recovery, spending less time with the blades in the air, and more
> time with the blades in the water.
> Please prove me wrong.
I agree completely.
> Take a video of any competent crew rowing at (say) 18, and then again
> at (say) 38 (or 40, or 50 during a racing start). Count frames with
> the blades in the water, count frames with the blades in the air.
> Calculate the "ratio" - it's very rarely "2:1"
It's also unlikely the two boats will have the same average speed at 18
spm and 50 spm. I think for Charles' example the low and high rates will
be much closer, e.g., 24 vs. 30, so I don't think the ratio has to
change a lot.
-Dave
Carl Douglas
That said, unless you do pull a bit faster, you will not actually go
much faster.
Walter's absolutely right - rate does not come up in the water.
Boat speed _is_ proportional to hand speed yet, due to the cubic
relation between speed & power, the boat speed does not rise very much
between a firm paddle & a flat-out row, even if the rate also rises from
26 to 40. So the only effective means of raising rate (while not
shortening stroke, which would be counter-productive) is to shorten
recovery time.
Increasing rate has the convenient effect of increasing the ratio of
time in water to time out. That allows, invites or even necessitates
some fall in loading or force applied, even though the power output
rises. Which gives the lie to those common exhortations to "Increase
the rate by increasing the pressure", or to "Raise the rate by going
faster through the water". Quite apart from the undesirability of
tearing blades through the water (only do-able by rowing less deep,
which increases dead losses), it makes scant sense to increase pressure
while increasing work rate since that must precipitate overload &
premature fatigue.
You can look on rating change as being a form of gear change. Already
at maximum physical load at say 26, you can pull no harder, so your boat
speed hits one natural limit. That limit, however, is likely to have
been determined at that rate by your strength, not your maximum power
output - the gearing is in effect to severe. Now raise the rate, so
that your blade is more often & in sum is for longer in the water (= a
step down in gearing) & your potential power output, if you can sustain
the same pressure, must rise. In fact your maximum sustainable loading
will be diminished by the demands of moving faster but, even though it
falls, your sustainable power output may well rise & with it your boat
speed. By careful investigation & adjustment of how hard you pull, you
will find that there is a set rate & loading at which you can best
maximise steady state boat speed for a given distance.
Ane important consequence of this consideration is that, while higher
rates should normally facilitate faster, more economical performances,
ultimately there comes a rate beyond which the bother of moving that
fast impairs your ability to row effectively & further rate increase is
damaging. If this technique-sensitive limitation is appreciated, then
the advantage of developing a smoother technique & practising higher
rates (including high rates at low pressure) becomes apparent.
Rate increase is not, as Dave may have been thought to have suggested,
to be achieved by rushing finishes. If you already have a good hand &
body speed profile through the recovery - finish to catch - it makes no
sense to rush any one part, or all of that process. Better to make the
same small increment in each movement's speed & keep it smooth, since
adding sudden surges disrupts rhythm, boat run & your physiological
functioning while having relatively slight effect on rating.
With most rowers there is scope to save time on the recovery at no cost
to rhythm or anything else - just cut out any hang over front-stops,
since that's the last place you should want to spend any time. Many
rowers waste some 10ths of a second between recovery & catch, & even 0.1
sec causes a needless loss of ~5% (~1.5spm) in rating.
One last thought:
Higher rates do not mean that you are moving up & down the boat faster.
They would on a fixed erg, but with a boat you are pretty much moving
at steady speed over the water, with the much lighter boat being pulled
& pushed back & forth beneath you. Cycling a mere 16kg (blades
included) through a short distance at a mere 40x per minute is not
particularly demanding for anyone calling themselves athletes.
Cheers -
carl
--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories
Write: Harris Boatyard, Laleham Reach, Chertsey KT16 8RP, UK
Find: http://tinyurl.com/2tqujf
Email: ca...@carldouglas.co.uk Tel: +44(0)1932-570946 Fax: -563682
URLs: www.carldouglas.co.uk (boats) & www.aerowing.co.uk (riggers)
Tinus
> They would on a fixed erg, but with a boat you are pretty much moving
> at steady speed over the water, with the much lighter boat being pulled
> & pushed back & forth beneath you. Cycling a mere 16kg (blades
> included) through a short distance at a mere 40x per minute is not
> particularly demanding for anyone calling themselves athletes.
Higher rates do not take much effort when unloaded (e.g. moving just a
weight back and forward without the interactions with water). But at a
certain rate higher rates will penalize because of faster boat speed
fluctuations which result into higher energy loss due to hydrodynamic
resistance forces.
Taking these types of penalties into account one could arrive at
formulae for relations between stroke rate and boat speed. These types
of formulae are always concave. A theorem for concave functions is
that if f(a)=f(b) than f(x)<f(a) for all x:a<x<b. If 26spm and 30spm
both result into the same boat speed than probably 28spm, which is in
between, results into a higher boat speed.
Tinus
> that if f(a)=f(b) than f(x)<f(a) for all x:a<x<b. If 26spm and 30spm
if f(a)=f(b) than f(x)>f(a) for all x:a<x<b
damn the non existing edit function.
Carl Douglas
No matter. You're right to say that if, with a given technique, 2
different rates give equal performance over set distance, then the
maximum speed will come at an intermediate rate.
However, until the recovery is so rapid that the boat actually
accelerates between finish & catch, you'll suffer no drag penalty from
speed oscillations due to higher rating (since the stroke speed rises so
relatively little with increasing rating).
cheers -
Tinus
> However, until the recovery is so rapid that the boat actually
> accelerates between finish & catch, you'll suffer no drag penalty from
> speed oscillations due to higher rating (since the stroke speed rises so
> relatively little with increasing rating).
It is true that at some low rating the boat speed fluctuations due to
non constant application of force are of more importance than boat
speed fluctuations due to rower motion relative to the boat. In this
case increasing the rating will probably increase average boat speed.
However, :-) , the relation is still a concave function.
Carl Douglas
Made all the more so by the eventual decline in technique with rating!
However, I believe that with no decline in technique the rating at which
boat-speed oscillations might start to increase drag is off the feasible
scale. FWIW, rating, even at near-infinite recovery speed, can never
exceed ~80spm, that crude upper limit being set by the irreducible
time/stroke in the water.
Of course, technique must suffer as rate reaches certain levels. That's
why it would pay dividends to practice higher ratings (just as musicians
practice hard to gain the necessary speed & fluidity for fast sections),
provided it is understood that useful rating increase comes not from a
rushed finish, a faster power stroke (which is nearly impossible) or
from shortening or washing out the stroke, but from speeding all parts
of the recovery action equally & from eliminating stasis over the catch.
Cheers -
Carl
Sagar
> URLs: www.carldouglas.co.uk(boats) &www.aerowing.co.uk(riggers)
Hello Carl,
Thanks for all your emails. Your insight is amazing. I have learnt
quite a bit from reading your mails. Your explanations bring more
certitude in the way I have started to perceive my stroke.
Cheers,
Sagar
Mike De Petris
aren't you taking into account that one can adjust gearing, blades
size, scull lenghts, any other settings to get a faster drive? Of
course it may just be academics, anyway do you remember that old ages
american succesful sculler that aimed at staying at 40 all the race
long?
Carl Douglas
You're right, Mike, to say we can adjust gearing. But I thought this
was an "all things being equal", i.e. change only 1 variable at a time,
exercise?
In reality, though obviously not in perception, the biggest real change
in gearing that you can make is by changing rating (the one variable
permitted to change in this virtual study). Compared with a 25% rate
change, a 1cm change in the inboard length of the oar is pretty small
beer in gearing terms. How much faster drive (assuming it is achieved
without also having exaggerated blade slip/stall) will a 1cm change of
inboard give you?
[Now I do accept that many will not, or not at first, accept my
confident assertion that changing rating is, in effect, changing
gearing, & I am happy to discuss this with those in doubt.]
History shows us scullers who went pretty well at low ratings, & those
who were winning with high ratings, but single data points like those,
taken at different periods in our sport, cast a very weak dim light on
the relative merits of high & low ratings. The proper way to explore
these is to develop a meaningful hypothesis & then subject that to
careful testing. That's not easy when the test object includes humans &
in an activity often beset by presumptions & prejudices, but I'd have
thought it well worth the effort.
Mike De Petris
> History shows us scullers who went pretty well at low ratings, & those
> who were winning with high ratings, but single data points like those,
> taken at different periods in our sport, cast a very weak dim light on
> the relative merits of high & low ratings. The proper way to explore
> these is to develop a meaningful hypothesis & then subject that to
> careful testing. That's not easy when the test object includes humans &
> in an activity often beset by presumptions & prejudices, but I'd have
> thought it well worth the effort.
I can only tell you that yesterday, as always in the last years, I
kept contact with other scullers while I was at 33/34 spm, and they
were all going away as soon as I had to slow down to 30/31. My best
race last year has seem me rating 36 all the way.
Should I just shorten my sculls by 10cm or so? :)
Carl Douglas
I think your tongue was in your cheek in that last remark ;) ?
I think Tinus & I might agree that your performance curve was rising
with rating at both 30/31 & at 33/34, & that it might still be rising at
36. At worst your optimum speed might lie just below rate 36 but, with
luck & a well-maintained technique, you might go even faster at above 36.
Mike De Petris
> Mike De Petris wrote:
> > On Mar 22, 1:45 pm, Carl Douglas <c...@carldouglas.co.uk> wrote:
> >> History shows us scullers who went pretty well at low ratings, & those
> >> who were winning with high ratings, but single data points like those,
> >> taken at different periods in our sport, cast a very weak dim light on
> >> the relative merits of high & low ratings. The proper way to explore
> >> these is to develop a meaningful hypothesis & then subject that to
> >> careful testing. That's not easy when the test object includes humans &
> >> in an activity often beset by presumptions & prejudices, but I'd have
> >> thought it well worth the effort.
>
> > I can only tell you that yesterday, as always in the last years, I
> > kept contact with other scullers while I was at 33/34 spm, and they
> > were all going away as soon as I had to slow down to 30/31. My best
> > race last year has seem me rating 36 all the way.
>
> > Should I just shorten my sculls by 10cm or so? :)
>
> I think your tongue was in your cheek in that last remark ;) ?
>
> I think Tinus & I might agree that your performance curve was rising
> with rating at both 30/31 & at 33/34, & that it might still be rising at
> 36. At worst your optimum speed might lie just below rate 36 but, with
> luck & a well-maintained technique, you might go even faster at above 36.
of course I was a bit joking but I suspect gearing a way I can hold
higher rates would help me going faster, anyway, I can do an all-the-
way-high-rated-race once a year, and I'm still unbeatable on short
distances, no matter how much I train for long distances, genetics, of
course.
Carl Douglas
Maybe it'd be more helpful to reduce pressure as you raise rating?
If you raise rate by 10% but reduce pressure by 5%, while keeping the
same stroke length, you will do 4.5% more work & the boat will go almost
1.5% faster (30 metres over 2k). The work increase is non-negotiable &
dependent on your cardiovascular output, but by reducing pressure as you
increase rating you delay muscle fatigue while still making the
necessary power increase.
You would alter blade gearing to allow you to do the same thing, but I
don't think you can make the effective 10% change in gearing that you
get from the rating increase by anything you can usefully do on the oars.
This is, of course, why we rate higher to win races!
Tinus
> However, I believe that with no decline in technique the rating at which
> boat-speed oscillations might start to increase drag is off the feasible
> scale. FWIW, rating, even at near-infinite recovery speed, can never
> exceed ~80spm, that crude upper limit being set by the irreducible
> time/stroke in the water.
Using a very crude two body (rower + boat) model I arrive at centre of
mass fluctuations about 1 m/s. Boat-Rower velocity peaks at the same
order between 30-40 spm and around the same point the model shows a
maximum average boat velocity (for the same power output).
http://kijkeensnaarhetvogeltje.nl/rates.ods (openoffice file)
That's in theory but I believe that also a lot empirical data shows
that boat speed fluctuations and boat speed during recovery start to
rise somewhere between 30-40 spm.
Tinus
Also if f(a)-f(b) than still f(x)>f(b) and f(x)>f(a) could be true
for x>b... because the relation between speed and stroke rate is very
flat and difficult to measure. While it appears that f(26) and f(30)
are the same it doesn't need to be like that.
Sagar
> URLs: www.carldouglas.co.uk(boats) &www.aerowing.co.uk(riggers)
I think this works when you have rigid boat with low surface contact.
The kind of rubber boat I own I don't think reducing pressure is
helping me keep speed.
Charles Carroll
In the past I have started threads like this only to find myself blindsided
by demands on my time. As a consequence, not only do I find it impossible to
participate in a thread I started, but it also can be weeks before I have
time to go back and reread the replies.
I thank everyone who participated. I am sure that in the future you will
find me "borrowing" many of your ideas.
Now, as to the original question, albeit in different words: Is it "better
to pull hard at a lower rating than to ease up at a higher rating?"
Mike De Petris, posting in Alistair's thread on "Timing," included a link to
Bill Atkinson's website, where I found the following:
http://www.atkinsopht.com/row/forcratg.htm
For those who don't want to visit the website, Bill has a figure which "[.]
shows the benefit of playing it strong and easy vs. light and fast."
Weeks ago before I even started the thread I put the question to a coach at
my Club. She told me that she would always recommend the lower rate if it
produced the same speed, but she didn't quite know why. It was just her
preference.
I have to email her the link to Bill's website.
Thanks again,
Charles
Mike De Petris
wrote:
Thanks for coming back Charls, I read
"igure 1 shows the benefit of playing it strong and easy vs. light and
fast. Light pull and high stroke rate are here compared to strong pull
and lower rating for equal total rower power output. Even though the
heavier pull causes greater blade slip and poorer blade efficiency it
wins out on increased rower efficiency largely owing to greatly
reduced internal momentum losses (from 355 to 213 J/stroke) which are
required whenever rating is increased. Keep in mind that the only way
that rating can be increased is by reducing the free return time
which, in turn, requires increased momentum effort.
The velocities agree with the rule: V2 = V1 [F2/F1 x R2/R1]^0.333
where V is shell average speed, F is oarhandle effort, and R is
rating. "
btw I'm a bit skeptical about how "equal total rower power output" is
obtained, but I'm impressed about how wide is the difference in term
of 2k seconds!