Comparing efficiency at different stroke rates

[dabatey]

I agree that the whole stroke does change at higher paces, but I do find that over R16-30 the work per stroke does stay pretty constant, although I am a slow lightweight. At higher ratings the whole stroke changes as it morphs into one more like a crossfit stroke with earlier back use and at the end of a piece the slide shortens and I probably use less leanback to maximise the use of my back as my legs weaken.

I pretty much agree with this. I stay in the same ballpark from 18 to 26 (all of which I tend to row strapless) The reason I pointed out to Annistropic that working out watts per stroke wouldn't work for shorter/faster stuff is because the stroke changes. (For me that is starting to haul myself back up using footstraps at higher stroke rates, and for very fast stuff stopping my recovery at a wider leg angle).

Funnily enough I start to pull ever so slightly harder watts/stroke again at the low end 16-18spm as I get plenty time to really set myself perfectly (and plenty rest) which JaapvanE kinda points out in one of his answers.

For me this is different. I find the higher I rate, the stronger the strokes get. On short stuff like a minute or 500m I get to averages of 13-14W/min, for 1 or 2k I fall into ~12W/min and slightly below that for longer efforts like 10k or HM, sometimes to 11W/min.
I can get to 14W/min also on lower rates, but I cannot maintain that for very long. Last 2k on r24 was at that stroke power, but I was done after that. No chance to hold that for a 10k or 30min.

I think you've just agreed with me (and Iain) there rather than being different. You say 11-12 except for shorter faster stuff where you get higher (13-14) due to shorter powerful strokes pulled for a short time. [Where I said about 16-18 as an extra it was only a small raise I was on about and not part of my main point so maybe I shouldn't have said that in order to be a bit clearer].

[Sakly]

I pretty much agree with this. I stay in the same ballpark from 18 to 26 (all of which I tend to row strapless) The reason I pointed out to Annistropic that working out watts per stroke wouldn't work for shorter/faster stuff is because the stroke changes. (For me that is starting to haul myself back up using footstraps at higher stroke rates, and for very fast stuff stopping my recovery at a wider leg angle).

Funnily enough I start to pull ever so slightly harder watts/stroke again at the low end 16-18spm as I get plenty time to really set myself perfectly (and plenty rest) which JaapvanE kinda points out in one of his answers.

For me this is different. I find the higher I rate, the stronger the strokes get. On short stuff like a minute or 500m I get to averages of 13-14W/min, for 1 or 2k I fall into ~12W/min and slightly below that for longer efforts like 10k or HM, sometimes to 11W/min.
I can get to 14W/min also on lower rates, but I cannot maintain that for very long. Last 2k on r24 was at that stroke power, but I was done after that. No chance to hold that for a 10k or 30min.

I think you've just agreed with me (and Iain) there rather than being different. You say 11-12 except for shorter faster stuff where you get higher (13-14) due to shorter powerful strokes pulled for a short time. [Where I said about 16-18 as an extra it was only a small raise I was on about and not part of my main point].

Not sure.
My steady states are around 10+-1, depending on the rate, length of the session (always >=60min) and fitness of the day. These sessions have not the intention to build a stronger stroke, so I don't utilise my strongest stroke. I could also work with a 12W/min stroke, but probably not for a HM or 60min.
When I compare the long sessions going for TTs (which is in fact the only valid comparison), the stroke gets a little bit stronger, but not much. Here is a list of PBs, their rate and average watts to get the stroke power:
HM: r25 and 250W average => 10W/min.
10k: r24 and 277W average => 11.5W/min
2k: r30 and 358W average => 12W/min
500m: r41 and 530W average => 12.9W/min
Shorter stuff like 1min or 100m doesn't get much higher in SPI in average, as I have very weak starts. I only get to higher SPIs in rate restricted sessions, were I pull as hard and long as I can, with a kind of unnatural and modified stroke. Then ~14.5W/min is possible, but that's my limit.
Based on the given list I would say my stroke gets stronger in shorter pieces and higher rates (without intention to do so, it happens naturally).

[jamesg]

MC's L4 tables include ratings from 16 to 26. I found it possible to use the same stroke from 18 to 24, which are the typical aerobic training ratings, but hardly easy. No doubt that's why they're so very effective.

If a 2k test time is 8 minutes at 32, the L4 line (from 16 to 26) is:
s/m Pace W Work
16 02:30 104 6.5
18 02:25 115 6.4
20 02:20 128 6.4
22 02:15 142 6.5
24 02:10 159 6.6
26 02:05 179 6.9

The specified paces are formatted in the text as times (but hh:mm) so can be used to calculate Watts, via W=kV³, and Work too (W/rate) if we so wish.

As far as I can see, the L4 tables are based on a race rate of 32-34, which was normal for 8s many years ago. A test time of 8 minutes is pace 2:00, 203W and at 32 work 203/32 = 6.3, so as might be expected, MC and colleagues added a little to their ladies training strokes.

[iain]

My steady states are around 10+-1, depending on the rate, length of the session (always >=60min) and fitness of the day. These sessions have not the intention to build a stronger stroke, so I don't utilise my strongest stroke. I could also work with a 12W/min stroke, but probably not for a HM or 60min.
When I compare the long sessions going for TTs (which is in fact the only valid comparison), the stroke gets a little bit stronger, but not much. Here is a list of PBs, their rate and average watts to get the stroke power:
HM: r25 and 250W average => 10W/min.
10k: r24 and 277W average => 11.5W/min
2k: r30 and 358W average => 12W/min
500m: r41 and 530W average => 12.9W/min
Based on the given list I would say my stroke gets stronger in shorter pieces and higher rates (without intention to do so, it happens naturally).

Personally for an all out HM I know that it is muscle soreness that will limit me and so I raise my rating a little to allow a weaker stroke, so HM could be doing something similar or tiring muscles. Given 10k only at R24 I suspect that this could also be tiring muscles a bit. 500m and R41 is likely to be a sprint stroke so not comparable. 2k could be affected either way. Personally I struggle to breathe and so holding R31+ doesn't work for the majority so I concentrate on harder strokes through the 3rd quarter. However in the final 500 I trade rate for pace and finish with compromised sprint stroke so work per stroke drops below normal. So I think this is inconclusive. Also I note that ratings are all integers. PM rounds down the average of the intervals that are rounded (I think down) so sometimes this causes big differences. This is exploited with some people doing "R20" at slightly >R21 for all but one intervals that is kept below R21 to give the stated R20.

I would say that all out TTs are NOT normal rowing and comparisson of training sessions might be more enlightening. That said some people do definitely increase work per stroke with rating some even maintaining a similar drive/recovery ratio. My first OTW coach recommended this, but for slower rowers like me it means a weak stroke over SS that hides technical errors so I keep SPI similar (although it drops a bit when fatigued).

[JaapvanE]

Given 10k only at R24 I suspect that this could also be tiring muscles a bit. 500m and R41 is likely to be a sprint stroke so not comparable. 2k could be affected either way. Personally I struggle to breathe and so holding R31+ doesn't work for the majority so I concentrate on harder strokes through the 3rd quarter. However in the final 500 I trade rate for pace and finish with compromised sprint stroke so work per stroke drops below normal. So I think this is inconclusive.

Hence my point that with a change of strokerate, the stroke itself changes (might become stronger, might become weaker). It really depends on the person, what his normal stroke is and other specific personal properties whether an increase in SPM will increase the efficiency of the stroke.

Also I note that ratings are all integers. PM rounds down the average of the intervals that are rounded (I think down) so sometimes this causes big differences. This is exploited with some people doing "R20" at slightly >R21 for all but one intervals that is kept below R21 to give the stated R20.

Completely true. That is why the PM5 delivers the underlying stroke data (drive time, recovery time) in 0.01 sec accuracy via Bluetooth, and RowingData even allows it to record it in the milisecond (i.e. 0,001 sec). Using that makes information a lot more useful.

As an aside: the formal unit of measurement for Work per stroke is Joules (or Watts * Sec). I can't seem to wrap my head around a unit that is W/min (as W = J/s). But perhaps someone can explain that one to me.

[Sakly]

I would say that all out TTs are NOT normal rowing and comparisson of training sessions might be more enlightening.

I don't get this point. I do training sessions exactly for the reason of TTs in specific distances (or times), so the respective training pieces are very likely to be the same in rate and stroke power. And this is what I see for specific training pieces, like 8x500 or 4x1000 - they are very similar to a 2k in terms of rate and pace (500s bit faster).
Steady state sessions are out of scope, they only build the aerobic base and have no specific other purpose (for me).

Regarding your other explanations: I tried to pace the HM and 10k exactly to hit my target, rate was only increased a little bit in the end (last 10% of distance) for a sprint or to counteract fatigue, which clearly kicks in by the end of any TT. The former 90% were more or less steady, in the HM as well as 10k. Rate followed the needs for target. In the HM I used a little higher rate with purpose to rely a bit more on CVS than strength.
For the 500 I use a very similar stroke like for longer distances, as I lack explosiveness. A full stroke with lower rate gets me to much better results than shorter "sprint strokes" on even higher rates. So I would expect that my 500m stroke looks very similar to a 2k or 5k stroke.

[jamesg]

I can't seem to wrap my head around a unit that is W/min (as W = J/s).

1W-min is 60J. Fundamental ISO units have names, F, J, K, C, N, V, A etc. Some are linked: W = VA = Nm/s = J/s for example, linking mechanical and electrical Work and Power.

1W-min is 60Ws so 60J, used since we see the two numbers on the PM, W and rating, offering control on the fly. Some even use HR.

Work is Force x Distance; and even air does Work: when hot and damp it rises, expands doing work against the surrounding atmosphere, so cools, water vapor condenses and rain falls.

Without the engineering concept of Work it's hard to see how anything works at all. When rowing, it makes things all too simple: pull long hard strokes and our boat will move, maybe even fast. In which case coach might decide to keep us aboard so that we can pull plenty like that and get fit.

[dabatey]

I can't seem to wrap my head around a unit that is W/min (as W = J/s).

1W-min is 60J. Fundamental ISO units have names, F, J, K, C, N, V, A etc. Some are linked: W = VA = Nm/s = J/s for example, linking mechanical and electrical Work and Power.

1W-min is 60Ws so 60J, used since we see the two numbers on the PM, W and rating, offering control on the fly. Some even use HR.

Work is Force x Distance; and even air does Work: when hot and damp it rises, expands doing work against the surrounding atmosphere, so cools, water vapor condenses and rain falls.

Without the engineering concept of Work it's hard to see how anything works at all. When rowing, it makes things all too simple: pull long hard strokes and our boat will move, maybe even fast. In which case coach might decide to keep us aboard so that we can pull plenty like that and get fit.

I think the answer is simpler. He put W/min instead of W/(strokes/min). So, Stroke Power Index. I tend to write it incorrectly as W/stroke so I'm just as bad in a different way.

[jamesg]

I missed that, tx. W/min would be a rate of change of Power. I see my erg loses 8 - 10 W/year.

[Tobias Stoehr]

[JaapvanE]

I see my erg loses 8 - 10 W/year.

Time for a new erg then?

You are way more active than the far majority in your age group James. I firmly believe that any meter rowed is a good meter. I certainly hope to be as active as you are when I reach your age. You (and some much more experienced people in my rowing group on EXR) are an inspiration to get back on that erg again, regardless of the aches and pains we "youngsters" sometimes feel.

[jamesg]

If true, it's luck: good coaches, reasonable size and father a Thames waterman, so I started early. But now it's the erg, no doubt about it, just slightly odd to get hooked after meeting a simple piece of ironmongery.

Meeting, that's the word. Reminds me of something I once wrote and most will have felt...

Dusk fell, and there on the edge
between red sun and blue night
I think I saw a flash of green;
I'm sure it's there, it must be there,
mind knows.

Meeting you, there on the edge
between cool mind and hot blood
I think I felt a shock of love;
I'm sure it's there, it must be there,
heart knows.