Comparing efficiency at different stroke rates

[JaapvanE]

Also, as a tangential question, I see people referring to their stroke length - how are they measuring this, please?

Distance per stroke is easy to determine nowadays. Upon my request they increased the accuracy of the distance in the logbook. So simply download a recent session from the C2 website as csv, and import it into Excel (older sessions will still have too inaccurate rounded distances...). Each row in Excel is a stroke, the second column is the distance. So add a calculated cell behind it that substracts the current distance with the distance in the previous stroke. And there you are.

In ORM we calculate it independently as other apps want it as well, and that is a bit more precise as you are not substracting two rounded numbers. But it is sufficiently precise to be useable.

What I find interesting of this number is that it is directly related to stroke rate (as stroke rate and distance per stroke essentially are the key ingredients of pace), but it will show fatigue setting in, or choices being made during a session.

[Dangerscouse]

Also, as a tangential question, I see people referring to their stroke length - how are they measuring this, please?

It's definitely registered on Ergzone, and I also assume it will be on Ergdata. I'm not sure if it's an average or you can see it for every stroke, as I don't pay it any attention.

[Annisotropic]

Some of this thread is going over my head, but I appreciate the discussion.

Looking at it another way, I've just done 10k in 47 minutes, @18spm = 846 strokes.

If I could maintain the same power at 19spm, those 846 strokes would have taken 44min,31.6 seconds.

Converting pace 2.20.9 to watts gives 125, and (125x19)÷18 =131.94 W, so a pace of 2.18.4 and a 10k time of 46 min, 8.0 seconds - a very different result. Am I completely missing something by just counting the strokes?

Of course it's academic but it feels like an interesting way to set target paces/play with the numbers, especially for someone with a naturally low stroke rate - I want to be able to row at higher stroke rates without the stroke falling apart.

[Sakly]

Some of this thread is going over my head, but I appreciate the discussion.

Looking at it another way, I've just done 10k in 47 minutes, @18spm = 846 strokes.

If I could maintain the same power at 19spm, those 846 strokes would have taken 44min,31.6 seconds.

Converting pace 2.20.9 to watts gives 125, and (125x19)÷18 =131.94 W, so a pace of 2.18.4 and a 10k time of 46 min, 8.0 seconds - a very different result. Am I completely missing something by just counting the strokes?

Of course it's academic but it feels like an interesting way to set target paces/play with the numbers, especially for someone with a naturally low stroke rate - I want to be able to row at higher stroke rates without the stroke falling apart.

You expect the power and the speed to be linearly increasing, but they are not. See what jamesg has written before.

For equal stroke length and force, a 10% higher Rating (so 10% higher Power too) gives about 3% faster pace, due to the cube law: 1.03³ = 1.093

This is due to aero- and hydrodynamics which say that to go twice as fast we need eight times as much Power. This cube law applies to both fans and boats, which is why C2 machines have a fan.

The exact formula is not so simple: Watts = 2.8 V³ on a C2, and Pace is 500/V, with V in m/s.

Ergdata has a page where we can choose to see both Pace and Watts.

[Annisotropic]

Ahh, thanks - yes that makes a lot more sense! 🫣

[JaapvanE]

Looking at it another way, I've just done 10k in 47 minutes, @18spm = 846 strokes.

If I could maintain the same power at 19spm, those 846 strokes would have taken 44min,31.6 seconds.

Converting pace 2.20.9 to watts gives 125, and (125x19)÷18 =131.94 W, so a pace of 2.18.4 and a 10k time of 46 min, 8.0 seconds - a very different result. Am I completely missing something by just counting the strokes?

Yes, you are missing a lot here. Changing the stroke rate by definition changes the stroke itself.

In your first attempt, you assume you can maintain the same distance per stroke, and just increase the strokerate to go faster. That ain't going to fly as I explained earlier: increasing the strokerate and keeping the rest more or less similar will decrease the distance per stroke, simply because you reduce the traveltime to do it. It actually is a typical sign of fatigue in steady state sessions: a stroke 'shortening up' and stroke rate increasing to compensate (to keep pace the same).

This is what makes these Olympic rowers so extremely impressive: they row at huge stroke rates (38 to 42 SPM), while still maintaining the distance per stroke we normal mortals make (typically 10 meters). Even their distance per stroke drops as their rate goes up (but often that is factured in, and they still go a faster pace).

In your second calculation, you seem to think that a specific Wattage is somehow related to strokerate. It isn't in any way. It is calculated on a per-stroke basis as it reduces calculation complexity and it is more easily digested by humans, but its units aren't related to strokes at all (as it is in Watts, or Joules per second). In essence, it is just the average speed of the flywheel given a certain drag due to air-resistance. Nothing to do with strokes, at all.

Strokes are a way to put energy into the flywheel (as some put it: Work per stroke). Strokerate just determines the amount of times you do that per minute. Think of a flywheel as a kid on a swing: putting energy in on the wrong time will create havoc, doing it at the right time will increase the energy in the swing. It is the swing that determines the amount of times you can put energy into it, not you. Giving the swing a harder push will actually require you to wait a bit longer before the next push. When you push harder on the flywheel, you either have to wait a bit longer or be faster on the next drive to catch it. Getting that good rythm, where each and every time you catch the flywheel at the right speed for you is the way to going faster, not increasing the strokerate per se.

A more practical addition: what you see is that increasing the strokerate often makes the flywheel too fast for people, and they basically start missing the catch, resulting in a drop in pace, instead of an increase. A bit like pushing the swing while it is already away. Lightweight rowers are often more capable of being faster, but heavyweights often are not.

Concluding, you are looking for a structure that will never be there. Just experiment with strokerates and see what they bring to you.

[Mike Caviston]

These are surprisingly difficult to track down - none of the links in archived forum threads work for me. I eventually found them buried in the website of a UK rowing club, but they may have been updated since then. Mike Caviston - if you see this, are you willing to share them again here, please?

When I recently re-posted links to info about the Wolverine Plan, I noticed the link to the original "Wolverine Plan" document that had been on the C2 web site for years is no longer active, so I googled and found this:
https://www.rathburn.net/rowing/trainin ... 20Plan.pdf
But it turns out that does not include the Level 4 tables. A little further googling turned up this:
https://www.rathburn.net/rowing/trainin ... Tables.pdf
Note these are the tables from the original training aid I prepared for the UM team, but are not the updated/expanded tables I later developed including odd stroke rates (17-19-21-23-25 spm). My personal files with the complete tables are not at my fingertips, but somewhere on an external hard drive and will take me a while to track down. If I find them I am willing to share them again.

DISCLAIMER: The original "Wolverine Plan - Training Plan of the University of Michigan Women's Rowing Team" is NOT a complete or definitive representation of the Wolverine Plan. It is just a training aid I provided for that team at that time and later agreed to share with the public.

[Annisotropic]

JaapvanE, thank you for the explanation - this is a great forum where members are so generous with their time and knowledge .

[Annisotropic]

A little further googling turned up this:
https://www.rathburn.net/rowing/trainin ... Tables.pdf
Note these are the tables from the original training aid I prepared for the UM team, but are not the updated/expanded tables I later developed including odd stroke rates (17-19-21-23-25 spm). My personal files with the complete tables are not at my fingertips, but somewhere on an external hard drive and will take me a while to track down. If I find them I am willing to share them again.

DISCLAIMER: The original "Wolverine Plan - Training Plan of the University of Michigan Women's Rowing Team" is NOT a complete or definitive representation of the Wolverine Plan. It is just a training aid I provided for that team at that time and later agreed to share with the public.

I'd love to see them if you find them easily, but please don't go to any trouble.

And the tables shared here are much clearer and easier to read than the version I had found.

[harrythehamster]

Here is my zipped file in OneDrive which includes all WP docs that i have saved years ago. Also "updated" tables included.

https://1drv.ms/u/s!ApCPg7-AqbvVn2MQ49u ... _?e=y7WF4I

This pic shows what's included


Those 2 included simple BPP table files (copies in ods and xlsx formats) were shared here by user Arnie, just ignore them.

[iain]

Strokes are a way to put energy into the flywheel (as some put it: Work per stroke). Strokerate just determines the amount of times you do that per minute. Think of a flywheel as a kid on a swing: putting energy in on the wrong time will create havoc, doing it at the right time will increase the energy in the swing. It is the swing that determines the amount of times you can put energy into it, not you. Giving the swing a harder push will actually require you to wait a bit longer before the next push. When you push harder on the flywheel, you either have to wait a bit longer or be faster on the next drive to catch it. Getting that good rythm, where each and every time you catch the flywheel at the right speed for you is the way to going faster, not increasing the strokerate per se.

A more practical addition: what you see is that increasing the strokerate often makes the flywheel too fast for people, and they basically start missing the catch, resulting in a drop in pace, instead of an increase. A bit like pushing the swing while it is already away. Lightweight rowers are often more capable of being faster, but heavyweights often are not.

You lost me there I'm afraid. While I have known some strokes at very high stroke rates to accelerate the flywheel a lot less than I would like and I have only started accelerating the flywheel several inches into the stroke, this was only when sprinting and so irrelevant for most rowing and pretty much all training as at ratings below mid-40s even on DF 100 the flywheel has decelerated significantly during the recovery. A swing can only be pushed when moving away from you. The C2 can be accelerated at any time, it just requires the chain to be going faster than the flywheel (ignoring the gearing effect). It is more like starting to pedal a cycle after it has free-wheeled.

[JaapvanE]

A swing can only be pushed when moving away from you. The C2 can be accelerated at any time, it just requires the chain to be going faster than the flywheel (ignoring the gearing effect). It is more like starting to pedal a cycle after it has free-wheeled.

I admit the analogy isn't perfect. Your analogy is better. Indeed the chain needs to be faster than than the flywheel to become effective. That is why I made my point:

When you push harder on the flywheel, you either have to wait a bit longer or be faster on the next drive to catch it.

However, accelerating more to catch the flywheel at higher SPM, changes the force. And that was my point.

While I have known some strokes at very high stroke rates to accelerate the flywheel a lot less than I would like and I have only started accelerating the flywheel several inches into the stroke, this was only when sprinting and so irrelevant for most rowing and pretty much all training as at ratings below mid-40s even on DF 100 the flywheel has decelerated significantly during the recovery.

Based on the data I see (I see a lot of other rowing data for OpenRowingMonitor), you see that the drivelength typically shortens when stroke rate increases. At what SPM this happens differs from rower to rower (being a heavyweight seems to have a signigicant effect here). For me, it starts around 26 to 28 SPM, but some are around 32 to 36 SPM.

Having a shorter drive length can have several causes. It could be an indication of slightly missing the catch, making it a bad thing. But it could also be that people shorten the stroke to avoid weaker positions at the begin/end of the stroke, potentially making it a good thing. And as you say, even with a shorter drivelength you can go faster.

However, a shorter drivelength will reduce the distance to produce a certain power, thus requiring more force to generate the same power when compared to a longer stroke. Might not be a big deal, but again this violates the assumptions made by james:

For equal stroke length and force, a 10% higher Rating (so 10% higher Power too) gives about 3% faster pace, due to the cube law: 1.03³ = 1.093

My overall point is that this is an unrealistic assumption and that there is no simple formula to predict the pace at a higher strokerate. It depends too much on where you decrease the stroketime to get to that SPM, what happens as a consequence of it, and if you start missing (parts of) cathes. Especially with beginners you often see the opposite: by reducing the strokerate, they gain pace and efficiency as they start to use the recovery better to get more powerful catches (a key point RowAlong often makes).

[iain]

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.

[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.

[Sakly]

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.