Dynamic C2 vs. the "D", musing of Recent Dynamic Purchaser

[Citroen]

That's fair, and it makes perfect sense.

Blame the folks who report your posts for moderation.

[JaapvanE]

Why lower Lactate? Lower efficiency for same power output should lead to more work done so more Lactate, not less. Or is the higher rating allowing better ventilation so L removal at a higher rate?

Or is the work done by different muscles? When you get a better distribution of the work done over the body, in total you might work harder, but individual muscles are kept within certain limits more easily? (just guessing here...)

[Sakly]

Why lower Lactate? Lower efficiency for same power output should lead to more work done so more Lactate, not less. Or is the higher rating allowing better ventilation so L removal at a higher rate?

Or is the work done by different muscles? When you get a better distribution of the work done over the body, in total you might work harder, but individual muscles are kept within certain limits more easily? (just guessing here...)

Not different muscles, as the stroke pattern should stay the same.
Used muscles are not recruited the same way as the load in each stroke is less intense (comparing same wattage output). Lower intensity leads to better muscle endurance and lower lactate, as lactate production is highly depending on intensity. Also more of the slow twitch fibers can be recruited on lower intensities, which are known to use lactate for energy, so the lactate removal could be better based on that.

[Ron Ginsberg]

I'm the guy who started this thread with my experiences comparing a well maintained 20004 model D with a Dynamic. I recounted how I was trying to decide whether to purchase a second D, for a different location, or a Dynamic. In my post, I recounted how I made the decision to buy a Dynamic and why I was so pleased that I did. However, I did not mention that I also researched online, but did not have any direct experience with, dynamic designs produced by other makers.

While I know this is an oversimplification, what I learned is that the more mass you are moving with the foot stretcher, the more like a boat of similar mass. It almost seemed to me that if you could put weights on the stretcher unit to match boat mass, you would have the most accurate rowing simulator for your boat. In any event, it seems my review and research indicated that some of these machines gave even more of an online feel for on water rowing than the Concept Dynamic. Various explanations were offered for why Concept 2 designed their Dynamic the way they did, but for my purposes, and certainly for the purposes of discussion on this Concept 2 sponsored and monitored forum, these explanations are irrelevant.

I concluded my research and decided that a Concept Dynamic was a great leap forward from the model D in terms of on water feel. And while there might be alternatives, I knew I wanted to go with the company whose robust quality and service had satisfied me for so many years. So I purchased a Dynamic.

Getting to the point, what is relevant is how to evaluate the studies of efficiency. It seems that the study in question was performed on rowing a machine that was not a Concept Dynamic. It was one of these other Dynamics with more moving mass than the Dynamic. In the Concept Dynamic, the flywheel housing and mass is stationary. On the other designs, the entire flywheel and mechanism is incorporated into the moving mass of the foot stretcher. So these machines are very different. We need to compare apples to apples.

To me the result is that for our purposes, we need to reference a well conducted study of rowers on Model D's and Concept Dynamics. Of course comparing the Concept Dynamic to other styles of Dynamics is also of more general interest.

I hope we can all maintain civil and respectville discourse on this.

[Slidewinder]

I'm the guy who started this thread

Getting to the point, what is relevant is how to evaluate the studies of efficiency. It seems that the study in question was performed on rowing a machine that was not a Concept Dynamic. It was one of these other Dynamics with more moving mass than the Dynamic. In the Concept Dynamic, the flywheel housing and mass is stationary. On the other designs, the entire flywheel and mechanism is incorporated into the moving mass of the foot stretcher.

To me the result is that for our purposes, we need to reference a well conducted study of rowers on Model D's and Concept Dynamics. Of course comparing the Concept Dynamic to other styles of Dynamics is also of more general interest.

I hope we can all maintain civil and respectful discourse on this.

I fully agree with your sentiment regarding respectful discourse.

The study linked by Nomath does compare the C2 stationary with the C2 Dynamic. It is easy to miss this because it opens with, "The aim of this study was to compare the physiological responses and rowing efficiency on two different ergometers: The Concept 2 stationary (Model D) versus dynamic ergometers." But then later in the paper under 'Methods' it states, "Two rowing ergometers with different designs were used: a stationary (fixed-foot stretcher) Model D Concept 2, and a dynamic (free-floating stretcher) Dynamic Concept 2."

The lower rowing efficiency of the users in the study related to the C2 Dynamic. But as you state, the C2 Dynamic is a different mechanical design than other available dynamic ergometers. Therefore, from the study, no conclusions can be drawn about the rower efficiency of all dynamic rowing ergometer designs.

[Slidewinder]

While I know this is an oversimplification, what I learned is that the more mass you are moving with the foot stretcher, the more like a boat of similar mass. It almost seemed to me that if you could put weights on the stretcher unit to match boat mass, you would have the most accurate rowing simulator for your boat.

Your thoughts on the moving mass agree with Casper Rekers' original patent for a 'Dynamically Balanced Rowing Simulator' (expired 2012). The most realistic OTW feel is obtained when the mass being moved at the foot stretcher is close to the mass of a single rowing shell - if the user is training for a single scull. If training for a double, then the most realistic feel would be obtained if the mass moved at the foot stretcher is the weight of a double scull divided by two. For single scull replication somewhere between 30 to 40 pounds at the foot stretcher. On the C2 Dynamic, Concept 2 added a steel plate inside each foot rest. I don't know what the entire foot rest assembly weighs on the C2 Dynamic. I suspect it is a bit on the light side. If you are ambitious and mechanically adept, you could remove the assembly and weigh it. If it is less than a single scull you could add weight. I suggest a cloth bag of sand inside the remaining space, left and right. It would be easy to adjust the weight by adding or removing sand. Of course, the more mass moved at the foot stretcher, the seat will move more relative to ground, which may or may not result in the seat hitting the stops.

In dynamic designs in which the forward moving mass is comprised of the footrests, flywheel and return mechanism, this assembly and the user are a dynamically balanced self-contained system. On the C2 Dynamic, the footrest assembly and user are not self-contained, because the pull cord/chain is linked to a pulley fixed to the frame. I don't know how this affects the performance characteristics, pro or con, but it is a reasonable hypothesis that it would have some effect.

[Ron Ginsberg]

Thanks so much for pointing this out to me. I stand corrected. I missed the very important fact that the Concept Dynamic WAS included in the study. And the study was between only the Concept D and the Concept Dynamic. If I understand you correctly (it's been a while since I read the research paper) the study concluded that the rowers included in the study were less efficient on the Dynamic. In my own experience, I'd say without any sort of measurement, I couldn't tell you. But it is very interesting and I would say bears further study. It would also be interesting to see how different dynamic designs compare to each other.

Sidewinders comment above explains how I learned that different Dynamic machines are constructed differently and may not perform alike. My conclusion at the time was since I wasn't a water rower attempting to train on an exact simulator, and I trusted the Concept brand and reputation, a Concept Dynamic would bring me closer to the water, improve my technique, and give me the peace of mind of owning and using a well made Concept product.

[Slidewinder]

Thanks so much...

Thanks for the thanks, Mr. Ginsberg. It is a pleasure to receive a friendly reply on this site. - from one septuagenarian baby boomer to another.

[Nomath]

...
Surely these scientists should know how to spell Oxide.

It’s a jolly practise to leave something in a manuscript for the nitpickers.

[Ombrax]

It’s a jolly practise to leave something in a manuscript for the nitpickers.

I see what you did there. ; )

[jamesg]

Like rats, if you see one nit at first glance, there's a hundred hiding. So I looked for others; and found they seem to think that lower "efficiency" causes lower Lactate.