Effects of the drag factor on performance and on physiological parameters

[hjs]

Roaming through a lot of scientific studies on ergometer rowing, I hit upon a paper from a Kinesiology group at Zagreb University, published in 2015, in which the drag factor was deliberately set at the lower end (90), in the middle (125) and near the maximum (200) to measure peak power.

...

An important and troublesome observation of this study is that for these short 'explosive' trials the power measured by sensors on the handle differs strongly from the power displayed on the C2 performance monitor "..our observations indicate that the power output values displayed on the Concept II rowing ergometer underestimates the true power output by a factor of ~3."
I scrutinized the paper whether they use the same definition of power as C2 (i.e. power profile in the drive is 'averaged' over the full duration of the stroke), but I couldn't find specifics. It is known from other studies that for short bursts the C2 power and power from sensors on the handle can differ strongly, but I have never seen a factor of 3.

I am an experienced cyclist and familiar with cycling power and my ability. I recently got my Concept2 and was expecting to see higher power rowing than cycling. I always thought rowers put out more power than cyclists because their VO2max is, typically, higher. I was appalled at how low the power was. So appalled that I contacted Concept2 about the discrepancy. They convinced me their algorithm was accurate. Now I am not so sure. Perhaps their algorithm takes into account losses between the oar handle and the water, representing the power to the water which is what is needed to calculate pace.

The actual number isn't that important from a training perspective as long as it is reliable and reproducible in that bigger is always better. But, from a research perspective it could be important.

Rowing versus cycling, two differences.
At rowing, if we use higher ratings, you maybe half of the time applay power, 1/1 drive/recovery, at lower ratings maybe 1/3 of the time, 1/2 drive/recovery. During cycling is way higher, close to 100%.
Second, rowing goes through the arms/hands, cycling throught the legs/ankle, arms being a much weaker link.

[frankencrank]

This was very interesting. I did not read the source materials, just your summary. Would the following conclusions that would apply to my situation (I consider myself in the active group) be correct:

1. higher DF equals higher watts vs lower DF, hence faster splits.

2. higher DF equals lower HR at same power output as lower DF.

3. higher DF results in lower rating vs lower DF.

If the above conclusions are correct, then I think I should experiment with a higher DF.

No, no and no.

The only certain thing a higher gives is slower movements. And the potential to row faster, but you still need the fitness and strenght to actually pull that off. There is no free lunch.

For short work/sprinting, the limiting factor is often speed of motion, a higher drag gives extra time to perform the stroke. A 100m almost always goes best at a higher drag.

Oh, crap!! Thought I was on to something. What's more troubling for me is coming to the wrong conclusion from the data & charts. Faulty thinking process. I guess that puts me that much closer to senility.

You were on to something. At any power your muscles will work best at a certain contraction rate. DF allows you to adjust that contraction rate to something better. There are two issues that need to be solved. You need to test to see what is best for you (stronger rowers will typically need higher DF's). And, then, you need to put in the time to train yourself to like that new feeling. That can take several weeks. Then, I would test again, because you have changed and so maybe your "best" setting.

The other issue, if you are also on the water, is changing the DF on the water to something better. That will involve changing the fulcrum point on your oars. Shorter handle length and longer blade length = increased DF.

[frankencrank]

As long as you think it, you are not.

Think about it, in the very big picture, drag can vary from close to zero up to indefinite high. At zero you can pull as fast as you can, but still put zero air. So no reading.
At indefinite heigh, we can’t move at all, so again, we can’t do any work again.

So there are 2 limitations, 1 the speed of motion and two, the amount of drag. We need to find something thats optimal between the two. Think the key is to found in the speed of motion, that should be kind of natural. To fast will mean inefficient, to slow will mean, to much force needed.

You figured it out. Drive speed is the one thing rowers can do to affect efficiency. it is generally ignored. Most are too fast. Only way to know is to test.

[frankencrank]

Roaming through a lot of scientific studies on ergometer rowing, I hit upon a paper from a Kinesiology group at Zagreb University, published in 2015, in which the drag factor was deliberately set at the lower end (90), in the middle (125) and near the maximum (200) to measure peak power.

...

An important and troublesome observation of this study is that for these short 'explosive' trials the power measured by sensors on the handle differs strongly from the power displayed on the C2 performance monitor "..our observations indicate that the power output values displayed on the Concept II rowing ergometer underestimates the true power output by a factor of ~3."
I scrutinized the paper whether they use the same definition of power as C2 (i.e. power profile in the drive is 'averaged' over the full duration of the stroke), but I couldn't find specifics. It is known from other studies that for short bursts the C2 power and power from sensors on the handle can differ strongly, but I have never seen a factor of 3.

I am an experienced cyclist and familiar with cycling power and my ability. I recently got my Concept2 and was expecting to see higher power rowing than cycling. I always thought rowers put out more power than cyclists because their VO2max is, typically, higher. I was appalled at how low the power was. So appalled that I contacted Concept2 about the discrepancy. They convinced me their algorithm was accurate. Now I am not so sure. Perhaps their algorithm takes into account losses between the oar handle and the water, representing the power to the water which is what is needed to calculate pace.

The actual number isn't that important from a training perspective as long as it is reliable and reproducible in that bigger is always better. But, from a research perspective it could be important.

Rowing versus cycling, two differences.
At rowing, if we use higher ratings, you maybe half of the time applay power, 1/1 drive/recovery, at lower ratings maybe 1/3 of the time, 1/2 drive/recovery. During cycling is way higher, close to 100%.
Second, rowing goes through the arms/hands, cycling throught the legs/ankle, arms being a much weaker link.

Muscle physiology doesn't change because you get on a rowing ergometer vs a bicycle ergometer. The goal of both sports is to get as much muscle work done to either the water or the road. Training in and of itself improves muscle capability but does nothing to address efficiency. VO2max is a measure of the amount of muscle mass being used. Rowers typically have higher VO2max than cyclists. Therefore, one would expect that rowers are generating more power. If they are not then they are very inefficient.

Let me add. While it would appear that cycling involves constant power application the individual muscles involved have similar power/rest ratios as seen in rowing. Few muscles contract with any vigor for more than a 30-40% of the cycle.

[hjs]

Muscle physiology doesn't change because you get on a rowing ergometer vs a bicycle ergometer. The goal of both sports is to get as much muscle work done to either the water or the road. Training in and of itself improves muscle capability but does nothing to address efficiency. VO2max is a measure of the amount of muscle mass being used. Rowers typically have higher VO2max than cyclists. Therefore, one would expect that rowers are generating more power. If they are not then they are very inefficient.

Let me add. While it would appear that cycling involves constant power application the individual muscles involved have similar power/rest ratios as seen in rowing. Few muscles contract with any vigor for more than a 30-40% of the cycle.

Rowers are not inefficient, the rowing motion is, and of course the goal is to use as much as possible muscle, but still the weakest link makes the strenght of the chain.
Other point, given the much lower frequency, peak power should be a lot higher on the rower. Max sprinting on the rower will at 60 spm, on a bike A good bit higher.
Recovery on the rower, does cost energy, buy nothing goes into the water/chain. 100% not usefull, but still needs to be used.
With cycling, the leg either pushes or pulls, everyhing goes into the chain. No other movements.

And if the movement should not matter, why do cross country skiers have the highest Vo2 maxes?

[frankencrank]

Muscle physiology doesn't change because you get on a rowing ergometer vs a bicycle ergometer. The goal of both sports is to get as much muscle work done to either the water or the road. Training in and of itself improves muscle capability but does nothing to address efficiency. VO2max is a measure of the amount of muscle mass being used. Rowers typically have higher VO2max than cyclists. Therefore, one would expect that rowers are generating more power. If they are not then they are very inefficient.

Let me add. While it would appear that cycling involves constant power application the individual muscles involved have similar power/rest ratios as seen in rowing. Few muscles contract with any vigor for more than a 30-40% of the cycle.

Rowers are not inefficient, the rowing motion is, and of course the goal is to use as much as possible muscle, but still the weakest link makes the strenght of the chain.
Other point, given the much lower frequency, peak power should be a lot higher on the rower. Max sprinting on the rower will at 60 spm, on a bike A good bit higher.
Recovery on the rower, does cost energy, buy nothing goes into the water/chain. 100% not usefull, but still needs to be used.
With cycling, the leg either pushes or pulls, everyhing goes into the chain. No other movements.

And if the movement should not matter, why do cross country skiers have the highest Vo2 maxes?

I think it matters how or where you measure rowing inefficiency. In cycling the power difference between what is put into the pedal and what makes it to the road is quite small. My guess is the power difference between what the rower puts into the handle and what makes it to the water (to actually propel the boat) is much larger (losses include boat, oar lock, and oar flexing plus blade slippage in the water - something that cyclists never see on pavement. If you add in losses due to rower slide movement they would be even bigger.). My guess is Concept2 made the decision to show what they calculate to be the power to the water (with the resulting pace) instead of the power the rower puts into the handle. From a training perspective it makes no difference. It was just shocking to me to see how low the power displayed is for how hard it feels.

Cyclists probably use the same amount of leg muscle mass as rowers (maybe even more) because they incorporate the antagonist muscles to the antigravity muscles (pretty much all a rower uses). They divide the work between more muscles. Doing so allows them to increase power without incorporating many fast-twitch fibers in the power generation. Rower 6-8 minute race efforts are much more forgiving of fast-twitch incorporation.

Peak power is probably much higher in the rower. What really matters though is the average power. The same holds true for cycling. Some cyclists think all you need do is push harder but pushing down is only effective for about 25% of the entire circle (50% when both legs are considered. This is slightly more than the rower. But, the rower, pushing harder, needs more recovery time between efforts. An, interesting fact, when pushing hard no blood flow occurs in the muscle (in fact, all the blood is pushed out of the muscle. After contraction, bloodlust return to the muscle before any oxygen delivery can occur. Lower stroke rates maximize that oxygen delivery percentage. That is another reason higher stroke rates are more fatiguing.

Actually, on the bike everything doesn't go into the chain. There is an energy cost just to make the pedals go around. Most of this cost comes from pumping the thigh up and down just like the rower going back and forth. The energy cost varies with the square of the cadence. The power cost varies with the cube of the cadence.

Nothing is as simple as it seems.

[Nomath]

...
I always thought rowers put out more power than cyclists because their VO2max is, typically, higher. I was appalled at how low the power was. So appalled that I contacted Concept2 about the discrepancy. They convinced me their algorithm was accurate. Now I am not so sure. Perhaps their algorithm takes into account losses between the oar handle and the water, representing the power to the water which is what is needed to calculate pace.

The actual number isn't that important from a training perspective as long as it is reliable and reproducible in that bigger is always better. But, from a research perspective it could be important.

The discrepancy of a factor of 2-3 that appeared in the paper from Zagreb University (2015), is mostly resolved. The study from Robert Sprague at Austin University in Medicine & Science in Sports & Exercise (2007) measured nearly the same peak power as Zagreb and it was clear that their definition of peak power is the average power during the drive phase only. When I mailed this to Prof. Goran Markovic in Zagreb -they didn't mention the Austin study in the References- , he agreed that Zagreb probably also calculated the power for the drive phase only. C2 calculates power as work during the drive phase divided by the total time for drive+recovery phase. The recovery phase is mostly 1-2 times longer than the drive phase, which explains the factor of ~3.

Since you are interested in oxygen transport and in the difference in power on a cycle ergometer and a rowing ergometer, I suggest that you read "Pulmonary O2 uptake on-kinetics in rowing and cycle ergometer exercise" by Claire L. Roberts et al. in Respiratory Physiology & Neurobiology (2005). You will see that the peak work rate for cycling is about 18% higher and at the Gas Exchange Threshold the oxygen uptake by rowers is about 5% higher.
This suggests that there is a significantly greater O2 cost of exercise during rowing than for cycling.

The case for an independant calibration of the C2 power measurement is still alive. I hope that in next year we will see publications on this topic from the University of Ulm. I am sure they will tackle this issue with German thoroughness.

[frankencrank]

This suggests that there is a significantly greater O2 cost of exercise during rowing than for cycling.

Isn't that the same as saying Rowing is less efficient? And, that, I presume, doesn't include the losses from the oar handle to the water.

[Nomath]

......
My guess is Concept2 made the decision to show what they calculate to be the power to the water (with the resulting pace) instead of the power the rower puts into the handle.

Concept2 truely calculates the power input into the flywheel. There is no power to the water in case of an indoor ergometer. Yes, in converting power to an imagined boat velocity (500m pace), they might include other factors. But power measured by the C2 erg is very comparable to power on a cycling erg, namely based on hard physics. In this case : deceleration of the flywheel due to air resistance.

Between the power put into the handle and the power input measured at the flywheel there are drivetrain losses (chain + sprocket wheel). The paper 'Power Responses of a Rowing Ergometer: Mechanical Sensors vs. Concept2 Measurement System" by S Boyas in Int. J Sports Med, 2006, estimates these drivetrain losses at approximately 25W, independent of power.

What a force sensor and displacement sensors on the handle cannot measure is the power for moving the body back and forth.

[frankencrank]

I suggest that you read "Pulmonary O2 uptake on-kinetics in rowing and cycle ergometer exercise" by Claire L. Roberts et al. in Respiratory Physiology & Neurobiology (2005).

I have requested the paper. I read the abstract. They report what I would expect from an oxygen transport perspective.

[frankencrank]

......
My guess is Concept2 made the decision to show what they calculate to be the power to the water (with the resulting pace) instead of the power the rower puts into the handle.

Concept2 truely calculates the power input into the flywheel. There is no power to the water in case of an indoor ergometer. Yes, in converting power to an imagined boat velocity (500m pace), they might include other factors. But power measured by the C2 erg is very comparable to power on a cycling erg, namely based on hard physics. In this case : deceleration of the flywheel due to air resistance.

Between the power put into the handle and the power input measured at the flywheel there are drivetrain losses (chain + sprocket wheel). The paper 'Power Responses of a Rowing Ergometer: Mechanical Sensors vs. Concept2 Measurement System" by S Boyas in Int. J Sports Med, 2006, estimates these drivetrain losses at approximately 25W, independent of power.

What a force sensor and displacement sensors on the handle cannot measure is the power for moving the body back and forth.

I understand what they are doing and they convinced me it is (supposedly) accurate. I would be happier if it were done in a more conventional fashion.

I will have to read that paper. chain losses on a bicycle are estimated to be 2-5% of the power, depending upon how clean the chain and system is. Those losses supposedly vary with power. 25W loss on someone rowing 100 watts is huge for chain loss. My guess is the shock cord comprises a bit of that loss but still, 25W!!!

It would be possible to measure those rower movement losses if stretcher forces were also measured and compared to handle forces. Stretcher forces include all the driving forces as it is not possible to either pull the handle or move the rower without putting force on the stretcher.

[frankencrank]

The paper 'Power Responses of a Rowing Ergometer: Mechanical Sensors vs. Concept2 Measurement System" by S Boyas in Int. J Sports Med, 2006, estimates these drivetrain losses at approximately 25W, independent of power.

I have taken a look at that paper. Nowhere do the authors claim this 25 W difference is due to chain losses that I saw. It could be shock cord losses but to see 25W it would require a shock cord force of 10 lbs being pulled 1 m 30 times a minute (22W by my calc). Shock cord pull doesn't seem that high to me but I haven't measured it. If it were shock cord losses I would expect the expert losses to be greater than the novice losses (they are pulling the chain further in the same time) but they are not. This difference is hard to explain.

I simply don't understand why Concept2 didn't simply measure the strain on the support where the cog is. It would be easy enough to then know the horizontal component add that to the speed of the chain (which they already measure) and they have actual power. It is what it is I suppose.

[frankencrank]

Here is the result of one reported experimental subject result today. I have asked my participants, before starting, to run through increasing drag factors looking specifically at how it changes drive speed and watts. After this they will go up more slowly to allow for some adaption. Here is what the report was. He did 1000 m intervals with about 1.5 min rest between. (blanks were not reported)

DF. Drive Speed. Power
131 --- 2.18 --- 307
142 ----------- 312
169 --- 2.14 --- 324
191 --- 1.99 --- 328
204 --- 1.92 --- 334
127 ----------- 318
Drive length didn't change (1.48 mostly)
"RPE was tough on 204df and this felt really heavy, but up to 169df it wasn't too bad. I struggled to get the same power when I dropped it down to 127df from 204df"

RPE was tough because he wasn't adapted to the stresses. Didn't keep him from improving though. Then when DF got "easier" he struggled. What would he do if he was adapted to higher DF? What DF would it take to cause his power to drop?

Please note that a 57% increase in DF resulted in a 13% drop in drive speed and an almost 10% increase in power.

Comments?

[hjs]

Muscle physiology doesn't change because you get on a rowing ergometer vs a bicycle ergometer. The goal of both sports is to get as much muscle work done to either the water or the road. Training in and of itself improves muscle capability but does nothing to address efficiency. VO2max is a measure of the amount of muscle mass being used. Rowers typically have higher VO2max than cyclists. Therefore, one would expect that rowers are generating more power. If they are not then they are very inefficient.

Let me add. While it would appear that cycling involves constant power application the individual muscles involved have similar power/rest ratios as seen in rowing. Few muscles contract with any vigor for more than a 30-40% of the cycle.

Rowers are not inefficient, the rowing motion is, and of course the goal is to use as much as possible muscle, but still the weakest link makes the strenght of the chain.
Other point, given the much lower frequency, peak power should be a lot higher on the rower. Max sprinting on the rower will at 60 spm, on a bike A good bit higher.
Recovery on the rower, does cost energy, buy nothing goes into the water/chain. 100% not usefull, but still needs to be used.
With cycling, the leg either pushes or pulls, everyhing goes into the chain. No other movements.

And if the movement should not matter, why do cross country skiers have the highest Vo2 maxes?

I think it matters how or where you measure rowing inefficiency. In cycling the power difference between what is put into the pedal and what makes it to the road is quite small. My guess is the power difference between what the rower puts into the handle and what makes it to the water (to actually propel the boat) is much larger (losses include boat, oar lock, and oar flexing plus blade slippage in the water - something that cyclists never see on pavement. If you add in losses due to rower slide movement they would be even bigger.). My guess is Concept2 made the decision to show what they calculate to be the power to the water (with the resulting pace) instead of the power the rower puts into the handle. From a training perspective it makes no difference. It was just shocking to me to see how low the power displayed is for how hard it feels.

Cyclists probably use the same amount of leg muscle mass as rowers (maybe even more) because they incorporate the antagonist muscles to the antigravity muscles (pretty much all a rower uses). They divide the work between more muscles. Doing so allows them to increase power without incorporating many fast-twitch fibers in the power generation. Rower 6-8 minute race efforts are much more forgiving of fast-twitch incorporation.

Peak power is probably much higher in the rower. What really matters though is the average power. The same holds true for cycling. Some cyclists think all you need do is push harder but pushing down is only effective for about 25% of the entire circle (50% when both legs are considered. This is slightly more than the rower. But, the rower, pushing harder, needs more recovery time between efforts. An, interesting fact, when pushing hard no blood flow occurs in the muscle (in fact, all the blood is pushed out of the muscle. After contraction, bloodlust return to the muscle before any oxygen delivery can occur. Lower stroke rates maximize that oxygen delivery percentage. That is another reason higher stroke rates are more fatiguing.

Actually, on the bike everything doesn't go into the chain. There is an energy cost just to make the pedals go around. Most of this cost comes from pumping the thigh up and down just like the rower going back and forth. The energy cost varies with the square of the cadence. The power cost varies with the cube of the cadence.

Nothing is as simple as it seems.

Its certainly not simple.

But key is, rowing is a linear movement, you move from A to B, at this point you ad energy to the system, from there you go back from B to A. No energy goes into the system, and it does cost energy to do so.
Cycling bring cyclical, has no begin/end energy gets added during the whole time, no energy is waisted in “false” movements.

[Nomath]

Isn't that the same as saying Rowing is less efficient? And, that, I presume, doesn't include the losses from the oar handle to the water.

Yes, a recent study by Lindenthaler ('Differences in Physiological Responses During Rowing and Cycling Ergometry in Elite Male Rowers', in Frontiers in Physiology, 2018) estimated 18.1% Gross Mechanical Efficiency at 50% of VO2max on a Concept2 and 22.1% on a WattBike. At 75% of VO2max, the GME on a Concept2 was 18.6% and on a WattBike 22.6%. So there is about 4% difference in GME between the two activities. Note that the participants were elite rowers who regularly used a cycle ergonometer, not elite cyclists. Part of the difference should be attributed to the way power is measured on a C2, about which the authors express some reservations.

Also interesting is the observation "it was noted how quickly rowers in this investigation recovered from maximal WattBike exercise when compared with maximal C2 exercise, despite similar VO2peak, Rating of Perceived Exertion and Blood lactate."