Just did an hour row, why is my watts so much lower than my bike?

[kini62]

Just did and hour row yesterday for the first time in about 18 months. Ended up at 156 watts average. That's around 55 watts less than my 1 hour on the bike. Why would there be such a large difference?

Thanks

[btlifter]

Couple of reasons:
1. You said it was your first time doing it in 18 months. Rowing is far more texhnique-dependent than the bike erg. Time off of the erg, or even time off of working st a particular pace/intensity, will negatively impact your performance much more on the rower than on the bike.
2. Actually lower wattage - particularly for longer duration pieces, will be lower for most people on the rower than the bike. I won't try to speak to the physiology of this, but it's common. My discrepancy for 1 hour is about 40 watts as well.

[kini62]

Thanks. I've not been off the erg at all just don't do the meters like before. I do nearly all my 1 hour and longer cardio on the bike. Just thought it would be a little closer.

[Tsnor]

Also

The rowing stroke is less efficient than cycling (even for athletes trained to both). Your body produces the same wattage, more waste energy with rowing (heat) and less wattage goes into the measured work. O2 consumption per watt of output in rowing is higher.

Here's a paper on it. https://pubmed.ncbi.nlm.nih.gov/3193864/ "A comparison of energy expenditure during rowing and cycling ergometry" "...Results indicated that energy costs for rowing ergometry was significantly higher than cycle ergometry at all comparative power outputs including maximum levels. .."

you'll see other threads on this if you want more info: ex viewtopic.php?t=11299

[Carl Watts]

Rowing is way harder to produce the power.

The RowedBiker App thats used with Zwift if you want to use the Erg for "Cycling" allows you multiple options to boost the Wattage. I used the 50% boost option so it takes my typical 200W Erg to 300W on the Bike.

[jamesg]

Why would there be such a large difference?

When training on the erg, the pull-recovery time ratio is roughly 1:3, since the pull time is about 0.7s; and 60/2.8 = 21 spm.

This implies that at 156 W shown on PM, the average power during the pull is about 600W and peak pull maybe 800W. It could be difficult to pull any harder than that for 1200+ strokes.

Peak handle speed 2m/s, pull 40 kg: 2 * 40 * g = 780 W; which even I do normally, if I decide to do it.

This is the characteristic of rowing that obliges us to learn to row, and lets us get the results we want. But we have to decide just what we want to train.

[Carl Watts]

Your also moving your entire bodyweight all the time and the legs are driving together so there is no assist with one helping the other.

The whole rowing action is inefficient compared to the bike and your also using even more of the upper body muscles including your core to transfer the power from the legs through the body to the handle.

I guess the best way is to use your heartrate and look at how the Watts on the bike compare to the Watts on the rower for the same heartrate during a steady state session.

[Nomath]

Others, above, have mentioned several qualitative reasons why your watts on a BikeErg are significantly higher than on a RowErg. However, they have not adressed the magnitude of the difference: 211 W versus 156W in your measurement (N=1).

Last year a quantitative study Physiological responses on the Concept II BikeErg and Concept II RowErg in well-trained male rowers was published that addresses physiological reasons and some mechanical reasons:
https://www.researchgate.net/publicatio ... ale_rowers
If you look at the top-left graph in Figure 1, you can see that there is a nearly constant difference of 50W between cycling and rowing, independent of the intensity (measured by oxygen consumption).

I find the statement in the Conclusion of this study ...confirm the notion that the Concept II RowErg is likely to under-report PO during the recovery phase of the rowing stroke a bit odd. The RowErg, just as the BikeErg, measures the power input to the flywheel. When the clutch is not engaged, which is the case for the RowErg during the recovery and also for a short period after the catch, the measured power input is zero.

In 2006 Boyas and co-authors compared the power measurement by C2 (i.e. from sensors on the flywheel) and the power determined from two mechanical sensors on the handlebar, a force sensor and a position sensor. They found that the C2 measurement was consistently 25W lower than the result of the mechanical sensors, over a broad range of input power (see Fig. 1A and 1B in the Boyas paper). This discrepancy is largely not due to the movement of the rower during the recovery, but probably caused by losses in the drive mechanism of the RowErg.

So, roughly, from the 50W difference about half may be due to physiological reasons related to differences in body kinematics and half due to mechanical losses in the drive mechanism of the RowErg.

[kini62]

My average HR over the hour for both is about the same. Within a few beats for the hour.

Thanks for the responses, they helped me understand the difference. I always assumed watts were watts.

[Carl Watts]

Watts are Watts if they are measured accurately. The differences is your bodies ability to produce them.

You can improve on some inefficacies on the rower, like rating only as high as you need for a given pace. There is now most noticeably a correlation to my spm and pace. The losses just moving your body up and down the slide become significant at higher ratings but conversely the lower the rating the higher the peak Watts on the drive which is also bad. There is definitely a sweet spot in between where your HR is a minimum for a given pace.

[jamesg]

Ended up at 156 watts average. That's around 55 watts less than my 1 hour on the bike.
My average HR over the hour for both is about the same. Within a few beats for the hour.

This could be interpreted in many ways; but it's hard to see how and where you could lose 25% of your power. What rating do you use on the rowerg?

[Carl Watts]

Ended up at 156 watts average. That's around 55 watts less than my 1 hour on the bike.
My average HR over the hour for both is about the same. Within a few beats for the hour.

This could be interpreted in many ways; but it's hard to see how and where you could lose 25% of your power. What rating do you use on the rowerg?

25% would be on the low side it's higher than that.

The RowedBiker App used for connecting your C2 Erg to Zwift recommends a 30% boost setting for the Watts conversion.

The rower is terrible there are no gears on it either to keep the power delivery at a point it's better for your HR and pace I mean you don't ride a single speed bike except in very specific events.

Your not losing Watts your body has to work harder to produce the same Watts as the bike pretty logical really.

[Nomath]

...
Your not losing Watts your body has to work harder to produce the same Watts as the bike pretty logical really.

Your body has to work harder on a RowErg to produce the same Watts (on the PM!) not only because of the intermittant body movements that require power, but also because more power is lost on the rowing machine.

If you really want to learn why, you should read the paper that I linked in my previous post. It can be downloaded free of charge.

The graph below is copied from Figure 1 in this paper. It shows that for the same oxygen consumption rate, the BikeErg (solid line) measures about 50W more power than the RowErg (dashed line).



In the full Figure 1 you can also find a graph (bottom-left) of the heart rate as a function of oxygen consumption. In this graph the experimental curves of BikeErg and RowErg overlap!
If we take oxygen consumption as a measure of fuel supply to the body and the heart rate as a measure of how hard the body is working, then the supposition could well be that the power produced by the body is less fully converted on a RowErg compared to a BikeErg. That is, the discrepancy is not due to the body, but due to processes outside the body!
There are at least two likely power loss mechanisms on a RowErg:
1. During the recovery the body is accelerated and decelerated on the slide. Probably some of the kinetic energy is lost.
2. As Boyas showed, there is about 25W loss between power measured at the handlebar and power measured at the flywheel.

[Carl Watts]

Lets just agree to disagree.

The next argument will be that you should be able to run at 15kmhr and cycle at 15kmhr with the same HR.

The OP has already worked it out. 200W on the rower is the same as 200W on the bike as long as the system measuring it is accurate. The difference is you HR is higher on the Erg than the bike to get that 200W into the machine due to your bodys efficiency due to the different muscles used and the way that they are employed to do the work.

30% is about right it would appear. This would just be a generalized conversion factor I suspect for someone who is a typical cyclist, so much lighter than a HW rower at about 75Kg. The heavier you are the worse the static rower losses become. Sitting on your static bike trainer it doesn't matter if your 75Kg or 125Kg.

The primary reason I would move to slides for the C2 Erg is that my performance would immediately increase and it would be significant.

[ArmandoChavezUNC]

Not looking to get into the weeds of this argument but as a data point of n=1, my watts on the erg are higher than my watts on the C2 bike. However, on my smart trainer, my watts on the bike are higher. The C2 bike watts are IMO not 1:1 to non-C2 bike watts. For one, you lose power by not having clip-on pedals. Two, the mechanism of producing power is via a chain and gear in one, a chain and fan in the other.

I wouldn't worry about it too much.