Erg wattage vs Cycling wattage

[jlawson58]

I found a thread from a few months ago that talked about this topic but nothing definitive was even shown concerning the relative differences between cycling and erging power outputs.

Can anyone point me to some scientific literature that compares the two?

How about those of you who do both (Goblin maybe?) How do your values compare? Someone has suggested a 25w difference but for me it is WAY more than that. Now, granted, I am much less fit when it comes to rowing than I was for cycling, but my differences are huge. For 7 min erging i do 258 vs 330-350 for cycling. I do 210w for 40 min yet I used to do 310-330 for an hour cycling.

Finally, on a related note, how accurate is the wattage measured by a C2, and do they ever change? Cycling power meters (SRM, PowerTap) use strain gauges and have to be recalibrated occasionally. I would think that measuring the power based on inertia of the flywheel etc would change over time as the bearings wore out or the amount of grease on the flywheel axle changed.

[Bob S.]

I would think that measuring the power based on inertia of the flywheel etc would change over time as the bearings wore out or the amount of grease on the flywheel axle changed.

It is based on the rate at which the flywheel slows down, so it doesn't matter. Any extra drag like bad or dry bearings would increase the rate of slowing and would thus be accounted for. What is not taken into account is any extra drag of the seat, like bad bearings in the seat wheels.

Bob S.

[Nosmo]

IFinally, on a related note, how accurate is the wattage measured by a C2, and do they ever change? Cycling power meters (SRM, PowerTap) use strain gauges and have to be recalibrated occasionally. I would think that measuring the power based on inertia of the flywheel etc would change over time as the bearings wore out or the amount of grease on the flywheel axle changed.

The power measured by the C2 is very accurate and does not need recalibrating. The only thing the PM needs to know is the moment of inertia of the fly wheel, which does not change, and the drag on the wheel which is measured. Even if the timer in the PM was fast or slow, this would cancel out in the equations.

However it is the power delivered to the flywheel, not the power generated by the rower. Rowing is an inefficient movement and cycling is very efficient. The erg does not measure the energy lost by moving your body; neither does a cycling power meter. However when cycling you are only loosing energy lifting your rear leg (which is mostly recovered) and in the friction in your joints. In rowing not only is the friction in the joints much higher but you loose a lot of energy moving your whole body. The 25W figure was from a measurement of force on the chain. Didn't read the study and I'm not sure why they don't give the same reading.

As for the difference between the erg and cycling. It will vary from person to person. You have your numbers. They don't sound too atypical. As you erg more the difference will decrease. IT will also decrease if you cycle much less.

[former lightweight]

What Nosmo said... there are going to be huge differences between the two. Here are my numbers for my best 30 minute efforts in rowing v cycling.

Rowing - 309 watts (70 kg) - 5 years ago
Cycling - 382 watts (68 kg) - 1 week ago

When I did the effort on the erg I was in very good shape so maybe I could push that number to 315 now, but I doubt it. The inefficiency of the erg also manifests itself in a higher VO2 max with elite rowers vs. other endurance sports. If you think about it, creating 1 watt on the erg requires the utilization of much higher percentage of your muscular system, therefore more oxygen. It is also why elite/pro cyclists are frightening when they have VO2s in the 85+ range, as they're only really utilizing the muscles in their lower extremities.

[annacico]

https://pubmed.ncbi.nlm.nih.gov/7957155/

If you look around this site, there is quite a bit of literature on various comparative studies.

[Nomath]

More recent :
Joshua R. Lindenthaler, e.a. : Differences in Physiological Responses during Rowing and Cycle Ergometry in Elite Male Rowers, in Frontiers in Physiology, July 2018, Volume 9, Article 1010

Kirstie J. Turner and Anthony J. Rice : Physiological responses on the Concept II BikeErg and Concept II RowErg in well-trained male rowers, in Int. J. of Sports Science &Coaching, 2020

I believe you can get these articles free of charge through Academia.

Regarding the wattage measurement at the flywheel : at high rotation speeds bearing resistance is negligible compared to air drag (proof of this is that the rotation period increases linearly with time during the recovery, see topic Watt readings on two Ergs). The C2 RowErg is self-calibrating for the power measurement. I don't know how this is implemented for the BikeErg because there is no pause in power-input while cycling. You probably have to rest the pedals for a few seconds to calibrate the BikeErg in order to get an accurate power measurement. This initial calibration is very stable during a cycling exercise as long as you don't change the damper setting.

All devices can only measure the power at the point of measurement. So the RowErg power does not include the work for moving the body on the slide and the power loss in the chain drive. A comparison of the power measured at the handle (force sensor and speed sensor) and the C2-measured power shows about 25W difference, roughly independent of the applied power (see S. Boyas e.a : Power Responses of a Rowing Ergometer: Mechanical Sensors vs. Concept2 Measurement System, in Int J Sports Med, 2006, 830-833).

[Nomath]

This topic is immensely popular: currently 9778 views and only 6 posts. Must be a record.

[flatbread]

I reckon it's about a 75w difference for UT1-2, 65-70 for AT, and 50-60w for a 2k.

Possible rule of thumb -- what you can do for 20min test on the bike is what you can do for 2k on the erg if you're equally adapted to both. My best 2k watts on the erg are far off my 60min best on the bike. My erg technique is better now, but I'm not pulling 370w for a 2k any time soon.

[btlifter]

I reckon it's about a 75w difference for UT1-2, 65-70 for AT, and 50-60w for a 2k.

Possible rule of thumb -- what you can do for 20min test on the bike is what you can do for 2k on the erg if you're equally adapted to both. My best 2k watts on the erg are far off my 60min best on the bike. My erg technique is better now, but I'm not pulling 370w for a 2k any time soon.

Imteresting to notice others' differences. 2k/4k and below I'm a bit quicker on the rower.

But I can hold my 1 hour pace on the rower for 3 hours on the bike.

[rtbrouwer]

I do about 25% more watts on the bike then I do on the erg. 345w on the bike for 20 minutes vs 275w on the erg for 20 minutes.

[Carl Watts]

I have settled on a 30% boost on the rowing Watts for Zwift, seems about right.

There are far to many variables to factor in from person to person. 30% works in general but I would need to stick to flattish riding and its no good for all out sprints.

[Nomath]

I think 30% is much too high. Are your cycling results on a BikeErg?

In my opinion a more objective estimate is to compare the 50th percentile points in the C2 rankings for RowErg and BikeErg. In this way you compare the average rower and the average cyclist on similar power measuring equipment.
The tabel below shows the data. The difference in power is in the order of 10-15% for the aerobic distances.

[Nomath]

My error : the power difference in the above table between 2000m rowing (192W) and 4000m cycling (226W) is 17% !

[MudSweatAndYears]

For endurance efforts, where the aerobic engine is the limiting factor, the most efficient motion wins. So in terms of wattages achievable the BikeErg outperforms the RowErg (and the RowErg outperforms the SkiErg). This is no longer true for sprint efforts where muscle power is the limiting factor. So for sprints the workouts that engage a large portion of your muscles (RowErg and SkiErg) beat the leg-only workout (BikeErg), and amongst the full-body workouts the most effiocient motion wins (the RowErg).

All of this is reflected in the WR performances on each machine:

1 min - - BikeErg 823 W / SkiErg 947 W / RowErg 1038 W
30 min - - - - - - - - - - - - SkiErg 370 W / RowErg 422 W / BikeErg 470 W

[Carl Watts]

No point taking the average person on the bike and the average person on the rower you need to take the SAME person on the rower as the bike and just look at HR for a given wattage.

The average person is irrelevant, your interested in just your personal performance if you had both bits of gear and were equally trained on both.

The difference on the bike is that you can avoid courses with hill climbs on Zwift, if your heavy just stick to the flat. Watts per Kg is not that high but your total Watts is.

Its impossible to just come up with a one size fits all and I have no intention of spends thousands on a smart bike trainer and then splitting my training between a bike and the Erg to find out.

30% looks about right to me. Rowing is a horribly inefficient way to get power out of your body if you think about it compared to cycling.