Cycling or Rowing?

[Nosmo]

One could get a reasonably accurate measurement for unmeasured power on the erg by calculating the mass of various parts of the rower and distance each moved during the stroke.

[ EDIT: That calculation was all wrong. Very stupid mistake on my part. Will do again and post later. ]

Also: I would not trust any measure of power on a machine in a gym unless I knew a lot about it. I've seen different machines produce vastly different results. Perhaps something out there is good. To measure power on the bike the vast majority of people use a Power Tap Hub or an SRM power meter cranks. Very good bicycle ergometers do exist but in my very limited experiece I've never seen one in a gym.

Nosmo.

[TurboCog]

Hi Nosmo
That's an interesting way of looking at it - does your calculation consider that the mass is reversed twice each stroke? I'm no mathematician or scientist so....

[Nosmo]

Hi Nosmo
That's an interesting way of looking at it - does your calculation consider that the mass is reversed twice each stroke? I'm no mathematician or scientist so....

EDIT: Yes it does (hence the factor of 2 in the power equation), but I stupidly did not do it correctly. One needs to estimate the acceleration and distance of the mass. Again, I'll redo the calculation and see what numbers I get.

I think I produce more power on the bike. I don't have a power meter on the bike but am estimating it from quickly I climb steep hills. On a steep hill greater then about 8%, the speed is slow enough so we can neglect both wind and rolling resistance--all the power goes in to lifting the bike and rider. So if you know the feet per minute climed and the total mass of the bike and rider power comes out fairly easily. One does need access to some fairly steep hills though.

Nosmo

[TurboCog]

I have my own little gym with a turbo bike next to the erg. I calibrate the turbo using a run down test. I've replicated several ramp tests done in the sports lab (supervised by a sports scientist) on my own machine and I reckon that they are within +/- 5% certainly +/- 10%. In my current state of fitness i can do a 16km TT on the bike @ 320watts and this evening I did a 5K erg @ 214 watts. Both pieces at similar HR and percieved effort. The times that I do on the turbo are about the same as I do in TT's on the road. In fact my 10 mile TT pb is identical on both (21:52). So my experience is that the erg produces about 2/3 the watts of a bike.

ps - I am a cyclist of course - so my erg performances will be worse than the erg. Maybe a rower will get closer wattages than I am capable of.

[johnlvs2run]

27.44 mph - that's quite a time trial for age 68 - I'm impressed!

[TurboCog]

27.44 mph - that's quite a time trial for age 68 - I'm impressed!

John - that pb is 4 years old - wish I could do that now. All of my bike pb's done since I was 62/64 tho'. 25m 55:14, 50m 1,51:53. 100m 3,59:52.
12h 262.68miles. I used to visit the gym twice a week during winter in those years and did 2 x 20 min on the erg. Didn't know anything about erging so set drag at 10 and went like a rabbit - but it had the desired effect of helping core strength and breaking monotony.

[hjs]

Nice thread,

I only erg at the moment and haven,t cycled at all in a year or so. Before that I did some cycling but never long rides. Mostly 30/60 min rides.
I am planning to to pick cycling up a bit when the weather permits me.

The reason I am reacting now is mostly the fact that the watts I get on an erg are absolutely impossible for me to get on a bike. So I definetly can improve my biking

[RR1 Kirk]

I started this thred last year regarding cycling watts vs. erging watts and received some interesting answers.

http://www.concept2.co.uk/forum/viewtop ... highlight=

Cheers,

[Orc]

I am curious about the comparison between erg and bike power readings. Last weekend I did a ballpark comparison. 2 x 20' effort on the road bike to measure functional power threshold. average 320W. heart rate suggests an AT of around 160, maybe a bit less. next day did a 20 minute erg piece, capping heart rate at 160 bpm. average wattage 240 bpm.

although this is not an exact comparison (for one thing , AT may differ by activity), it confirms the large difference Turbocog sees, and with a similar disparity. I am 90kg and about 86kg at race weight. An all out 20 minute effort on both devices would make more sense for the comparison, but doesn't really fit with my current training.

I have a lot of experience as an on the water rower, but these days I bike a lot more than I row ( I race in both sports). I also have not been erging this year, so I am curious to see if my erg moves up relative to my bike power later in the season.

Btw, I used a Power tap on the bike. measured power on a PT is less than applied power due to losses in the drivetrain (something like 10W?,it's basically a constant). comparisons to erg power should correct this loss with the power tap, as well as unrecorded work on the erg.

after adding back the 10 watts. 240W/330 W = 72 %

marc

I have my own little gym with a turbo bike next to the erg. I calibrate the turbo using a run down test. I've replicated several ramp tests done in the sports lab (supervised by a sports scientist) on my own machine and I reckon that they are within +/- 5% certainly +/- 10%. In my current state of fitness i can do a 16km TT on the bike @ 320watts and this evening I did a 5K erg @ 214 watts. Both pieces at similar HR and percieved effort. The times that I do on the turbo are about the same as I do in TT's on the road. In fact my 10 mile TT pb is identical on both (21:52). So my experience is that the erg produces about 2/3 the watts of a bike.

ps - I am a cyclist of course - so my erg performances will be worse than the erg. Maybe a rower will get closer wattages than I am capable of.

[becz]

I am curious about the comparison between erg and bike power readings. Last weekend I did a ballpark comparison. 2 x 20' effort on the road bike to measure functional power threshold. average 320W. heart rate suggests an AT of around 160, maybe a bit less. next day did a 20 minute erg piece, capping heart rate at 160 bpm. average wattage 240 bpm.

although this is not an exact comparison (for one thing , AT may differ by activity), it confirms the large difference Turbocog sees, and with a similar disparity. I am 90kg and about 86kg at race weight. An all out 20 minute effort on both devices would make more sense for the comparison, but doesn't really fit with my current training.

I have a lot of experience as an on the water rower, but these days I bike a lot more than I row ( I race in both sports). I also have not been erging this year, so I am curious to see if my erg moves up relative to my bike power later in the season.

Btw, I used a Power tap on the bike. measured power on a PT is less than applied power due to losses in the drivetrain (something like 10W?,it's basically a constant). comparisons to erg power should correct this loss with the power tap, as well as unrecorded work on the erg.

after adding back the 10 watts. 240W/330 W = 72 %

marc

I have my own little gym with a turbo bike next to the erg. I calibrate the turbo using a run down test. I've replicated several ramp tests done in the sports lab (supervised by a sports scientist) on my own machine and I reckon that they are within +/- 5% certainly +/- 10%. In my current state of fitness i can do a 16km TT on the bike @ 320watts and this evening I did a 5K erg @ 214 watts. Both pieces at similar HR and percieved effort. The times that I do on the turbo are about the same as I do in TT's on the road. In fact my 10 mile TT pb is identical on both (21:52). So my experience is that the erg produces about 2/3 the watts of a bike.

ps - I am a cyclist of course - so my erg performances will be worse than the erg. Maybe a rower will get closer wattages than I am capable of.

I'm guessing the effect of the derailleur has a significant impact on the difference in sustained power output between the bike and the erg. What gearing were you using for your 16km TT? Since there is no derailleur on the erg, it might be a better comparison to do the TT at the closest to a 1:1 ratio that you can get and see how that effects the power output you can sustain. The larger lever arm of the pedals vs. the sprocket on the erg is probably a factor as well.

[Nosmo]

I'm guessing the effect of the derailleur has a significant impact on the difference in sustained power output between the bike and the erg. What gearing were you using for your 16km TT? Since there is no derailleur on the erg, it might be a better comparison to do the TT at the closest to a 1:1 ratio that you can get and see how that effects the power output you can sustain. The larger lever arm of the pedals vs. the sprocket on the erg is probably a factor as well.

From the point of view of physics this does not make sense. Both the bike and the erg have been optimized to match the physics of the human body. Changing the gear is simliar to changing the drag factor. One chooses the stroke rating/drag factor, or the RPM/great for whatever works best for the situation.

Forcing a 1:1 ratio on the bike would be like forcing someone to row with a DF of 60. Of course he could produce the same power with a 1:1 ratio if he was climbing a hill at the appropriate angle

[becz]

Both the bike and the erg have been optimized to match the physics of the human body.

Optimized? In what way?

Changing the gear is simliar to changing the drag factor.

I disagree. Changing the drag factor may make the load heavier or lighter, but you still move the handle the same distance with each pull. In contrast, changing the gear allows a greater equivalent lever arm. The analogy would be a lever lifting a weight. With the erg, you can change the load, but not the length of the lever. With a derailleur, the load stays the same, but you can vary the length of the lever (more turns of the wheel for one turn of the crank). They are completely different. Imagine you are asked to produce a certain amount of power (work per unit time) by repeatedly lifting a weight with a lever. You have the choice of a short lever and variable load (the erg) or an adjustable lever and a set load (the bike). I'm guessing you can sustain a higher output with the bike (due to biomechanical reasons).

Of course he could produce the same power with a 1:1 ratio if he was climbing a hill at the appropriate angle

That's exactly my point. If that was required, he probably wouldn't be able to sustain that power output.

[yehster]

Changing the drag factor may make the load heavier or lighter, but you still move the handle the same distance with each pull. In contrast, changing the gear allows a greater equivalent lever arm.

But you still move your feet the same distance regardless of what gear you are in. The distance the bike moves/pedal stroke is a dependent variable in the whole power equation. Shifting gears makes your pedal stroke higher or lower just as changing the drag factor does.

[Orc]

I'm not sure what you are trying to equalize. Nevertheless, the cog size on the Concept2 could easilly be changed if the power range was found to be inadequate. The model A ergs had 5 cog sizes to choose from and the Model B had 2. So, the choice of cog size is another way to modulate load. So, the gearing chosen for the erg is designed to give a suitable training load- it's not some magical 1:1 ratio.

The differences in watts are probably primarily due to unrecoverable unmeasured work done in moving your body weight up and down the slide. This work isn't reflected in the wattage reading (though it is added in the calorie estimate).

Also, there is a vast different in turnover rate between rowing and cycling.
I think this must have an impact on power output. Typical cadence in cycling is about 3 times as high at a typical erging rating, and cycling is a more efficient form of human power.
If you were forced to use an extrememly heavy high gear on the bike and extremly low cadence to make the efforts of the 2 sports more comparable, you might alter the relative watts. However, I think this is not nearly as interesting as learning about the power of each sport when you are trying to optimize performance, not artificially constrain them.


marc

Changing the gear is simliar to changing the drag factor.

I disagree. Changing the drag factor may make the load heavier or lighter, but you still move the handle the same distance with each pull. In contrast, changing the gear allows a greater equivalent lever arm. The analogy would be a lever lifting a weight. With the erg, you can change the load, but not the length of the lever. With a derailleur, the load stays the same, but you can vary the length of the lever (more turns of the wheel for one turn of the crank). They are completely different. Imagine you are asked to produce a certain amount of power (work per unit time) by repeatedly lifting a weight with a lever. You have the choice of a short lever and variable load (the erg) or an adjustable lever and a set load (the bike). I'm guessing you can sustain a higher output with the bike (due to biomechanical reasons).

Of course he could produce the same power with a 1:1 ratio if he was climbing a hill at the appropriate angle

That's exactly my point. If that was required, he probably wouldn't be able to sustain that power output.[/quote]

[hjs]

Tried some rowing versus biking.


first 20 min row, ut1 ish pace, av watts 261 (240/280)

3 minutes rest

20 min stationaire bike 170 watts (150/190)


That biking of mine is very poor