Rate connection with watt/pace ?

[n1x0n]

This topic has properly been handled before but can't find the topic.
I wonder if there are any connection between stroke rate and watt and how to calculate pace in a simple way.

Let's say I row 20spm 2:00/500m 200watt. If I gear up to 22spm and still use same amount of 200watt, what will the pace be ?
The same question can be turned around. If I gear down to 18spm what will the watt be ?

Rgs

[jackarabit]

At 10spi (10 W'/stroke), pace at 22 spm will be 1:56.7/500m and power at 18 spm will be 180 watts. The expression "same amount of 200 watts" harbours a built-in ambiguity which makes me very nervous!

[Pie Man]

My understanding of this is that if you can put the same power in each stroke (in your example 200/20 or 10 watts per stroke) but stroke faster then your 500m time will come down. However as the formula for calculating your 500m time is not a simple linear formula you would be best putting the numbers into the concept watts calculator

So for your example 200w = 2:00.5 pace

220 watts (22*(200/20)) = 1:56.7 pace for 22spm with same 10w/stroke

240 watts (24*(200/20) = 1:53.4 pace for 24spm with same 10w/stroke

180 watts (18*(200/20) = 2:04.8 pace for 18spm with same 10w/stroke

If you meant that the 22spm gave the same 200w output then the pace would be the same, but I don't think that is what you meant.

HTH

[jackarabit]

Pre-effing-cisely! You're OK in my book Pie!

[Carl Watts]

Its not a simple calculation.

I had an Excel spread sheet that had the ratings vs pace for the "Same perceived exertion" which must be connected to your heartrate. You cannot throw simple math at it because your body is not a linear machine, things change for the worse at both ends of the ratings both low and high and you have a sweat spot in the middle.

The above math is totally wrong. if your putting out 200W, then thats average power and not over one minute but its going to be continuous. Power is only going into the flywheel during the drive time so lets simplify it slightly because although your drive power should approach a square wave, it is not.

lets say 20spm and your monitor has 200W = 2:00.5 pace and 1 sec drive and 2 sec recovery to keep it easy. To get 200W average you need to put in 600W on the drive and this then averages out to 200W.

This is why when you dramatically drop the rating, things get very nasty. You have a very limited amount of time to get the power into the flywheel and the peak power required jumps disproportionately. This is why you will find it impossible to row at 2:00.5 pace at 10 spm. With the above math thats simply 20W per stroke or a doubling of power, think again.

You also cannot just continue to rate up forever to maximize the drive time and try and minimize your recovery time because you begin to waste massive amounts of energy just going up and down the slide if your doing the proper full stroke and not some special modified stroke just to get a 500M WR.

[G-dub]

You might find the calculator useful on this link below. There is an excel file that enables you to predetermine a satisfactory rate for 2K (I chose 34 based on what feels right to me) and it converts that to paces for different ratings. I don't think it is linear, but it could never presuppose percieved exertion or whether you are fit enough to hold a rate for a given pace for the length needed. There are other calculators on here that I know nothing about! This came from Rodney, who used to have the handle RJR I think, who was a pretty knowledgable cat. He didn't make the table though.

http://www.biorow.com/Downloads.htm

[jackarabit]

Check out "Model 1" at link http://www.biorow.com/Downloads_files/S ... S%2012.xls. Appears to fit both the limited terms of the question and the answers supplied by Jack and Pieman. So the computational basis of that particular pace chart is also "totally wrong"? It must have some use? Probably just there for simpletons like myself without the imagination to appreciate the constructions of mathematical mud daubers. Folks, for most garden variety problems short of rocket surgery, pi might just as well be 3.000000000000000000000.

[jamesg]

Let's say I row 20spm 2:00/500m 200watt. If I gear up to 22spm and still use same amount of 200watt, what will the pace be ?
The same question can be turned around. If I gear down to 18spm what will the watt be ?

If the Power in Watts is the same, the Pace is the same. This is reality and is how the erg does its sums: Power and Erg Speed relate as to a cube law, W = 2.8 V³, where V is the conventional speed in m/s. Pace is 500/V in seconds.

Since you say "same amount of 200W", what changes in your examples is not the Pace or speed, but the Work done in each single stroke: more strokes per minute, less Work in each; or fewer strokes, more Work in each.


If on the other hand you rate up from 20 to 22 (+10%), but do the same amount of Work in each stroke, your Power will also increase by 10%; and your speed by about 3% due to the cube law.


The engineering ideas and units relate as here:
Work = Force x Distance, unit Newton meter or Nm: the Work done by a 1 N Force moving a distance of 1 m.
Power is in Watt, where 1 W = 1 Nm/s, Newton-meter per second.
So in dimensional terms, Power is Work/Time. NB, Rating has dimensions 1/Time, so Watts/Rating has dimensions (Work/Time)/(1/Time) = Work.

So we can calculate, if interested, our average Work per stroke, dividing Watts by Rating. The unit is unusual (Watt-minutes) and nowhere near as big as a kWh, but it can help tell us what's going on if we listen.

Naturally it's up to us to get the best possible numbers on screen with least possible effort; it's called technique, but a certain amount of sweat could also be involved if you overdo things.

[Carl Watts]

The error is taking strokes per minute and thinking its power per minute. There is no such unit it is per second. if it is kW/hr then its converted and expressed as that.

Put simply 200W on the erg is 200W per second not per minute.

Unfortunately the rower is not like a bicycle where the power delivery is more constant and the legs assist one another, there is one hell of a lot of time where there is no power going into the flywheel and hence you have to make up for this only during the drive time.

[jackarabit]

Have to admit I'm a complete dullard about the building blocks of Newtonian mechanics but I most assuredly don't measure the tea in my teacup in gallons!

Deer should not toy with Tiger. --Charlie Chan

[Tim K.]

Put simply 200W on the erg is 200W per second not per minute.

200W = 200j/s

[Carl Watts]

Put simply 200W on the erg is 200W per second not per minute.

200W = 200j/s

Correct.

[jamesg]

The error is taking strokes per minute and thinking its power per minute

Rating has dimension 1/Time, not Time. As in 20 per minute, where 20 is a number.

200 W/s is a rate of increase of Power, 200 Watts more every second; akin to acceleration: 1 m/s² is 1m/s faster per second.

As well as 1 W = 1 J/s, 1 W = 1 Nm/s = 1 VA. All praise and thanks to Messrs Watt, Joule, Volta, Ampère and Newton for simplifying the universe for us; and for the electro-mechanical connection.

[n1x0n]

Many answers here. Thanks for good feedback
I'm an fairly new rower and are doing some low rate work, the reason I'm curious is that I would like to know how to pace sessions gearing up and increasing pace maintaining same or similiar watt. Stroke lenght will be affected yes.

If there are any relationship between low rate work training and pulling off an 2k & 5k effort. If I can pull off an 30r20 1:56/500m can I make an assumption what an 2k or 5k time would be gearing up. Off course there are other factors involved.

[jamesg]

Sure. Base your calculations on Work and allow for 2k at rating 30, same work per stroke. Though usually we pull a bit harder in 2k than in 7.