Watts versus pace

[hypatiaswan]

Hi All

I'm well aware that the time used to row a given distance (e.g. the pace) can be converted to average watts via a simple calculation (I've seen the online calculator etc.). What I'd like to know is if the average watts displayed on the PM for a given piece gives any "new" information that the average pace wouldn't give. The way I understand it, is that average pace and average wattage are really measuring the same things (different units, but if one gets better, the other will too). If you want to know if you're getting better for a certain distance, you can either look at the average pace for the piece, or look at the average watts. Pick whichever unit is most meaningful to you. Wattage is a unit of power, but actually, on the rower, that power is converted to pace with the touch of a button. So it's 6 of one, half a dozen of the other.

Recently, I read somewhere that the watts displayed on the PM actually measure only the wattage at the catch, and not the average over the entire stroke. I read that looking at watts gives you an idea of the stroke efficiency, and that stroke efficiency cannot be discerned from the average PACE of a piece. I don't think this statement is correct, but was looking for comments and verification of my understanding of the way the PM calculates/measure watts/pace. When the rubber meets the road, both are determined by the accelleration/decelleration of the fly wheel; whether you choose to optimize your pace or your watts, you're going to be optimizing the same physical thing.

On the water,
Hype

[Citroen]

You get an average watts reading per stroke.

The PM2/PM3/PM4 gets a sawtooth wave from the flywheel tacho, so it can tell when a stroke starts and ends (so it can register stroke rate). There's then a bunch of maths/physics done http://www.atm.ox.ac.uk/rowing/physics/ergometer.html to get from tacho pulses to watts then from watts to pace and calories.

ALL the numbers are calculated from the wattage measured by counting tacho pulses.

Note: that web page is a bit old, it's based on the model B which had a different system of vents and two sprockets on the flywheel axle.

[Bob S.]

When the rubber meets the road, both are determined by the accelleration/decelleration of the fly wheel; whether you choose to optimize your pace or your watts, you're going to be optimizing the same physical thing.

Exactly. The difference between them is the usage. Watts would be the best measure to use, since it is a direct (linear) measure of how hard you are working. However, for common use, most everyone uses the non-linear measure, pace. I have a hunch that this is historically derived from track racing, especially the mile, where it was a common practice to time each quarter mile lap.

Bob S.

[Carl Watts]

At the end of the day the Watts is not that useful since everything results wise is time based.

The two are directly linked anyway by a nasty cubic law where the Watts required just takes off in relation to the pace.

[Nosmo]

Just to clarify, watts and pace are entirely equivalent as far as the reported values from monitor is concerned. There is a one to one correspondence between the two.

[carlb]

The PM measures Watts...power exerted by the rower to spin the flywheel.

Pace/500 calcs directly from Watts and a formula with a constant that someone picked so the time shown was about right for the effort. Author in link below says "Ergometer readings have to be more or less realistic and to motivate the rower they must indicate a slightly better performance than in the boat."

Pace/500 is the best to display on the PM and use as a target. Watt numbers move more. Pace moves less so is easier to hold, also easy for quick calculations of how much time or distance is left in the workout e.g. the next 1000m will take 2xPace/500.

Watts are best when you are trying to calculate pace changes, e.g. you rowed a 5k at 2:10/500 and want to try 30 minutes, you guess you'll ease up 5% of your 5k pace. Convert 2:10/500 to 159 watts, multiple by .95, then convert 151 back to a Pace of 2:12.3.

Watts also seem a number useful for comparing to other exercises. Also kind of curious to think about, I can power a ### watt light for 30 minutes.

The article Behind the Ergometer Display here is interesting http://home.hccnet.nl/m.holst/RoeiWeb.html

[Bob S.]

At the end of the day the Watts is not that useful since everything results wise is time based.

The problem with time-basing is that it is very misleading - especially those programs (like the Pete Plan) that recommend using your 2k pace as a base for training. For example, consider plans based on a 6' 2k and an 8' 2k

For the 6' 2k, the pace is 1:30 or 480.1 watts. If a plan calls for a pace of 2k+1, that would be 1:31 or 464.5 watts, a difference of 15.6 watts.

For the 8' 2k, the pace is 2:00 or 202.5 watts. In this case 2k+1 would be 2:01 or 197.6 watts, a difference of only 4.9 watts.

The UK Interactive Programme (sic) avoids this by specifying that the various levels are at certain percentages of the 2k power (as calculated from the watts). The programs themselves provide the appropriate paces already calculated from the wattages for the user's convenience. There is none of this 2k+x bullshit.

Bob S.

[carlb]

At the end of the day the Watts is not that useful since everything results wise is time based.

The problem with time-basing is that it is very misleading - especially those programs (like the Pete Plan) that recommend using your 2k pace as a base for training. For example, consider plans based on a 6' 2k and an 8' 2k

http://thepeteplan.wordpress.com/the-pete-plan/

Pete does not "recommend using your 2k pace as a base for training". Pace is based on prior session

Pacing the sessions:
If you read other sources of information about the Pete Plan, ignore any reference to how to pace the sessions. It is possible to give a rough guide of how the pace of a session might fit in compared to your best 2k or 5k pace, but everyone is different, everyone has different strengths, and not one number for this will fit everyone. So simply follow the pacing guidance I’ll give you here, and you should never fail to finish a session while following the Pete Plan.

For all the interval sessions, both speed intervals and endurance intervals, the key thing is doing your first attempt at a new session at a pace you know you can achieve. It doesn’t matter if that makes the first cycle of the plan very easy; it is for the best in the long run. For a first attempt at each session simply look at a total distance of the session as a whole, and estimate how fast you could row that as a single piece, from the nearest distance you have done. For example, for the speed interval sessions where the total distance is 4k, look at the pace of your best recent 5k perhaps. Then for your first attempt at any of those sessions, simply do all but the last rep of the session at that pace. When it comes to the final rep, go as fast as you can. Then at the end of the session look at the average pace on the monitor from the session, and write it down – this will be your target the next time you attempt that session.

Then down below he does offer some 2k / 5k based suggestions, but he doesn't want to reccommend them...

I know everyone is different, but I still want to know what are good times for each of the interval sessions!

Ok, but these are neither targets for the first time you try a session, or even for the longer term.

8 x 500m = 3seconds faster than 2k pb pace (2k – 3)
Speed pyramid = 2k pb pace (2k)
4 x 1000m = 1second slower than 2k pb pace (2k + 1)
5 x 1500m = 5k pb pace (5k)
4 x 2000m = Half a second slower than 5k pb pace (5k + 0.5)
3k, 2.5k, 2k = 1second slower than 5k pb pace (5k + 1)

[Bob S.]

Pete does not "recommend using your 2k pace as a base for training". Pace is based on prior session

O.K., so current versions don't use that. I was only going by a simplified three week program that was easily available on the net a long time ago. It wasn't really my intention to disparage the Pete Plan as currently practiced.

My point was that just adding (or subtracting) seconds from the pace of any kind of trial to use at a different distance (or set time) is not practical, since the number of seconds that would be appropriate vary a great deal with the pace. In my example, a one second increase for a 6' 2k rower would be equivalent to about a three second increase for an 8' 2k rower. A system based on watts would not have that problem.

Bob S.

[Tinus]

The PM measures Watts...power exerted by the rower to spin the flywheel.

Pace/500 calcs directly from Watts and a formula with a constant that someone picked so the time shown was about right for the effort. Author in link below says "Ergometer readings have to be more or less realistic and to motivate the rower they must indicate a slightly better performance than in the boat."

Pace/500 is the best to display on the PM and use as a target. Watt numbers move more. Pace moves less so is easier to hold, also easy for quick calculations of how much time or distance is left in the workout e.g. the next 1000m will take 2xPace/500.

Watts are best when you are trying to calculate pace changes, e.g. you rowed a 5k at 2:10/500 and want to try 30 minutes, you guess you'll ease up 5% of your 5k pace. Convert 2:10/500 to 159 watts, multiple by .95, then convert 151 back to a Pace of 2:12.3.

Watts also seem a number useful for comparing to other exercises. Also kind of curious to think about, I can power a ### watt light for 30 minutes.

The article Behind the Ergometer Display here is interesting http://home.hccnet.nl/m.holst/RoeiWeb.html

The situation is reversed. The PM measures speed and converts this into watts. You can notice this when decelerating or accelerating which requires respectively a little or a lot work but the watts displayed is more like related to the current speed.

The OP is right in watts and pace being practically the same thing on the PM monitor. In section 10 of Dudhia's website http://www.atm.ox.ac.uk/rowing/physics/ ... #section10 it is explained that power and speed are not a one on one relation but stroke rate plays a role as well. However his conclusion is wrong:

For a given split, the indicated power (but not necessarily the rower's actual power output) will be lower for a high rate than a low rate

It should be

For a given split, the actual mechanical power (but not the displayed power) will be lower for a high rate than a low rate

This is because the displayed power is directly calculated from a given split and not affected by rate.

[carlb]

The PM measures Watts...power exerted by the rower to spin the flywheel.

The situation is reversed. The PM measures speed and converts this into watts. You can notice this when decelerating or accelerating which requires respectively a little or a lot work but the watts displayed is more like related to the current speed.

I wouldn't say reversed. The PM measures the speed of the flywheel over time (acceleration) and converts that into watts, not the same as measuring the speed of the boat (Pace) should on the PM.

The C2 is called an Ergometer because it measures the Energy(work) provided by the person = power(watts) x time.

See these 2
Power supplied http://www.atm.ox.ac.uk/rowing/physics/ ... l#section4
Measuring Power http://www.atm.ox.ac.uk/rowing/physics/ ... l#section8

[carlb]

At the end of the day the Watts is not that useful since everything results wise is time based.

The problem with time-basing is that it is very misleading - especially those programs (like the Pete Plan) that recommend using your 2k pace as a base for training. For example, consider plans based on a 6' 2k and an 8' 2k

For the 6' 2k, the pace is 1:30 or 480.1 watts. If a plan calls for a pace of 2k+1, that would be 1:31 or 464.5 watts, a difference of 15.6 watts.

For the 8' 2k, the pace is 2:00 or 202.5 watts. In this case 2k+1 would be 2:01 or 197.6 watts, a difference of only 4.9 watts.

Bob S.

I do agree with you fully on your point about quick rule-of-thumb pace adjustments. Watts are the way to calc.

One other point I would make about Pete Plan adjustments is Pete is one fast rower, probably 80%-90% of people are slower. So a 2k-5 time adjustment that works for him when viewed from a watts % change is going to go easy on the other 90% of us that row slower.

[Tinus]

The PM measures Watts...power exerted by the rower to spin the flywheel.

The situation is reversed. The PM measures speed and converts this into watts. You can notice this when decelerating or accelerating which requires respectively a little or a lot work but the watts displayed is more like related to the current speed.

I wouldn't say reversed. The PM measures the speed of the flywheel over time (acceleration) and converts that into watts, not the same as measuring the speed of the boat (Pace) should on the PM.

The C2 is called an Ergometer because it measures the Energy(work) provided by the person = power(watts) x time.

See these 2
Power supplied http://www.atm.ox.ac.uk/rowing/physics/ ... l#section4
Measuring Power http://www.atm.ox.ac.uk/rowing/physics/ ... l#section8

The equations from that section 8 are not used by the PM. You can check it experimentally!

It are the equations from section 4 which are used but those are approximations when using averaged speed and power and they use speed instead of speed over time.

See also the calculator which only asks for speed or pace and returns power.
http://www.concept2.com/us/interactive/ ... /watts.asp

[Nosmo]

Bob, the numbers you have give a 3.2% and 2.5% increase in power for the 6' and 8' 2k's. So while 2k-1 is not constant, the difference is not huge. Recognizing that these numbers are general rules of thumb not iron clad laws, one can use changing in pace. If you want instead of 2k-1 paced you could use 99% of 2k pace, which would correspond to about a 3% change in power (really 2.97%). So for a 6' 2K that would be 2K pace - .9 seconds, and for an 8' pace it would be 2K-1.2 seconds. Not a big deal if you use 2k-1 as a general rule instead.

Just to be pedantic, the C2 monitor measures time between pulses from the fly wheel. So really it is measuring flywheel rotational velocity. Every thing else, (pace, power, calories) comes from a calculation.

[jamesg]

The main reason for using Watts is that we can see immediately the Watt/Rating ratio, which is identical to the work done in each single stroke. Using pace we are blind to this.

Work control is a very powerful technical tool, as it lets us put quality in each single stroke and also set up a simple training protocol. Just make sure every single stroke has roughly the same (i.e. plenty) of work in it, at all ratings. But keep the ratings low to avoid over-training.

This approach puts the accent on how far the boat goes every single stroke, which is what rowing is all about. It exploits the unique aspect of rowing, which is that we can adjust the overall load by adjusting the rating while still pulling full strokes at all times. The non-rower may think a good crew is idling at 20-23; but a glance at where their puddles go may give an entirely different impression.

For racing, pace is the obvious choice, but it's still of use to remember that it's an inverse cube function of Power. One second slower might be 3% less power, which could put us in aerobic mode and leave all our anaerobic resources for the last 500.. if needed.