Why I'll Never Give Up My Power Meter

RapDaddyo said:

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Wow, thanks for sharing. And don't tell any of my competitors. 🙂

I'll agree, except for the pacing aspect. For the purpose of training, it may be okay to keep constant power if power is all that matters.

However, if speed matters, as in a race, it's better to apply more power uphill. The reason is simple: uphill, the extra power results in a relatively greater increase in speed. At higher speeds, i.e., downhill, power is better saved because the exponential increase in wind resistance makes it more costly to go faster.

How much to modulate power is a matter of experience and I guess you could say is the art of time trialing.

jws said:

I'll agree, except for the pacing aspect. For the purpose of training, it may be okay to keep constant power if power is all that matters.

However, if speed matters, as in a race, it's better to apply more power uphill. The reason is simple: uphill, the extra power results in a relatively greater increase in speed. At higher speeds, i.e., downhill, power is better saved because the exponential increase in wind resistance makes it more costly to go faster.

How much to modulate power is a matter of experience and I guess you could say is the art of time trialing.

I don't think I agree with your logic. In a TT, one is theoretically going within a few watts of one's maximum sustainable power for that duration. To put out more watts is to put yourself in the position of having to back off later. If that's not the case, then you're not going hard enough. Yet, the reverse is not true. If one puts out, say, 20w less than his target power for a few minutes is not like making a bank deposit, where you can make a withdrawal later. To take it to an extreme, if my maximum sustainable power over 1 hour is 250w, that doesn't mean that if I put out 200w for the first half hour that therefore I can put out 300w the second half hour. If you save it, you never get it back. Do you have any data to back up your assertion, or is this your personal experience.

RapDaddyo said:

To take it to an extreme, if my maximum sustainable power over 1 hour is 250w, that doesn't mean that if I put out 200w for the first half hour that therefore I can put out 300w the second half hour. If you save it, you never get it back. Do you have any data to back up your assertion, or is this your personal experience.

I agree with jws. I thought in your original post you were just referring to intervals. Think of it this way - the only thing that matters in a TT is finishing time. If you spend too much time doing isopower you end up spending too much time in the slow portion of the time trial - either uphill or against the wind. Where ever you go slow your average speed goes down. The trick is balance going as hard as you can go in the hard parts and not going so hard that you blow up or don't have anything left to keep going moderately hard on the easy parts (downhill/tailwind). This is entirely course dependent. If it's possible to go maximum steady state for the entire course *and* maintain constant speed that's the best possible strategy.

sportsci.orgpacing.htmlOpen ↗

However, this does not hold true for non flat courses if one can match the model. 🙂

http://www.ms-se.com/pt/re/msse/abstract.00005768-199708000-00017.htm;jsessionid=CN1E1OFjQjtg0ag22h8b5K1VtcT4nfD14HxqPJo1UebtFqYMU9Dq!1707623050!-949856031!9001!-1

Or empirically there's a long wattage discussion here.
lists.topica.commessage.htmlOpen ↗

Woofer said:

I agree with jws.

Well, if I read the references correctly, the only empirical evidence supports the steady power pacing strategy. Other pacing strategies, specifically "go harder uphill and upwind," seem to be opinion only. Am I reading the references incorrectly?

RapDaddyo said:

I don't think I agree with your logic. In a TT, one is theoretically going within a few watts of one's maximum sustainable power for that duration. To put out more watts is to put yourself in the position of having to back off later. If that's not the case, then you're not going hard enough. Yet, the reverse is not true. If one puts out, say, 20w less than his target power for a few minutes is not like making a bank deposit, where you can make a withdrawal later. To take it to an extreme, if my maximum sustainable power over 1 hour is 250w, that doesn't mean that if I put out 200w for the first half hour that therefore I can put out 300w the second half hour. If you save it, you never get it back. Do you have any data to back up your assertion, or is this your personal experience.

I certainly understand your logic, and it works great for flat, calm conditions. This is not something I came up with, but there have been many discussions about pacing stategy on variable terrain. The consensus is that it's fastest to apply more power under more resistance(wind or gravity) and recover a bit downhill or downwind. Here's one reference:

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9268969&dopt=Abstract

Here's a post by Andy Coggan at "Wattage":

http://lists.topica.com/lists/wattage/read/message.html?mid=907401691

Jimmy

Woofer said:

I agree with jws.

I think the fundamental question is whether one can ever reclaim "saved" power. I think not. I think that if I put out 20w less than my maximum sustainable 1 hr power for 10 minutes that I'd be lucky to get back 1/2 of that (10w for 10 min) later. Look at how flat the power/duration curve is from 30 min to 1 hr. There is very little difference between one's 1/2 max. power and 1 hr. max power. I say, "use it or lose it."

RapDaddyo said:

I think the fundamental question is whether one can ever reclaim "saved" power. I think not. I think that if I put out 20w less than my maximum sustainable 1 hr power for 10 minutes that I'd be lucky to get back 1/2 of that (10w for 10 min) later. Look at how flat the power/duration curve is from 30 min to 1 hr. There is very little difference between one's 1/2 max. power and 1 hr. max power. I say, "use it or lose it."

You are right in that, in terms of average POWER, you never get it back. However, the question of TIME is different.

Jimmy

RapDaddyo said:

I think the fundamental question is whether one can ever reclaim "saved" power. I think not. I think that if I put out 20w less than my maximum sustainable 1 hr power for 10 minutes that I'd be lucky to get back 1/2 of that (10w for 10 min) later. Look at how flat the power/duration curve is from 30 min to 1 hr. There is very little difference between one's 1/2 max. power and 1 hr. max power. I say, "use it or lose it."

What one needs to consider is that once you go below your average speed, your average speed goes down. The longer one goes below your average speed, the faster one's average speed drops. One wants to minimize the time that you go slow, physiology allowing.

I'm going to make up a scenario as I type. Let's pretend we have an out and back course that goes uphill for four miles and back downhill for four miles. If you can uphill at four miles an hour and downhill at forty miles an hour your time is one hour and six minutes. Now if you go uphill at five miles an hour and downhill at thirty six miles an hour your time is about fifty five minutes.

This is way oversimplified but illustrates the problem space - realistically almost no one wins a time trial on the downhill portions unless technical skills prevail.

Instead of thinking in terms of average power, using normalized power makes more sense in this case (and in most real world situations).

http://www.cyclingpeakssoftware.com/defined.html

btw, CyclingPeaks software is the only way to "fly"

jws said:

You are right in that, in terms of average POWER, you never get it back. However, the question of TIME is different.

Jimmy

Well, that could be. It's an interesting modeling (and race tactic) question. I can buy into the argument of an unequal tradeoff such as I posited -- something like a 2 for 1 tradeoff in watts over time, within limits (e.g., +/- 10% of max sustainable steady state power for the course duration). If used strategically, I suppose one could cover a course faster with such a strategy even though his average power would be less.

RapDaddyo said:

Well, that could be. It's an interesting modeling (and race tactic) question. I can buy into the argument of an unequal tradeoff such as I posited -- something like a 2 for 1 tradeoff in watts over time, within limits (e.g., +/- 10% of max sustainable steady state power for the course duration). If used strategically, I suppose one could cover a course faster with such a strategy even though his average power would be less.

re:+/-10% - that's something you are going to have to figure out for yourself what those numbers are, and for how long.

Now mass start, that's a different animal. Do the minimum amount of work possible to stay with the pack until you don't want to be with the pack. 🙂

jws said:

Instead of thinking in terms of average power, using normalized power makes more sense in this case (and in most real world situations).

cyclingpeakssoftware.comdefined.htmlOpen ↗

btw, CyclingPeaks software is the only way to "fly"

I agree. In fact, I have never even taken the PT software out of the sleeve. Paul

Woofer's speed example is a good one. Think of it this way: you get much more "bang for the buck" by using more power on slower portions. At 36mph, a big increase in power gets you a relatively smaller increase in speed than it would at slow speeds, and you have less time to save on fast portions because you are there for less time.

RapDaddyo said:

I agree. In fact, I have never even taken the PT software out of the sleeve. Paul

And the new PowerLink software available on the website (and maybe the new CDs) is worse than the original. It has more "features", but is literally unusably slow.

Woofer said:

What one needs to consider is that once you go below your average speed, your average speed goes down. The longer one goes below your average speed, the faster one's average speed drops. One wants to minimize the time that you go slow, physiology allowing.

I'm going to make up a scenario as I type. Let's pretend we have an out and back course that goes uphill for four miles and back downhill for four miles. If you can uphill at four miles an hour and downhill at forty miles an hour your time is one hour and six minutes. Now if you go uphill at five miles an hour and downhill at thirty six miles an hour your time is about fifty five minutes.

This is way oversimplified but illustrates the problem space - realistically almost no one wins a time trial on the downhill portions unless technical skills prevail.

I understand what you are saying, but your data seem to have been chosen to support the point. If I model a hill at a reasonable level of TT power (e.g., ~200w) that would result in a speed as low as 4mph, I get a grade of 15%. If I apply the same power for the downhill, I get a speed of 61mph. So, your cyclist in your example needs to get a bigger gear so he can pull 200w on the downhill half of the course (and get the women and children and dogs off the road). Anyway, I agree that often one gets capped out by the drivetrain and can't pull as many watts on the downhill sections of a course as he is capable of. If such a section is the last section of a course, I would use up all my reserves leading up to that section because I would know I am going to max out below my capacity on the downhill. Paul

jws said:

Woofer's speed example is a good one. Think of it this way: you get much more "bang for the buck" by using more power on slower portions. At 36mph, a big increase in power gets you a relatively smaller increase in speed than it would at slow speeds, and you have less time to save on fast portions because you are there for less time.

Again, all of this talk of power tradeoffs must take into account the fact that it is not symmetrical. I just don't believe that if I put out X watts less than my steady-state max power (SSMP at a given duration) for T minutes that I can therefore increase my power to SSMP+X for T minutes in the future. I imagine the tradeoff is different for each cyclist, but I think it's pretty severe (e.g., 2:1).

RapDaddyo said:

I understand what you are saying, but your data seem to have been chosen to support the point. If I model a hill at a reasonable level of TT power (e.g., ~200w) that would result in a speed as low as 4mph, I get a grade of 15%. If I apply the same power for the downhill, I get a speed of 61mph. So, your cyclist in your example needs to get a bigger gear so he can pull 200w on the downhill half of the course (and get the women and children and dogs off the road). Anyway, I agree that often one gets capped out by the drivetrain and can't pull as many watts on the downhill sections of a course as he is capable of. If such a section is the last section of a course, I would use up all my reserves leading up to that section because I would know I am going to max out below my capacity on the downhill. Paul

Paul,

Here's a better example using: http://www.analyticcycling.com

A 75kg rider + equip. on a 10% grade, 1.2 air density, A=0.45 (frontal area):

At 200W constant ............ 5.77mph uphill 54.08mph down

At 250W up, 100W down .... 7.18mph up 52.69mph down

That's about the same absolute increase up as down and a much greater % with variable power. Of course, there are lots of variables. For example, if the climb is long, using 250/100W may get your average power higher than 200 pretty quickly, but the general idea is that it makes sense to push more when it gains you more.

Jimmy

jws said:

Paul,

Here's a better example using: analyticcycling.comanalyticcycling.comOpen ↗

A 75kg rider + equip. on a 10% grade, 1.2 air density, A=0.45 (frontal area):

At 200W constant ............ 5.77mph uphill 54.08mph down

At 250W up, 100W down .... 7.18mph up 52.69mph down

That's about the same absolute increase up as down and a much greater % with variable power. Of course, there are lots of variables. For example, if the climb is long, using 250/100W may get your average power higher than 200 pretty quickly, but the general idea is that it makes sense to push more when it gains you more.

Jimmy

Jimmy, I agree that your example at least recognizes an asymmetric relationship between plus watts and minus watts, but it still isn't realistic. Look at the time difference between the two climbs. Your cyclist can sustain 250w for 44 minutes. If that were true, his max power for 1 hr wouldn't be 200w. It would be closer to 240w. The power/duration curve is very flat that far out. Paul