Re: Something borrowed...something FAST! [RChung] [ In reply to ]

May 28, 08 10:42

Post #426 of 571 (21011 views)

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As for the second issue, I pointed to analyticcycling.com where you can do the exact calculation to figure out how a change in m^2 of CdA translates into a change in seconds/km. At Tom's speed and CdA, I think you'll find that the "change in CdA of .01 means about 1 sec/km" rule of thumb is pretty good. As a reminder, Tom's precision on his CdA estimate is around .002 m^2.

But that rule of thumb rests on the assumption that the entire CdA delta between the P2K and P3C is attributable to the frame alone, rather than to any systematic changes in Tom's position while on the two frames, correct?

???. That rule of thumb depends only the power equation.

???. I thought the rule of thumb being bandied about on this thread implied that the P3C was 2s/km faster than the P2K. So I ask again, does that rule of thumb rest on the assumption that the entire CdA delta between the P2K and P3C is attributable to the frame alone, rather than to any systematic changes in Tom's position while on the two frames? Does it also rest on the assumption that there was no systematic change in power meter measurement between the P3C and P2K runs, as mentioned by roady?

Re: Something borrowed...something FAST! [Frank Day] [ In reply to ]

May 28, 08 10:44

Post #427 of 571 (21007 views)

In Reply To:

Dixon's subjects were self controlled. The study was conducted at the end of the racing season. The hypothesis was that the performance of each participant would be at a maximum at that time they started the study and that the expectation is that these participants would normally either maintain or lose performance at this time of the year normally using the training intensity studied, such that any improvement seen could be assumed to come from the PC intervention.

That's a pretty novel interpretation of the "controlled." I don't think you'll find much support for your usage in the scientific literature.

You would have to ask Luttrell why they did what they did if you really want to know for sure but as I read it, our power claims required a 6 to 9 months intervention, so they only decided to look at early changes that might eventually lead to such improvements. If no changes were seen in 6 weeks it is unlikely they would suddenly appear at 3 or 6 months.

Yikes.

Re: Something borrowed...something FAST! [RChung] [ In reply to ]

May 28, 08 10:49

Post #428 of 571 (21001 views)

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In Reply To:

Dixon's subjects were self controlled. The study was conducted at the end of the racing season. The hypothesis was that the performance of each participant would be at a maximum at that time they started the study and that the expectation is that these participants would normally either maintain or lose performance at this time of the year normally using the training intensity studied, such that any improvement seen could be assumed to come from the PC intervention.

That's a pretty novel interpretation of the "controlled." I don't think you'll find much support for your usage in the scientific literature.

You would have to ask Luttrell why they did what they did if you really want to know for sure but as I read it, our power claims required a 6 to 9 months intervention, so they only decided to look at early changes that might eventually lead to such improvements. If no changes were seen in 6 weeks it is unlikely they would suddenly appear at 3 or 6 months.

Yikes.

OK...I've had enough. Will you guys please take this to a thread that's actually about PCs? :-)

http://bikeblather.blogspot.com/

Re: Something borrowed...something FAST! [donm] [ In reply to ]

May 28, 08 10:57

Post #429 of 571 (20990 views)

In Reply To:

???. I thought the rule of thumb being bandied about on this thread implied that the P3C was 2s/km faster than the P2K. So I ask again, does that rule of thumb rest on the assumption that the entire CdA delta between the P2K and P3C is attributable to the frame alone, rather than to any systematic changes in Tom's position while on the two frames?

Boy, you are grasping at straws here, aren't you?

You're right, my rule-of-thumb implies that the P3C should be ~2 s/km faster than a P2k*. As Robert said, however, the derivation of that rule-of-thumb has absolutely nothing at all to do with the source of any difference in CdA.

*In 2004, I clocked a 54:12 40 km TT at the Missouri State TT while riding my wife's P2T and producing an average power (at the crank) of 294 W. Anybody want to bet against me getting under 53:00 this year? ;-)

Re: Something borrowed...something FAST! [donm] [ In reply to ]

May 28, 08 10:57

Post #430 of 571 (20989 views)

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As for the second issue, I pointed to analyticcycling.com where you can do the exact calculation to figure out how a change in m^2 of CdA translates into a change in seconds/km. At Tom's speed and CdA, I think you'll find that the "change in CdA of .01 means about 1 sec/km" rule of thumb is pretty good. As a reminder, Tom's precision on his CdA estimate is around .002 m^2.

But that rule of thumb rests on the assumption that the entire CdA delta between the P2K and P3C is attributable to the frame alone, rather than to any systematic changes in Tom's position while on the two frames, correct?

???. That rule of thumb depends only the power equation.

???. I thought the rule of thumb being bandied about on this thread implied that the P3C was 2s/km faster than the P2K. So I ask again, does that rule of thumb rest on the assumption that the entire CdA delta between the P2K and P3C is attributable to the frame alone, rather than to any systematic changes in Tom's position while on the two frames? Does it also rest on the assumption that there was no systematic change in power meter measurement between the P3C and P2K runs, as mentioned by roady?

The rule of thumb is that a difference in CdA of .01 is about equivalent to .1 s/km. That rule of thumb depends on the power equation and is independent of the PM one is using, and it most definitely does not rest on the assumption that changes in CdA from one source count differently than changes in CdA from another source. The estimated change of CdA in this case is .023 m^2. A change of CdA of that magnitude is equivalent to 2 - 2.5 s/km. Roady's point may or may not apply -- it sounds as if Tom kept the bike in an unheated garage -- but in any event it's not related to lack of blinding bias.

Re: Something borrowed...something FAST! [RChung] [ In reply to ]

May 28, 08 10:59

Post #431 of 571 (20981 views)

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In Reply To:

Dixon's subjects were self controlled. The study was conducted at the end of the racing season. The hypothesis was that the performance of each participant would be at a maximum at that time they started the study and that the expectation is that these participants would normally either maintain or lose performance at this time of the year normally using the training intensity studied, such that any improvement seen could be assumed to come from the PC intervention.

That's a pretty novel interpretation of the "controlled." I don't think you'll find much support for your usage in the scientific literature.

You would have to ask Luttrell why they did what they did if you really want to know for sure but as I read it, our power claims required a 6 to 9 months intervention, so they only decided to look at early changes that might eventually lead to such improvements. If no changes were seen in 6 weeks it is unlikely they would suddenly appear at 3 or 6 months.

Yikes.

Huh? That isn't my usage. It is simply what they did. Hardly any different that what Tom did here or what Joaquin did. He used himself and his expectation as to what he could do as his basis for measuring improvement or change. You seem to think it perfectly appropriate even though Tom is n=1 and Dixon was n=8 I believe. Yet Tom gets "frame" improvements between the P3C and P2K that are larger than the biggest theoretical frame improvement noted in the study earlier referenced by Dr. C and you are all accepting Tom's numbers without question.

You can, of course, criticize the Dixon study all you want. I have never claimed the study was perfect, it is what they did, I have only put out what they did and their results. At least they tried to look at the issue. Same with the Luttrell study. What are your criticisms there?

--------------
Frank,
An original Ironman and the Inventor of PowerCranks

Re: Something borrowed...something FAST! [Tom A.] [ In reply to ]

May 28, 08 10:59

Post #432 of 571 (20979 views)

FWIW....

do you have the older (all aluminum) version? I never experienced this with the older hub--and as a matter of fact, I never experienced it with the first generation SL. What I have noticed is that the newer hubs (particularly the wireless ones) seem more susceptible to this phenomena. I wonder if the torque tube isn't 'sealed' differently, resulting in it taking longer for the hub to 'warm up' (or cool down, whatever the case may be).

In talking to the good folks at Saris, I got the distinct impression that I'm not the first person to mention this to them.

I'm not claiming this to be some magic bullet to invalidate your results--just throwing it out there.

Re: Something borrowed...something FAST! [roady] [ In reply to ]

May 28, 08 11:05

Post #433 of 571 (20967 views)

In Reply To:

FWIW....

do you have the older (all aluminum) version? I never experienced this with the older hub--and as a matter of fact, I never experienced it with the first generation SL. What I have noticed is that the newer hubs (particularly the wireless ones) seem more susceptible to this phenomena. I wonder if the torque tube isn't 'sealed' differently, resulting in it taking longer for the hub to 'warm up' (or cool down, whatever the case may be).

In talking to the good folks at Saris, I got the distinct impression that I'm not the first person to mention this to them.

I'm not claiming this to be some magic bullet to invalidate your results--just throwing it out there.

My personal PT hub (the one not used in this test) is a yellow-cap PT Pro (i.e. the older design without carbon "windows" on the hub shell).

The hub used in the testing for this thread is a first generation wired SL hub...~2 years old.

I appreciate the questions and the information. It's all good in establishing or debunking the validity, right?

http://bikeblather.blogspot.com/

Re: Something borrowed...something FAST! [Andrew Coggan] [ In reply to ]

May 28, 08 11:06

Post #434 of 571 (20966 views)

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suppose that same scenario was duplicated while using 2 different computer heads, and 4 different wheels?

Then I'd be a bit more concerned. However, the fact that some version or versions of the PowerTap hub aren't as stable as they should be is fairly well known, so the first questions I'd ask are 1) did you ever have yours checked by Saris, and 2) is it the same model as the one Tom used?

I'd be more likely to question the SRM :-)

Re: Something borrowed...something FAST! [Frank Day] [ In reply to ]

May 28, 08 11:10

Post #435 of 571 (20955 views)

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Hardly any different that what Tom did here or what Joaquin did.

Don't even THINK of comparing what I reported to what can only be nicely described as a "hoax".

In Reply To:

Yet Tom gets "frame" improvements between the P3C and P2K that are larger than the biggest theoretical frame improvement noted in the study earlier referenced by Dr. C and you are all accepting Tom's numbers without question.

Without question? Really? I seem to see 18+ pages of mostly "questions"....

In Reply To:

You can, of course, criticize the Dixon study all you want. I have never claimed the study was perfect, it is what they did, I have only put out what they did and their results. At least they tried to look at the issue. Same with the Luttrell study. What are your criticisms there?

Like I said above...take it OUTSIDE!

http://bikeblather.blogspot.com/

Re: Something borrowed...something FAST! [Frank Day] [ In reply to ]

May 28, 08 11:15

Post #436 of 571 (20948 views)

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Dixon's subjects were self controlled. The study was conducted at the end of the racing season. The hypothesis was that the performance of each participant would be at a maximum at that time they started the study and that the expectation is that these participants would normally either maintain or lose performance at this time of the year normally using the training intensity studied, such that any improvement seen could be assumed to come from the PC intervention.

That's a pretty novel interpretation of the "controlled." I don't think you'll find much support for your usage in the scientific literature.

You would have to ask Luttrell why they did what they did if you really want to know for sure but as I read it, our power claims required a 6 to 9 months intervention, so they only decided to look at early changes that might eventually lead to such improvements. If no changes were seen in 6 weeks it is unlikely they would suddenly appear at 3 or 6 months.

Yikes.

Huh? That isn't my usage. It is simply what they did.

Frank, that's what they did but no one (except, evidently, you) would describe that as a controlled study. On your website, you claim: "PowerCranks really does increase [..] power (see Dixon) in trained cyclists over training with regular cranks." You can't say "over training with regular cranks" unless they were compared against training against regular cranks. That's a false claim.

Here's something else I've found vaguely interesting: you seem to know quite a bit about exactly what's legal in this area. In this post you wrote:
"I also understand it is not necessary to have scientific proof of something in order to make a marketing claim. As long as that claim is made in good faith and there is some evidence to back it up and no substantive evidence to refute it then one is on strong grounds legally."

Re: Something borrowed...something FAST! [Tom A.] [ In reply to ]

May 28, 08 11:16

Post #437 of 571 (20941 views)

In Reply To:

Like I said above...take it OUTSIDE!

OK.

Re: Something borrowed...something FAST! [rmur] [ In reply to ]

May 28, 08 11:19

Post #438 of 571 (20933 views)

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suppose that same scenario was duplicated while using 2 different computer heads, and 4 different wheels?

Then I'd be a bit more concerned. However, the fact that some version or versions of the PowerTap hub aren't as stable as they should be is fairly well known, so the first questions I'd ask are 1) did you ever have yours checked by Saris, and 2) is it the same model as the one Tom used?

I'd be more likely to question the SRM :-)

Nah. As roady points out, the nice thing about the SRM is that any consistent drift is readily obvious (I do sometimes wonder about short-term hysteresis, though). In contrast, it's harder to spot drift in the zero offset of a PT because 1) the resolution of the displayed zero offset value is ~10x poorer, and 2) the auto-zero feature tends to constantly minimize it (which is good on the whole, but makes it harder to know when something's gone wrong).

Last edited by: Andrew Coggan: May 28, 08 11:22

Re: Something borrowed...something FAST! [Tom A.] [ In reply to ]

May 28, 08 11:54

Post #439 of 571 (20902 views)

In Reply To:

Here are the VE plots for both races (2007 and 2008) using the "assumed" Crr and CdA as measured in separate testing. A couple of things jump out at me; first you can see variability in the wind strength/direction just during the run by comparing the first 10K to the last 10K (which are along the same leg of the course). Secondly, you can see that the wind direction and strength in 2007 made those same 2 segments appear "downhill", when in actuality the grade was uphill. Here's a link to the course (w/elevation) on MapMyRide:

http://www.mapmyride.com/...angeles/168322294943

I don't know...which conditions do you think were faster overall?

Since you have a "zero-wind VE" profile for 2008, you might be able to do a "what-if." Re-construct what the time would have been in 2008 using that profile under zero wind with the 2008 power but 2007 CdA.

Re: Something borrowed...something FAST! [RChung] [ In reply to ]

May 28, 08 11:55

Post #440 of 571 (20899 views)

In Reply To:

In Reply To:

In Reply To:

In Reply To:

Dixon's subjects were self controlled. The study was conducted at the end of the racing season. The hypothesis was that the performance of each participant would be at a maximum at that time they started the study and that the expectation is that these participants would normally either maintain or lose performance at this time of the year normally using the training intensity studied, such that any improvement seen could be assumed to come from the PC intervention.

That's a pretty novel interpretation of the "controlled." I don't think you'll find much support for your usage in the scientific literature.

You would have to ask Luttrell why they did what they did if you really want to know for sure but as I read it, our power claims required a 6 to 9 months intervention, so they only decided to look at early changes that might eventually lead to such improvements. If no changes were seen in 6 weeks it is unlikely they would suddenly appear at 3 or 6 months.

Yikes.

Huh? That isn't my usage. It is simply what they did.

Frank, that's what they did but no one (except, evidently, you) would describe that as a controlled study. On your website, you claim: "PowerCranks really does increase [..] power (see Dixon) in trained cyclists over training with regular cranks." You can't say "over training with regular cranks" unless they were compared against training against regular cranks. That's a false claim.

Here's something else I've found vaguely interesting: you seem to know quite a bit about exactly what's legal in this area. In this post you wrote:
"I also understand it is not necessary to have scientific proof of something in order to make a marketing claim. As long as that claim is made in good faith and there is some evidence to back it up and no substantive evidence to refute it then one is on strong grounds legally."

I haven't made any claims as regards that study or any other study. I simply put out what others have done. They did X, they reported Y changes. I also questioned how they determined statistical significance without a control group until I ran across a copy of their proposed protocol when I saw they intended to have the people act as their own controls. It is not perfect, but it is what they did. It was such they were able to do a statistical analysis. It is not what I would have done but it is a lot better than doing nothing, AFAIAC. Are you saying that you would have expected these trained cyclists, as a group, to be able to improve their VO2 max in 6 weeks, at the end of the racing season, 17% doing normal training? Any studies to support such a contention.

The studies are what they are. Where are the studies that show there is no benefit? Oh yeh, that one that evaluated the changes after 10 uses.

--------------
Frank,
An original Ironman and the Inventor of PowerCranks

Re: Something borrowed...something FAST! [donm] [ In reply to ]

May 28, 08 12:15

Post #441 of 571 (20877 views)

donm, for my entertainment at least, it's fun to see someone playing skeptic for the group that usually plays skeptic. I think you raise interesting questions. Regarding the magnitude of impact that positional changes might have, see this thread: http://forum.slowtwitch.com/...earch_engine#1791404

If I understand the ROT and my math is correct, a "shrug" putting the head down lower, can account for the entire Cda difference Tom's experiment revealed. (I know Tom insists his position was the same, and I certainly do not suggest he changed his position to the degree that Psycholist did with his markedly different "shrug" position).
.

________
It doesn't really matter what Phil is saying, the music of his voice is the appropriate soundtrack for a bicycle race. HTupolev

Re: Something borrowed...something FAST! [Andrew Coggan] [ In reply to ]

May 28, 08 12:16

Post #442 of 571 (20873 views)

In Reply To:

*In 2004, I clocked a 54:12 40 km TT at the Missouri State TT while riding my wife's P2T and producing an average power (at the crank) of 294 W. Anybody want to bet against me getting under 53:00 this year? ;-)

Anyone? Anyone? ;-)

Re: Something borrowed...something FAST! [HH] [ In reply to ]

May 28, 08 12:20

Post #443 of 571 (20866 views)

In Reply To:

Regarding the magnitude of impact that positional changes might have, see this thread: http://forum.slowtwitch.com/...earch_engine#1791404

If I understand the ROT and my math is correct, a "shrug" putting the head down lower, can account for the entire Cda difference Tom's experiment revealed.

In particular, take note of the fact that psycholist felt that he couldn't hold that position for a full 40 km, or at least not w/o some additional time to get used to it.

Re: Something borrowed...something FAST! [Andrew Coggan] [ In reply to ]

May 28, 08 12:27

Post #444 of 571 (20858 views)

In Reply To:

In Reply To:

Regarding the magnitude of impact that positional changes might have, see this thread: http://forum.slowtwitch.com/...earch_engine#1791404

If I understand the ROT and my math is correct, a "shrug" putting the head down lower, can account for the entire Cda difference Tom's experiment revealed.

In particular, take note of the fact that psycholist felt that he couldn't hold that position for a full 40 km, or at least not w/o some additional time to get used to it.

I'm considering getting a tailored skinsuit in which I have to shrug, turtle, and pray to Mantis - or else -
breathing during a TT is highly over-rated :-0)

Re: Something borrowed...something FAST! [Andrew Coggan] [ In reply to ]

May 28, 08 13:11

Post #445 of 571 (20821 views)

In Reply To:

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1:17 to 1:44 is the equivalent of 80 watts????

77-104 s/40 km = 1.9-2.6 s/km = approx. 19-26 W. However, that's 1) not at pursuit speed, and 2) is based on the benefit provided by now-outdistanced aerodynamic frames, e.g., the Hooker. You're also again overlooking the fact that I said "...essentially..." and "...largely...", not "...exactly..." and "...entirely...", but no surprise there: as I said before, it's crystal-clear that you'd have fit in quite well in the Bush Administration. ;-)

In Reply To:

Well, to me if you use the term largely, you are probably referring to something above 50%. You attributed 80 watts improvement "largely" to the frame alone. So, at a minimum I would have taken your improvement to be over 40 watts due to the frame alone from your statement. If you have better data by which you would like to correct this misperception as to what the real data is and your actual assumptions regarding the benefit of the frame you should post it here.

In Reply To:

What part did I fail to absorb or understand?

That for trained cyclists, there's quite often more to be gained by focussing on reducing aerodynamic drag than there is to be gained by attempting to further increase power output.

Only if the aero position is not near optimum and there is little room for power improvement. In the instant case of this aerodynamic improvement and Tom's time trial improvement, more than half his speed improvement came about because of a measily 18 watts improvement in power. Once one has "optimized" ones aerodynamics, the only further performance improvement is going to come from increasing power.

--------------
Frank,
An original Ironman and the Inventor of PowerCranks

Re: Something borrowed...something FAST! [Andrew Coggan] [ In reply to ]

May 28, 08 13:27

Post #446 of 571 (20804 views)

If it is the same course, I'll bet $50 you don't get under 53:00.
.

________
It doesn't really matter what Phil is saying, the music of his voice is the appropriate soundtrack for a bicycle race. HTupolev

Re: Something borrowed...something FAST! [HH] [ In reply to ]

May 28, 08 13:51

Post #447 of 571 (20783 views)

In Reply To:

If it is the same course, I'll bet $50 you don't get under 53:00.
.

It will be the same course, so consider it a bet.

Re: Something borrowed...something FAST! [Frank Day] [ In reply to ]

May 28, 08 13:56

Post #448 of 571 (20800 views)

In Reply To:

Well, to me if you use the term largely, you are probably referring to something above 50%.

"Largely" = the most quantitatively important factor.

Re: Something borrowed...something FAST! [Frank Day] [ In reply to ]

May 28, 08 14:21

Post #449 of 571 (20786 views)

In Reply To:

In the instant case of this aerodynamic improvement and Tom's time trial improvement, more than half his speed improvement came about because of a measily 18 watts improvement in power.

More than half? Umm...no. Conservatively speaking it was about half of the recorded gain...in my estimation it was more likely closer to 1/3rd than 1/2. Besides that, the remainder of the gain was in line with the predicted s/km.

Once again...what? Can't I do BOTH???

And what are you calling "measily"(sic)? 18W is 18W. There are a lot of people who'd love an extra 18W (as you well know).

http://bikeblather.blogspot.com/

Re: Something borrowed...something FAST! [Tom A.] [ In reply to ]

May 28, 08 18:26

Post #450 of 571 (20730 views)

In Reply To:

In Reply To:

In the instant case of this aerodynamic improvement and Tom's time trial improvement, more than half his speed improvement came about because of a measily 18 watts improvement in power.

More than half? Umm...no. Conservatively speaking it was about half of the recorded gain...in my estimation it was more likely closer to 1/3rd than 1/2. Besides that, the remainder of the gain was in line with the predicted s/km.

Once again...what? Can't I do BOTH???

And what are you calling "measily"(sic)? 18W is 18W. There are a lot of people who'd love an extra 18W (as you well know).

Back in post 297 I showed what analytic cycling says about the relative improvements. No one corrected my observations that I saw.

Now, the course was 50 seconds slower so your overall improvement of about 1:48 suggests to me that your total improvement was about 2:40. Looking at the power and the atmospheric conditions themselves predicted an improvement of about 1 minute, which when added to the slower course means the power increase accounted for an improvement of 1:50. The remainder of the improvement is coming from the aerodynamic improvement about :50.

I take this to mean that the majority (about 2/3) of your improvement came from the power. I am sure you will correct me if my figures are wrong as I would love to see how you got the exact opposite breakdown.

Edit: 18 watts is well under 10% and you are only in the mid 200's. Lots of room for improvement there. It may have come hard for you but I think it is pretty easy to see those kinds of improvements if one has the right tools and is willing to do the hard work. You are obviously willing to do the hard work. Maybe you are lacking the right tools. :-)

--------------
Frank,
An original Ironman and the Inventor of PowerCranks

Last edited by: Frank Day: May 28, 08 18:30

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