RPE (+HR?) vs Power for TTs

Some people have suggested to me that perceived exertion becomes a better measure of intensity after you have trained extensively with power - eg, you learn to feel your power level better after a while, even without looking at the power readout. Have people found this to be true? Given the importance of pacing strategies to TT performance, I am wondering about the merits of pacing with a powertap on an average wheel (eg training wheels) versus riding race wheels (disk or tri-spoke) with RPE or RPE + HR. Which is going to yield the faster time? What is the most effective way to adopt the latter strategy? Or should I just sell my soul/body so I can afford an SRM professional and ride whatever wheel I want?

Very interesting questions. Speaking only for myself, I can do a reasonable job of estimating my power at certain levels on the flat, but I do a terrible job of estimating my power uphill, upwind, downhill and downwind. For example, when I start uphill I always underestimate my power initially. I also do a terrible job of estimating my power at levels significantly above my normal, everyday levels. For example, I would probably be off by up to 50w over 350w. If you've been following the threads on TT pacing strategy and recovery times, I can't imagine in my wildest dreams employing a highly variable pacing strategy with much precision without a PM. As to your wheel issue, a PT Pro for your training wheels and a PT SL for your race wheels is less than $2K total, whereas a SRM Pro is ~3.4K. The receiver and computer are the same.

Cheers, good answer. Can I ask how long you have been training with power? Do you have a feel for how you would go in TT's by feel versus a pre-planned pacing strategy with power? I am especially interested in comparing the diffences you see in your results using a well thought out pacing strategy to the benefits of using aero equipment - eg a Disk, or deep dish race wheel versus training wheels. Have you (or anyone else reading this) done any work blinded to power (eg - covering the head unit) then checked your results against a similar interval looking at the power? If so what were the differences? This would be particularly interesting as if completed around the same time whilst similarly rested it would separate out any training effect from the advantage of pacing strategies. (Eg - I would expect that you are better trained now than before you started working with power, so I'm worried about using any data you have from before then and comparing).

Seems the PT is the economical option. The major disadvantage for me is that I tend to borrow race wheels for TT's as I can't afford good stuff. Ironically, this problem would be solved by spending a truckload of money and getting an SRM pro. I think I will start with one PT pro on training wheels, use the rear training wheel for non-target races, then perhaps build an SL onto a race rim when I can afford it. No getting around swapping out the PT for a Disk in TT's though.

As an aside, I have been following the threads you mention - with considerable interest!

About 2 1/2 months. HRM before that.

No, but I may try it sometime. Without a PM, I would probably rely more on RPE than HR because training with power has shown me how unreliable HR is. My pacing strategy would be simply to try to keep bike speed up -- apply more power uphill and upwind and back off downhill and downwind. But, I am anticipating that it will be up to 2 mins slower in a 40K TT.

The benefits of aero equipment and position are pretty well documented. As to the benefits of precision variable power pacing strategy, that'll vary as a function of the course (flat or rolling) and wind. The ideal TT for variable power pacing would be 1/4 - 1/2 mile hills followed by 1-2 mile downhills at about 1/4 the grade of the uphill segment and any flat segments would be zig-zag with a howling wind.

No.

~100w+ sustainable 40K power.

The #1 advantage of a PM (IMO) is the gain in total power, at all durations, through a more precise way of measuring performance and planning training rides. I'd take that added power in a heartbeat over the ability to precisely manage less power in a TT. Give me LA's power and I'll happily ride a Huffy with fat tires and no bike computer at all. When you've got 450+w, who needs it?

Cool. Stay tuned. We've got Andy, Ric and Lindsay engaged now. We're rockin'!

When blinded to power output, people -- even highly experienced professional male cyclists (world champion) tend to overestimate their ability and completely mess up pacing.

For e.g., in our study looking at laboratory 10-mile TT performance, riders had to ride an ergometer fitted with their own bike and asked to ride at their fastest pace possible to cover the distance in the shortest time. In such a scenario a constant or a negative second split would be best. however, as riders we blinded to power etc, their brains couldn't cope and everyone started as if they were riding a for just a few minutes. Even ex (current at the time) world champions displayed the same poor pacing skills (they weren't part of that study, but were undertaking a different study that used the same protocol).

you can see the mean minute by minute power outputs in figure 9 here
http://www.cyclingforums.com/articles/a-3-3.html

All riders in this study were experienced racers

ric

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You're kidding yourself if you think that the high dollar wheels you're borrowing are giving you a significant advantage in your races.

I race and train with a PT open pro but slap a wheel cover on it for TTs (nobody minds around here).

If I could, I'd love to have an additional PT with a deep section (like a Zipp 404 or HED alps/Jet or whatever) for RRs Crits, but I also know that in reality the advantage those wheels provide is pretty minuscule.

I actually own a real disc wheel but I can't bring myself to use it anymore. BTW, anyone wanna buy a zipp carbon disc, tubbie?

I think there's plenty of evidence that a disk rear and a deep dish or tri-spoke front give a significant advantage over any other configuration for almost all time trial courses. I don't think I'm kidding myself. I'd be willing to believe, though, that I might be doing myself out of time by not pacing off power, in which case it becomes important to quantify the advantage of both.

Do you have a feel for the amount of time that this pacing strategy cost them (or would cost me, for example, in a 40km TT)? I guess I could analyse it with that algorithm that Andy Coggan gives?

I missed the part that you were only worried about TTs, I was talking RRs&Crits. No doubt that a deep front and a disk rear are better for TTs (actually I do run a deep front for all races including mass start and TTs), but firstly, last time I checked, powertap doesn't require a specific front wheel so you can continue to borrow, and secondly, if you live in the U.S. (and possibly other countries, I don't know) nobody is going to protest you for using CH aero covers on your PT wheel which work just as well as a real disc, and it will only add like $50 to the bill.

If you don't believe me though I'd be more than happy to sell you my disk wheel for cheap.

Your question is very complex, but let me simplify it and give you an off-the-top-of-my-head answer. Fundamentally, you are asking an economic optimization question: "If I have, say, $1,000 available, should I invest in a PM or in wheels if my objective is the greatest reduction in my 40K TT time?" The answer lies in several assumptions: (1) what is my 40K MP? (2) what is the nature of the course (flat or rolling or major climbs) and the conditions (e.g., wind)?; and (3) what pacing strategy do I intend to employ? We have a basis for estimating the effect of aero wheels vs. standard wheels in the study by Jim Martin http://www.cervelo.com/tech/articles/article5.html. This analysis suggests that the min/max time savings over a 40K TT is 1:06-1:32 (I am ignoring the time savings for recreational cyclists). So, let's bias the analysis in favor of wheels and use 1:32 as the decision criterion. IOW, if the PM would result in <1:32 of time savings, buy the wheels; otherwise, buy the PM. That brings us to the very complex question of TT pacing with and without a PM. Obviously, this is going to vary from cyclist to cyclist based on their individual abilities to produce a desired power without reference to a PM. But, let's assume Ric is correct when he says that even world-class cyclists do a poor job of managing power without a PM. The real problem with this is that the price is so high of inadvertently riding at a power greater than one's sustainable power for the duration (in this case, >40K MP), due to the 4th power IF penalty when one goes over sustainable power. The net of this is that variations in power above and below one's sustainable power will result in a reduction in average power for the event, assuming these variations net out to normalized power exactly equal to one's 40K MP. I'm going to make a wild guess that average power without a PM would be at least 5% below NP on a board flat course with no wind. If one's 40K MP is 300w, that would result in a time loss of 1:13. If one's 40K MP is 250w, it would be a time loss of 1:22. So, assuming the best case for aero wheels (1:32) and the worst case for the PM (1:13), the advantage goes to the wheels, by :19. If the course is rolling and/or there is wind and one plans to employ a variable power pacing strategy, I think the advantage goes quickly and strongly to the PM. If it were my choice, I'd take the PM. And, this doesn't even take into account the suggestion of buying a PM and some cheap wheel covers. If you go that route, I think the wheels investment get killed. Sorry if this is kind of rambling. I just don't have the time to make it tight.

That's the equipment strategy I settled with in the end -- PT Pro on a training rim. I'm hoping that over time that my pacing 'by feel' will improve as a result of my training BY power, and that my race results will benefit from that even when I'm not using my PT wheel.

Analyticcycling.com just began offering SL hubs built into HED Alps 24 spoke wheels, but I still think Cycleops is missing the boat by not producing a disk compatible PT system.

This is slightly different to real world conditions as there you at least have some estimation of speed either from a bike computer or from watching things go buy, including changes in gradient, observations of wind conditions, etc, which gives the brain marginally more info than when just sitting on a lab cycle. It also seems possible to me for experienced cyclists that cues like the feeling of the wind rushing past may help. Admittedly, the brain may not be very good at using this information. Do you have a feel for how this works out in the real world?

having seen data files from how people ride out on the road in a TT, it's still very similar. For e.g., i've seen people that average ~ 300 W do starting efforts at 900 W riding pretty much 'all-out' for the first several minutes (obviously power is decling rapidly here, but it's still way above mean power). They then typically continue decreasing until they are recovered enough to start picking things up in the last few kms.

i've seen people pace badly (but not as badly) who average 350 to 450 W.

ric

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Hey, Roadie_scum. You're working real hard to convince yourself that you don't need a PM to manage your power in races. I think you want to buy the race wheels and you're rationalizing it as the best investment decision. But, I think the evidence is against you. Why don't you ask any of the PM users if they would trade their PM for race wheels in a TT? I don't think you'll find many who would make that trade.

Not to argue, but the author of that VP strategy article did find that experienced riders naturally apply the VP principles in their rides even without access to a PM. Also, a disk wheel provides a tangible benefit on *every* TT, regardless of whether the course is suitable for VP pacing or not.

The choice between a disk wheel or *second* PT hub on a high-end spoked wheel for use during races isn't exactly cut and dried in terms of optimal benefit. Certainly a disk is cheaper as well.