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RD pacing special

post #1 of 32
Thread Starter 
here's a pop quiz. Take a look at the TT pacing example presented on page 12 of the linked Saris/Powertap/Lim PdF and tell me what you think is wrong (if anything).

http://www.cycleops.com/culture/Power_basics.pdf

Assume 332W is the rider's current FT power.

rmur
post #2 of 32

Re: RD pacing special

Someone spent a lot of effort on that presentation. Too bad...
post #3 of 32

Re: RD pacing special

if i read it right then i'd say the sticking point in the constant velocity strategy could be the need to maintain almost 600 watts for 4k at one point!

it might have been idea to put some upper bound on the power.
post #4 of 32

Re: RD pacing special

Having spent a lot of time working on the issue of riding an optimal (variable power) pacing strategy on courses with variable grades and conditions (wind), I was very interested to see what approach this author was taking to the topic. Unfortunately, the author doesn't disclose any of the underlying principles or computations to arrive at the variable power pacing strategy, so it's impossible for me to figure out what's going on here. And, there is no discussion whatsover on the real hard subject: how to actually ride an optimal pacing strategy. Until one has an answer to that topic, it's just a math exercise.
post #5 of 32

Re: RD pacing special

Quote:
Originally Posted by rmur17
here's a pop quiz. Take a look at the TT pacing example presented on page 12 of the linked Saris/Powertap/Lim PdF and tell me what you think is wrong (if anything).

http://www.cycleops.com/culture/Power_basics.pdf

Assume 332W is the rider's current FT power.

rmur
I'd say that it is an overly contrived example, as only a complete neophyte (to cycling) would attempt to maintain precisely the same power up hill and down dale. Heck, even people just using a bicycle to get from point A to point B without any concern for the time required to do intuitively know that they should work harder going uphill, and relax coming downhill.
post #6 of 32

Re: RD pacing special

I was too lazy to calculate the NP and IF for the example but clearly, one wouldn't be able to sustain a lot of those high power bits.

On the other hand, sorta constant velocity is a good strategy so long as max power is constrained.

Is anyone else disappointed that Lim turns his nose down on all of the power based training and experimentation that's going on down here at our level? Ironically to me it seems he's missing a lot and is being left behind...of course he doesn't seem to share a whole lot so who knows.
post #7 of 32

Re: RD pacing special

Quote:
Originally Posted by RapDaddyo
Unfortunately, the author doesn't disclose any of the underlying principles or computations to arrive at the variable power pacing strategy, so it's impossible for me to figure out what's going on here.


One's a constant velocity (40 kph) ride which produces an average power of 332w, and the other's a constant power ride at 332w.

You getting enough sleep Rap?
post #8 of 32

Re: RD pacing special

Quote:
Originally Posted by frenchyge


One's a constant velocity (40 kph) ride which produces an average power of 332w, and the other's a constant power ride at 332w.

You getting enough sleep Rap?
Probably not. I've had a cold for a week, but have kept up the training anyway. And, it's cold here -- had to ride yesterday in 35 degree temps until it warmed up to 50. I'm sure I have your sympathy. Anyway, as soon as I scanned the slides, I realized this was a trivial example of VP pacing and just hit the "x" in the upper right corner. I think Saris should apply their full resources to making reliable power meters (including HRM receivers) and forget about software and power management strategies and such. They ain't no good at it.
post #9 of 32
Thread Starter 

Re: RD pacing special

Quote:
Originally Posted by acoggan
I'd say that it is an overly contrived example, as only a complete neophyte (to cycling) would attempt to maintain precisely the same power up hill and down dale. Heck, even people just using a bicycle to get from point A to point B without any concern for the time required to do intuitively know that they should work harder going uphill, and relax coming downhill.
IF = 1.26 for the hour and NP= 418W with "Regulated Velocity Pacing".
There's not a snowball's chance in h_ll that anyone could perform that ride (with an FT of 332W).

I assume this is an example he uses in presentations etc. and I found it surprising that it was SO far off what one could actually ride. NP is severely violated for the hour and I'm sure at least typical P-D curves would be knackered by the hill power suggestions. I did not take the time to calculate where running NP would fall off the chart.

I read that he doesn't use NP or any form of adjusting average power to reflect the actual metabolic demands. I think this example shows why that's not a good thing.

rmur
post #10 of 32

Re: RD pacing special

Quote:
Originally Posted by frenchyge


One's a constant velocity (40 kph) ride which produces an average power of 332w, and the other's a constant power ride at 332w.

You getting enough sleep Rap?
I haven't given this slide presentation much thought, but it just occurred to me that the example argues in favor of pacing by speed vs. power. Interesting marketing strategy for a manufacturer of a power meter.
post #11 of 32

Re: RD pacing special

Quote:
Originally Posted by RapDaddyo
I haven't given this slide presentation much thought, but it just occurred to me that the example argues in favor of pacing by speed vs. power. Interesting marketing strategy for a manufacturer of a power meter.
You're right, there. Maybe while that slide is on the screen the instructor says something to the effect of: "while it would seem by this example that pacing by speed would be the best strategy, many of these ride segments are far too difficult to manage according to this strategy. Therefore, we recommend buying one of our power meters and spending a fair bit of time hanging out on CyclingForums.com learning about a *real* variable power pacing strategy from a poster named RapDaddyo...."
post #12 of 32

Re: RD pacing special

Quote:
Originally Posted by frenchyge
You're right, there. Maybe while that slide is on the screen the instructor says something to the effect of: "while it would seem by this example that pacing by speed would be the best strategy, many of these ride segments are far too difficult to manage according to this strategy. Therefore, we recommend buying one of our power meters and spending a fair bit of time hanging out on CyclingForums.com learning about a *real* variable power pacing strategy from a poster named RapDaddyo...."
It is sort of comical that I can make a more persuasive argument for pacing with power than Saris.
post #13 of 32
Thread Starter 

Re: RD pacing special

Quote:
Originally Posted by RapDaddyo
It is sort of comical that I can make a more persuasive argument for pacing with power than Saris.
And it definitely shows what sort of nonsensical results one can derive when using only Average power constraints. It looked bad on 1st inspection but when I popped the data into Excel and found IF was 1.26 ... well I couldn't resist

I do a fair of amount of TT's on the Computrainer and, there being no wind to consider, it's reasonably easy to work out a reasonable pacing strategy for course of sufficient grade % and length.

On the road yes I consider what would be ideal but wind has such a large effect that any calcs. must really be based on wind conditions on the starting line. No I don't bring my laptop to local races

rmur
post #14 of 32

Re: RD pacing special

Quote:
Originally Posted by rmur17
And it definitely shows what sort of nonsensical results one can derive when using only Average power constraints. It looked bad on 1st inspection but when I popped the data into Excel and found IF was 1.26 ... well I couldn't resist
My guess is that the guy doesn't actually ride a bike. Nobody who has actually tried to ride those sort of numbers could put together such a ridiculous example.

Quote:
Originally Posted by rmur17
I do a fair of amount of TT's on the Computrainer and, there being no wind to consider, it's reasonably easy to work out a reasonable pacing strategy for course of sufficient grade % and length.
The problem isn't working out a reasonable pacing strategy on paper. The problem is putting the pacing strategy to use on the course, unless the grade changes are very few and very easily detected. Real-world courses have frequent grade changes and many are not easily detected.

Quote:
Originally Posted by rmur17
On the road yes I consider what would be ideal but wind has such a large effect that any calcs. must really be based on wind conditions on the starting line. No I don't bring my laptop to local races
I agree about the effect of wind conditions. I don't bring a laptop to local races either -- too much wind resistance.
post #15 of 32
Thread Starter 

Re: RD pacing special

Quote:
Originally Posted by RapDaddyo
My guess is that the guy doesn't actually ride a bike. Nobody who has actually tried to ride those sort of numbers could put together such a ridiculous example.

The problem isn't working out a reasonable pacing strategy on paper. The problem is putting the pacing strategy to use on the course, unless the grade changes are very few and very easily detected. Real-world courses have frequent grade changes and many are not easily detected.
My favorite grade detector is speed given constant power Surely you're not talking about a real-time grade and power 'adviser' are you?

I certainly look at courses beforehand and work out roughly where I'll try to ride each grade/hill and just as importantly where to conserve power or even tuck. If you have a familiar course, I think folks learn this reasonable quickly - the analytical approach is most effective on a new course. I do, of course, look at my TT's postscriptively too see how I've done.

Quote:
Originally Posted by RapDaddyo
I agree about the effect of wind conditions. I don't bring a laptop to local races either -- too much wind resistance.
Okay. But my onboard CPU isn't rated for anything other than 'feel'. P^4 calcs are a little too tough and I can only remember things like FT, Vo2 power.

RD, how about posting your best advice for how the Lim rider should ride that course? I'll go out on a limb and say that one can save only about half the 1:48 claimed.

Assumptions:

(1) FT=332W

(2) NP and rolling NP are constrained to a typical Power-duration curve droop of 5% listed as 60/30/etc minutes:

60NP <= 335W, 30NP <= 350W, 15NP <= 365W, 7.5NP<= 385W,
3.75NP <=405W (rounded to nearest 5W)

(3)1-min power ~700W

all for now,
rmur
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