Why I'll Never Give Up My Power Meter

jws

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.

RapDaddyo

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

RapDaddyo

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).

jws

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

RapDaddyo

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

RapDaddyo

Let me put it another way. Your cyclist has a max 1 hr power of 200w, but he can pull 250w for 44 minutes? Watch out, we'll get Flyer revved up on his PED theory of the world.

rule62

LOL...yeah the first time that I rode in a big fast pack I looked down at my readings and thought that there must be something wrong with my Powertap. You know in the movies how they thump on gauges to make sure that they are reading right? That's what I felt like doing. Then when I took a pull, it all became painfully clear.

jws

He can't do 250W for 44min, but he can do it for 1 or 2min without blowing. This works well on rolling terrain; for mountains the numbers would change, but it's still better to do maybe 215W for the toughest 20min or so of a long climb and recover back down.

If you don't believe the links I sent, test it out on a rolling course. Use isopower on one run and on the other run ride like you described you used to do, careful not to overcook it. Make sure conditions don't change between runs(do one immediately after the other) and compare times.

The exact balance of power and duration is where the art of pacing begins.

Ciao, Jimmy

mises

One of the reasons variable power can work better is that all power levels don't draw from the same metabolic pathways. Shorter 10 second blasts use different energy sources than 20-45 second ones which are different from 1 hr, so drawing from one won't necessarily compromise another.

Because longer intense efforts become more similar to the energy pathways of a constant power TT pace I would expect those to quickly become too costly to be of benefit, and if not an indication you were slacking to start with.

acoggan

And to follow up on that post:

At my instigation, Kraig Willett did as I suggested and incorporated normalized power as a constraint in a physics-based model that allows assessment of different pacing strategies (hunt around on www.biketechreview.com to find some examples of some applications...although I think that Kraig is now selling this as a service, so he may have taken some of them down). The results were also as I predicted: experienced riders seem to intuitively choose a pacing strategy that minimizes the time required to complete a TT, even if this requires large variations in power. Thus, from an application perspective I don't see this modeling effort as a large breakthrough, but merely confirmation of what has already been learned empirically - however, it can also be a good teaching tool to help speed up somebody's "learning curve", especially if 1) they are a relative newcomer to the sport of cycling, and/or 2) they don't have the opportunity to train on a particular course in advance.

jws

I'm no physiologist, but I think that going above threshold which uses some anaerobic stores, DOES compromise your overall output. Despite that, the time gained is still worth the cost. That is, you gain more time uphill than you lose during the necessary recovery time.

Your average power will be lower with variable power, yes, but it's time that matters.

jws

Thanks, Andy....and here it is:

http://www.biketechreview.com/power/supercomputers.htm

RapDaddyo

That's a very interesting article. Thanks for finding it, Jimmy. Actually, I tried to do a variable power experiment today on my 20 mile TT course (mostly flat). Now, I'm not very fit yet because I've only been back on my bike for 3 1/2 months. I'm not even absolutely sure what my 40K max power is but I estimate it's about 250w. I didn't want to go at full 40K power because I have a group ride tomorrow and didn't want to have to worry about holding back. So, my goal was to ride my course at ~215w, but with pushes up a couple of short hills and easing up a bit on the downhills. I basically found that I was able to bring my power up to ~270w on the climbs (well, I got carried away a couple of times and pushed it to ~330w for a brief time) and recover at ~190w on the downhill for an equal amount of time. So, that's a plus ratio for gain/loss and would favor charging the hills. But, it could just reflect the fact that I wasn't pacing myself close enough to my 40K TT power. I think if I had done the ride at ~250w I would have had a negative ratio of push/recover. I also think that there's no point in "saving" watts for later use. I don't think I can store them up and use them later. Rather, I think you ramp up the power over your max sustainable power only when you're going to have a chance to back off and recover immediately after. But, I suppose this relationship changes as one becomes more fit and recovers faster from a push. Whatever the optimal pacing strategy, having a PM to play with the variables makes a world of difference. Thanks for the info. Paul

stormer94

stop, you're killing me... <waiting for mine to show>

Also, I think if you sell your clothes, your riding buddies will insist that you take shorter turns on the front.......

__________________
-------
"Was" 39 year old guy Blood pressure: 143/84, Resting Pulse: 68, weight: 230
"summer 2004" 40 year old guy. Blood pressure: 121/66, Resting pulse: 45, weight: 175
1-1-2005 Blood pressure: 115/55, Resting pulse: 44, weight: 170
6-1-2005 Blood pressure: 105/52, resting pulse: 40, weight: 175
40k-TT, 1:05