Correct power zones

SteveR_100Milers

Are the Coggan zones based on the 20' test or the 1 hour value calculated on 20'=105% of 1 hour value?

And what would be a typical power / weight ratio to achieve a 55 minute 25 and a 21' 10 time? on the assumption that x sectional area is proportional to weight.

Alex_Simmons/RST

SteveR_100Milers wrote:

Are the Coggan zones based on the 20' test or the 1 hour value calculated on 20'=105% of 1 hour value?

They are based on Functional Threshold Power, which is your best quasi steady state average power for about an hour. Neither of the above are that.

SteveR_100Milers wrote:

And what would be a typical power / weight ratio to achieve a 55 minute 25 and a 21' 10 time? on the assumption that x sectional area is proportional to weight.

I don't think you can make that assumption and apply it to an individual.

You need to focus on W/m^2, not W/kg.

Depending on how aero you are, you could do a 55-min 25 with 3.8W/kg (e.g. I have a client who rode > 46km in an hour on 4.0W/kg). Or you might need 4.8W/kg. And then what's the course like, and conditions? They make a massive difference.

But you'll need ~ 1250W/m^2 or better.

For the 21-min 10 you need somewhat more, like 1420+ W/m^2 and up.

SteveR_100Milers

Alex, what is the point of doing the 20' test then if they cannot be used to calculate training zones? I thought that was THE whole point of doing it, to estimate your ftp.

I have used this calculator:

http://mtbcoach.com/zonecalc/index-pwr.php

so how do you calculate your ftp?

The assumption of x sectional area to mass from here:

http://velodynamics2.webs.com/rcgtp1.pdf

see page 10. I did wonder if it was a sweeping assumption, but is written as if based on measured data.

I only asked, as I managed 22:40 on a 10 TT last year, on and out and back course with no net gain or loss in altitude, and fairly flat and windless evening. My power to weight ratio is probably around 3.0 - 3.2 W/kg at best.

Alex_Simmons/RST

SteveR_100Milers wrote:

Alex, what is the point of doing the 20' test then if they cannot be used to calculate training zones? I thought that was THE whole point of doing it, to estimate your ftp.

The point of a 20-min test is to establish your 20-min power.

If you want to then guesstimate your 60-min power from that, then you'll need to know what your ratio of FTP to 20-min power is. 95% is pretty uncommon IME and more often than not overestimates FTP.

Another means may be to add to that test another within the same week of say 4-6 minutes duration and then use the Monod & Scherrer Critical Power model to estimate Critical Power, which is generally a pretty good way of estimating FTP.

SteveR_100Milers wrote:

so how do you calculate your ftp?

I use a multitude of sins, depending on the athlete and individual circumstances. See here:
http://alex-cycle.blogspot.com/2008/05/ ... -sins.html
and here:
http://alex-cycle.blogspot.com/2009/07/ ... ftp-2.html

SteveR_100Milers wrote:

The assumption of x sectional area to mass from here:

http://velodynamics2.webs.com/rcgtp1.pdf

see page 10. I did wonder if it was a sweeping assumption, but is written as if based on measured data.

I only asked, as I managed 22:40 on a 10 TT last year, on and out and back course with no net gain or loss in altitude, and fairly flat and windless evening. My power to weight ratio is probably around 3.0 - 3.2 W/kg at best.

There are probably half a dozen equations in existence that take morphological data to provide an estimate of CdA. But since you have a power meter, why not directly measure it yourself?

Well you could do a couple of things.

1. run a virtual elevation analysis over the TT and attain an estimated CdA (coefficient of drag x frontal area) for an assumed Crr (rolling resistance) value.

Then with that you can work out what change in CdA and or power is required to attain the target speed.

The tools to do this are contained within Golden Cheetah software (Aerolab), or via the spreadsheets I have posted at the files section of the Google groups wattage forum. It's not all that difficult to do.

2. Since you have a time/speed for a 10TT and know your power, then you can use ananlyticcycling.com to estimate current CdA and then work out what change in power and/or CdA is required to attain the desired speed.

Use an estimate for Crr (rolling resistance) of 0.004 if you have good tyres and the road surface is pretty good, or 0.0045 or 0.005 if it gets a bit rougher.

Then you adjust the Cd and A values accordingly until you arrive at one that matches your speed for your known power. Easier to set one of those to 1 and just adjust the other (they are simply multiplied together in the equations of motion for a cyclist). It'll be something like 0.24m^2.

Then increase the power needed for your new speed.

But I can tell you that to knock 100 seconds off the 1360 seconds you are doing now, will require an increase in your power to aero drag ratio of about 27%.

So you will either need 27% more power, or be significantly more slippery than you are now (or of course a fair bit of both). Of course you will become more aero by being lighter, but not by anywhere the same margin that you drop weight.

SteveR_100Milers

Thanks Alex.

I should point out that the power is Tacx watts, so probably wildly inaccurate. I have used the 20' test figure in that zone calculator, and its probably too high. but, I am fairly confident that my 20' turbo effort was probably more like my 25m TT effort (based upon HR and PE). I now this is all rather vague, but if for no other reason I am finding riding to a target number means I can go harder and for longer on the turbo, which has always been a problem for me.

Alex_Simmons/RST

Well just go with an estimate, say 93% of a 20-min best. Might be 90% might be 96%.

If the subsequent intervals and training rides are too hard, then you know to adjust the levels down. If they are too easy, well bring them up.

Base training and intervals on what you have actually been able to do, rather than an arbitrary % of an anchor point. You really only use that as a guide to begin with.

Lightning

What I do (using the same turbo as you) is I do a 20 min all out test and then use 95% as my "ftp". I then use that value to plan my intervals until the next test and it always works out fine. I suggest you do the same and if you feel like you can't do it (and I really mean can't do it, not "it hurts too much" to do it), lower the value by 2% or something and do the intervals again.

Whenever you find the "right" %, just start doing that every time you retest the value and you're good to go.

SteveR_100Milers

Lightning wrote:

What I do (using the same turbo as you) is I do a 20 min all out test and then use 95% as my "ftp". I then use that value to plan my intervals until the next test and it always works out fine. I suggest you do the same and if you feel like you can't do it (and I really mean can't do it, not "it hurts too much" to do it), lower the value by 2% or something and do the intervals again.

Whenever you find the "right" %, just start doing that every time you retest the value and you're good to go.

OK, good - that's exactly what I was planning to do. I just wasn't sure if my 20 minute test was used to calc zones or 95% of it. It probably doesn't make that much difference, and to be honest, I'd probably ride the threshold sessions as hard as i can (just like a TT) in an case, just that the numbers show when you are slacking.