## Help from Power Gurus

A light bike doesn't replace good fitness.

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pagey
Posts: 33
Joined: Sun Jul 11, 2010 3:03 am
I need some help deciphering the following power numbers. I'm newish to power having had a PM since Sept last year, and am struggling to determine my FTP.

Last August I conducted a VO2max lab test, with the following results

VO2Max Peak - 57.3 @ 325W @ 186bpm
Threshold - 250W @ 158bpm
Weight - 68kg

On Sat I conducted a 20min FTP Test on my turbo trainer with the following results

Avg W = 210w @ 166bpm (so FTP @ 95% = 200w)
I thought was really pushing hard in this test.

On Sun I conducted a 2hr ride that included 2 x 20min sustained climbs (Mt Dandenong if anyone knows it)

1st climb after 20min warm up - 5km avg grade 6.6% 20min
Avg W = 280w @ 170bmp

2nd climb after 10min downhill recovery - 5.4km avg grade 5.8% 20min
Avg W = 232 @ 164bpm

Not sure what to make of these numbers. Any insight would be grateful.

Tapeworm
Posts: 2585
Joined: Thu May 03, 2007 10:39 am
First, two questions.

1) What was the testing protocol for the VO2max test?
2) What kind of power meter do you use?
"Physiology is all just propaganda and lies... all waiting to be disproven by the next study."
"I'm not a real doctor; But I am a real worm; I am an actual worm." - TMBG

pagey
Posts: 33
Joined: Sun Jul 11, 2010 3:03 am
1. The testing protocol was conducted on my bike attached to their machine. The crux of it was a ramp test wearing an oxygen type mask taking measures throughout until I could not hold the interval.

2. The power meter is a power2max

Pagey

Tapeworm
Posts: 2585
Joined: Thu May 03, 2007 10:39 am
1) This more akin to a Maximal Aerobic Power test. Normally FTP is derived from this in the 72-77% range being 234-250 FTP.

2) Ah. These cannot be calibrated from what I know and do suffer from large variance. If the above was done on a lab power meter I would be inclined to believe that one. However given that the test was done in August it would be very redundant.

From the numbers on the trainer it is usual that numbers are lower inside. From the climb the first is far higher than the second which could be either fatigue or power meter variance or both. I'd split the difference and call FTP at around 243. Test again in two weeks preferably on the same climb or in better race conditions - like a TT.

Repeatability of testing is crucial for accurate training.
"Physiology is all just propaganda and lies... all waiting to be disproven by the next study."
"I'm not a real doctor; But I am a real worm; I am an actual worm." - TMBG

Rick
Posts: 2032
Joined: Sat Aug 29, 2009 4:30 pm
Your experience tracks pretty well with mine.
I can never get anywhere near the same intensity on a windtrainer than outdoors.
I can always get higher numbers on a sustained climb than on flats.

I can speculate why, but in the end, I don't know. I just accept it and only compare like-like conditions to track improvement.

In fact, I was just killing myself doing some intervals on rollers the other night, with very low power numbers. Then, on the road I was cruising along effortlessly and noticed it was higher power than during my intervals. Same bike and powermeter.

mrfish
Posts: 1630
Joined: Wed Mar 28, 2007 12:49 pm
Location: Near Horgen, Switzerland
I think it's also to do with temperature - indoors your heart needs to pump lots of blood to the skin to exchange heat to stop you boiling, as your 250W is generating almost 1KW of heat which has to go somewhere. If unused to this, the brain's self protection mechanisms cut in quite early.

If you ride hard on the trainer on a regular basis you will get better at it and find that either your body is getting more used to the heat, or more likely that your brain's reflext to slow you down and stop you boiling cuts in later. It's probably not the best way to train to ride a bike fast, but it does mean that you will be better equipped than most to ride when it's 40 deg C.

Brian1946
Posts: 13
Joined: Sun Jul 10, 2011 9:02 pm
Quoting OP not required

The two test experiences are not comparable at all, a few things to consider...

In August you're probably at your fittest after a summer of riding/racing?
The temperature was probably significantly higher and in a lab setting maybe at optimum for testing?
The two/three day time period prior to the two tests may have been significantly different... rest, preparation, diet etc?
The two test machines are not comparable, the one in the lab probably calibrated precisely, your turbo... who knows where it's at?
The test you undertook at the lab, did you do exactly the same on the turbo? (It won't count anyway because of the above)!!
There is nothing to be gained from comparing the two results.

What you can take from it is that your lab test is most probably an accurate assessment of your fitness at that time.
Your turbo results are what they are and shouldn't be compared with anything else. What you can do with the results is use them as a baseline from which to undertake repeat tests. However you must use exactly the same protocol each time, roller pressure on the tyre, tyre pressure, warm up and test, doing so will provide information from which you will be able to gauge any progression.

Edit - sorry, just re-read your post! The 2x20 minute hill climbs are also different and so are not comparable a) with each other; and, b) with either your Turbo test or your lab test. There just isn't any consistency between your testing. Many riders report that they are able to produce higher wattages 'on the road', it is suggested that it's due to barely perceptible micro rest intervals allowing the body to gain some recovery. Even using the same hill, bike, tyre pressure, calibration etc will be weather affected.

The real trick in testing is to keep as many of the possible variables consistent from test to test, your turbo provides the best opportunity for this, but you have to ensure you eliminate those inconsistencies.

Try to forget about achieving the 'big' number and refocus on securing progression against an accurately established, recorded and repeatable baseline test. You should be looking to test every 4-6 weeks in order to see progression (if you're training properly).

Hope the above helps.

Dalai
Posts: 1491
Joined: Wed Dec 15, 2004 10:54 am
Location: Melbourne, Australia
Brian1946 wrote:In August you're probably at your fittest after a summer of riding/racing?

From the clue about Mt Dandenong which is in Australia, Pagey is in the Southern hemisphere. So still winter, though mild compared to many northern winter photos posted in the on the road topic...

pagey
Posts: 33
Joined: Sun Jul 11, 2010 3:03 am
Thanks for the feedback. I'm not trying to make a comparison per say, really trying set a baseline to ensure that my TSS measures are usable

Pagey

Andrew69
Posts: 142
Joined: Thu Feb 19, 2009 10:52 am
pagey wrote:2. The power meter is a power2max
Pagey

Unfortunetly, this may well be to blame. As others have said, P2M suffer a fair degree of drift with temperature.

While it may not cure it totally, it will help if you leave you bike outside for 15-20 minutes for the PM to acclimatise. That should minimise any drift.

tcramer
Posts: 169
Joined: Mon Jun 05, 2006 3:19 pm
Location: Greve, Denmark
Andrew69 wrote:
pagey wrote:2. The power meter is a power2max
Pagey

Unfortunetly, this may well be to blame. As others have said, P2M suffer a fair degree of drift with temperature.

While it may not cure it totally, it will help if you leave you bike outside for 15-20 minutes for the PM to acclimatise. That should minimise any drift.

You don't need to put the bike outside before riding. Just go riding and get your self warmed up good. By the time you are warmed up the PM will have acclimatised. Hold frewheel for 4-5 seconds (power must be zero for at least 2 seconds) and you are ready. By the way the reported drifting of P2M seems to be far less once it has been used a couple of times. But you can alwas make the zero offsett as described and then powerreadings should be spot on.
Bring the mountains to Denmark!!

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