Power comparisons

by Old Cranky   November 19, 2009  

I read that Sir C.Hoy puts out 2,300 to 2,500 watts during his 200 metre sprints and I recall some of the TdeF riders averaging over 450 watts for long stages.

There are various ways of measurement - at the pedal, at the crank, at the rear hub and on a turbo trainer - but what's the baseline measurement to do reasonable comparisons between riders?

Presumably there different tests and figures for endurance riders and sprinters, so you couldn't compare Sir Chris with Bradley Wiggins CBE. Does anyone know what they are and how we, mere mortals, compare? Nerd

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I don't think there is a baseline figure, each discipline uses a different baseline I would think.

The standard measurement for basing most training on tends to be FTP (functional threshold power) which is the max power you can sustain for an hour, but often also taken as your your 10 mile TT power.

As they are training such different power systems, a track sprinter and a grand tour rider are not going to have any meaningful comparisons.

The pro road racers will be the ones to compare ourselves to, and will have horrifyingly high FTP.

Complicating matters since 1965

DaSy's picture

posted by DaSy [644 posts]
19th November 2009 - 14:31

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It's commonly taken that in order to win the Tour de France you need to have a power-to-ratio of 7W/kg at functional threshold power, which DaSy has so eloquently explained. So, if you're an average 65 kilo pro rider then yes, your FTP needs to be a shade over 450W. One thing weighing against Wiggo in the GC is his height: even at 4% body fat he's still over 70 kilos, meaning that to maintain the same power-to-weight ratio he needs to push out nearly 500W at FTP. because power-to-weight takes account of your weight too it's a much better indicator of your performance than simple power. The top guys manage a 7, mine's less than 3 Sad

Sprinting is another thing entirely, it's all about anaerobic effort and power. it's not as meaningful a measure of performance. unless your chosen discipline is sprinting, of course Smile

incidentally i'd doubt that any tour rider would *average* 450W over a stage. On the flat they push out much less than FTP, and sitting in the peloton can save you as much as 30% of your effort

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posted by Dave Atkinson [7036 posts]
19th November 2009 - 14:52

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incidentally, most power meters work in a similar way, they have a strain gauge that measures the torque and then they do the sums from that. Some turbos don't have a measuring device per se, but they're calibrated with one in the factory and extrapolate power from your speed and the calibrated data

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posted by Dave Atkinson [7036 posts]
19th November 2009 - 14:55

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If FTP is the benchmark measurement then can you do it yourself - say by renting a powertap wheel with ANT+ to a Garmin - or where would you go to be assessed?

Dave - Where did you get your FTP 3 measured

posted by Old Cranky [275 posts]
19th November 2009 - 15:25

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i took mine from a ten effort that i borrowed a powertap for. if you rented a wheel you could work it out. Some people will have it that a 25 is a better measure of FTP, there's no concensus.

One other test that you can try is hill reps: pick a steady hill and ride it repeatedly at power increments (say 150, 175, 200 etc) with a set recovery in between. if you plot your heart rate at the end of each effort you should see a linear progression which tails off at a certain point: that point is your FTP, where your CV system is no longer capable of upping the ante to provide the extra power and you start working anaerobically.

sorry to any sports scientists if i've massively oversimplified that, or just got it wrong Smile

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posted by Dave Atkinson [7036 posts]
19th November 2009 - 15:45

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incidentally my FTP was about 285W and my weight was 108kg, so my Power to weight ratio was 2.63. I'm a bit fitter now and a fair bit lighter (97kg) so the number has no doubt gone up a bit Wink

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posted by Dave Atkinson [7036 posts]
19th November 2009 - 15:51

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Right - I'm going to have a go. Best place to rent a powertap wheel?

posted by Old Cranky [275 posts]
19th November 2009 - 15:56

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you can have one off www.cyclepowermeters.com for £9 a week, min four weeks so long as you cancel before two weeks is up, otherwise it's 12 weeks

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posted by Dave Atkinson [7036 posts]
19th November 2009 - 16:03

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Any full on effort for an excess of 30 mins is considered about right. FTP should strictly be a 1 hour effort, but mine was done on a steady climb that took me 40 minutes.

I had an FTP of 336W and a power to weight of around 4.6 W/Kg in May of last year.

FTP and power to weight are easily measured yourself, just requiring the purchase or loan of a power measuring device such as a Powertap or SRM cranks. Some of the turbo's that measure power can be a bit out, my Fortius is good for comparison, but absolute figures are best done with a calibrated device like SRM or PT.

Lactate threshold is the one that requires more specialist equipment, to test the build up of blood lactate for different amounts of effort. Mine was 200W, but whilst I've increased my FTP gradually, I haven't made much headway with LT.

Complicating matters since 1965

DaSy's picture

posted by DaSy [644 posts]
19th November 2009 - 16:08

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Quote:
I had an FTP of 336W and a power to weight of around 4.6 W/Kg in May of last year

another reason to not go out riding with you then Smile

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posted by Dave Atkinson [7036 posts]
19th November 2009 - 16:37

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Most people find many other reasons than that to not ride with me, apparently my dazzling personality is one that is high up on the list.

Complicating matters since 1965

DaSy's picture

posted by DaSy [644 posts]
19th November 2009 - 16:52

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