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Carlo Algatrensig

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6w/kg
« on: July 18, 2015, 19:58 »
Can anyone help me here. I've seen quite often that it is said that 6 W/kg is the maximum that can be produced by a rider naturally for an effort over a one hour period. I've done a bit of googling to try and find where this might have come from but haven't found much. If anyone could direct me to any studies or reports that support this or any other info it would be appreciated as I've always wondered where this figure has come about from.
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  • Flo

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    Re: 6w/kg
    « Reply #1 on: July 18, 2015, 20:04 »
    Wasn't is Aldo Sassi?

    But then again Ross Tucker said Quintana's 5.9W/kg for 40 minutes on Pierre-Saint-Martin was probably the clean max.
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    Mellow Velo

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    Re: 6w/kg
    « Reply #2 on: July 18, 2015, 21:28 »
    How convenient...............for Ross.


     6w/kg is a slightly arbitrary figure generally considered to be the theoretical maximum power that the top contenders should produce on the longer climbs used in Grand Tours. i.e. those of approx 35-50 minutes.
    However, there are many factors that can effect this figure, such as wind direction, road surface, single or multiple climb stage etc.

    Some "easy" reading can be found here:

    http://sportsscientists.com/2011/07/the-tour-de-france-power-2011-outputs-from-the-outside-in/

    http://cyclingtips.com.au/2009/07/just-how-good-are-these-guys/

    Trouble is, all calculations are subject to a degree of error.

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  • "Science is a tool for cheaters". An anonymous French PE teacher.

    Carlo Algatrensig

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    Re: 6w/kg
    « Reply #3 on: July 18, 2015, 21:38 »
    6w/kg is a slightly arbitrary figure generally considered to be the theoretical maximum power that the top contenders should produce on the longer climbs used in Grand Tours. i.e. those of approx 35-50 minutes.
    However, there are many factors that can effect this figure, such as wind direction, road surface, single or multiple climb stage etc.]

    This is why I've asked the question about whether there are any studies or is it as you say an arbitrary figure.

    However what you say about road conditions, wind direction shouldn't effect maximum power output as that should not be effected by those factor. what should be effected by those factors is the actual speed that those powers produce.
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  • Joelsim

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    Re: 6w/kg
    « Reply #4 on: July 18, 2015, 21:52 »
    This is why I've asked the question about whether there are any studies or is it as you say an arbitrary figure.

    However what you say about road conditions, wind direction shouldn't effect maximum power output as that should not be effected by those factor. what should be effected by those factors is the actual speed that those powers produce.

    The figures are estimated by the watchers so those factors play a part. The only people who know what the actual power outputs are are the teams.
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  • AG

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    Re: 6w/kg
    « Reply #5 on: July 19, 2015, 02:16 »
    actually quite a few riders release their data for speicific rides/climbs/days etc.

    Carlo wasnt asking whether the data was accurate or estimated - he was asking where the idea of 6 w/kg max comes from.


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  • QuintanaWiggo

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    Re: 6w/kg
    « Reply #6 on: July 19, 2015, 05:10 »
    I think it's a recipe for a solid cake.   :shh
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  • Mellow Velo

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    Re: 6w/kg
    « Reply #7 on: July 19, 2015, 13:05 »
    This is why I've asked the question about whether there are any studies or is it as you say an arbitrary figure.

    However what you say about road conditions, wind direction shouldn't effect maximum power output as that should not be effected by those factor. what should be effected by those factors is the actual speed that those powers produce.

    Exactly. This is what I meant but didn't make clear. "Indirect variables" they might be termed.

     Thibault Pinot's new record on the Rettenbachfurner. A slightly longer climb than Pierre-Saint-Martin, generated a very similar number (both by my calculations) to the one currently receiving all the attention. If one employs Mr Tucker's slight lowing of the bar, it looks extremely suspect.
    Yet it was viewed in a completely different manner, by a certain French PE teacher.

     Personally, I think when walking in border territory, expect minefields.
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  • AG

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    Re: 6w/kg
    « Reply #8 on: July 19, 2015, 13:14 »
    very interesting chat with Flo earlier

    Echoes:      how can anybody talk about a w/kg ratio while they don't even know the exact weight of any rider?
    Flo:      Echoes,  you can calculate it with the climbing time, gradient and vertical gain
    Echoes:      I know you can calculate wattage but the weight ???
    search:      yeah, those are estimations
    Echoes:      thanks Searchy
    Flo:      It's simple. Climbing time is directly related to w/kg.  So from the time and vertical gain you can calculate VAM.  And with VAM and the gradient factor you can calculate the w/kg
    Echoes:      Vayer & Portoleau used standard weight for their data
    Joelsim:      Kristoff only produces 123W/kg. That's because he weighs the same as a baby elephant :D
    Mellow Velo:      Flo speaketh the truth. She is correct.
    Echoes:      in Elizabethan English correct writes "correcteth"
    Mellow Velo:      True. ;)
    AG:      but the watts produced are a guess, the riders weight is a guess ... so overall its a sometimes vague / sometimes accurate estimate
    Flo:      no AG... the climbing time is directly linked to W/kg.. you dont have to know the Watts produced or the riders weight. if you know the stats of the climb and the climbing time, you can calculate the relative power output (W/kg)
    AG:      with climbing time and vertical metres, you can calculate speed and estimate wattage ... but wind and other conditions will always affect the calculations, so its still an estimate.  and the weight is an estimate.  so its still got a reasonable margin of error.
    AG:      not saying they cant calculate it ... but its not the be all and end all of everything.
    AG:      and what a rider can produce at hte end (legitimtely) will also be affected by the racing conditions earlier.  A fresh rider who has had an easier time will be able to produce and sustain a higher w/kg than if they have raced hard over 4 mountain passes already.
    AG:      its informative ... but its not all there is.
    Flo:      no. there is no weight in the calculation. you dont use weight to calculate the relative power output out of the climbing time. so there is no estimation.
    Flo:      there is always wind involved.. but it doesnt make the difference between 5.5W/kg and 6.2
    AG:      but in watts per kilo ... the kilo is a weight.   which you are estimating.
    search:      I don't think you can calculate W/kg without the weight
    AG:      and when you are multiplying that with another estimation ... which also might be slightly out .. you get bigger variations
    Flo:      "pseudosciece" estimated Froomes relative power on ventoux as 5.8/5.9 W/kg. actual power out of the file: 5.88W/kg. it's surprisingly accurate.
    AG:      in calculation watts, there is also road conditions, whether or not they are riding in a group or by themselves, following or leading, fighting for position ... all those things take energy
    Flo:      yes you can search. because climbing is all about w/kg not about pure watts. there is a direct link between w/kg and climbing time.
    AG:      it can be accurate at times.   it can also be out considerably.
    AG:      I am not arguing you are wrong Flo.   Not at all.    Just saying there are other things to take into consideration as well ...
    Flo:      "whether or not they are riding in a group or by themselves, following or leading, fighting for position .." exactly... but those are things that influence the actual relative power output, not the estimated relative power output
    Flo:      ammatipyoraily (or however you write it) on twitter often gets files from riders. then compares the actual relative power output with the calculated one. It is surprisingly accurate.
    Flo:      The calculation: VAM = (metres ascended x 60) / Minutes it took to ascend
    Flo:      Relative power (Watts/kg) = VAM (metres/hour) / (Gradient factor x 100)
    Flo:      no weight estimation involved.. neither a watts estimation. Just raw facts: climbing time, the vertical gain and the gradient factor
    AG:      but power is measuring the power required to climb a particular gradient climb.   therre are other factors that influence the power required other than just vertical metres gained
    Flo:      it is not always 100% accurate. And when it comes up with an atrocious number you have to look at a potential cause. For example Contador on Verbier was calculated as 7.1W/kg for 20 minutes IIRC. Turns out there was a heavy tailwind.
    Flo:      No, AG. You divide the VAM by the gradient factor times 100 and it gives you W/kg as an answer
    AG:      yep - my point exactly.   I think we are arguing the same thing   ... just different ways   :D
    Flo:      Example:
    Flo:      vertical gain = 300m. Time it took to ascend = 12 minutes
    Flo:      VAM = (300x60) divided by 12
    Flo:      that gives 18,000 divided by 12 which is 1500
    Flo:      VAM = 1500 meters per hour
    Flo:      lets say the gradient of the climb is 7%. The gradient factor, is 2 + (gradient/10). So the gradient factor is 2.7
    Flo:      Therefore, 1500/(2.7x100) is the relative power output.
    Flo:      1500/270 = 5.56. Relative power output = 5.56 W/kg
    Flo:      the 270 is the gradient factor times 100 - "Relative power (Watts/kg) = VAM (metres/hour) / (Gradient factor x 100)"
    Flo:      this is what wiki says about gradient factor: "This gradient factor ranges between 2.6 for a gradient of 6% and 3.1 for a gradient of 11%. To work out the gradient factor take 2 + (% grade/10)"
    Flo:      here you can read about VAM and how to calculate VAM and W/kg [link])
    Flo:      it seems confusing at first but once you get it it's very easy and quite handy
    AG:      but again - it is calculating hte pwoer required to climb a specific gradient ... without taking in any account of other factors which affect the power required
    Joelsim:      But Florry, let's assume we have 2 climbs as long as each other, with the same average gradient. Climb 1 is half at 12% and half at 4%. Climb 2 is all at 8%. Can each climb be described as equal? Wind too, plus the rest of the stage beforehand, plus the tow of a teammate, plus the actual stage of the Tour with regards to tiredness will all be factors
    Flo:      as you can see, there are no estimations involved. The actual number, is of course an estimation, because as you said, there;s win etc involved.
    Flo:      Yes Joel, but many of those things you mentioned influence the *actual* W/kg, not the one we calculate.
    search:      ok, it makes sense in a way, that the weight is of no importance there
    search:      because a 50kg rider needs to push less Watts than a 100kg rider, but the W/kg ratio is the same, for the same climbing time
    AG:      yep agreed.   I see better now what you are meaning.    still ... I dont think it tells us all that much to be honest
    Flo:      in other words, if it is after 3 weeks hard racing, you will be tired and W/kg will be low. But the calculation isn't faulty. We just cannot draw any conclusions out of the number because the circumstances are special. But the actual number calculated, isn't wrong.
    Joelsim:      I agree AG. It can give you some parameters for sure
    AG:      yep fair enough.
    Flo:      exactly search. An 80kg rider can climb as fast as a 50kg rider, they just need to push a different wattage
    AG:      interesting discussion.   I will copy and paste for the thread   :)
    Flo:      I think many people who dismiss these calculations as pseudo-science, haven't actually looked into it. They just see a load of numbers and assume someone pulled it out of their arse. But the fact that sports physiologists are using it, shows us it is a good formula.
    Flo:      lol [link]
    Flo:      I do think Walsh would be better off just keeping his mouth shut :P
    AG:      it is good to be able to say 'this is how much power you need to climb those metres in that time" ... but again, to calculate the actual power it took ... you also need to account for a number of other factors that might make it more or less power .... so it has its limitations
    Flo:      exactly.. and that's why you need to look at the circumstances.. but, to use Verbier again as an example, 7.1W/kg was obviously a faulty calculation, AC's climbing time was influenced by a heavy tailwind. However, that 7.1W/kg won't become a "normal" 6.1W/kg with no wind. It was obviously an insane performance. So wind and road conditions have some influence, but it isn't the difference between a stratosperic performance and a natural one
    AG:      and that is where those factors come it.   Can a rider manage 6.4 for a shorter climb if there is a tail wind and if he has taken it easy throughout the race?   5.9 might be off the charts if the rider has had a hard 3 weeks.
    AG:      agreed though - some numbers are just out there :D
    Flo:      FWIW short and long climb is taken into consideration. Contador did 7.5W/kg in Pais Vasco last year. But it was a 7 minute effort. It's high, but not impossible.
    Flo:      6.4W/kg for example, on a 20 minute climb can be clean. while 6.2W/kg on a 50 minute climb is unlikely to be clean.
    AG:      to be totally honest - I am still not convinced that it tells us that much.
    Flo:      I think it tells a lot - IF you look at the circumstances :)
    AG:      a heavier rider that is all mucle is going to be able to push more w/kg than a heavier rider that has a lot of fat.
    Flo:      well there's that, and that;'s why that fat rider will have a lower W/kg than the muscular rider :Pbecause he can push more Watts per kg of body weight :P
    AG:      you need to be looking at the total power used/required to ride that climb ... and for that you need much more than just VAM and speed.
    Flo:      why at the total power used?
    AG:      anyway- thanks for the lesson.  it was interesting and informative  :D
    AG:      total power is what you are trying to estimate ... w/kg is a way of comparing different riders who have different weights ... but its the total power required that is what we should be measuring
    AG:      lopoking at Froome who has so little body fat ... and measuring his w/kg against say pozzovivo who might have a similar weight but is more body fat ... what Froome can push and what Pozz can push are different
    Flo:      well yes. And that's why Froome climbs faster than Pozzovivo (not that they're similar in weight :P)
    AG:      yeah but you get my point.  You are saying 6.2 over 50 mins is not possible ... but with some body types it might be, and with other body types/road conditions it might be clearly way OTT
    Flo:      yes... a rider with 2% body fat will have a higher W/kg.. but generally 6W/kg for an hour is considered the absolute clean maximum, with no influence from the wind conditions, for an incredibly in-shape rider.
    AG:      considered by who?
    AG:      and going back to the calculation - how did they come up with the gradient factor?   that seems a bit ... I dont know ... odd to me
    Flo:      by experts AG, see the 6 W/kg thread, no one is sure where it came from
    Flo:      gradient factor, not sure, but I wouldn't be surprised if they came up with it after some trial and error. Ie. see which "factor" works.
    AG:      yeah
    AG:      right - I gotta go do some stuff.   will be back later
    AG:      thanks   :)
    Flo:      hmm "VAM tends to be higher on steeper gradients so the extension that estimates Relative Power (watts per kilo) relies on a gradient factor relating to the average gradient of the climb. This gradient factor is defined as 2 + (%grade/10), in the Ape d´Huez example 2+(8.1/10) = 2.81. Relative Power is then calculated as VAM / (Gradient Factor x 100), in the example 1606 / (2.81 *100) = 5.72. "
    Flo:      bye ag :wave
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  • Carlo Algatrensig

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    Re: 6w/kg
    « Reply #9 on: July 20, 2015, 19:48 »
    While looking for stuff relating to climbing powers I've come across this webpage

    http://www.u.arizona.edu/~sandiway/bike/climb.html

    I decided to put in what I could find in terms of Froome and Quintanas performances on the final climb of stage 10

    I made some assumptions. That both riders bikes were at the UCI minimum of 6.8kg and that for both of them and I used a rider weight of 66kg for Froome and 58kg for Quintana (these were what I found for the 2 of them but if anyone knows anything more accurate I'm happy to be enlightened)

    This produced figures of

    410 watts absolute power for Froome and so 410/66 = 6.2w/kg

    360 watts for Quintana as an absolute power and so 360/58 = 6.2w/kg

    This might seem strange to start with as all of the other suggestions are that there is a direct relationship between w/kg and climbing time.

    this got me thinking that is the variance due to what part of the absolute mass a rider has to transport up a climb is there body weight and what is the mass of the bike.

    If froome is 66kg and his bike is 6.8kg then he has to transport a total mass of 72.8kg up the climb 90.7% of which is his body and 9.3% of which is his bike

    The total mass that quintana has to get up the climb is 64.8kg of which 89.5% is his body and 10.5% is his bike.

    Now theres is the chance i've got my figures wrong and the calculation is way out but it does make me wonder if the apparently linear relationship that would be produced by the formula mentioned in the chat AG has copied and pasted doesn't take into account the fact that it isn't only the riders mass that is carried up the climb but the total mass of the rider and bike and for lighter riders the bike will make up a greater percentage of the total.
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  • Havetts

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    Re: 6w/kg
    « Reply #10 on: July 21, 2015, 00:17 »
    The remarks about 6 w/kg being the limit of human performance come from Sassi & JVaughters' remarks in the Clinic iirc.


    The thing is, if that were to be true that'd be around 5 people per generation as that 6 w/kg figure is so far off the standard deviation. It definitely isnt what you used to see and still sometimes see where its a group of five or more riders doing it on one stage.

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  • Merckx Index

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    Re: 6w/kg
    « Reply #11 on: July 22, 2015, 19:00 »
    W/kg is determined from three parameters: V02max; % of V02max possible on a sustained climb; and efficiency.* The 6.0 W/kg figure (and there is a lot of disagreement about this, even Tucker drew the line at 6.2-6.-3 a couple of years ago) comes from making what are thought to be reasonable assumptions about these three parameters. E.g., if you have a V02max of 85, which is quite high even for an elite rider, 90% utilization, which is about the limit for a sustained effort, then you need about 23% efficiency. A lot of work indicates that is close to the maximum efficiency possible, but some researchers have reported much higher values among elite riders, thus leading to disagreements about what’s possible.

    To complicate the issue further, two of the studies reporting very high efficiencies found an inverse correlation between efficiency and V02max. So if a rider had a very high V02max, he was likely to have a relatively low efficiency. That relationship makes it even less likely that 6.0 W/kg can be exceeded. And in fact, of the 23 elite riders participating in those two studies, only one, it appears, had a high enough combination of V02max and efficiency to make it likely he exceeded 6.0 W/kg.

    *Actually, there is another factor rarely mentioned, the amount of energy released per liter of oxygen. Most calculations assume 20.9 kilojoules, but it does depend on exactly what substances are being metabolized.

    Quote
    However, there are many factors that can effect this figure, such as wind direction, road surface, single or multiple climb stage etc.

    Just to be clear, environmental conditions don’t affect W/kg per se at all (except for altitude, which affects oxygen concentration). They affect climbing speed at a particular W/kg value, and thus impact power calculations based on climbing speed or VAM (as opposed to those based on power meters). OTOH, the difficulty of the stage can affect W/kg.

    But in most cases, these environmental conditions don't seem to have a major impact. Last year Veloclinic published a study of 250 climbing times in which power meter data were also available, and found a very strong correlation, viz.:

    Quote
    Statistically the estimate are “likely” to be within +/- 1.6% (75% confidence interval) of power meter measurements and “very likely” to be within +/- 2.7% (95% confidence interval). For perspective, the “gold standard” SRM power-meters are only reported to be accurate to within +/- 1-2% themselves.

    http://veloclinic.com/intro-to-power-estimate-modelling/

    Quote
    Thibault Pinot's new record on the Rettenbachfurner. A slightly longer climb than Pierre-Saint-Martin, generated a very similar number (both by my calculations) to the one currently receiving all the attention. If one employs Mr Tucker's slight lowing of the bar, it looks extremely suspect.

    Pinot’s released data indicate a maximum of 5.9 W/kg for 45 minutes.


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  • « Last Edit: July 22, 2015, 19:35 by Merckx Index »

    Mellow Velo

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    Re: 6w/kg
    « Reply #12 on: July 22, 2015, 19:26 »

    No, environmental conditions don’t affect W/kg at all (except for altitude, which affects oxygen concentration). They affect climbing speed at a particular W/kg value, and thus impact power calculations based on climbing speed or VAM (as opposed to those based on power meters). OTOH, the difficulty of the stage can affect W/kg.

    Yes. Also mentioned above.


    Pinot’s released data indicate a maximum of 5.9 W/kg for 45 minutes.

    I agree. I came up with a 5.9w/kg, which RT and others claim to be the new, downgraded theoretical max for a 40 minute effort.
    It does make Mr Vayer had to say at the time quite interesting.

      https://www.twitter.com/festinaboy/status/611233845858435072"
             
             
         

         
           
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