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    22-07-2015
    Klik hier om een link te hebben waarmee u dit artikel later terug kunt lezen.Froome's numbers

    The Froome controversy is becoming a never ending story. It all started with a tweet from Amatti Pyoraily with a calculated average power of 6.1 W/kg during the  40:43 climb of La Pierre Saint Martin.

    Indeed, this number is a little high but was is correct and is it really alarming? It was based on a simplistic formula from Dr. Ferrari that does not take into account the possible influence of wind (tailwind? headwind?) ,or the effect of drafting.  Anyway, this number was the start of accusations by a well-known group of negativists

    Then came the number of 7.1 W/kg due to the great scientist Pierre Sallet. Absolutely ridiculous. The first thing a real scientist should do when he obtains a surprising number is to have doubts and verify his own calculations. Obviously Mr. Sallet has no doubts.

    On 22nd July Froome and Sky then disclosed the numbers from his powermeter; 5.78 W/kg

    One would think this ends the discussion but at the contrary it all starts again because this number is too low and thus it must be “manipulated”.

    So let us see how wrong this number may be. Robert Gesink produced 5.72 W/kg on the same climb and lost 1:27 to Froome. Nobody doubts about this Gesink number and you do not need to be a scientist to infer from this that Froome really produced  5.93 W/kg. Exit 6.1 and exit 7.1 W/kg…

    So where does the difference between 5.93 W/kg and 5.78 W/kg come from? The difference between these numbers is 2.5%
    There are 3 reasonable causes.
    First, the very best powermeters (SRM, Pioneer etc…) will give you numbers with a possible error of 1.5 – 2 %. This is true both for the Gesink-data and the Froome data, which means that they may differ by as much as 3 % without any specific reason.
    Second, the difference may partly be due to Froome’s use of a non-circular chainring.  As an example SRM computes the average power over each full revolution with the assumption that the angular velocity is constant over the revolution, which is true for any circular chainring. However this angular velocity is not constant for the Froome chainring: it is lower in the downstroke and upstroke, and higher in the dead-point zones. This adds an extra 1 – 2 % of possible systematic error.

    Finally and despite all non-believers the non-circular chainring does have a positive effect on Froome’s performance. This is no place to start a detailed explanation but science has shown that a proper oval chainring is indeed more efficient than the circular one. (See the excellent papers by L. Malfait and G. Storme at www.noncircularchainring.be  )

    Altogether, much ado about nothing.

     


    0 1 2 3 4 5 - Gemiddelde waardering: 5/5 - (2 Stemmen)
    Tags:Froome, Tour de France
    22-07-2015, 13:33 geschreven door Fietsica  
    30-07-2013
    Klik hier om een link te hebben waarmee u dit artikel later terug kunt lezen.Froome and Contador 2013
    Klik op de afbeelding om de link te volgen

    Froome told to the world that his victory in the Tour de France will withstand the test of time. To the many people who still have doubts about this, I propose to examine closely a detailed analysis and comparison of the performances of Froome, Contador and Indurain.
    The graphics at the left (click for larger picture) shows the climbing time on the horizontal axis and the corresponding climbing power, in Watt per kilogram, of their performances  in relevant final climbs.

    Where did these data come from? Froome 2013 and Contador 2013 are my own computations. Contador 2009 and Indurain 1994-95 are historical data by Mr. Vayer and Mr. Portoleau. For the red Froome-data  and the black Contador-data I used the final climbs on AX 3 Domaines, Mont Ventoux, Alpe d’Huez and Annecy-Semnoz. For Froome also the data from La Planche des Belles Filles and La Toussuire in le Tour 2012 were included.  The three blue data points for Contador 2009 correspond to the final climbs on Verbier, La Colombière and Mont Ventoux. Finally the purple data points are the final climbs of Indurain in his Top-Epo tours.
    At first sight we see that with the exception of Indurain the data series are very well presented by smooth theoretical curves, from which we may learn some of the hidden secrets.
    The Indurain data are “all over the place” . No theoretical model whatever can be fitted to these data. The best way to describe this is to state that Indurain rode at the same high power regardless of the length of the climb. In fat this means that he had an extremely high maximum aerobic power, but he had no, or did not need to use,  any significant anaerobic energy. In plain words; due to his unlimited  use of Epo he had an extreme aerobic power and a corresponding VO2max.
    The Froome curve lies entirely and far below all Indurain data, thus anyone claiming that Froome was riding in 2013 at the Indurain level of 1994 should know better.

    First some words about the theoretical curves. We can consider a cyclist to be a hybrid machine. He gets energy from aerobic and from anaerobic chemical processes. His aerobic energy reservoir  is virtually unending, but the intensity at which he can use it is limited by his maximal oxygen uptake and his maximal aerobic power. Let us name this maximal aerobic power which can be sustained “endlessly”  as CP – Critical Power. On top of CP he can use some anaerobic power from a limited reservoir. The best possible climb will be when he throws his anaerobic energy into the battle in such a way that he is exhausted exactly on the finish line, not before and no after.

    If the foregoing model is realistic then the highest average power on an all-out climb can be computed and/or predicted.

    Climbing Power = Critical Power + (Anaerobic Energy)/ Time of the climb

    Or in shorthand ;             P = CP + AEC/t

    I am personally very surprised and pleased that all the real-world data (except Indurain) could be perfectly well reproduced by this simple formula. Further we now replace our belly feelings by reliable and undeniable numbers as  in the following table.

     

    Critical Power  Watt/kg

    VO2 at CP  ml/min/kg

    Anaerobic Energy  kJ/kg

    Froome 2013

    5.16

    67.3

    1.58

    Contador 2013

    5.20

    67.8

    0.88

    Contador 2009

    5.42

    70.7

    1.81


    We see that in the Tour 2013 Froome and Contador had the same critical power (within less than 1%),  and the same oxygen uptake at the CP level. These numbers of CP and VO2 at CP are so low that we may state beyond any doubt that both riders were clean with regards to Epo-like products and/or practices. However Contador had a much lower AEC than Froome. We all saw that Contador indeed lacked the extra anaerobic explosiveness. Unfortunately almost nothing is known about reasonable numbers for the AEC, nor about possible drugs or practices to boost AEC.
    Because AEC is directly related to the capacity to go beyond the aerobic  limit we suppose that this capacity can be raised by intensive and scientifically targettted training. Is this the real secret of Froome and his team?  Maybe Sky and Mr. Brailsford may open the box and give us the complete openness he promised some years ago.

    Last but not least we look at Contador in 2009. His blue curve may even supersede most of the Indurain points… and there is a gigantic difference between Contador 2009 and 2013. His CP was in 2009 a full 4% higher, and his AEC was even more than double with respect to 2013.
    About Contador in 2009 I have no doubt; doped. About Contador in 2013 ; probably clean but badly prepared.

     

     


    0 1 2 3 4 5 - Gemiddelde waardering: 2/5 - (76 Stemmen)
    30-07-2013, 21:18 geschreven door Fietsica  
    30-10-2012
    Klik hier om een link te hebben waarmee u dit artikel later terug kunt lezen.A new Antidoping Watchdog
    Klik op de afbeelding om de link te volgen A few days ago on 27th october  a number of newspapers a.o. HET NIEUWSBLAD (Belgium), LE SOIR (Belgium), THE TIMES (U.K), LA GAZZETTA DELLO SPORT (Italy), L’ÉQUIPE (France) published a manifesto for a clean cycling world.
    This is a commendable initiative but all together too general and too little.

    What really is needed is a new Antidoping Watchdog, based on the physical science of the power production.
    While  the biochemical analysis of urine and blood will always be the most logical method to find residues of doping, we need an alternative method that is less invasive to the cyclist and is less vulnerable to all sorts of cheating and masking.

    Considering that doping is supposed to enhance performance it is only logical that we should monitor performance itself.
    Monitoring the climbing power in the Tour de France over the last 28 years shows extremely clearly the effect of successive periods of doping practices and also shows clearly the physical limits beyond which performance without heavy doping is not possible.
    (See my blog "Dopig en Klimvermogen" on www.bloggen.be/fietsica  - soon to be translated into English)
    The method was first described by Mr. Antoine Vayer and Mr. Frédéric Portoleau and today is still applied in a rather complicated way.
    First we have to register the live TV reports of the great tours, Italy, France, Spain. After painstaking timing of the climbs and detailed knowledge of the elevation profiles  we can compute the power that was developed.
    However with today's methods all could be much faster and easier.

    Here is my 6-point proposal.

    1. A new Watchdog is created. The members of this agency should have no function within the established agencies such as the UCI, WADA etc..
    2. All top-class cyclists should ride with an on-bike powermeter such as an SRM, a Powertap, Quarg etc...
    3. After each stage all these cyclists and/or the top 10 of the stage must transfer their data files to a central database belonging to the Power Watchdog
    4. The powerdata files are analyzed by the watchdog but must also integrally be accessible to the public and the media. Special attention is given to the final climbs in the mountain stages.
    5. A scientific commission will establish procedures and performance levels that identify ALARM levels

    What will happen when a cyclist rings the Alarm bell is still to be decided, but very special attention will at least be given.

    0 1 2 3 4 5 - Gemiddelde waardering: 1/5 - (51 Stemmen)
    30-10-2012, 00:00 geschreven door Fietsica  
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