Login to VeloClub|Not a member?  Sign up now.
  • Using a stages power meter and oval chainrings… what could possibly be wrong with these values?

    • Marcus Mendez

      Huh, I trained with several power meters and stages is my go to . Try reading dc rainmaker on others . As for ovals , research is mixed and incomplete , but it has been put out there that they over report , nothing new

  • Sam Edwards

    Do the Osymmetrics still skew the data if the strain is taken from the left side crank arm? Either way they could feed us anything and expect us to soak it up but without independent review of the raw data it means nothing.

      • JBS

        Interesting. If you take Stages’ low end estimate of inflation (4%), Froome’s power ends up being 5.90 W/kg.

        • Also as soon as you start changing Froome’s weight the values change (a lot) http://veloclinic.tumblr.com/post/124660307808/is-it-5-78-or-5-95-w-kg

          • JBS

            Yep, and you need to factor in that Stages are an estimate based on left leg only, as well. If Froome’s L-R balance is skewed one way or the other the numbers will fluctuate even more.

            …and yet power numbers are seen as the holy grail for proving (or disproving) doping. Gonna shake my head and leave the rest of that argument well alone.

            • jules

              when I was using Vectors (when they were working), the L-R balance would be out massively at low power, but converge to 50-50 when I ramped it up.

              • JBS

                Sure, but was that just you jules or is the case for all riders? That’s the unknown, I haven’t see any solid data the subject.

                • Rodrigo Diaz

                  It is a well known phenomenon and relatively consistent in trained riders. I am sure you haven’t seen much solid data because it’s relative arcane and inconsequential. The Wattage google list that has decades of discussion on power, power meters, etc. has a well documented train for this.

                  Anecdotally, I report the same. At TH and above my power is relatively balance. On sprints the right leg pushes a bit harder. Just patzing around my left leg will do 60% of the work. Coggan reports something similar as well.

            • Although, I wouldn’t be surprised if SKY have been testing the dual sided Stages http://forum.slowtwitch.com/forum/Slowtwitch_Forums_C1/Triathlon_Forum_F1/Double_sided_Stages_Powermeter_(pic)_P5550358/

            • nathan ong

              yes, but i’d take a guess that froome has been using the dual sided prototypes shown here

    • JBS

      From what I’ve been reading, yes they do. All to do with how the angular velocity and torque are calculated:


    • Sean Doyle

      Exactly. Numbers in isolation.

    • Sean_S36

      Would be good if the people equally attack the media when producing stories without proper facts, This way the medias reporting might start to become real news with facts not just rumors to satisfy a gullible population that believes everything that’s reported, for their narrow minded entertainment.

      • Sam Edwards

        The media are reporting on a team that’s trying to pull the wool over our eyes with numbers that can only be verified by the team themselves.

        • Sean_S36

          Again, based on what Facts are they pulling the wool? What is your intention here? Are your intentions good or bad? Think clearly Sam.

          • Sam Edwards

            All I am saying is Sky have basically given us a bunch of numbers and expected us to gobble it up. We don’t know its real. Its as good as me saying that I averaged 6.7 watts per kilo for an hour today (which I did) How do you know I did or didn’t?

            • Marcus Mendez

              U couldn’t do that , try doing it , they could say anything but most educated cyclist on power would laugh at you’re number . In the day and age of strava it’s quite easy for athletes to compare themselves .

              • Froome_dawg

                Ok mate. Maybe I wasn’t being sarcastic enough.

                • Marcus Mendez

                  very unlikely. and people would still laugh at that. that said i can’t give you a confidence interval. people who actually are into this stuff aren’t that stupid. You have alot of old school guys that don’t train with power, heart beats blah blah .

                  • Froome_dawg

                    you’ve missed the point entirely

  • Sean_S36

    Can’t anyone see that the media needs news and stories to survive? They will jump on anything these days, What happen to the days of having solid evidence before breaking a story? Now everything is based on non factual hearsay. This goes for most News reports these days it’s all Stories to make news/ profits for murdoch and his share holders and fairfax as well . Wake – up society, Use your own common sense based on real evidence.

    • Aaron J HS

      I suppose this is what happen’s when the race for all bar 1 jersey is perceived to be over. In regards to the yellow and white jerseys that happened the stage after the first rest day. The tour was created by the media and arguably, still exists to feed the media. When there is little storyline within the race to report, another storyline needs to be found. Sure anything can happen in the Alps, but I think the perception of the vast majority of the audience is that only disaster can change the status quo and while that disaster is possible it is no more than an outside possibility. We are now effectively marking time until Paris, before the inevitable is confirmed. Probably with a few more carbon copy Froome attacks between now and then.

      I’m not suggesting that this is Sky’s fault, they’re there to win a race and the best way they know to do that is in a predictable style. ASO tries every year to mess around with the parcour to try and make it less predictable, but to Sky’s credit they’ve dealt with that a ridden the race they’re comfortable with. Unfortunately the by product of that is predictable racing and a starved media, hence every time they’ve done well in the tour these same questions have arisen.

    • Whippet

      Another interesting twist: Some of the sports and corporate news stories are written by software now. I wonder how the algorithms are reporting on team sky?

    • Matt DeMaere

      Not sure you can lay this at the feet of the professional media/journalists. Since anyone can quite effectively get their opinion out there — and in this case they certainly have been — you should really trace that blame back to the original sources. Those who generated these _super precise_ analyses and put them up on their personal websites, twitter, etc.

      No professional code of conduct to abide by, just page impressions and egos.

  • Jaybo

    good on them for releasing the data. though they didn’t have to and nor should they have to.
    will be interesting to see if this changes anyone’s opinion, even with proper independent analysis i’m sure there will be plenty of people. i think it’s incredibly sad that it’s gotten to the stage where if you’re the best in the world you’re just assumed to be cheating.
    i’ve never been a huge fan of Froome or team Sky, but I’m starting to have a great deal of respect for the way the Froome and the team are handling all this.

    • jules

      they only seem to have released average data?

      • Yes, and by release you might say that they have shown (but not really shown) the media the data

  • Peter

    I always have a hard time accepting the energy needs/fatigue level of froome weighing 67.5kg at his height of 1.86 (from Wikipedia). And how much different could he be training compared to the other elite cyclists and ride away from them like he does. ..

  • jules

    is it just me? but I don’t find these figures outrageous. I’m a lay observer, but these are not completely out of proportion to what I’d put down (they’re significantly more, but not twice as much or anything). it’s impressive as he’s sub-70kg and I’m 80+, and it was for 41 mins. in the middle of a GT with fatigue – but how do you make a concrete assessment on this stuff?

    there’s a basic principle in statistical analysis (I’m gonna get this wrong now, but the gist is there I think) that when you’re trying to measure a given delta (in this case – power difference between clean and doped elite rider) that is a value less than standard error (and error is high here – given so many variables), you can’t draw a reliable conclusion.

    also, Sky’s claim of 5.8 W/kg seems dubious to me – see (https://twitter.com/maximus_hoggus/status/623588440244883456)

    lastly, I have respect for journos like Kimmage, but scientific analysis isn’t their strength. I read an article on Laurens Ten Dam (http://rouleur.cc/journal/riders/laurens-ten-dam), who gave all his data to a professor – who concluded only that he couldn’t prove LTD was clean or doped. this is what a proper, ethical academic may do in the interests of objectivity and protecting their integrity. I wonder whether guys like Anton Vayer operate the same way? it also seems clear to me who may be the better go-to person for journalists after a story..

    • Jules, you’re right – you can’t prove either way based on an analysis of numbers. However, you can estimate the probability that it is a performance that is out of this world. See http://veloclinic.com/estimating-the-probability-of-doping-as-a-function-of-power/

      • jules

        that’s an interesting piece. I can’t speak authoritatively, and I’m not a statistican, but I’ve worked with statistical studies (i.e. others do the studies and I try and interpret them) and they often go like this:
        1. make assumptions
        2. build statistical model
        3. assess the subject of model using model

        now sure, you can incorporate confidence intervals/error bands etc. into that – but those themselves are highly dependent on the validity of the original assumptions. what I’ve observed (not here with power models) is that sometimes the “stake in the ground” assumptions gently evolve to be treated as certainties – acting to artificially limit the confident width. to me that’s a sleight of hand.

        also another point that I read was the risk of attempting to model doping probability based on performance of the general peloton. the difficulty with that is that – correct me here – it models the probability of the average rider. if Froome is clean, he’s certainly a freak and far from average. and of course, someone inevitably has to be the outlier.

        I think those models are still useful for demonstrating doping in crazy performances (~7 W/kg) – so what I’d like to see with Froome is an independent assessment of his power-weight cos I’m unconvinced by Sky’s quoted figures.

    • donncha

      Worth listening to this interview with Kimmage to see where he’s coming from. He acknowledges he doesn’t understand the numbers and defers to e.g: Ross Tucker (Sports Scientists) on power and physiology. His concerns are more based on SKY’s behaviour and comparing what they say they will do versus what they actually do, and also the simple question: “if riders are climbing as fast as Armstrong was, HOW are they accomplishing that”


      • jules

        I listened to that and they are all fair questions, but Kimmage is really delving into 2nd and 3rd order matters – not evidence of doping, but frustration as to why Sky won’t help verify the integrity of their program and riders. I’m not dismissing it but to me the key conclusion from that is that Sky should be more open about their data, not that they are doped or clean.

      • Karl

        These result appear to be comparable to his effort up Mount Ventoux in 2013, which is well below the times of the late 90’s/early 2000’s – and yet somehow he is seen as being a doper. He doesn’t even make it into the top 100 up Alpe d’Huez. I really don’t see what all the excitement is about.

      • Thanks for this @donncha. I hadn’t found this yet. Very good listen.

      • Simon

        So, in all this discussion about doping, and in particular to Kimmage’s question ‘if riders are climbing as fast as armstrong was, HOW are they accomplishing that?’, there seems to be no mention of technological advancement. Remeber, according to Pinarello, the Dogma F8 is 12% more rigid, 16% more balanced, 120 grams lighter with 47% improved aerodynamics (then what they don’t say).
        Now I know all of these numbers are marketing speak, but surely we must be able to assume that power ouput using a bike manufactured this year is more efficiently transferred to the actual rubber on the tyre than it was in 1999-2000 – through stiffer cranks, stiffer bottom bracket, stiffer wheels etc. etc.. So why should we be surprised by fast times? Otherwise, there would be no benefit from all of this technological advancement. Even if it is ust a few percent more efficient, this would be quite a lot over a 40 minute climb.

        • Sean Doyle

          Hook line and sinker. Stiffer is not necessarily faster. Aero would help by a small percentage.

    • Andy B

      If you are getting down to specifics how do these figures factor for bike weight, Rolling Resistance, Aerodynamics, Water Bottles, Drafting.. etc etc

      Obviously these wouldn’t vary much but if 1kg of body weight alters the w/kg notably surely these need to be factored in too

    • Marcus Mendez

      is teejays van garderen’s claim dubious. people are naturally skeptical and risk averse, this is scientifically documented. Cycling fans seem to get of on being skeptical, like where did those numbers come from you quoted, what is you’re source. And do you believe them too?

    • Matt DeMaere

      Scientific analysis is also not the strength of the people releasing these tweets. I say that, because they’ve demonstrated it repeatedly. A pursuit of biased hypothesis from the outset, which is not an ideal recipe for scientific discovery. Further, no where do you see error bars or anything demonstrating that a degree of conservativism or pessimistic thought was exercised in performing these estimations.

      In statistics, everything is ultimately subjective. Though they might fumble through some steps, in the end every parameter is treated as perfectly accurate.

  • Bart

    Clean as a whistle.

  • Robert Merkel

    One thing I find surprising is how low his maximum heart rate is on the climb, particularly as Kerrison states that it was a very high heart rate for Chris.

    That’s significantly lower than my typical max HR after a race, and I’m nearly a decade older than he is.

    • jules

      I was under the impression a lot of the GC guys had low max. HRs

  • Cleanasbro

    Yep. Accurate

  • LeeRoy

    Is it Stages data or from an SRM? Sky use Stages but heading for article suggests the latter. Surely they are not using both?

    • donncha

      Using Stages. You can see the Stages unit on some of the press photos from Stage 10.

  • LeeRoy

    also, just get on the racing. I have no particular liking for Chris Froome but he shouldn’t have to put up with these ‘allegations”.

  • Luke Meers

    The figures look pretty reasonable. Great transparency shown from Lotto, who allow Gesink to upload his full power data to Strava. His numbers for that same climb (https://www.strava.com/activities/345923267) where he finished 4th @ about 1.5mins off Froome seem to correlate well with the supplied number from Sky. His power meter (Pioneer I believe) showed max 42min power of 409w which according to his manually entered strava weight put him at 5.68W/kg.

    • jules

      the irony is that the power nos. add little to transparency if he’s manually entering his weight

      • Luke Meers

        I don’t agree Jules. I think a lot can be understood from the power and VAM figures. The weight he entered would be 72kg, which whilst it might be a kilo or maybe two kg above his race weight, is clearly in the ball park. If he were 70kg the power to weight would come out at 5.84w/kg. I think the more transparent thing, is actually having the full HR data on Strava (which he has) because this allows us to read much more into his condition.

        • jules

          the weight he gave is 67.5kg?

          also I don’t see what HR data shows – it varies by rider.

          • There’s a reasoned analysis here: http://sportsscientists.com/2015/07/great-power-great-responsibility-less-power-greater-speeds/

            5.78w/kg estimate is a joke for all the reasons mentioned in this post and elsewhere.

            • Luke Meers

              Yeah a very good analysis. Thanks. I agree with his assumption that Froome’s weight would be less than the quoted 67.5kg. When he reportedly was about 66kg at the Dauphine. Surely Sky would be smarter than to get that wrong though, knowing that every man and his dog will be looking at the numbers. Odd.

            • jules

              interesting. I don’t understand Sky’s approach here either, but it seems even allowing for their providing fudged, conservative figures – there’s no smoking gun.

              • Tour de force Todd

                i would like to see Contadors numbers for day he pulled everyone back on that Giro climb. All stage winners should have their power data – Now wouldn’t that be something to stick your teeth into.

            • Tom Wells

              All that article really says is that Froome’s weight is likely wrong. 6w/kg still doesn’t really imply doping.

          • Luke Meers

            Sorry I was referring to Gesink’s weight. I think HR data says a lot. You’re right though, in isolation, the data from one ride does not show much as each rider’s HR is different But when combined with a history of data to give context, then power and HR data are both give much more powerful insight.

  • Charlene

    Cycling tips, the key to getting people to trust ones publication is accuracy! Chris froome is on a Stages power meter NOT SRM.

    • jules

      I suspect Sky are more concerned with pseudo-scientists declaring that Froome is ‘definitely doped’ than a typo about SRMs

    • I think of SRM for powermeter the same as “kleenex” or “Asprine”. Thanks for the correction. Fixed.

  • Shane H

    Wow, he’s a beast-master. I believe him when he expresses his frustration at people being suspicious of him. He’s talented, stubborn and super strong!

  • Derek Maher

    The data shows Chris Froome,s form on stage 10.Nothing really far fetched for that stage ?.
    Looking at Chris and his climbing style he has modelled his very high cadence on Lance Armstrong and also the way Lance rode with his Team.
    Regarding HR All pro riders will have a low resting HR although if a rider uses a very high cadence on low gears climbing their HR can expect to be higher on average.I would suggest Chris has a threshhold HR of 174 and his max is far higher than quoted given his age and fitness levels.This is an area where the data thats given looks wrong.
    Of course it maybe that the opposition were so sub par without decent team support to ride tempo that Chris was not pushed into the red and Chris does not need to hurt himself enough to blow up.

  • Jim ( I should register)

    Not sure it proves anything one or the other ??

    If they’ve have access to some wonderful all natural herb that makes them ride faster than everybody else does that mean they’re cheating or not ?
    Guess it’s called science or incremental improvements….

  • Tom Wells

    Even if Sky over-compensated for the oval chainrings and got his weight wrong (which even I’d put him at 66-66.5kg) then it’d only put up his w/kg to about 6. That’s nothing like the EPO era and is well established to be within the realms of possibility without doping.

    I just think he had a good day to be honest. He’s not shown that kind of dominance since and I would assume everyone here knows you can have good days in the saddle as well as bad ones.

    Sky could have been a bit more accurate with the data they provided though.

  • Michael

    If the data is correct, the result isn’t unbelievable at all. I’d hazard a guess that 435w is his ftp (most top tour riders are at the same level) which he could push for an hour let alone 41min. As for the fatigue, he was sucking wheel for the entire stage so would have approached the climb fairly fresh. To give you an idea, his team mate on the front was prob pushing 300-350watts riding tempo, in the draft Chris would have been at about half the power taking advantage of less wind resistance.

    I was a bit of a sceptic, but if these figures are correct I’d say the other 4 top riders were waiting for the alps, so let him go. Contadors ftp is 425w from memory and a bit lighter at 65kg, so catching him wouldn’t have been an issue. They were taking it easy which is why it could have looked like he rode away so easy.

    • Sumodog

      186 cm and 66kg – that’s borderline anorexic !

      • Albert

        Google pictures of Wiggo at his Tour weight – pretty disturbing. He’s looking much “healthier” preparing for Rio!

  • TomG

    Feel sorry for Froome and Kerrison – try to provide some numbers and people assume you’ve knocked a zero off to pull the wool over everyone’s eyes. I don’t think that, in any sport, you expect the fans to react rationally to a dominant force. In UK soccer, this is the Manchester United effect, you either love them or hate them without any real basis.

    Whether you think it is good or bad for the sport that Sky’s budget allows them to buy up 5 or 6 of the 20 or so guys in the world who could do 6W/kg up the last climb of a 4 hour stage is a moot point. That they then go and ride in exactly the way you would expect, in a train, full gas up the big ramps is no surprise either. I actually think the racing is still much better than in the Indurain years.
    I don’t think the numbers are that shocking and reckon Froome would see them as pretty routine if he was fresher +/- not at altitude. There is a huge error budget (2% for the powermeter, ?1-2% for measured body mass, ?5% for time spent in the wheel of a teammate which is worth a decent amount even at <20kph). Add these together and the people bleating about how Gesink put out more power but went slower make themselves look like idiots. A decent sized piss could account for the margin between the two. Disappointed in the tone of the posts by Ross Tucker etc. who introduce a whole load of innuendo, doubt and suspicion and then finish by saying they can't prove anything.

  • Osymetric Aust

    I think everyone is missing the point. The so called 6% over statement of Froome’s power because of the Osymetric rings is false. The tests I have done do not overstate actual power at the back wheel, it is a real power advantage. The reason is that there is less energy wastage at top and bottom points of the pedal stroke and more power on the downward points of the pedal stroke. The only reason that more pro riders do not use them is because of sponsorship issues. Take a careful look at the number of riders using Q-Rings, there must be something in non round rings. I can declare a vested interest, I am the Australian importer of Osymetrics, none the less, if Froome wins, that will be three out of the last four TDFs that Osymetric have been on the top of the podium! Cheers – Barry


Pin It on Pinterest

August 23, 2017
August 22, 2017
August 21, 2017
August 20, 2017