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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 |

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 |

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 |

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 |

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 |

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 |

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 ) |

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 |