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#1
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Fans' Skiing Commentary and Analysis
A friend and I - both citizen racers and fans of World Cup XC skiing -
have started a little project to offer some commentary and analysis on the elite racing scene - a little more in-depth than what, for instance, Fasterskier.com does. So far we've done a podcast recapping the 2007-2008 season, and he's added two great posts analyzing Lukas Bauer's dominance last year and comparing skiing and cycling power outputs. You can find it at http://nordiccommentaryproject.blogspot.com/ Some RSN readers might find it interesting. Comments on the site are welcome. Best wishes, Christopher |
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Fans' Skiing Commentary and Analysis
tassava wrote:
A friend and I - both citizen racers and fans of World Cup XC skiing - have started a little project to offer some commentary and analysis on the elite racing scene - a little more in-depth than what, for instance, Fasterskier.com does. So far we've done a podcast recapping the 2007-2008 season, and he's added two great posts analyzing Lukas Bauer's dominance last year and comparing skiing and cycling power outputs. You can find it at http://nordiccommentaryproject.blogspot.com/ I liked the power budget calculations, but I believe the friction numbers might severely understate the case: As the article noted, it was a warm day, and they were skiing a steep uphill, right? In such conditions the actual friction almost certainly increase when you need to angle the skis more and push off harder, i.e. the 0.025 value is too optimistic. Secondly, the base power calculation assumes that all energy output actually is used in the direction of travel, to gain altitude. This might be a reasonable assumption for a fit cyclist, sitting on his seat, but not for a skier, no matter how good his technique. I.e. I'm pretty certain the article numbers are most useful as an absolute minimum value, but the real energy usage might have been significantly higher. Terje -- - "almost all programming can be viewed as an exercise in caching" |
#3
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Fans' Skiing Commentary and Analysis
On May 7, 5:12 am, Terje Mathisen
wrote: I liked the power budget calculations, but I believe the friction numbers might severely understate the case: As the article noted, it was a warm day, and they were skiing a steep uphill, right? In such conditions the actual friction almost certainly increase when you need to angle the skis more and push off harder, i.e. the 0.025 value is too optimistic. Secondly, the base power calculation assumes that all energy output actually is used in the direction of travel, to gain altitude. This might be a reasonable assumption for a fit cyclist, sitting on his seat, but not for a skier, no matter how good his technique. I.e. I'm pretty certain the article numbers are most useful as an absolute minimum value, but the real energy usage might have been significantly higher. Terje -- - "almost all programming can be viewed as an exercise in caching" (Author here) Thanks for the feedback! You make a good point about pushing off on skis -- the normal force during the pushoff probably exceeds the skiers weight by a fair margin. That was not something I had thought of. On the other hand, I was concerned that a friction coefficient of 0.025 was possibly underestimating modern waxing improvements. Having experienced the joy of Cera F on a warm day it seems completely possible that it glides more than twice as well as whatever was available in 1976. Secondly, the base power calculation assumes that all energy output actually is used in the direction of travel, to gain altitude. Well, energy must go *somewhere.* If you treat the skier as a closed system, then the effects of that system's work are to move it forward and up the hill at a certain rate depending on power output, which is where gravity/air resistance/ski friction come in. As for how efficient that system is at producing energy (a human body making the nordic skiing motion vs a human pedaling a bike), that is a whole new issue! I certainly agree with you that a load-bearing sport like skiing (or running) is going to be much less efficient than a supported sport like cycling -- that is, Soedergren has to keep a lot of muscles flexed just to keep himself upright (unlike a cyclist), and that work is "wasted" outside the system, as it doesn't move him forward or up the hill. |
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Fans' Skiing Commentary and Analysis
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Fans' Skiing Commentary and Analysis
Have you looked at the Handbook on Cross Country Skiing put out by the
Olympics Medical Committee? I think there is some similar or parallel discussion and reference to research articles that may be relevant. rm |
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Fans' Skiing Commentary and Analysis
Impressive job. THis blog is promising
Fore those interested in power caclulation figures TDF 2007 figures http://www.cyclismag.com/article.php?sid=3466 Giro 2007 figures http://www.cyclismag.com/article.php?sid=3362 According to the author (on other articles) 470 Watts seems to be a physiological maximum on a several minutes effort, WITH an exogene helper. i.e EPO, autotransfusion...anything trendy. A "human" maxi with no help being arround 420W. Bike calculation are easier as friction is well measurable. On steep uphills aero interaction is minimized. |
#8
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Fans' Skiing Commentary and Analysis
The cyclismag.com articles referred to calculate power using an
assumption that all the riders weigh the same 70kg (154lb), plus 8kg for their bikes, so if a rider is lighter than this, his power output is actually lower than that calculated, and if heavier, higher. It would be interesting to see the tables calculated on the basis of real weight, and see which riders are putting out more power but because of their weight not winning the climbs. Something that struck me when I first found myself standing beside world cup biathletes in their casual clothes was how thin and gaunt they looked close up: even people like Sven Fischer and Halvard Hanevold, who look so bulky and burly on TV, had hollow cheeks and looked like 18-yr olds. I had been calculating how many calories and how much pasta to consume from formulae supplied by sports nutritionists, and found that even with my gargantuan love of food it was hard to eat as much as they said I should, and indeed I reckoned these guys looked a lot thinner than I did. I wonder whether the advice from the nutritionists is tuned more for general health than for peak performance - it seems that there are many areas where what top athletes do contradicts the advice generally given. On May 7, 4:15 pm, wrote: Impressive job. THis blog is promising Fore those interested in power caclulation figures TDF 2007 figureshttp://www.cyclismag.com/article.php?sid=3466 Giro 2007 figureshttp://www.cyclismag.com/article.php?sid=3362 |
#9
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Fans' Skiing Commentary and Analysis
Hugh P wrote:
The cyclismag.com articles referred to calculate power using an assumption that all the riders weigh the same 70kg (154lb), plus 8kg for their bikes, so if a rider is lighter than this, his power output is actually lower than that calculated, and if heavier, higher. It would be interesting to see the tables calculated on the basis of real weight, and see which riders are putting out more power but because of their weight not winning the climbs. Something that struck me when I first found myself standing beside world cup biathletes in their casual clothes was how thin and gaunt they looked close up: even people like Sven Fischer and Halvard Hanevold, who look so bulky and burly on TV, had hollow cheeks and looked like 18-yr olds. This is pretty typical for endurance athletes, in fact I've spoken with one triathlete who said: "When people tell me I look fit & strong, I know I'm too heavy." Terje -- - "almost all programming can be viewed as an exercise in caching" |
#10
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Fans' Skiing Commentary and Analysis
On 8 touko, 10:48, Terje Mathisen
wrote: I.e. world class orienteers maintain a higher percentage of their max heart rate than marathon runners, and xc skiers would seem to be similar. (The main difference being that xc skiers do get some rest periods on the downhills, where orienteers stay close to max heart load all the time.) It takes from 1.40 to just under 2.00 hrs for a world class orinteer to finish a long event, i.e. the duration is 15-25 min shorter than in the marathon, but that isn't probably a big enough difference to make the comparison pointless. What would a comparison between orienteers in shorter events and runners in shorter races show? Would cross country runners (in races of the same duration) fall somewhere between the two? FWIW I can easily accept (and, I think, comprehend) that xc skiers use more major muscle groups than track or road runners do, but it would instinctively seem to me that what orienteers do is, despite the often enormous difference in terrain, nothing more than running, i.e. they don't use their arms to push themselves or locomote themselves in any non-running way. OTOH life itself has taught me not to trust my instincts when it comes to the natural sciences, so I'm asking what is(are) the major muscle group(s) that runners don't use but orienteers do? BTW I have anecdotal evidence that it can be possible to maintain a higher HRavg for a certain duration by doing a few very short pauses - although, of course, a certain distance will be covered faster without anyt such pauses - and I wonder if this could be the case generally and world class orienteers especially, assuming the very short periods of "active rests" due to moments of map reading or chip-marking? Anders |
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