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Fans' Skiing Commentary and Analysis



 
 
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  #1  
Old May 7th 08, 02:52 AM posted to rec.skiing.nordic
tassava
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Posts: 136
Default 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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  #2  
Old May 7th 08, 09:12 AM posted to rec.skiing.nordic
Terje Mathisen
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Posts: 262
Default 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
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"almost all programming can be viewed as an exercise in caching"
  #3  
Old May 7th 08, 05:46 PM posted to rec.skiing.nordic
[email protected]
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Posts: 1
Default 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.
  #4  
Old May 7th 08, 06:51 PM posted to rec.skiing.nordic
Terje Mathisen
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Posts: 262
Default Fans' Skiing Commentary and Analysis

wrote:
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.


Twice as good on wet snow, sure, but 1976-era skis didn't get even close
to maximum glide on those conditions, i.e. the starting point probably
wasn't 0.05.

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.


But it also moves significant parts of his body sideways, back & forth
across the hill, and this is mass that has to be started and stopped on
each stride.

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.


Exactly right.

Terje

--
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"almost all programming can be viewed as an exercise in caching"
  #5  
Old May 7th 08, 07:29 PM posted to rec.skiing.nordic
[email protected]
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Posts: 74
Default 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


  #6  
Old May 7th 08, 08:15 PM posted to rec.skiing.nordic
[email protected]
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Posts: 59
Default 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.






  #7  
Old May 8th 08, 07:48 AM posted to rec.skiing.nordic
Terje Mathisen
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Posts: 262
Default Fans' Skiing Commentary and Analysis

wrote:
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.


The reason xc skiers are such max O2 freaks are supposed to be because
they use every major muscle group in the body, and this allows the total
energy output to be significantly higher than for a bike rider where the
upper body is (mostly) dead weight.

As I've written here a few times, it seems like activities where you can
vary the load across multiple muscle areas allow higher total energy
output than something like bike riding or track running.

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.)

Bike calculation are easier as friction is well measurable. On steep
uphills aero interaction is minimized.


Right.

Terje

--
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"almost all programming can be viewed as an exercise in caching"
  #8  
Old May 10th 08, 10:07 AM posted to rec.skiing.nordic
Hugh P
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Posts: 30
Default 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  
Old May 10th 08, 03:42 PM posted to rec.skiing.nordic
Terje Mathisen
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Posts: 262
Default 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  
Old May 12th 08, 06:04 AM posted to rec.skiing.nordic
Anders
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Posts: 77
Default 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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