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Ski Skating in cross country skiing
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Oct 3, 2006:
VO2max is a tricky concept to use, because people use
it with different meanings, and it can carry unhelpful connotations.
I believe that the theoretical concept is something like that VO2max is
the maximum rate of oxygen consumption by a person in their current
state of health and athletic fitness, measured as the difference between
the volume of oxygen going into the lungs and the volume coming out of
the lungs.
?? more to be added
Sep 29, 2006: Recruiting more muscles versus central
VO2max limit post on
rec.skiing.nordic
- subject: VO2max versus technique: bicycling vs skiing
I've been working on improving my pedaling technique in bicycling,
started researching buying some devices for measuring or developing
specific stroke phases or muscle groups -- and found out that there are
really smart well-informed experts who think this is mostly a waste and
unlikely to improve my speed or endurance any more than would just
getting more serious about following a better-designed training program.
Some people have made similar claims about trying to improve techniques
for XC skiing -- but I think there's a key difference between skiing and
bicycling about VO2max.
The main argument for bicycling that normal pedaling already uses the
big obvious "natural propulsion" muscles from walking + running +
climbing so effectively, that it's straightforward for bicycling to take
the central cardio-vascular system close to its limits in delivering
pressure and volume of oxygenated blood to the muscles. So adding +
developing some some non-obvious muscle mostly just takes blood pressure
away from the obvious muscles, so not as much oxygen gets pushed thru
the capillaries into them, and they either have to operate more
anaerobically or else slow down. So achieving sustainable gains in power
by this approach are not impossible, but tricky and difficult to
achieve. That's the theory, and in practice lots of training concepts
and special devices like this have been tried for bicycling, but it's
been hard to demonstrate their superior effectiveness in
carefully-designed, well-controlled studies.
XC skiing? The obvious thought is that since bicycling uses only
legs, and XC skiing uses both arms + legs, then of course skiing must
put more load on central cardio-vascular systems than bicycling (so then
trying to improve skiing technique is going to be tricky and unlikely).
But there are critical differences: * XC skiing does not use _all_ the
big bicycling leg muscles. * XC skiing uses muscles at higher speeds
which are less effective.
Classic "diagonal" striding on flat terrain does not use the big
quadriceps muscles. And at higher speeds the hip extensors and knee
flexors must be used with very high acceleration ("plyometric") in order
to match speed with the kick grip zone on the surface of the snow. They
can't deliver as much power in this "explosive" high-acceleration+speed
mode, so they cannot fully load the Central CV system. Elite racers just
give up on using their legs for direct pushing on the flat, instead
switch to pure double-poling.
Skating leg-push does not require matching speed with ground, so
higher overall forward skiing speed does not require the big leg muscles
to go into an ineffective high-acceleration+speed mode, so ski-skating
speeds on gentle terrain are clearly faster than Classic striding. But
there's still a problem with using the obvious gluteus + quadriceps +
calf muscles: Because the obvious "piston" leg-extension push roughly
along the line from hip to ankle cannot have a significant propulsive
(horizontal) component of force until the foot is way out to side from
the hip -- so far out that the upper body is rapidly falling down. So
trying to get more range-of-motion out of the obvious big extension
muscles requires compromising something else.
Uphill skating -- Skating up a steep hill seems like it should be
able to fully load the skier's Central Cardio-Vascular capacity. Since
elite racers can Skate up faster than Classic striding or herringboning
or non-ski running up the same hill -- and at least two of those other
techniques are usually thought able to achieve "true" VO2max. So you'd
think this would be the situation where the elite racers could use the
obvious "piston" leg-extension (bicycling) muscles _plus_ poling and
that would put them as close to VO2max as they would chose to go in the
current race situation. Here would be the case where the VO2max approach
says there's no point in trying to add new non-obvious muscles.
But the elite racers _do_ add more muscles for skating up a steep
hill. The land the ski roughly underneath their hip with the knee and
ankle joints pretty much in the line from the hip joint to the (roughly
flat) ski. Before the finish of the stroke, the knee joint moves
strongly inside the line from the hip to the ankle, and the ankle joint
is obviously inside the line from the knee to the ski. There's nothing
like those two sideways-bending moves in normal seated bicycling. The
skiers have definitely and strongly added non-obvious muscles to their
technique (medial hip-rotation and ankle-pronation) even in a potential
VO2max limited situation. It's certainly possible to skate up a hill
without adding those -- using only "bicycling" muscles -- funny that was
my normal method two years ago.
This seems to show that skaters cannot sufficiently utilize the
obvious bicycling muscles to achieve VO2max . . . or something else?
Ken
P.S. Ice speedskating has a different story from bicycling. Although
the same big "natural propulsion" gluteus + quadriceps muscles are used
for skating propulsion, elite racers _also_ devote lots of attention to
adding and using non-obvious sideways-pushing muscles like the hip
abductors and ankle-pronators -- landing the skate blade way underneath
obviously on its outside edge -- with many elite racers developing large
muscles on the _outside_ of their upper legs. And when a new device was
introduced to engage another muscle -- the klap-frame to use
ankle-extension for propulsion -- very soon a whole bunch of new world
records were set.
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