Ski Skating in cross country skiing

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Oct 3, 2006:



different meanings of VO2max

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?


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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