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Why the flailing arms in these race sequences?

post #1 of 5
Thread Starter 
I was looking at the LeMaster photo-montages (damn, are they beautiful, or what), and these two struck me as odd.



Why is it that, at least in these photos, that racers at the transition point have their arms so far from their body. Is't it the moment of the least amount of force? Is it a result of their up motion (in which case we might not see it as much in photo's of this year's racers, heck, those photos are from 99). Certainly from a strickly aerodymanic point of view it isn't very efficient (but the effects are probably negligible at SL and GS speeds.)

Any thoughts?


(who's sitting here at work on a very rainy, dreary Saturday afternoon, just wishing he were skiing somewhere.)
post #2 of 5
Arms are balance adjusters. In Maier's case he clearly has lost it to the inside. Notice his shoulders are not level(tipped in). He raises the arm to counter-balance.
In Campengionni's case it appears that the forces at the end of the turn may have rotated her, or she may be moving across her skis by moving the arm.
post #3 of 5
In addition to being a balance adjuster the arms also serve as a pressure adjuster and are a big influence on rotary inertia.
The outside arm up in the air usually means there is more pressure on the inside ski. As the racer nears the gate than outer arm and upper body move to put more pressure on the outside ski.
Extending arms to the sides during the transition phase, increase srotary inertia of the upper body. This decreases upper body motion related to rotary movement of the skis.
post #4 of 5
Those are great photosequences, aren't they? Ron does good work!

While there's a lot of arm movement in these sequences, I would not describe it as "flailing." Arms, and their extensions, poles, become increasingly important as speeds and the resulting forces and movement intensity increase. I've used the analogy to walking and running before. When we amble along slowly there is little need for arm swing--I might have my hands in my pockets. But it is difficult to RUN without using arms. The more vigorous the movement, especially when it involves quick changes in direction and/or speed, the bigger the role of the arms. As I type here, I'm watching the USA vs. Mexico World Cup Soccer match (recorded from last night). For a game played with the feet, soccer may involve more arm movement than any other sport! That's one of the great things about soccer, I think. Because the hands have no other role--they don't throw, catch, or a carry a ball, hold a stick, etc.--they are fully free to support balance and movement.

In skiing, as in soccer, the arms (and hands and poles) often help direct and lead movement of the rest of the body. They can also stabilize the body, by countering other movements, and by extending wide to increase the body's resistance to rotation--the way that a figure skater slows a spin by extending her arms.

A lot of the reason for the wide extension in the transition relates to the arms' effect on rotation--the "rotary inertia" that Nord brings up. Both Maier's and Campagnoni's arms are widest in that transition, during which both of them redirect their skis actively. When both feet are on the snow, separated to create two pivot points, with enough pressure so that each foot can provide the resistance for the other to turn against, the skier can turn them solely with the legs. This is the mechanism of "independent leg steering" that I've described often. But when there is NO pressure on the skis, they must turn against something else--namely, the upper body. That's the case in these turn transitions, and the widely spread arms help stabilize the upper body to allow the lower body and skis to turn against it. Maier supplements the wide arms with a gentle pole plant, too (frame 4, or just a moment before), further stabilizing the upper body while he actively pivots his skis.

Balance, stability, directing and enhancing movements--these are the primary roles of the upper body. The arms are critical in this role. There is, indeed, a lot of movement in these photosequences, but it is highly disciplined, and beautifully purposeful!

Thank you, Hermann and Deborah!

Best regards,
Bob Barnes
post #5 of 5
As SLATZ and NordtheBarbarian have said, the main purpose of the arms out are simply as balance enhancers. It's similar to a tightrope walker using a long balance beam.

It's essentially at the point of transition between turns when both skis are flat that arms are at their widest. At this point the athlete is balancing themselves to get just the right amount of edge to start the turn. Not too hard, so as not to have it dig in abruptly and slow down the ski, but just enough to have them start carving smoothly. Also the longer the skis can stay 'flat', the more speed they can keep or pickup.

You"re right in saying that this is less aerodynamic. Everything being equal the athlete would try to keep their arms in to maintain more speed. It's a trade-off the athlete makes between risking losing speed skidding or losing speed to air resistance. In downhill because of the higher speeds and the type of turns, the tradeoff is more towards keeping arms in. What's ironic about downhill is that any turn where your arms can be kept in is an easy turn. Turns where the athlete has to come out of their tuck and put their arms out are the hard turns. In GS then you mostly have hard turns. That's what GS is about.

When skiing a GS course the arms have to come in to go by the gate. This contrasts markedly with the wide arms at turn transition and makes it seem as if the athlete has ‘wild’ arm movement. In freeskiing the arms have no real need to come in and are more quiet. They still do come in to 'drive forward' the turn and extend somewhat at turn transition. The faster you are skiing and/or the rougher the terrain where you need to turn, the wider the arms tend to be for balance.

The arms are usually kept wider and quieter in freeskiing because we are not as concerned to get all the possible speed out of a turn. We are not very concerned about aerodynamics. We’d rather have a more carved turn then a more aerodynamic position. We are not as concerned to keep our skis flat as long as possible between turns to maintain speed. Our turn transitions can be more abrupt and less aerodynamic so as simply to maintain more control.

If you ever get a chance to see World Cup skiers freeski or at least simply training gates, it’s usually much nicer then having them going 100% (and sometimes more) down a course. It’s really the way I would like to be able to ski. At race speeds down a course, there are many mistakes and wild movements that are often mistaken as being part of their skiing technique.

(hey..it was long, but it’s summer and months till ski season)
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