analyzing high energy powder turn

[Mike King]

The fifth fundamental, magnitude, illuminates skiing as a 3D experience. No longer do you think of the slope as a plane, but rathe a surface to be penetrated. So, particularly as the snow becomes unconsolidated, rather than thinking about lateral displacement of the feet from the body, you start thinking about the. Feet moving and even diving into the snow and porpoising out of it. Ankle movements are a big part of this and move from tipping actions to flexion actions (both plantar and dorsi). And that is what I see in Marcus’s movements.

mike

 

[Mike King]

Ok so Marcus can use any style he wants and be powerful in powder, and look good doing it what about Scot Schmidt and his style , which to me looks like independent leg action ( in interviews he will tell you he copied Stenmark and Gustavo for his way of turning ).
For me I love to get my uphill ski out of the snow and almost use a telemarking style and let my arms and upper body get loose and playfull.
Of course I can also use a more traditional two ski style but my ILA style is my favorite.

Believe me, Marcus’s skiing uses a lot of independent leg action, it’s just more simultaneous rather than sequential.

 

[Mike-AT]

Love his move(s)!

In this article his signature turn is shown in a series of frames. Description is good but not enough for me to replicate

https://www.skimag.com/ski-performance/steep-clinic-got-vert

It is definitely some kind of jump turn as you can see in the last two images. But so smooth and with style!

 

[geepers]

Love his move(s)!

In this article his signature turn is shown in a series of frames. Description is good but not enough for me to replicate

https://www.skimag.com/ski-performance/steep-clinic-got-vert

It is definitely some kind of jump turn as you can see in the last two images. But so smooth and with style!

I'd be a little careful reading too much into the 'jumping'. Here's another Caston article...

https://www.skimag.com/ski-resort-life/hop-to-it

One of the most common mistakes when people try a hop turn for the first time is actually using their legs to “hop” from one turn to the next. But jumping is hard, and not a very efficient use of energy. Instead, let the skis work for you, not against you. Think about using your skis as a spring to shoot into the sky...

​

Even that may need some thought. Ron leMaster writes in Ultimate Skiing (page 104) that

Contrary to common belief, the skis themselves don’t contribute appreciably to rebound through a trampoline effect. Compared to a skier’s weight, the skis are simply not stiff enough to store and return much energy. In addition, the skis are supported by the snow directly underneath the skier’s feet, unlike a trampoline, which is supported only along its edge.​

leMaster reckons the rebound comes from

...edgeset at the end of the turn, resulting in an abrupt increase in the snow’s reaction force. The sudden force from the snow and accompanying deceleration of the skier’s feet produce two effects that cause the unweighting:
1. The first is an effect something like a pole vault. The box in which pole vaulters plant their poles is below their centers of gravity. The reaction of the box to the pole and the vaulter redirects the center of gravity into a circular arc with the box at its center.
2. The second source of rebound unweighting is a rubber-band effect of the leg and hip extensors: the thigh, buttock, and lower-back muscles. To get the sharp increase in pressure needed for the edgeset, the skier allows the center of gravity to fall toward the feet, then catches it with a quick contraction of those muscles. When the contracting muscles catch the falling mass of the upper body and upper legs, they stretch a bit, then recoil, tossing the center of gravity back upward.
​

That sure makes it important the body continues moving down the hill and seems to fit well with Caston's description with the 1st image in that article:

Load the Spring
This is where the energy for the hop turn starts. Pressure the downhill ski into the fall line through the heel. Anticipate the pole plant by reaching down the hill parallel to your leg.​

 

[Doug Briggs]

I agree about the pole-vaulting effect mentioned above.

'Hop' turns for me are more 'retraction' turns. When you are in 3D snow pushing off your skis will generally cause them to sink deeper into it.

 

[SSSdave]

In pursuit of the most fun, he's actively relaxing balanced as gravity pulls and compresses him down then enjoys feeling a reverse cambered rebound that quickly becomes a massive soft gravity drop with resulting explosion of cold dry powder getting on the video camera lens. He knows when to rebound because it is like many of the others he's been making this day as he's long been locked into the incredible visceral feel of its softness and elasticity for a smooth rebounding ride.


...too much fun for an old guy

 

[Mike-AT]

I'd be a little careful reading too much into the 'jumping'. Here's another Caston article...

https://www.skimag.com/ski-resort-life/hop-to-it

One of the most common mistakes when people try a hop turn for the first time is actually using their legs to “hop” from one turn to the next. But jumping is hard, and not a very efficient use of energy. Instead, let the skis work for you, not against you. Think about using your skis as a spring to shoot into the sky...

​

Even that may need some thought. Ron leMaster writes in Ultimate Skiing (page 104) that

Contrary to common belief, the skis themselves don’t contribute appreciably to rebound through a trampoline effect. Compared to a skier’s weight, the skis are simply not stiff enough to store and return much energy. In addition, the skis are supported by the snow directly underneath the skier’s feet, unlike a trampoline, which is supported only along its edge.​

leMaster reckons the rebound comes from

...edgeset at the end of the turn, resulting in an abrupt increase in the snow’s reaction force. The sudden force from the snow and accompanying deceleration of the skier’s feet produce two effects that cause the unweighting:[...]​

Thanks, super valid point(s). Fully agree, everyone who tried to do hop/jump turns realizes how much energy this takes. I'd love to be on the snow with Marcus Caston to really analyze what he is doing. So hard to extract from videos or text (at least for me).

On the one extreme there are surely jump turns just produced by leg pushing. If you watch old Scot Schmidt movies in the steeps, you see the jumps, "fall into snow", jump, etc., with almost no skiing inbetween. Like classic steep skiers such as Anselme Baud did and his followers still do today.

Then you have the linked, fluid jump/hop - however you call them - turns "in the air" that Caston shows. No idea how he can generate this level of springforce from his skis. I (think I) know the kind of hard edge set at the end of the turn that leMaster mentions. I can use that in short turns followed by leg flexion to unweight and transition to the next turn. But no way I can launch off the ground like in the initial video. Also not sure if the hard edge set works in deep snow? (edit: I think this is what @Doug Briggs mentioned above) The short turns I just mentioned are on groomers.

Keep the discussion going, much to learn!

 

[geepers]

Thanks, super valid point(s). Fully agree, everyone who tried to do hop/jump turns realizes how much energy this takes. I'd love to be on the snow with Marcus Caston to really analyze what he is doing. So hard to extract from videos or text (at least for me).

On the one extreme there are surely jump turns just produced by leg pushing. If you watch old Scot Schmidt movies in the steeps, you see the jumps, "fall into snow", jump, etc., with almost no skiing inbetween. Like classic steep skiers such as Anselme Baud did and his followers still do today.

Then you have the linked, fluid jump/hop - however you call them - turns "in the air" that Caston shows. No idea how he can generate this level of springforce from his skis. I (think I) know the kind of hard edge set at the end of the turn that leMaster mentions. I can use that in short turns followed by leg flexion to unweight and transition to the next turn. But no way I can launch off the ground like in the initial video. Also not sure if the hard edge set works in deep snow? (edit: I think this is what @Doug Briggs mentioned above) The short turns I just mentioned are on groomers.

Keep the discussion going, much to learn!

Yep, leMaster's ref to 'edge set' is on firmer snow. Or at least something with a bottom.

In pow I believe the 'edge set' comes more from a vertical component, as the skis compress the snow as described by Klaus making snowballs at 1:50.


There still has be some lateral component otherwise it would become a straight run down the fall line. As demo-ed here at 1:50 (by co-incidence).

 

[KingGrump]

There still has be some lateral component otherwise it would become a straight run down the fall line.

@karlo had a similar discussion regarding skis and mechanics for powder turns couple years back.

https://www.pugski.com/threads/skis-for-carving-in-powder.6590/

We talked about the lateral component in post #89 of that thread.

 

[geepers]

@karlo had a similar discussion regarding skis and mechanics for powder turns couple years back.

https://www.pugski.com/threads/skis-for-carving-in-powder.6590/

We talked about the lateral component in post #89 of that thread.

Being antipodean I relate to an upside down sun. Also post#84.

I think we are on the same page. (?)

 

[KingGrump]

QUOTE="geepers, post: 406157, member: 3211"]I think we are on the same page. (?)[/QUOTE]

Yup.

 

[karlo]

I'd be a little careful reading too much into the 'jumping'. Here's another Caston article...

https://www.skimag.com/ski-resort-life/hop-to-it

One of the most common mistakes when people try a hop turn for the first time is actually using their legs to “hop” from one turn to the next. But jumping is hard, and not a very efficient use of energy. Instead, let the skis work for you, not against you. Think about using your skis as a spring to shoot into the sky...

​

Even that may need some thought. Ron leMaster writes in Ultimate Skiing (page 104) that

Contrary to common belief, the skis themselves don’t contribute appreciably to rebound through a trampoline effect. Compared to a skier’s weight, the skis are simply not stiff enough to store and return much energy. In addition, the skis are supported by the snow directly underneath the skier’s feet, unlike a trampoline, which is supported only along its edge.​

leMaster reckons the rebound comes from

...edgeset at the end of the turn, resulting in an abrupt increase in the snow’s reaction force. The sudden force from the snow and accompanying deceleration of the skier’s feet produce two effects that cause the unweighting:
1. The first is an effect something like a pole vault. The box in which pole vaulters plant their poles is below their centers of gravity. The reaction of the box to the pole and the vaulter redirects the center of gravity into a circular arc with the box at its center.
2. The second source of rebound unweighting is a rubber-band effect of the leg and hip extensors: the thigh, buttock, and lower-back muscles. To get the sharp increase in pressure needed for the edgeset, the skier allows the center of gravity to fall toward the feet, then catches it with a quick contraction of those muscles. When the contracting muscles catch the falling mass of the upper body and upper legs, they stretch a bit, then recoil, tossing the center of gravity back upward.
​

That sure makes it important the body continues moving down the hill and seems to fit well with Caston's description with the 1st image in that article:

Load the Spring
This is where the energy for the hop turn starts. Pressure the downhill ski into the fall line through the heel. Anticipate the pole plant by reaching down the hill parallel to your leg.​

Sounds good. In the 2019 Women’s World Cup thread, in the Racing section, there was a discussion about Vlhova’s crash at yesterday’s race in Levi. Would anyone like to take a stab at describing that catapult in terms of LeMaster’s two points and how, if at all, that relates to what Marcus is doing in the powder?

A video of the crash is found here

Some video here: https://www.eurosport.com/alpine-sk...ith-victory-in-finland_sto7548829/story.shtml

Here are some posts analyzing the crash

Skis left the surface, and when she landed, with some “heat”, her left ski hooked up,

Was a bit difficult to see and haven’t watched any reruns, but to me it looked like she momentarily lost outside pressure and got catapulted (spun around) when her edges bit rather harshly mid turn.

Based on the shadow of her outside ski, it looks like the ground dropped away a few inches and her outside ski came off the ground.

Looked to me like Shiffrin was a little lighter on her edges and drifted through that spot and then pressured the ski once it was safe. Vlhova had edge and pressure earlier & actually looked stronger on the gate. A little air under her outside ski maybe caused too much pressure all at once when it engaged and surprised herself and everyone else when she got catapulted.

Here are frames from the video

 

[geepers]

...discussion about Vlhova’s crash at yesterday’s race in Levi. Would anyone like to take a stab at describing that catapult in terms of LeMaster’s two points and how, if at all, that relates to what Marcus is doing in the powder?

A video of the crash is found here

Unfortunately that Eurosport vid of Vlhova blocked in country after the 1st viewing yesterday. Which is better than what happened to the men's event vid - which didn't even provide a 1st viewing this morning.

i'm not sure what else to say that others have not already commented on. Maybe a different but similar crash will provide some illumination.

In the 1st image below, skier is rounding the gate, direction of travel is mostly still down the hill.

But then he loses grip on the outside ski. Note the extended outside leg.

The outside ski continues to slide out... His CoM is downhill of the inside ski so it's not going to provide much help.

His outside ski begins to engage again - remember his body is moving mostly down the hill so that outside ski now has weight on it and plenty of platform angle for a good solid grip! His outside ski now wants to go across the hill, not down the hill so it has become the fulcrum and his body is about to be projected over that fulcrum by the 'pole' of his outside leg.

And here the body goes up and over the outside ski which has not moved down the hill at all.

Enough momentum to get completely airborne. Ouch, that's going to hurt.

And again in animation.

 

[karlo]

i'm not sure what else to say that others have not already commented on. Maybe a different but similar crash will provide some illumination.

Nice video!

Any thoughts on whether or not there is any commonality between the forces that catapulted the racers and that which Marcus Caston or LeMaster’s wrote of?

 

[geepers]

Nice video!

Any thoughts on whether or not there is any commonality between the forces that catapulted the racers and that which Marcus Caston or LeMaster’s wrote of?

For the racers it's as described by leMaster. It's just out of control.

Here's a vid of MH doing it in control with appropriate explanation.


For the powder skier, the ground reaction force comes from the whole ski (not just the edges) compressing the snow until the skis stop going down and start back up. MC's timing of his movements - extension/retraction is helping him to get the most from that effect. When the GRF push back at him he does a big flex/retraction to lift his feet/skis clear of the snow. For me, that's the key point. Doing that by jumping with leg power alone would quickly prove exhausting. As anyone who has ever been sentenced to a daily quota of speiss turns finds out.

 

[KingGrump]

Frame grabs from Petra Vlhová crash.


Photo #1.

Photo #2.

Photo #3.

Photo #4.

Photo #5.

Photo #6.

Photo #7.

Photo #8.

Photo #9.

Photo #10.

Photo #11.

Photo #12.

Photo #13.

Photo #14.

Photo #15.

Photo #16.

Photo #17.

Photo #18.

Photo #19.

 

[karlo]

Frame grabs from Petra Vlhová crash

Thank you.

Photo 9 is where, to me, it’s quite apparent something’s gone wrong. Photo 8, maybe, maybe not; could be just rising to transition if we didn’t know outcome. I know folks have said the cause is too aggressive a line or such. But, to have successfully accomplished this line and this level of aggressiveness, what would she have had to have been able to do, where and when in that turn? Was there someplace in the turn where forces got super-humanly high; i.e., impossible to handle?

Then, where in that turn, that line, might she have done something different to yield a successful outcome, gotten through it, and win the race?

 

[KingGrump]

where in that turn, that line, might she have done something different to yield a successful outcome

Between #4 & #5.

 

[karlo]

Between #4 & #5.

At #5, others have pointed out that the skis have left the snow. Actually, zooming in on 4, the ski has already started coming up. Was is a misjudgment of the change in fall line? Misjudgment is perhaps the wrong word, since she may not have been able to see where the fall line is before going over that roll; but, you get what I mean.

 

[geepers]

At #5, others have pointed out that the skis have left the snow. Actually, zooming in on 4, the ski has already started coming up. Was is a misjudgment of the change in fall line? Misjudgment is perhaps the wrong word, since she may not have been able to see where the fall line is before going over that roll; but, you get what I mean.

Here's a gif of me testing some Volkl Racetiger SCs in August. (That's the less stiff one with carbon instead of metal and supposedly a large sweet spot.)

Ok, it's an exaggeration. But only slight - resulted in a bad headache and a new helmet. Certainly felt like I would have cleared the bar.

Can't speak for the racers who are utilizing much larger forces than I am capable of generating however getting flung doesn't necessarily mean super-human forces. Just skis that have been commanded to go in one direction when your body is travelling in another.