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Are Fat Skis Killing Knees - Page 4

post #91 of 114

Yes it's true. I know this.

post #92 of 114

This is more a "do you know how to ski" thread than anything else.

Please believe me that if you actually  know how to ski, there is there is the same pull on a any ski.

But that assumes you actually know how  to ski.....why reply to this?

post #93 of 114
I get the sense that the original article is saying something got worse... than what?

I occasionally out of a sentimental foolishness, like to bust out my old P10s and ski the for a day, on piste. They were a heavy, dampened, solid feeling ski back in the day, but, frankly, after the first run I'm in the knee pain not because of edging torque, but because the ski doesn't naturally track the "parabolic" arc, so it requires a lot more "micro movements" to stay on line, and similarly is giving you tons of feedback from the snow, particularly if you don't drive it hard and force it to engage.. All this vibration has my knee starting to throb after the first blue run. In contrast, if I charge them hard there is a heck of a lot more torque on the edges than when I'm Sunday driving, but I don't get the knee pain.

The change to shaped ski design got rid of that problem.

Now if your wide ski also happens to have a modest sidecut that doesn't mesh with whatever radius turns you want to carve, you're going to be back in the 1980's as far as stability.

Back on edge torque, you also have to think about the absorption properties of the ski before you start demonizing fat skis. Maximal torque is going to occur at the widest part of the ski - the tips - not directly underfoot. A modern soft ski will tend to mitigate that torque by twisting itself. But a rigid "stiff" ski will transfer that torque right back to the binding - boot - leg. So you have to distinguish between fat stiff skis vs. fat soft skis.

If you want to compare a 120 underfoot soft utility ski to "narrow" DH race ski that is 120 at the tip, my money is on the race ski as far as which is going to stress out your knee with lateral torque. Not to mention the "micor torque" of each vibration that happens to the edge... something that the better racing skis employ all kinds of tech to keep those vibrations in the ski and out of your let. Does your average fat ski have that kind of tech? Or the average all mountain ski.

I think vibration is the knee killer. Consider water skiing - an uber fat ski with lots of potential torque from the edges. But if I ski on a glass surface lake I pretty much feel nothing but the wind in my hair (assuming you don't mess up, catch the outside edge, and then I think you can say it's your technique or lack thereof, that's the problem). Ski in choppy water, just in a straight line without applying any edge torque, and my knees will feel like someone just buzz-sawed them within 10 minutes.
post #94 of 114
Some injury statistics from a University of Utah study:

 

http://medicine.utah.edu/pmr/conference/presentations/fri/M.Henrie-SkiInjuryData-Fri-Track1.pdf

 

Doesn't really breakdown knee injury to surface type but interesting nonetheless; it does break down number of injury by surface type. 

 

Regarding the article in the OP: when/if the doc puts out a study or writes his own article, that should be more valuable. The article we're discussing is kind of speculative about what the Dr. might eventually conclude based upon his findings regarding torque (and whatnot).

 

Also, sounds like he would advise people to reign in the width on packed days, its not like the advice is to abandon the fat skis altogether regardless of the conditions. 

post #95 of 114

We're discussing apples and oranges here. The author of the first study cited seems to be speculating that the increased torque with wide skis on packed snow might be causing chronic knee problems. And that article had no data on knee injuries--chronic or otherwise--just the torque data. At this point the link between increased torque and chronic knee problems is speculative. Ththe moe UU article talks about acute injuries. Completely different issue, other than that acute knee injury often leads to chronic.

 

As is common with medical articles, people, especially the lay press will try to overstate the conclusions and make the findings seem much more dramatic and important than they are.

post #96 of 114
Quote:
Originally Posted by oldgoat View Post

We're discussing apples and oranges here. The author of the first study cited seems to be speculating that the increased torque with wide skis on packed snow might be causing chronic knee problems. And that article had no data on knee injuries--chronic or otherwise--just the torque data. At this point the link between increased torque and chronic knee problems is speculative. Ththe moe UU article talks about acute injuries. Completely different issue, other than that acute knee injury often leads to chronic.

As is common with medical articles, people, especially the lay press will try to overstate the conclusions and make the findings seem much more dramatic and important than they are.

Also the UU article has nothing the is knee specific. Talks mainly about head and wrist, and injury incidence among park vs. non-park skiers.

His source on knee injuries are from 1998 - not exactly the age of the fat ski.

Still it was interesting read - thanks for sharing HooDoo.
post #97 of 114
Quote:
Originally Posted by mdf View Post

There are plenty of engineers here. It's a cross product, not a dot product. Not complicated.

My point was using the correct formula shows a riser does not change the knee torque in the 2D drawing.

I believed above too untill dr. Nacbauer made study for FIS calculating correctly in late 90'. Rise has effect on knee torque in aproximate ratio 10:1 for every milimeter of width to every milimeter of raiser, therefore could be neglected. I will try to digg into my arcives to get things right :-) (ate 10:1 rati there is no point doing that)

 

Jurij

post #98 of 114

deleted

post #99 of 114
Quote:
Originally Posted by LUSST SKI View Post
 
Quote:
Originally Posted by mdf View Post

There are plenty of engineers here. It's a cross product, not a dot product. Not complicated.

My point was using the correct formula shows a riser does not change the knee torque in the 2D drawing.

I believed above too untill dr. Nacbauer made study for FIS calculating correctly in late 90'. Rise has effect on knee torque in aproximate ratio 10:1 for every milimeter of width to every milimeter of raiser, therefore could be neglected. I will try to digg into my arcives to get things right :-) (ate 10:1 rati there is no point doing that)

 

Jurij

I suppose the difference is that the force is not quite parallel to the lower leg.  Still not seeing it though, seems like that would make the torque get smaller, not larger, as the riser increases.

post #100 of 114

The wider tips suck you into turns, if you're not carving, the ski is catching and chattering, hence the knee stress.

 

If you're carving the forces that build up, and the acceleration out of the turn can be hard to handle, forced turn shapes, etc, all stress on the knees.

 

Those 2 occur..1st being less skilled skiers, 2nd being for more skilled skiers.

 

2 examples of how "fat" ter skis stress the knees more. Another example is slarving, sliding sideways with chatter .

post #101 of 114

Funny to me how many posters in this thread without a clue about biomechanics or physics respond along the lines of, "if you know how to ski, no problem." I'm sure you'll all enjoy President Trump. 

 

News flash, guys: we've had countless posts and a few threads about this. The article is not revolutionary, it just adds empirical data to back up what physics predicts. While back I even posted a diagram with the force vectors.

 

The short version: Yes, wider skis require more force to get up on edge in the same period of time, and yes, in motion they produce more rotary torque (and shear) on the knee. It is not a dramatic difference, but it is real. If there is slippage in the arc, rather than tracking, some of that difference in torque is reduced. Thus the comment in the linked blurb about about a change in technique. So the added torque is not about technique. It's not about chatter or handling the tips, or how we tip, or whatever other imaginative scenarios we come up with. It's just basic physics of a ski linked to our hip. The technique issue is not about whether we know how to ski. It's that we shouldn't be trying to carve wider skis on groomed snow, regardless of whether we can. 

 

Whether this additional torque produces damage over time is another issue for another study. But as someone missing part of a knee, and who knows how to ski, the difference between a 85 and a 100 is noticeable. Between that, and the more variable conditions we all face year to year, my solution has been to evolve toward a narrower daily driver quiver for variable conditions including firm, and then save fatties for real powder and different technique. Length will also play a role in this, BTW. 

post #102 of 114

Just to add a comment from another patroller who is skiing the "mountain issue"(some kind of HEAD ski) fat skis.

 

"My knees ache more than they ever did on narrow skis."

 

I trust her comment. 

 

We have had a lot of "loud powder" this year.  I sharpen the Fischer RCs every week to keep up. Fats would be fun for some of the "fast grass" ventures  ;-)

post #103 of 114
Quote:
Originally Posted by Cgrandy View Post
 

Just to add a comment from another patroller who is skiing the "mountain issue"(some kind of HEAD ski) fat skis.

 

"My knees ache more than they ever did on narrow skis."

 

I trust her comment. 

 

We have had a lot of "loud powder" this year.  I sharpen the Fischer RCs every week to keep up. Fats would be fun for some of the "fast grass" ventures  ;-)

If you look at the skis outside the patrol shack at a Western ski area you will rarely see skis under 90 mm, regardless of the conditions that day.  

post #104 of 114
Quote:
Originally Posted by oldgoat View Post
 

If you look at the skis outside the patrol shack at a Western ski area you will rarely see skis under 90 mm, regardless of the conditions that day.  


If you look at the type of skiing that a patroller performs during an average day it bears little resembalance to an average skier too. In the morning the patroller will go to the boundaries and beyond to control snowpack. Often they will use traverse of cross cut on runs or slide the cornice edge to break it off.  During the day the patrollers duties include sliding the edge of the runs to move or raise ropes. When accidents occur the patroller will be hauling sleds which requires slipping to slow the sled. All the patroller I know keep a pair of chargers handy for fun skiing.

post #105 of 114
Conversely, most instructors seem to be on <90 waisted skis for daily drivers, and save the fatties for free skiing in powder or off-piste.
post #106 of 114
Quote:
Originally Posted by imatlas View Post

Conversely, most instructors seem to be on <90 waisted skis for daily drivers, and save the fatties for free skiing in powder or off-piste.


That seems to be pretty true where I ski although the age/width distribution does seem to skew wider as the age goes lower.

 

I partially attribute that part to younger knees not knowing the difference yet.  ;) 

post #107 of 114

-accidental post, ignore sorry-

post #108 of 114
Quote:
Originally Posted by imatlas View Post

Conversely, most instructors seem to be on <90 waisted skis for daily drivers, and save the fatties for free skiing in powder or off-piste.

 

Makes sense because most of them are going to be spending most of their time teaching on groomers or in mild variable terrain.  Unless they teach specialised freeride classes they aren't generally going to have a need.  Plus no doubt you can do cleaner demos on a narrower ski.

post #109 of 114

Ive read your post on fat and skinny skis.very interesting.i use to skis alot back in the 80",

early 90.started skiing last year took out my old skis and when arriving at the station i realize

that i was away for to long.so i did rentals and this year i bought dyna 79 powertrack did make a good choice?

post #110 of 114
Quote:
Originally Posted by canheat View Post
 

Ive read your post on fat and skinny skis.very interesting.i use to skis alot back in the 80",

early 90.started skiing last year took out my old skis and when arriving at the station i realize

that i was away for to long.so i did rentals and this year i bought dyna 79 powertrack did make a good choice?


With no more info than that to go on... yes.

post #111 of 114
Quote:
Originally Posted by fatbob View Post
 

 

Makes sense because most of them are going to be spending most of their time teaching on groomers or in mild variable terrain.  Unless they teach specialised freeride classes they aren't generally going to have a need.  Plus no doubt you can do cleaner demos on a narrower ski.


That brings up an interesting thread drift.  I'd be curious to know how many instructors spend what percentage of their time on groomers or in mild variable terrain?

 

Personally, I spend MOST of my instructor time off groomers and in what I would call non-mild variable terrain.  I don't teach specialised freeride classes, I simply take people that want to ski our whole mountain.

 

Once two days have gone by since the last snowfall, my preferred ski width for all the terrain here at Jackson Hole is sub-82mm.  My FAVORITE ski width once three days have gone by since the last snowfall is 68mm.

 

I'm exceedingly lucky in that I have multiple skis at my disposal and they are easy to get to while on the hill.  I also realize that I'm way off the grid as far as my width preference is concerned.

 

That said, I'm really curious as to whether most ski instructors at other WESTERN resorts spend most of their time teaching on groomers or in mild variable terrain.

post #112 of 114

Bob

 

Perhaps instructors have greater options (lockers and racks of alternate skis)

 

But

 

I feel your conditions and criteria are fitting to both pro and recreational skier alike.

 

Does anyone need the float of 100mm under foot when the snow is compacted as not to dent under a >80mm width?

 

But I can see getting locked in with the mornings selection in order to save the walk to the car park. 

 

Me?  I've no problem switching from fat to skinny at noon time.  When the fresh is gone...It's gone!  What I need is a crud buster! 

What's the modern version of the Volkl G4? 

post #113 of 114
That's what I don't understand - snow once it has been tracked doesn't instantly transform into packed powder - it's just tracked snow. OK it gets a bit chunky depending on moisture content/ sun effects etc but it's still 3d. It' can take days to get packed down and firm like a groomer during which time I find a wider ski better for skiing it ( appreciating for some that tipping point comes earlier.
post #114 of 114

I gotta say, actually possessing two knees that are potential candidates for replacement within 3 to 5 years, I agree with Bob on the ski width thing.

 

My bone-on-bone parts can inarguably FEEL the fatigue of wider skis on the knees at the end of a day.

 

But once things start getting corny/slushy, my sweet spot moves back up to 80-ish, with narrower skis yanking the knees around a bit more.

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