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The effect of wide skis on knees

mountainwest

Ski Diva Extraordinaire
I bought a pair in February and have skied them in every condition imaginable, probably about 40 days on them. They made everything I skied easier and more fun.
Good to hear! Decisions, decisions... still on the fence because the 93s would be a little more versatile.
 

marzNC

Angel Diva
I was pretty underwhelmed by the article itself, everything seemed very subjective, and it didn't go into any description of where the information was coming from.
Here's the original paper by Prof. Seifert and his colleagues at Montana State. Note that they were studying "elite skiers." The presentation was made at the PSIA National Academy in this late spring 2019. Only one skier was involved: "The subject was a 53 y old female. She is an Olympic gold medalist in Giant Slalom, National Alpine Skiing Champion, a two-time PSIA National Demonstration Team member, and an elite level ski instructor." Debbie Armstrong was the skier and the testing was done at Steamboat.

Does Ski Width Influence Muscle Action in an Elite Skier? A Case Study
John G. Seifert 1, Heidi Nunnikhoven 1, Cory Snyder 1, Ronald Kipp 2
1 Montana State University Movement Science Laboratory Bozeman, MT 59717

 

liquidfeet

Ski Diva Extraordinaire
Here's the original paper by Prof. Seifert and his colleagues at Montana State. Note that they were studying "elite skiers." The presentation was made at the PSIA National Academy in this late spring 2019. Only one skier was involved: "The subject was a 53 y old female. She is an Olympic gold medalist in Giant Slalom, National Alpine Skiing Champion, a two-time PSIA National Demonstration Team member, and an elite level ski instructor." Debbie Armstrong was the skier and the testing was done at Steamboat.

Does Ski Width Influence Muscle Action in an Elite Skier? A Case Study
John G. Seifert 1, Heidi Nunnikhoven 1, Cory Snyder 1, Ronald Kipp 2
1 Montana State University Movement Science Laboratory Bozeman, MT 59717


I was there for the lecture this researcher gave at National Academy this last April. The video circulating around the ski forums is from this lecture. I almost fell asleep because I was so worn out, and fought to stay awake since I was definitely interested in the subject.

The reason Seifert chose to use Deb Armstrong as the guinea pig in those measured runs was because her skill level meant she would be extremely consistent in repeat runs. Her form's consistency removed any technical variations a skier might exhibit from one run to another as an independent variable. Her consistency meant the results on the stress on her knees from different skis would be more reliable. The body mechanics she used to control her turns would be as close to identical as possible, from run to run, as would the turn radius and speed. Her skill meant she could control for that. All that was left to cause variations in knee stress were the differences among the skis.

Since the study was so well controlled, the results they found do not only apply to Olympians, nor only to women, nor only to fast skiing around gates. The study was shaped so that the results will apply in general to all skiers.

I thought the study was well done, with a lot of thought being put into it.
 
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marzNC

Angel Diva
When I started taking more lessons after knee rehab, I instinctively used skis that were shorter and narrower than my all-mountain skis because they were easier to turn. At the time, I was using the original Black Pearl, 88 underfoot, @159cm at big mountains out west. What I used at Massanutten for a couple seasons were older skis that were 70 underfoot, 149cm. I started paying more attention to Turn Radius when demo'ing skis. The Black Pearls have a radius around 17 while the carvers had a radius about 12. No surprise they feel different.

When I started skiing powder more, my Alta instructor didn't want me to rent skis wider than 100mm for lessons when we were going off-piste after a storm. My current all-mountain skis are 85mm with radius 17, 159cm. Given that I'm petite and have a knee that's not normal, wouldn't want to own anything wider for big mountain skiing. I stick with the Head Absolut Joy, 78mm, 148cm for smaller mountains in the southeast, Mid-Atlantic, or northeast where snow conditions are much more likely to be hard pack or icy.
 

mustski

Angel Diva
Her consistency meant the results on the stress on her knees from different skis would be more reliable. The body mechanics she used to control her turns would be as close to identical as possible, from run to run, as would the turn radius and speed. Her skill meant she could control for that. All that was left to cause variations in knee stress were the differences among the skis.
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I am confused by this statement. If the goal was to "control" for turn radius and speed does that mean that she forced skis into a shorter radius than their normal sweet spot? If so, that would cause stress that would not be part of the normal experience with that ski. The big mountain, wide waisted, skis have a much larger turn radius than a carver does.
 

contesstant

Ski Diva Extraordinaire
Good to hear! Decisions, decisions... still on the fence because the 93s would be a little more versatile.
Mine have demo bindings on them. If I'm at Targhee late November (as I typically am) you might be able to pry them out of my hands for a run or two :becky: I'm on a 165. I've skied the 93s and if I recall correctly, they come in tweener lengths for me (161 or 169) and the 169s at that width with the beefy construction was just more than I wanted to deal with. I got really tired on them. It's been a full season since I skied them, though, so I might not feel that way now. The 88s are magical, though. Crud, powder, slush, scraped off hard pack, baby bumps, I declared almost every time I skied them, "man I LOVE these skis!"

@mustski, my hips also hurt after skiing on wider skis for more than a day (or less if it's harder snow.) That torque does travel up the body. Even my ankles get sore sometimes on my 100s/102s. My whole body just feels more beat up after skiing them. Did you ever get a mid-80s width ski? (I think you were shopping for some?) If so, you should think about skiing those exclusively for several days in a row then hop on the wider skis for a full day.

On that note, I just watched the Skiessentials review of the Black Pearl 82. That is a FUN ski. I almost didn't even have to think about skiing them, they were so effortless and fun. I think a lot of women, especially those who stick to more groomers and maybe want to dabble in bumps and trees some, would do well to try a pair of them.

Wow am I ready for ski season!
 

mustski

Angel Diva
@mustski, my hips also hurt after skiing on wider skis for more than a day (or less if it's harder snow.) That torque does travel up the body. Even my ankles get sore sometimes on my 100s/102s. My whole body just feels more beat up after skiing them. Did you ever get a mid-80s width ski? (I think you were shopping for some?) If so, you should think about skiing those exclusively for several days in a row then hop on the wider skis for a full day.
!
I bought the z90’s to fill that space. I would be interested in trying something narrower as long as they don’t toss me around in our SoCal crud. My right hip just hurts all the time- it’s actually better after skiing, walking, pretty much any activity. It’s not skiing related - it’s a piriformis muscle issue. Sitting seems to set it off and at least I am not driving 45 minutes each way to work anymore.
 
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liquidfeet

Ski Diva Extraordinaire
I am confused by this statement. If the goal was to "control" for turn radius and speed does that mean that she forced skis into a shorter radius than their normal sweet spot? If so, that would cause stress that would not be part of the normal experience with that ski. The big mountain, wide waisted, skis have a much larger turn radius than a carver does.


She was running gates, same gates each run. I don't know what the set was on those; can't remember. It probably was not super short turns. The point of running the same run over and over was to see what effect the different skis had on knee stress when other factors were controlled. To do that, they had to keep other factors constant.

The point they already knew, or at least expected, is that skiers on wider skis - on groomers - ski differently than they do when on narrow skis. The research explains that skiers might be choosing to keep skis flatter when the ski is fat - on groomers - in order to avoid the strain on their knees. The strain is real, and the difference in skiing technique to compensate for that is observational but not documented.

Why care? Skiing with flat skis - on groomers - deletes a big part of one's grip, and thus lowers one's control of turn shape and speed. This loss of control increases with hardpack and icy snow.

Another part of the study was the pass rates of ski instructors taking certification exams. Those on fat skis had a lower pass rate for Level II and Level III. I think, but am not sure, that the pass rates were in Colorado, but not sure.
 
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Jenny

Angel Diva
@contesstant - I demoed the BP88 last year and was planning on trading in my Kenjas for them. Then they came out with the 82, darn it. I still think I'm going for the 88, since I spend half my time skiing out west on vacations anyway, but just wondering - did you post somewhere what you think the biggest differences are between them?
 

elemmac

Angel Diva
The reason Seifert chose to use Deb Armstrong as the guinea pig in those measured runs was because her skill level meant she would be extremely consistent in repeat runs. Her form's consistency removed any technical variations a skier might exhibit from one run to another as an independent variable. Her consistency meant the results on the stress on her knees from different skis would be more reliable. The body mechanics she used to control her turns would be as close to identical as possible, from run to run, as would the turn radius and speed. Her skill meant she could control for that. All that was left to cause variations in knee stress were the differences among the skis.

I understand where they're coming from when bringing in a consistent skier for these tests. But I think they should have brought in skiers for other disciples other than race...maybe compare a Olympian racer to a Freeride Tour participant. Both would exhibit excellent technique, but they come from different backgrounds, and I think this would have taken a little bit of the bias out of the study. The main bias is that they are running gates on groomers, regardless of the turn radius, this is a bias towards a narrow ski...it's what they're made to do.

I understand there are difficulties to perform a test in other conditions...but that's where wide skis are made to perform. They did branch out into testing in untouched powder, which was a step in the right direction. As expected the results showed that wide skis are easier on your muscles in powder...I don't recall if they mentioned anything about the knee joint specifically in this section.

She was running gates, same gates each run. I don't know what the set was on those; can't remember. It probably was not super short turns. The point of running the same run over and over was to see what effect the different skis had on knee stress when other factors were controlled. To do that, they had to keep other factors constant.

If I recall correctly, at least one of the studies presented, they changed the gates to match the ski's radius. The narrow ski with a small radius were tested on a course with gates closer together than the wide ski with a long radius.

The strain is real, and the difference in skiing technique to compensate for that is observational but not documented.

One of the things touched upon was knee extension, and how they did measure it. They documented the results that people tend to stand more upright when carving a wide ski. I thought this was interesting...and I'm curious on the "why"...maybe because you do tend to lose edge grip? So people are a bit more defensive rather than offensive in their turns? I wonder if this changes when you have softer groomers vs. hard groomers.
 

contesstant

Ski Diva Extraordinaire
@contesstant - I demoed the BP88 last year and was planning on trading in my Kenjas for them. Then they came out with the 82, darn it. I still think I'm going for the 88, since I spend half my time skiing out west on vacations anyway, but just wondering - did you post somewhere what you think the biggest differences are between them?
I haven't commented about the differences, because other than width, they have a very similar feel, with the 82s being quicker, as you can imagine. I wouldn't hesitate to tell anyone who would be better suited to the 82s due to location/where they ski the most to get the 82s instead of the 88s. I do wish I had gotten off piste in some crud with them, but I didn't.
 

liquidfeet

Ski Diva Extraordinaire
....One of the things touched upon was knee extension, and how they did measure it. They documented the results that people tend to stand more upright when carving a wide ski. I thought this was interesting...and I'm curious on the "why"...maybe because you do tend to lose edge grip? So people are a bit more defensive rather than offensive in their turns? I wonder if this changes when you have softer groomers vs. hard groomers.

Yes, this is the way many people tend to ski on fat skis when on harder snow. The uprightness of the whole leg lessens or eliminates the strain on the knees. Edging the skis on top of hard snow and keeping them up on edge strains the knees. Embedding the skis in soft snow, tipping them and keeping them tipped while in that snow, doesn't cause knee strain. There was no issue with skiing these skis in powder while tipped; that's what they are made for.

I found the ski instructor exam results interesting.
 

elemmac

Angel Diva
I found the ski instructor exam results interesting.
It'd be interesting if they dove into this further...what happens when you put instructors that normally ski wide skis on narrow skis and have them retake the exam. Do the results change?

Is the fail is truly because of the wider skis, or if skiers that wouldn't pass anyways tend to gravitate towards wider skis? Just thinking out loud...

I'm also curious to what skis they used on all of these studies. What rocker profiles, radius(es), construction, etc,? Not all skis with the same width are created equally. So if they're comparing a Stockli AX with a Blizzard Sheeva....I would think you could get very different results than if you're comparing a Volkl RTM to a Mantra. Then length comes into play too...wider skis tend to have shorter effective edges due to their rocker profile. Did they compare the same size ski, or did they scale it for the same effective edge?
 

marzNC

Angel Diva
I'm also curious to what skis they used on all of these studies. What rocker profiles, radius(es), construction, etc,? Not all skis with the same width are created equally. So if they're comparing a Stockli AX with a Blizzard Sheeva....I would think you could get very different results than if you're comparing a Volkl RTM to a Mantra. Then length comes into play too...wider skis tend to have shorter effective edges due to their rocker profile. Did they compare the same size ski, or did they scale it for the same effective edge?
This study was a case study. The focus was on taking a variety of measurements related to how the muscles around the knee function under controlled conditions. The fact that turning a wide ski vs a narrow ski is different was a given. The idea was to document the kinematic differences.

Does Ski Width Influence Muscle Action in an Elite Skier? A Case Study

ABSTRACT
Zorko et al. reported significant differences between wide and narrow ski widths on knee joint kinematics. Those authors reported skiers on WS had more knee extension and less internal knee joint rotation than when on narrow skis. The purpose of this case study was to investigate the differences in muscle activity, ski, and skier actions in an elite skier when skiing slalom skis (SL) and WS. An Olympic Giant Slalom gold medalist, who is also an elite level ski instructor and national demonstration team member, completed a run on SL skis (66 mm underfoot) and a run on wide skis (WS; 95 mm underfoot). Each run was divided into standardized turns with 13 gates and a free ski sections. EMG was assessed from the gluteus medius (GMED) and maximus (GMAX), rectus femoris (RF), vastus medialis (VM), tibialis anterior (TA), and peroneus longus (PL). A 9 channel motion sensor was used to define turns and ski edge angles. Results: Turn time was 35% slower and ski edge angle 15% less for WS than SL during free skiing. In the course, turn time was 31% slower and edge angle 12% less with WS compared to SL. RMS values for GMED, RF, VM, and TA were less (about 24%) in the WS trial than SL during the free skiing section. Only the GMED RMS data was less for WS than SL when skiing in the course. The GMAX and PL RMS values were greater for WS than SL in the free skiing and course (GMAX: by 131% and 116%; PL: by 23% and 27%). Average knee extension was greater for WS than SL during free skiing (136o vs. 118o), but similar in the course (116o vs. 113o). Conclusions: Skiing WS substantially changes skier movements, muscle activity, and ski actions compared to SL. The greater GMAX values during free skiing and the whisker course with WS may be indicative of greater effort to maintain pelvic stability, increase hip extension, or of greater lateral femoral rotation compared to SL. The increased lever arm of the WS may also explain the greater PL activity through eversion when edging.
 

Jenny

Angel Diva
I haven't commented about the differences, because other than width, they have a very similar feel, with the 82s being quicker, as you can imagine. I wouldn't hesitate to tell anyone who would be better suited to the 82s due to location/where they ski the most to get the 82s instead of the 88s. I do wish I had gotten off piste in some crud with them, but I didn't.
K - thanks. I guess if I felt the 88s were quick enough for me when I tested them here that maybe I'll just stick with those instead of trying to find 82s to demo.
 

elemmac

Angel Diva
This study was a case study. The focus was on taking a variety of measurements related to how the muscles around the knee function under controlled conditions. The fact that turning a wide ski vs a narrow ski is different was a given. The idea was to document the kinematic differences.

I understand the intent of the study. My curiosity towards what skis were used is based on the fact that not all skis of the same width perform the same, and therefore I would guess that they would have a different effect on the body...it would be interesting to add that aspect to one of these studies.
 

liquidfeet

Ski Diva Extraordinaire
There are all kinds of interesting things that researchers could look into re ski design and its impact on knees. I wish this work would be done. But it all costs money, and no one is interested in funding the research. Certainly not manufacturers. And advertisers in ski magazines (manufacturers) don't want the results published. These guys have tried.

Manufacturers market wide skis to everyone as a one-ski-do-it-all-quiver ski. And the NSF turned down funding further research because skiing is a niche activity. The results wouldn't impact enough members of the population to warrant the use of tax dollars.
 

tinymoose

Ski Diva Extraordinaire
Yes, this is the way many people tend to ski on fat skis when on harder snow. The uprightness of the whole leg lessens or eliminates the strain on the knees. Edging the skis on top of hard snow and keeping them up on edge strains the knees. Embedding the skis in soft snow, tipping them and keeping them tipped while in that snow, doesn't cause knee strain. There was no issue with skiing these skis in powder while tipped; that's what they are made for.

I found the ski instructor exam results interesting.

I think this may be where I'm having my issues. Since I've been doing the adult race clinics, I try to ski (to the best of my ability) my Yumis on hard snow like I would my race skis. Meaning, I try to angulate as much as I can. It's a lot more work to get them up on edge at 83?? 84?? than my race skis that are sub-70. And my knees definitely talk more after skiing them than what I'd get from skiing my race skis. Although, I think I get some min. level of stiffness/soreness even from my race skis. It's possible something is faulty with my technique that is putting extra strain on my knees the more I try to angulate and carve.
 

liquidfeet

Ski Diva Extraordinaire
I think this may be where I'm having my issues. Since I've been doing the adult race clinics, I try to ski (to the best of my ability) my Yumis on hard snow like I would my race skis. Meaning, I try to angulate as much as I can. It's a lot more work to get them up on edge at 83?? 84?? than my race skis that are sub-70. And my knees definitely talk more after skiing them than what I'd get from skiing my race skis. Although, I think I get some min. level of stiffness/soreness even from my race skis. It's possible something is faulty with my technique that is putting extra strain on my knees the more I try to angulate and carve.

Right! The problem is not your technique. If you get them up on edge, you have excellent technique. Many people can't, or won't. The conclusion of the study is that the torque on the knees is caused by getting those wide skis up on edge (on hard snow, when the skis are on the snow, not in it). People don't have to wonder any more. Even Deb Armstrong, who definitely got her wide skis up on edge in the gates, went slower on the wider skis and experienced more torque at the knees.

This is why it's good to say what kind of snow one is skiing on when giving a recommendation about wide skis.

Given all this, I love my FX84s on hard groomers. They don't feel wide to me any more because I've been skiing them for 3 years. I like my Super Joys (75) on hard groomers; not sure why it's not love. I LOVE my Atomic FIS SLs (oh, around 65) on very hard groomers when it's not crowded, and I always use only this ski when there's true ice and everyone else has gone in to the bar. Skis do have other characteristics that impact our affection for them.
 
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tinymoose

Ski Diva Extraordinaire
The problem is not your technique. It's the torque on the knees caused by getting wide skis up on edge. Narrow skis would be better for your knees in the gates. This is the conclusion of the study.

Do narrow skis still put some level of torque on your knees though? Just less because narrower? Because I honestly only skied my Yumis maybe two days last season, and both days were on hard snow at Montage. So the rest of my season was spent on my race skis, and I still developed some knee stiffness/soreness over the course of the ski season. That's why I was questioning my technique, since I barely skied the Yumis last year.
 

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