The Influence of Ski Waist-Width and Fatigue on Knee-Joint Stability and Skier Balance

[Rod9301]

I looked around a bit to see if any of the 'technical skiers' have videos of themselves on mid fat all mountain skis on a groomer. Do you know of any? I couldn't find much of anything. The few bits I found they were skiing longer radius turns, not the high performance short carved turns. I do not think that people who have the skills to arc short radius turns choose to ski fat/midfat skis like a narrow ski. They ski them differently. It is also harder to manage the transition onto the new edges with a fatter ski, so it sort of limits you to more smeary turns anyway unless you are more precise than with the narrower skis - or the snow is softer which holds the ski a bit better (and now it's soft snow, so the knee torque is a non issue).

I have done a bit of skiing back to back between Stöckli SR95 (95mm) and AX (78mm). In soft snow they felt the same with the 95 being more fun/playful. On hard pack, the SR95 did not feel good for my knees when arcing carved short turns relative to the AX. My solution was to do what the doctor says - if it hurts, don't do that!

Not true, fat skis make short radius turns just as well as a narrower ski, provided the turn radius is the same.

 

[Dave Petersen]

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@Dave Petersen we need a bumper sticker!

 

[David Chaus]

What is "narrower" in this case? Does this mean to go for an 85 instead of a 95? Or is it like a 70 instead of a 110?

For me, the 85 instead of 95. Actually I picked up a Blossom AM77, so it'll be interesting to see how well that works as an all mountain ski compared to my Renoun Z90.

 

[cantunamunch]

What is "narrower" in this case? Does this mean to go for an 85 instead of a 95? Or is it like a 70 instead of a 110?

Still 25mm too wide

 

[AmyPJ]

I own a laser AX. To be honest, I usually prefer a stiffer, more responsive race ski on hard pack snow. But I do like my AX's. Anything off piste or moguled, I prefer my Liberty Origin 96 cm ski. It pivots and turns much quicker and easier. Not quite as quick a carver, but to me that is the key of the whole waist width debate.

If you told me to carve turns down a mogul field, even a soft one, I would pick the narrow carver. If you told me to ski any style down a mogul field, I pick the Origin 96 with its rocker and mostly pivot through it. Its all about what ski fits your style, and what style do you use for the conditions and terrain. All carvers will prefer a narrow ski in most conditions, and I think the corollary is narrow ski enthusiasts are predominantly carving style.

I definitely choose which ski is more fun for the conditions. I consider myself an expert and can ski any ski on any terrain. I was teaching a teenager one day and unfortunately had him out in soft spring snow on a 72mm intermediate carving ski. He couldn't maneuver it in the mashed potato snow. I traded skis with him and on my 101mm twin tips he could ski in those conditions, did pretty well actually. The skis floated on top and he could smear them easily through the snow. To get to my point, I skied on 70mm, about 160cm long intermediate carver all day long. It met all this criteria: Because they’re quicker to edge, easier to maneuver in moguls and crud, and are easier on the knees and hips. But it was really sensitive to my body position and movements, and I could not relax for a second on them. It wasn't a lot of fun, but I never fell or lost it either. (I am 6'4", 240lbs an usually on a 185cm ski). Wider skis are more forgiving and therefore more fun for a lot of skiers. If you want to rip carved turns, they are NOT.

My Laser AX, or any 70-80mm wide carver, is really fun on hard pack and packed snow. For me, it looses its appeal in soft spring conditions, maritime dense snow, and deep snow. Why, because it provides zero float and becomes much more sensitive or resistant to being slarved or brushed in a turn. They will demand a pure carved turn or start to fight back. Width and skier weight are very tied together, so a lighter woman will have tremendously more float on a given width ski as my Clydesdale body. Nothing to do with skill, either. Last spring I started the day on my AX, and after one run I said, nope, need more width, and never regretted the choice. I think I bumped up to a 101mm width. And like @James said : "I could've pulled out a sandwich, a beverage, and made a phone call, all without affecting my stable platform"

Outliers on the size spectrum definitely will have different thoughts/needs.

None of it changes the findings in the study that many of us already knew anecdotally--it's just physics. And yes, we all need a quiver of at LEAST 3 skis!

 

[Tony Storaro]

I am sure @Tony Storaro would love to pitch the Stöckli WRT ST to you...

You cant go wrong with WRT ST. It is impossible to go wrong, It is science.

 

[Tony S]

I'm definitely an outlier here...
I have one active ski that I use 90% of the time. I got tired of traveling with 2 pairs, and got tired of second-guessing which ski to take out in the morning. A few times I even carried two pair to the hill and wound up staying on the same pair all day.
My daily driver is 85 mm wide. I also have a 104 mm and a true slalom ski mounted, tuned, and waxed, but haven't been on them in a long time.

(Though I did have a lot of fun on a pair of @KingGrump 's slaloms last spring at Mammoth... enough that I might travel with two pair if if I owned those.)

Dude. You want to talk about being an outlier and you bring up your skis?

 

[Tony S]

However I keep having to deal with the inconvenience of frequent snowfall and forced to use my 102's and 116's.

Mods!

 

[David Chaus]

 

[dbostedo]

Mods!

You rang?

 

[cantunamunch]

He's being triggered.

 

[crgildart]

So where's the variable for how cool they look in the lift line?? Its definitely fun to look cool in the lift line

 

[tromano]

For me, the 85 instead of 95. Actually I picked up a Blossom AM77, so it'll be interesting to see how well that works as an all mountain ski compared to my Renoun Z90.

Got me a whiteout last year. Its more of a chill frontside carver than an am ski imo. Decent in bumps and nastar course but not really purpose built for anything. It's super power is popping short turns in the fall line on the wildflower downhill.

 

[James]

I think we were actually allowed to watch Mod Squad. Perhaps counterpoint to “The FBI” with Ephrem Zymbliss Jr. Can’t forget that name, though spelling is another thing.

How interesting that the hip blonde star, Peggy Lipton, was married to Quincy Jones and their daughter is Rashida Jones.

 

[David Chaus]

So where's the variable for how cool they look in the lift line?? Its definitely fun to look cool in the lift line

I never worry about how cool my skis look in the lift line. I mean, the top sheets are frequently covered in snow, so who can tell what they are?


Is @Tony S triggered yet again?

 

[David Chaus]

Not true, fat skis make short radius turns just as well as a narrower ski, provided the turn radius is the same.

Having owned a 105 with a 15m turning radius, I disagree, the width is much slower to get on edge and more (torque if that’s right term) on the knee. On firm snow, that is. Soft snow, a 15m radius can be a little hooky and it take patience and finesse to manage in crud and chop.

 

[dan ross]

I think we were actually allowed to watch Mod Squad. Perhaps counterpoint to “The FBI” with Ephrem Zymbliss Jr. Can’t forget that name, though spelling is another thing.

How interesting that the hip blonde star, Peggy Lipton, was married to Quincy Jones and their daughter is Rashida Jones.

Zimbalist - his daughter , Stephanie, was on Remington Steele with Pierce Brosnan, speaking of daughters. I need to scrub my internal hard drive of such trivia but it’s futile.

 

[wallstreetoneil]

This is a great study...

Abstract​

Alpine skiing is a complex sport that demands a high level of motor control and balance. In general, skiers are prone to deterioration in the state of fatigue due to using inappropriate equipment. As a consequence, the risk of injury might increase. This study aimed to examine the influence of fatigue and ski waist-width on knee-joint stability and skier’s balance. A laboratory skiing simulation in a quasistatic ski-turning position was conducted where the lower-limb kinematics was recorded using an optical system, and the balance-determining parameters were captured using a force plate. It was demonstrated that the knee-joint kinematics and skier’s balance were hampered in the state of fatigue, as well as when using skis with a large waist-width. The results of the study suggest avoiding the fatigue state and the use of skis having a large waist-width while skiing on hard surfaces to decrease the risk of injury.

Full report here...

The Influence of Ski Waist-Width and Fatigue on Knee-Joint Stability and Skier’s Balance

Alpine skiing is a complex sport that demands a high level of motor control and balance. In general, skiers are prone to deterioration in the state of fatigue due to using inappropriate equipment. As a consequence, the risk of injury might increase. This study aimed to examine the influence of...

www.mdpi.com

If you take an average man's size 9 foot, who wears a 25.5-26.5 shell, that fits into a 98-100 last shell as a base to perform measurements on, then what you find is the following approximate numbers:

1) If you measure the flesh area, under your heel bone (calcaneous), not to the edges, but what actually supports your mass, the width of this cross-section is 5cm
2) If you do the same measurement, under the ball of your foot, which is where the midfoot Metatarsal bones meet the base of your toes (Phalanx bones), and measure from the midpoint of the small toe bone to your big toe bone, this cross-section is 7cm
3) Of no practical importance, but interesting, the distance from the ball of your foot to the middle of your heel is 15cm

This Trapezoidal balancing zone that your body uses, 7cm in front, 5cm in back, and 15cm in length (excluding the toes - yes they are important), just happens to have as the mid-point cross-section, a width of 6cm or 60mm - which just happens to be very close to the narrow point 65mm on race-skis (not a coincidence).

I have a number of front side carvers (Volkl RaceTigers, Blizzard GS with Race-plate, Rossi Multi-turn, plus a few more that I share with my former Canadian level racing partner), and I can tell you that in my experience, 67-68 is where the cross over point is from being able to roll the ski on edge, without the feeling of the width creating leverage, because when I use the Rossi Multi-turn, that has a 70 waist, it becomes very obvious that the width of the ski is wider than my brain wants to feel, and I can feel the extra force needed to get it on edge. My soft/heavy snow ski is an Enforcer 88, a ski I love, but I only love it after a few runs where I have to completely change the way I ski - where I develop a somewhat brutalized forced tipping onto the edge with speed type of skiing (it kind of feels like a large SUV just running over everything in its way type of feeling - which is great in heavy crud type snow)

I came at all of this as a lifetime hockey player and someone who only came to skiing much later in life. I had to experiment and buy many different types of skis until I finally figured out that the type of ski that my brain wanted was a race ski that was narrow underfoot so that I could get the feeling that I was on an edge, like in hockey, and I could just turn/carve when I wanted to without thinking - and that is what 65-67/68 feels to me - it's so intuitive you don't have to think and you don't need to expend the energy to 'launch' the ski up onto its edge to carve a turn. I also happen to be a person that badly blew apart my left knee so I'm extra sensitive to the feeling of leverage being applied to this joint.

 

[Tony Storaro]

I never worry about how cool my skis look in the lift line.

 

[Noodler]

If you take an average man's size 9 foot, who wears a 25.5-26.5 shell, that fits into a 98-100 last shell as a base to perform measurements on, then what you find is the following approximate numbers:

1) If you measure the flesh area, under your heel bone (calcaneous), not to the edges, but what actually supports your mass, the width of this cross-section is 5cm
2) If you do the same measurement, under the ball of your foot, which is where the midfoot Metatarsal bones meet the base of your toes (Phalanx bones), and measure from the midpoint of the small toe bone to your big toe bone, this cross-section is 7cm
3) Of no practical importance, but interesting, the distance from the ball of your foot to the middle of your heel is 15cm

This Trapezoidal balancing zone that your body uses, 7cm in front, 5cm in back, and 15cm in length (excluding the toes - yes they are important), just happens to have as the mid-point cross-section, a width of 6cm or 60mm - which just happens to be very close to the narrow point 65mm on race-skis (not a coincidence).

I have a number of front side carvers (Volkl RaceTigers, Blizzard GS with Race-plate, Rossi Multi-turn, plus a few more that I share with my former Canadian level racing partner), and I can tell you that in my experience, 67-68 is where the cross over point is from being able to roll the ski on edge, without the feeling of the width creating leverage, because when I use the Rossi Multi-turn, that has a 70 waist, it becomes very obvious that the width of the ski is wider than my brain wants to feel, and I can feel the extra force needed to get it on edge. My soft/heavy snow ski is an Enforcer 88, a ski I love, but I only love it after a few runs where I have to completely change the way I ski - where I develop a somewhat brutalized forced tipping onto the edge with speed type of skiing (it kind of feels like a large SUV just running over everything in its way type of feeling - which is great in heavy crud type snow)

I came at all of this as a lifetime hockey player and someone who only came to skiing much later in life. I had to experiment and buy many different types of skis until I finally figured out that the type of ski that my brain wanted was a race ski that was narrow underfoot so that I could get the feeling that I was on an edge, like in hockey, and I could just turn/carve when I wanted to without thinking - and that is what 65-67/68 feels to me - it's so intuitive you don't have to think and you don't need to expend the energy to 'launch' the ski up onto its edge to carve a turn. I also happen to be a person that badly blew apart my left knee so I'm extra sensitive to the feeling of leverage being applied to this joint.

I could "buy" all this if it weren't for the simple fact that we don't ski in a boot that's only the height and width of a foot. The ski boot itself changes the physics involved in the interaction between our foot/leg and the ski (and of course how we "feel" the width). The additional girth and height of the boot becomes an "extension" of our body parts and provides additional power over the skis that are under our feet.