Originally Posted by at_nyc
A few answers:
If I ski my old 80mm skis all day on groomer and tried to carve all the time, my knee would tell me they're not exactly happy also. But again, I don't do it on firm groomers all that often.
Neither the new ski nor the old ski bother my knees all that terribly, only a little bit. And the new skis are bothering my knees a tad more. This year, I happened to ski quite a bit more firm groomer than the past. The new skis are more inviting to carve, so I did it more often than I used to. So the knee pain starts to register.
I must admit I'm not all that good at carving still. So I probably could benefit from a few targeted lessons on that area, which may even help with the issue. Who knows what horrible habit I have that might be contributes to the increase stress too. At the minimum, I could learn a few more different ways to enjoy groomer, so I could figure out what works best for me.
I won't "live with" the pain. It'll hopefully get better, either through technique change or just my leg muscles responsible for that particular movement gets stronger. If it doesn't get better, I'll just have to ski groomers in less stressful way (short swing/straightline more) while look for another skis that's a bit narrower but have similar characteristic.
think you'll find some answers in your answers.
the new skis may be better carvers, because they engage the edge in a stronger/cleaner radius/arc and prolly slip less, especially if you're skiing them harder and for longer periods. see my comments below.
the diagrams in a prior post need some addressing - as they are too simplistic, to a flaw.
the actual ski width difference applied to the right angle lever is really 4mm - thatz the extra length, center to side from 80 to 88.
The actual 'lever' (illustrated above) creating torque, affecting the lateral side of the knee joint is - right angle (L-shape) - is the half width of the ski mated (at right angle) to the lowerleg/boot from ski bottom up to the knee joint. 'Force' is applied at the ski edge, the 'fulcrum' is at the knee joint. Extending the skiwidth side of the lever 4mm is almost negligible.
'waist' may be less important than sidecut and engaged edge length, or more important, depending on the ski design characteristics.
things which will affect the torque felt laterally at the knee
skis mostly have sidecut, skis have varying flexibility to 'hold' an edge in 'snow' over the edge length. skis have varying flexibility longitudinally.
more sidecut (smaller radius) over a certain edge length will generate more forces as they are bent to design radius.
more edge hold extended over an edge length generates more forces
stiffer longitudinal flex, combined with sidecut and edge hold, generates more forces
all these combined in some fashion, apply more forces at the ski end of the 'lever'
skis with rise and/or rocker will apply less forces for a certain edge length (all else being equal, which they never are...)
skis with less sidecut will apply less forces for a certain edge length (as you approach the actual designed radius)
softer flex skis will apply less forces for a certain edge length
4mm in lever length would be very hard to actually feel a difference - 15 mm may be perceivable...
a stiffer ski, with firmer edge hold, with similar radius, with similar edge length will definitely 'feel' different, at the knee, than a softer ski with less edge hold.
will your knees adapt? that depends. Ligaments don;t really get stronger. They are what they are. But one can strengthen the muscles surrounding the joint and they provide some additional support. Muscle strength and muscle mass are also the shock absorbers of the body. Strengthen them to relieve significant amounts of shock.
As we age our muscle mass does decrease - it's a good idea to keep on working to gain/keep muscle mass to help reduce the effects of shocks to the skeletal system.
There are exercises which help strengthen the legs, hips, lower back, core we use for skiing - I like a lot of cycling and yoga. All one needs to do is google youtube for routines which World Cup racers like Svindal & Vonn do, to realize the possibilities. things I need to apply more, myself... ;-(