Dorsiflexion and its role in skiing

Discussion in 'Ski School' started by LiquidFeet, Jun 2, 2019.

  1. Tony S

    Tony S aka qcanoe Skier

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    Well, except when it doesn't. A lot of "ifs" have to be in place before your statement becomes true. Like, "If there is enough edge angle," etc., etc.
     
  2. James

    James Skiing the powder Instructor

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    Are there instruction religions in tennis?

    Not so!

    IMG_6527.JPG
    Snorgtees.com
     
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  3. Rod9301

    Rod9301 Out on the slopes Skier

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    Ok
     
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  4. geepers

    geepers Out on the slopes Skier

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    If I stand in skiing stance in bare feet, with my heels and balls of feet engaged and then lean whole body forward without changing the flex at the ankles my heels unload. Which is what I understand JB is referring to.

    Of course we can open/close our ankles to keep the heels engaged while the rest of the body does whatever it needs to do. But that requires use of the TA and its antagonist muscles. (That's certainly the case in open chain situations when the ankle is unloaded like in the float. Not clear what happens when the legs are loaded and gravity is assisting ankle flex - I suppose the TA still has to contract otherwise where would it go...)

    The lifting of the toes is a little trick to ensure the heel is engaged - lifting the toes makes it harder to stay solely on the balls of the feet. It certainly worked for me. But I understand YMMV. (I just learnt what that meant so I'm going to way overuse it for a while ogsmile.)

    On JB boot fit - the way he skis I may have to go find some boots that fit that badly!:)
     
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  5. Mike King

    Mike King AKA Habacomike Instructor

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    Good luck with that.

    Mike
     


  6. geepers

    geepers Out on the slopes Skier

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    Notwithstanding JB's interview (in which he says a great deal about the need to hyper-engage the ski at the top of the turn) I'm not so convinced that pressuring the tips will tighten the turn radius. (JB doesn't say this - he only talks about the need for early engagement. Then again we're still awaiting part III of that talk.)

    As we see from the vid if we move the center of pressure forward the back of the ski dis-engages. So any loading of the front, without a corresponding unloading of the tail can only be momentary. This is a point Jurij Franko keeps making. He also points out that the sum of all torques on the body is zero or else we will rotate.

    My own experience has been that the less I was concerned about loading the ski tip the better my fore/aft balance and the more I could focus on clearing the inside leg and inclining, the tighten the turns.

    Of course you may be skiing at performance levels ahead of my modest achievements. (JB and those other dudes certainly are.) So I'm going to ask the same thing Franko generally asks when people claim this loading the tips thing - what evidence do you have that this in fact is the case for a pure carving ski?


    An addition... just saw a reply by @Mike King to your comment "When you pressure the tips the ski bends more." That doesn't make sense to me. Once the edge of the ski bends to contact the snow then it cannot bend any further without deforming the snow. The Jurij vid also shows that. Surely the only way to get more bend is more angle so the edge has more room to travel?
     
    Last edited: Jun 5, 2019
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  7. Tony S

    Tony S aka qcanoe Skier

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    I'm sure there are, but I was just thinking about how much less constrained the motions are, to your earlier point.
     
  8. geepers

    geepers Out on the slopes Skier

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    You may be interested in this Tom Gellie / JFB interview where there's this discussion on pronation. There are no muscles to flatten/lengthen the foot at pronation. It's a letting go movement and takes time. So in skiing, need to be patient at transition.

    Here's a rough transcript of a little of the discussion. Note I only came across this after season end so I have not had time to check this out. Soon (with a bit of luck)...

    Humans built to walk so TG practises there. One foot in front of other, CoM behind front foot and brings it over top of lead foot and as it comes over feels that pronation and the lengthening and effect on the body. Does this in front of a mirror or vid cam to see the body is ready.
    It really takes patience. There are no muscles to flatten/lengthen the foot at pronation. It's a letting go movement and takes time. So in skiing, need to be patient at transition.
    For example, during walking when we put the new foot down in front, , if we are not ready to balance on it, for it to accept our weight and be a good platform, then we'll try to get off that foot asap. There's an element of timing and being relaxed. If rushed, there's no time for that foot to pronate and get that balance established, if toes are trying to grip, if back behind feet then there's no relaxation along the bottom of the foot.
    So practise being patient, taking time, being balanced, letting the foot pronate, letting all the bones open before getting into the turn. (Ted Ligerty is a good example of this patience.) Give the system time to load. If loading by tensing up then there's no spring to it - like jumping on concrete vs jumping on a trampoline.
    So play with this in medium to wider turns.
     
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  9. Tony S

    Tony S aka qcanoe Skier

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    Read my earlier post reacting to the same statement. ogwink

     
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  10. Tony S

    Tony S aka qcanoe Skier

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    The way I think of it, the ski is moving past my COM during the course of the turn. At the start of the turn the ski is behind my COM, so the pressure naturally tends toward the shovel. (If I can pressure the arch or heel at this point, maybe my COM is not as far ahead as I think it is - very common. In which case that is the problem.) In the middle of the turn - roughly skis pointed down fall line - pressure is in the center. At the end, COM is behind, so pressure drifts a bit towards the heel. Reset during transition, rinse, repeat.
     
  11. markojp

    markojp mtn rep for the gear on my feet Industry Insider Instructor

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    Yeah.... not really IMHO and experience. Sure, we need to get to the forebody of the skis above apex, but at apex, we have to bend the whole ski. Ankles closed, weight and pressure directed toward the outside ski, and pressure on the inside ski. If we need to tighten the arc, just shorten the inside leg (and keep that inside foot under you as the inside of the pelvis rises to make some more room), and the ski will bend in a tigher arc. Just pressuring the tips often leads to the school of the ineffective rotary stem.
     
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  12. Mike King

    Mike King AKA Habacomike Instructor

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    @markojp, why do we have to get to the forebody of the ski prior to the apex of the turn? How does that affect ski performance?

    I'm not a full subscriber to the infinity move, but the infinity move would suggest that you are probably a bit more on the tail of the ski prior to the apex...

    Mike
     
  13. markojp

    markojp mtn rep for the gear on my feet Industry Insider Instructor

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    Pressure probably isn't the word I'm looking for, but we have to find the front of the boot and tip the new outside ski on edge with enough pressure (ok, pressure ) to start the process of managing centripital forces that are rapidly approaching. In the moment as the skis flattens and our CoM is moving in a shorter path down the hill that our skis, yes, we might open our ankles and find the 'squirt', but we'd better be sorted to get our feet back under us. If we're on our tails as the ski is tipped on the new edge, we're probably doomed to a life of back and in... unless we have the superhuman strength of 20 and young 30 something WC skiers. Clear as mud. There. Fin. ogsmile
     
  14. Mike King

    Mike King AKA Habacomike Instructor

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    Thanks. Personally, I think of it somewhat differently. The skis are accelerating as you tip and turn them downhill. As a consequence, the CoM has to move forward to keep up with the acceleration of the skis. But I don't think that it requires pressuring the front of the boot -- in fact, if I find myself on the front of the boot, I've moved too far and I do not get the impulse in the finish of the turn as the tails wash out and add drag.

    Mike
     
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  15. markojp

    markojp mtn rep for the gear on my feet Industry Insider Instructor

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    Agreed. I don't want to be crushing the front of the boot, particularly after apex. I generally do like some cuff contact, but neutral in transition.
     
    Last edited: Jun 6, 2019
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  16. James

    James Skiing the powder Instructor

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    To drive your foot into pronation- Weight the inside foot just before/during transition. Inside foot on little toe side. When you release and extend that leg, boom, pronated, on big toe edge and carving.
     
  17. Rod9301

    Rod9301 Out on the slopes Skier

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    I'm not saying that pressuring the tip of the only thing you do, of course you need to get big or bigger edge angles too.
     
  18. James

    James Skiing the powder Instructor

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    JF is a vastly better interviewer than Tom G. He listens, recreates what was said, and brings up relevant and interesting questions that get more out of the subject. He'll also remember things and bring them up again.
    Gellie in his interviews will often say things like "right...", "yeah..." in a way that could be interpreted as "hurry up and move on". In person, it would be really poor form. In the skype world he kind of gets away with it. But, kudos for doing them at all.
    His thing on the foot is somewhat muddled, but that's the issue with off the cuff speaking. It would be much better in writing because you can see what you've said and if it'ts really what you want to communicate.

    Here's a video on the ankle. Lots of medical terms. Settles the definition though. In closed chain kinematics, foot on the ground, dorsiflextion is the limb moving towards the foot.

    I can't picture -the axis of the ankle of 82deg in the sagital plane? Seems too high.

     
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  19. JESinstr

    JESinstr Lvl 3 1973 Skier

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    In terms of carving a turn, consider that shin to boot pressure is a result of and in direct relationship with the managing of centripetal pressure through the arch/footbed. The more the turning force increases, the more we invoke the flex complex (ankles, knees and hips) to activate the associated muscle groups. The more I flex, the more the shin moves into the boot. When carving, If I focus on edge building and maintaining balance through the arch, I don't have to worry about my COM, it will be where it needs to be. Regarding the inside foot, I do want to keep that underneath because not to do so destroys the workings of the flex complex for that leg.

    Now, in a rotary induced redirection, I do intentionally pressure the tongue (off center) because I am taking a "shortcut" to the carving state but once there, any shin to boot pressure is as stated above.
     
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  20. Rod9301

    Rod9301 Out on the slopes Skier

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    Are you saying that you keep flexing your legs in a turn as the turn forces increase?

    I do the opposite, i straighten my leg as the forces increase, to better resist them.

    Then in transition, i flex my legs to release
     

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