Ankle Flexion--Active or "Passive"?

[James]

I'll just bug the reps, I know them But still, not sure if they can move the binding even one click forward with such a short BSL.

What’s your bsl, 266?
Looks like minimum is 262 on Warden Demo, so you could get 4mm perhaps.

The problems with being at the end of the bell curve…

 

[AmyPJ]

What’s your bsl, 266?
Looks like minimum is 262 on Warden Demo, so you could get 4mm perhaps.

The problems with being at the end of the bell curve…

263...

 

[Corgski]

Except, it's not really possible to apply any significant shin pressure without moving the COM forward. Flexing the boot is not possible without using the weight of the body, and the weight of the body needs to be forward to flex the boot. Therefore, pressuring the cuffs does pressure the front of the ski. By the time the pressure is so light that the boot isn't even flexing, then yes that wouldn't pressure the front of the ski, but that's not the kind of pressure people are asking for when they say pressure the cuffs. They mean enough pressure to flex the boot at least some. Go ahead and try to flex your boot without bringing your COM forward. It's impossible. You can't flex your boot with just your ankles, for example.

I replied to your second post without even seeing this post. Pressuring the cuff means moving the COM forward which pressures the front of the ski, because it's impossible to flex the boot without moving the COM forward. Dorsiflexion against a rigid bracket without moving the COM forward would be like your example of a bridge with internal stresses, but the boot won't flex, and the amount of pressure on the cuffs is insignificant. The boot flexing is like a spring where the displacement is proportional to the force. So, zero displacement means very little force relative to several degrees of flexing. By the time the boot doesn't flex at all, then that's not really what most people mean when they say pressure the cuffs. Crushing the cuff means the boot is well flexed, and you're still pushing more. Some boot flex is not considered crushing the cuff, and any boot flex requires the COM forward.

Look, much what you are saying is generally true, most of the time cuff pressure and CoM position are strongly correlated. Nevertheless beginner and intermediate skiers in soft, relatively upright boots can pressure cuffs without bringing their weight forward enough. Awkward, but not hard. But even a smaller mismatch between CoM and cuff pressure can undermine one's skiing in a more subtle way. Sure, this is a secondary effect but if someone is struggling with fore aft issues in this forum it is unlikely to be something that can be solved by just telling them to pressure the cuffs.

I also get it if a heavily physics oriented approach is not how you approach skiing, most skiers regardless of ability do not approach it that way. Personally I found a more rigorous physics approach helpful when faced with setup issues, couple of examples:
Some boots have adjustable forward lean or spoilers. Does changing the forward lean of the boot without changing the skier stance change the pressure on the tip of the ski?
All else being equal, (cuff angle, skier stance) does a stiffer boot result in greater ski tip pressure?

Anyway, I am not currently an active poster, not planning on becoming one for now. I only posted because I felt that you and @dj61 behaved disparagingly towards someone who came up with a sophisticated technically correct explanation which you did not understand and wanted to come to their defense. No big deal that you did not understand it, there are a lot of engineering/science types around here who try to explain skiing in a way that people find incomprehensible. Nevertheless, understanding that a cuff mechanically behaves as a foot brace and that tip pressure is a function of CoM (and unaffected by cuff pressure) may help someone else resolve some difficulties.

 

[Sanity]

Look, of course what you are saying is generally true, most of the time cuff pressure and CoM position are strongly correlated. Nevertheless beginner and intermediate skiers in soft, relatively upright boots can pressure cuffs without bringing their weight forward enough. Awkward, but not hard. But even a smaller mismatch between CoM and cuff pressure and undermine one's skiing in a more subtle way. Sure, this is a secondary effect but if someone is struggling with fore aft issues in this forum it is unlikely to be something that can be solved by just telling them to pressure the cuffs.

I also get it if a heavily physics oriented approach is not how you approach skiing, most skiers regardless of ability do not approach it that way. Personally I found a more rigorous physics approach helpful when faced with setup issues, couple of examples:
Some boots have adjustable forward lean or spoilers. Does changing the forward lean of the boot without changing the skier stance change the pressure on the tip of the ski?
All else being equal, (cuff angle, skier stance) does a stiffer boot result in greater ski tip pressure?

Anyway, I am not currently an active poster, not planning on becoming one for now. I only posted because I felt that you and @dj61 behaved disparagingly towards someone who came up with a sophisticated technically correct explanation which you did not understand. No big deal that you did not understand it, there are a lot of engineering/science types around here who try to explain skiing in a way that people find incomprehensible.

Some coaches say pressure the cuffs, and some students get a lot out of that and ski great. Ski however you want. It doesn't bother me if it doesn't help you.

Keep the personal analysis out of it. Keep it about skiing. If you don't like my posts, then don't read them. Generally, your type of post means that you're upset and lashing out trying to make me upset, but that's a waste of time. I don't give a crap. Perhaps that's why I'm such a lovely person. Though, I do sense a video skioff coming. Those are fun.

Changing the forward lean of the boot affects the tip pressure, because the predominant force applied to the cuff is from body weight, which is multiplied by sine of the lean angle.

A stiffer boot doesn't necessarily end up with more tip pressure. If the boot doesn't flex, then the effective forward lean will be less, which will give less tip pressure. If the built in forward lean for this stiff boot is more, then the final angle might be the same as a softer boot, and the tip pressure would be the same. If the boot is super soft, then it's counter productive to flex the boot fully, so you'd end up with less pressure, because even though the boot is somewhat flexed there wouldn't be much cuff pressure.

 

[Henry]

I'm late to the party and have read only page 1, and I especially noted posts #17 and 19. In 19 Amy says that she's so flexible that she can pressure the cuff and still be in the back seat. I've seen that with young women who have great flexibility. They were pressuring the cuffs and the ski tips were fluttering (not big floppy rocker skis, either). They were bending back that much. When they hinge forward at the ankle and move their CoM forward, and use the cuff pressure as a gauge of their position, their skis engage into the snow and perform as designed.

 

[AmyPJ]

I'm late to the party and have read only page 1, and I especially noted posts #17 and 19. In 19 Amy says that she's so flexible that she can pressure the cuff and still be in the back seat. I've seen that with young women who have great flexibility. They were pressuring the cuffs and the ski tips were fluttering (not big floppy rocker skis, either). They were bending back that much. When they hinge forward at the ankle and move their CoM forward, and use the cuff pressure as a gauge of their position, their skis engage into the snow and perform as designed.

Working on this diligently...it's getting better and the boots without gas pedals are making it much easier.

 

[Sanity]

I'm late to the party and have read only page 1, and I especially noted posts #17 and 19. In 19 Amy says that she's so flexible that she can pressure the cuff and still be in the back seat. I've seen that with young women who have great flexibility. They were pressuring the cuffs and the ski tips were fluttering (not big floppy rocker skis, either). They were bending back that much. When they hinge forward at the ankle and move their CoM forward, and use the cuff pressure as a gauge of their position, their skis engage into the snow and perform as designed.

Put on your ski boot. Put the toe of the ski boot on a weight scale. If you can do some sort of flexible contortion where you can flex that boot and the weight of the toe doesn't increase, then you will have proved me wrong (adequately buckled, reasonable stiffness of boot). Put up the video, and I will be happy to stand corrected. But, if you can't flex your boot without the toe weight increasing, then that shows what I already know by physics is that only torque on the tongue from weight of the body will flex that boot, and the boot will just keep rotating instead of flexing unless there's an equal and opposite torque pushing back. The push back comes from the toe of the boot. The shin levers on the tongue, and the boot levers on the ski. Then the ski experiences a torque where it will rotate, unless there's a reaction force from the ground to keep it from rotating. So, there will be more pressure on the tip and less pressure on the tail. Sometimes, the ski will be supported by the ground just in front of the boot, and the tips can be in the air. Also, maybe the shin pressure you're talking about isn't really adequate shin pressure. Maybe their shins are against the tongue, but they are not flexing the boot. Flexing the boot can only be done by applying a torque to the ski boot, and that torque is transferred to the ski. It is impossible for a human to flex a ski boot without a counter rotational force on the boot (coming from the ground ultimately), because it's not dorsiflexion that's flexing the boot. It's weight leveraging against the tongue.

 

[AmyPJ]

More updates: I am adapting really well to the new boots and my Stocklis, so much so that I'm skiing literally 10 mph faster than I was two weeks ago! Actually, more like 15 mph faster, which is insane for me! I don't care too much about speed, but it IS a good indicator of how I'm feeling confidence-wise.

Active dorsiflexion seems to only come into play in bumps or crud. Otherwise, I'm finding just shifting my entire upper body forward and standing taller and standing hard on the new outside ski do the trick. I experimented with a temporary shim on the medial side of my left shin/calf today as I find that leg wants to A-frame a bit, or tuck in behind moreso than the right leg. It evened out my turns and made it easier to release my right turns, which I've been kind of struggling with.

Having super responsive, tight-fitting boots and high performing skis has been an absolute blast. I've always had good skis, the Nelas just kick it up a notch and reward me when I really step on the gas.

 

[joseph349]

Sorry for replying to an old thread. Just started skiing last year. I've had the same questions Amy had in the original post. I've tried to do what Amy did by flexing my tibialis anterior to pull my shin to the cuffsduring the turn. It sorta worked then I was using really soft rental boots on greens. But on steeper terrain that would quickly tire out my feet and I would still be backseated at the end of the turns. I've tried pressuring the big toe, but that just tenses up my foot and I lose more ankleflexion.

Except, it's not really possible to apply any significant shin pressure without moving the COM forward. Flexing the boot is not possible without using the weight of the body, and the weight of the body needs to be forward to flex the boot. Therefore, pressuring the cuffs does pressure the front of the ski. By the time the pressure is so light that the boot isn't even flexing, then yes that wouldn't pressure the front of the ski, but that's not the kind of pressure people are asking for when they say pressure the cuffs. They mean enough pressure to flex the boot at least some. Go ahead and try to flex your boot without bringing your COM forward. It's impossible. You can't flex your boot with just your ankles, for example.

Just had to post to say that this ^^^ assertion helps me a lot. Most people I know seem to all have pretty good ankle mobility (able to asian squat). Always thought I needed more ankle mobility to ski better. Spent a lot of time trying to improve ankle mobility. Went to a physical therapist. Have been able to get my knee over my toes when pushing against the wall. But dorsiflexion without load hasn't improved much. Also makes sense now that trying to flex the boots by just using the ankle is not the way to go.

This is the problem with jumping into a conversation two months later, people are not sure what I am responding to! My argument justifies foot pullback by explaining why pressuring the cuffs WITHOUT moving the CoM forward does NOT pressure the front of the ski. If you pressure the cuffs without changing CoM, the ball of the foot lifts up and the force under the front of the sole of the boot stays the same. That is an observation, not advice on how to ski.

This is not an issue for a skier who knows what foot pullback is and how to control their center of mass along the ski. A less experienced skier who is told to pressure the cuffs is not going to think "Ahh yes, pressure cuff by pulling back feet using hamstrings", they are probably going to do something else. This is why a few of us object to the pressure the cuff advice, it is way too optimistic to assume the person is going to do what they should. I think a mental model where one understands that the cuff behaves like a brace that redistributes load from the ball of your foot to your shin is better than thinking of the cuff as a lever that pressures the front of a ski.

Exactly me ^^^

Sounds like I should try to get my CoM forward by using my hips and hamstrings and not just the ankle. Maybe this is quite obvious to some. But these two posts helped me a lot.

 

[Tony S]

I've tried to do what Amy did by flexing my tibialis anterior to pull my shin to the cuffsduring the turn.

It's a cue to an effective move, not an effective move in itself. It's necessary but not sufficient. Closing the ankle using the TA is not enough to do anything, but if you're NOT doing it the natural plantar flexing instinct needed to keep you vertical in regular shoes kicks in and tends to prevent you from flexing the boot.

 

[Chris V.]

Yes...passive vs. active...why should you have to choose one? How about both at the same time? How about timing with your lateral move so that one promotes the other?

 

[James]

Sorry for replying to an old thread. Just started skiing last year. I've had the same questions Amy had in the original post. I've tried to do what Amy did by flexing my tibialis anterior to pull my shin to the cuffsduring the turn. It sorta worked then I was using really soft rental boots on greens. But on steeper terrain that would quickly tire out my feet and I would still be backseated at the end of the turns. I've tried pressuring the big toe, but that just tenses up my foot and I lose more ankleflexion.



Just had to post to say that this ^^^ assertion helps me a lot. Most people I know seem to all have pretty good ankle mobility (able to asian squat). Always thought I needed more ankle mobility to ski better. Spent a lot of time trying to improve ankle mobility. Went to a physical therapist. Have been able to get my knee over my toes when pushing against the wall. But dorsiflexion without load hasn't improved much. Also makes sense now that trying to flex the boots by just using the ankle is not the way to go.


Exactly me ^^^

Sounds like I should try to get my CoM forward by using my hips and hamstrings and not just the ankle. Maybe this is quite obvious to some. But these two posts helped me a lot.

Stand there in boots, move your knee forward by flexing at the ankle. There, you’ve dorsiflexed. If you can’t do it the boots are likely too huge or the cuff and power strap is too tight.

Then bend the knee and hip joints so you’re not a ski jumper. You could do it in a mirror to see your body position.
.

 

[markojp]

Stand there in boots, move your knee forward by flexing at the ankle. There, you’ve dorsiflexed.
.

In my book, no. You're pushing the knee, not closing the ankle from the feet up.

 

[Chris V.]

Old debate/ambiguity...dorsiflexion, position or action?

 

[Noodler]

Old debate/ambiguity...dorsiflexion, position or action?

Both.

 

[Tony S]

Then bend the knee and hip joints so you’re not a ski jumper.

That one made my morning.

 

[ThomasD]

In my book, no. You're pushing the knee, not closing the ankle from the feet up.

But, strictly speaking, if all you do is close the ankle then the rest of your body must arc forward, putting your shoulders forward of your hips, and your hips forward of your knees. In order to avoid this both the knees and the hips must flex in opposing directions. In my book this is what I call body compression. I get the focus on doing everything from the ground up, but think we also need to accept that there are multiple ways to describe the combined compensatory movements that must be involved. Even if some of it goes unstated - similar to the way the other poster described counter flexion of the ankle and knees, which properly should also include hip flexion as well.

"Retracting" the heel, "pushing" the knee, "closing" the ankle, are all merely descriptors. They each can have value if understood/recognized by the skier, and done while making - consciously or unconsciously - the proper adjustment of everything else.