Dorsiflexion and its role in skiing

[Mike King]

Carving hard snow is kinda my thing, but let's leave that alone for a moment and consider skiing thick wet heavy snow; some call this snow Sierra cement. Just like a trowel will cut in the direction it is pointing due to being bent by the applied pressure, so will the ski. A flexible trowel in a vertical plane will be bent with the tip pointing left when the front of the trowel is pushed into the snow to the right. A ski tipped to the left and having it's forebody loaded will be bent so that the tip points more to the left. In the simplest most general terms, it's the well know "A properly tipped and pressured ski will take you where you want to go."

Skis have some give to them, so does most snow. Sierra cement is near one end of the spectrum, ice is near the other end.

There's a difference between a trowel and your ski. The trowel has no sidecut; a ski does. In order to create bend in the trowel, you have to create a steering angle; then the pressure differential will bend it as you push it (initially, at least) obliquely forward. The ski will bend simply by tipping (rotating it around it's longitudinal axis).

In order for the ski to turn and turn you, you do not need to load the tip -- it will turn simply by tipping the ski.

I don't know how much prep work you do in a kitchen but you do not use just the middle of a knife to carve. You can start near the tip of the knife and move it along the edge. A knife is designed to be moved along it's edge, not just from one section of it. I think there is a very close analogy to skiing where you start near the front of the ski and move along it, tip to tail.

I realize that right now it's the thing to keep your pressure only under foot, but these things change. Flavor of the day and all. Yet studying race technique and moving tip to tail hasn't changed.

We do appreciate your sharing what is the current approach with us, it's quite valuable. But like the weather in New England, wait a few minutes and it will change.

You seem to think I believe that you must stand in the center of the ski at all times. Nothing could be further from the truth. Most of the time in my skiing and certainly in my dynamic short turns and in my terrain skiing, I'm loading the tip of the ski in the initiation of the turn, moving to the center at the apex, and using the tail in the finish. But there's a purpose to where I'm trying to be on the ski. In high performance short turns, I'm trying to get on the front of the ski in the initiation to create a steering angle and allow the ski to start turning in a radius that's inside of the radius the sidecut of the ski would allow. I go to the center of the ski to get the maximum deflection of my center of mass across the hill, and I move to the tail in the finish for grip. In terrain skiing, I want the tip to bite high in the turn to impart a rotation to the ski, and I want the tail to catch in the finish to impart a rotation into the new turn. This preserves vertical distance down the hill.

Shifting weight from fore to aft is not a question of do it or not; it is a question of how much, and the answer ranges from none to lots and depends on intent and conditions.

Absolutely.

 

[François Pugh]

A ski being skied in Sierra cement is curved due to its load. Yes, tipping is required. The "steering angle" is provided by the curve and the tipping angle. No sidecut required, it works even with reverse-sidecut skis. Yes, a ski skied will turn by simply tipping it. It will turn more if you load the front more.
If you can't see that yet, I'm sorry.

 

[geepers]

Skidding with intent is a skill.

Yeah, it's not so much the skidding with intent. It's skidding without the intent.

I realize that right now it's the thing to keep your pressure only under foot, but these things change. Flavor of the day and all. Yet studying race technique and moving tip to tail hasn't changed.

Yep, unlike tomato slicing which hasn't changed at all.

There's a difference between a trowel and your ski.

^^ This.

It will turn more if you load the front more.
If you can't see that yet, I'm sorry.

Getting kinda circular.

 

[Mike King]

A ski being skied in Sierra cement is curved due to its load. Yes, tipping is required. The "steering angle" is provided by the curve and the tipping angle. No sidecut required, it works even with reverse-sidecut skis. Yes, a ski skied will turn by simply tipping it. It will turn more if you load the front more.
If you can't see that yet, I'm sorry.

did you read this?

You seem to think I believe that you must stand in the center of the ski at all times. Nothing could be further from the truth. Most of the time in my skiing and certainly in my dynamic short turns and in my terrain skiing, I'm loading the tip of the ski in the initiation of the turn, moving to the center at the apex, and using the tail in the finish. But there's a purpose to where I'm trying to be on the ski. In high performance short turns, I'm trying to get on the front of the ski in the initiation to create a steering angle and allow the ski to start turning in a radius that's inside of the radius the sidecut of the ski would allow. I go to the center of the ski to get the maximum deflection of my center of mass across the hill, and I move to the tail in the finish for grip. In terrain skiing, I want the tip to bite high in the turn to impart a rotation to the ski, and I want the tail to catch in the finish to impart a rotation into the new turn. This preserves vertical distance down the hill.

When you load the front of the ski, it turns more rapidly than it would had you simply tipped it. It does so, however, by causing the tails to take a wider path than the tips. It skids.

 

[François Pugh]

My last attempt.

Tracks don't lie.

When tipping a ski on hard snow the front of the ski points in the direction tipped, and thus provides a steering angle at that part of the ski. When tipping a fully weighted ski that is not moving forward, the ski remains in place at the what would be the only two contact points if the ski were not weighted and the middle of the ski moves to the side (whether on boiler plate or ice or a hardwood floor); if you do it on hard snow you may be able to see the proof in the track it leaves.

When tipping a fully weighted ski on hard snow that is moving forward, the front of the ski points to the inside of the turn and that is the way the front of the ski cuts its new groove in that direction; the middle of the ski does not move sideways - the proof is in the tracks, at least the tracks I leave behind when carving arc-2-arc.

 

[Uke]

How do you account for the overlap in grooves when the new groove starts before the old grove ends. It seems to me that your way of looking at this would have the new groove starting at the soonest when the old groove ends. But if the whole length of the ski begins carving at once then it is easy to see how the tracks left by the two sides of the ski can overlap.

uke

 

[geepers]

My last attempt.

Tracks don't lie.

When tipping a ski on hard snow the front of the ski points in the direction tipped, and thus provides a steering angle at that part of the ski. When tipping a fully weighted ski that is not moving forward, the ski remains in place at the what would be the only two contact points if the ski were not weighted and the middle of the ski moves to the side (whether on boiler plate or ice or a hardwood floor); if you do it on hard snow you may be able to see the proof in the track it leaves.

When tipping a fully weighted ski on hard snow that is moving forward, the front of the ski points to the inside of the turn and that is the way the front of the ski cuts its new groove in that direction; the middle of the ski does not move sideways - the proof is in the tracks, at least the tracks I leave behind when carving arc-2-arc.

The bit that some of us have a little trouble seeing is the claim that more loading on the front will cause a carving ski to tighten it's radius. Assuming that we are at the point where the tip is engaged with the snow why would that be?

It's sort of like this:

 

[François Pugh]

I think we will have to wait for someone to take the finite element model written about up-thread and vary the loading on it, to show how the ski deforms to closer match the shorter radius near the tip of the ski than the longer radius further back of the ski.
I'm not inclined to spend that much time on it. In fact I've spent about all the time I'm going to on it.

In the meantime we have our experimental observations, and the knowledge that the ski and snow both have some give to them.

 

[markojp]

So here's something..they are rebroadcasting the Canada Cup from 1987 and one of the greatest hockey skaters, Paul Coffey, was playing in that series and I happened to watch a few bits. I also read that he re-taped his ankles after every shift. Which is odd to me because I've always been floppy skate guy..I find more forward flex is necessary for mobility especially when skating backward. I also notice Pavel Bure was very rigid in the ankles. Not sure what any of that means..I'm not a pro at skating or skiing technique..but I read this title and thought, that's curious... I can only guess he was very good at manipulating the whole skate edge at a very fine level to generate the most power along the edge. No cheating by rolling onto the toe..mobile hips.
Here's a clip of Paul Coffey...

Different individuals, different levels of natural ankle mobility... just like skiing. Hyper mobile ankles/feet need stiffer boots.

 

[Mike King]

Different individuals, different levels of natural ankle mobility... just like skiing. Hyper mobile ankles/feet need stiffer boots.

Rather than stiffer boots, perhaps what's needed is a focus on stiffening the feet, or so Tom Gellie would say. This allows you to use the feet and ankles as a type 2 lever as opposed to a type 1 lever.

It's an interesting point of view. Tom's view also reconciles with Dave McPhail's Birdcage Experiment that showed that WC racers do not exert much force on the cuff of the boot. He'd argue that's because they are stiffening the arches of the foot to transform the foot and ankle into class 2 levers, where the lateral and fore/aft directions of pressure are much faster and more effective.

Mike

 

[LiquidFeet]

Following along. Here's a diagram.

 

[LiquidFeet]

....Tom's view also reconciles with Dave McPhail's Birdcage Experiment that showed that WC racers do not exert much force on the cuff of the boot. He'd argue that's because they are stiffening the arches of the foot to transform the foot and ankle into class 2 levers, where the lateral and fore/aft directions of pressure are much faster and more effective.
Mike

How is this different from crediting the super stiff boot with delivering lateral and fore/aft pressure much faster and more effectively?

 

[Mike King]

When you use the arches of the feet and stiffen the ankles/feet, the transfer of force from the edging and fore/aft pressure management actions are more direct. If you allow the feet and ankles to become class 1 levers then you have to move the tibia to the boot cuff to create the action on the skis. For fore/aft, this results in more movement in the body above the knee to create fore/aft movements. It also can lead to a disengagement of the feet from the ski.

Tom's has two very informative webinars on this topic -- nearly 4 hours of video. I'll paraphrase a bit of the conversation that was on the issue:

• Participant: I have floppy ankles and need support from my equipment, particularly on a wide ski. I don't think given my ankle mobility issues that stiffening my feet the way you suggest is going to work.
• Tom: I disagree. When I was in Aspen, I worked with the clinic group all morning on tightening the arches of the feet and feeling that the three points of the tripod are almost magnetically connected to the ski. We skied all morning with the cuffs completely undone and the power straps disengaged. After about 15 minutes, everyone had more or less forgotten that the cuff was undone. We were skiing high performance short turns and even ventured into double black terrain.
• Tom pointed out that there's a over reliance on the action of the shin -- that is, engaging the shin against the boot for leverage. A sign of those who may have this tendency are those who are constantly cranking down on their boot buckles to try to get greater engagement of the boot cuff. Instead, look to use the feet as class 2 levers.

Tom believes that one of the most important things you can do to transform your skiing is to start using the levers in your body to affect your equipment more directly. There are times when you want a type one lever (absorption), but mostly a class 2 lever will be more direct and more effective. He's got a lot of video to use as evidence of the difference and the result in ski performance.

Perhaps this is just another plug to plunk down the moolah for Tom's videos. They are truly mind blowing. I think the short period of time that I had to ski with some of the ideas I got from them were transforming to my skiing. And they certainly have helped me to tie everything together...

Mike

 

[markojp]

Rather than stiffer boots, perhaps what's needed is a focus on stiffening the feet, or so Tom Gellie would say. This allows you to use the feet and ankles as a type 2 lever as opposed to a type 1 lever.

It's an interesting point of view. Tom's view also reconciles with Dave McPhail's Birdcage Experiment that showed that WC racers do not exert much force on the cuff of the boot. He'd argue that's because they are stiffening the arches of the foot to transform the foot and ankle into class 2 levers, where the lateral and fore/aft directions of pressure are much faster and more effective.

Mike

I don't want to get into it, but if it were merely a matter of 'stiffening the feet', why aren't WC'ers skiing 110 to 120 flex boots? Personally, I have hyperflexive feet primarily in the lateral plane. I have no foot pain or pedorthic issues. My feet are strong and stable, just flexible. I don't roll or sprain ankles or tweak knees. I see ankle mobility as an advantage in a ski boot. Yes, I use custom footbeds in my boots and of late, cycling shoes. The latter is an experiment. And yes, I think Tom's thoughts are valuable.

 

[Mike King]

I don't want to get into it, but if it were merely a matter of 'stiffening the feet', why aren't WC'ers skiing 110 to 120 flex boots? Personally, I have hyperflexive feet primarily in the lateral plane. I have no foot pain or pedorthic issues. My feet are strong and stable, just flexible. I don't roll or sprain ankles or tweak knees. I see ankle mobility as an advantage in a ski boot. Yes, I use custom footbeds in my boots and of late, cycling shoes. The latter is an experiment. And yes, I think Tom's thoughts are valuable.

Good question. I don't know how Tom would respond, but one reason might be the obvious one: for when you make a mistake, or when the forces become too great for the strength in your feet and ankles.

 

[geepers]

When you use the arches of the feet and stiffen the ankles/feet, the transfer of force from the edging and fore/aft pressure management actions are more direct. If you allow the feet and ankles to become class 1 levers then you have to move the tibia to the boot cuff to create the action on the skis. For fore/aft, this results in more movement in the body above the knee to create fore/aft movements. It also can lead to a disengagement of the feet from the ski.

Tom's has two very informative webinars on this topic -- nearly 4 hours of video. I'll paraphrase a bit of the conversation that was on the issue:

• Participant: I have floppy ankles and need support from my equipment, particularly on a wide ski. I don't think given my ankle mobility issues that stiffening my feet the way you suggest is going to work.
• Tom: I disagree. When I was in Aspen, I worked with the clinic group all morning on tightening the arches of the feet and feeling that the three points of the tripod are almost magnetically connected to the ski. We skied all morning with the cuffs completely undone and the power straps disengaged. After about 15 minutes, everyone had more or less forgotten that the cuff was undone. We were skiing high performance short turns and even ventured into double black terrain.
• Tom pointed out that there's a over reliance on the action of the shin -- that is, engaging the shin against the boot for leverage. A sign of those who may have this tendency are those who are constantly cranking down on their boot buckles to try to get greater engagement of the boot cuff. Instead, look to use the feet as class 2 levers.

Tom believes that one of the most important things you can do to transform your skiing is to start using the levers in your body to affect your equipment more directly. There are times when you want a type one lever (absorption), but mostly a class 2 lever will be more direct and more effective. He's got a lot of video to use as evidence of the difference and the result in ski performance.

Perhaps this is just another plug to plunk down the moolah for Tom's videos. They are truly mind blowing. I think the short period of time that I had to ski with some of the ideas I got from them were transforming to my skiing. And they certainly have helped me to tie everything together...

Mike

Didn't get any chance to play with Tom's thoughts on this before season end. And the extra info in his web seminars is more recent. Really looking forward to trying some of this on snow - if the southern season goes ahead. Remains to be seen how much I'll be willing to follow the boot mod ideas.

In the meantime there's the off snow exercises and preparations.

 

[geepers]

Following along. Here's a diagram.

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[Scruffy]

When you load the front of the ski, it turns more rapidly than it would had you simply tipped it. It does so, however, by causing the tails to take a wider path than the tips. It skids.

It certainly can skid, but it's not a given it will if the pressures are managed correctly.

When you use the arches of the feet and stiffen the ankles/feet, the transfer of force from the edging and fore/aft pressure management actions are more direct. If you allow the feet and ankles to become class 1 levers then you have to move the tibia to the boot cuff to create the action on the skis. For fore/aft, this results in more movement in the body above the knee to create fore/aft movements. It also can lead to a disengagement of the feet from the ski.

Tom's has two very informative webinars on this topic -- nearly 4 hours of video. I'll paraphrase a bit of the conversation that was on the issue:

• Participant: I have floppy ankles and need support from my equipment, particularly on a wide ski. I don't think given my ankle mobility issues that stiffening my feet the way you suggest is going to work.
• Tom: I disagree. When I was in Aspen, I worked with the clinic group all morning on tightening the arches of the feet and feeling that the three points of the tripod are almost magnetically connected to the ski. We skied all morning with the cuffs completely undone and the power straps disengaged. After about 15 minutes, everyone had more or less forgotten that the cuff was undone. We were skiing high performance short turns and even ventured into double black terrain.
• Tom pointed out that there's a over reliance on the action of the shin -- that is, engaging the shin against the boot for leverage. A sign of those who may have this tendency are those who are constantly cranking down on their boot buckles to try to get greater engagement of the boot cuff. Instead, look to use the feet as class 2 levers.

Tom believes that one of the most important things you can do to transform your skiing is to start using the levers in your body to affect your equipment more directly. There are times when you want a type one lever (absorption), but mostly a class 2 lever will be more direct and more effective. He's got a lot of video to use as evidence of the difference and the result in ski performance.

Perhaps this is just another plug to plunk down the moolah for Tom's videos. They are truly mind blowing. I think the short period of time that I had to ski with some of the ideas I got from them were transforming to my skiing. And they certainly have helped me to tie everything together...

Mike

Try experimenting with a flat boot bed; no custom foot bed or orthotic ( assuming you have no podiatric issues that require an orthitic ). I ditched mine 3 years ago and have not looked back. The full range of the foot and the entire superficial front line can be hampered by artificial arch support blockage. Pronation is a natural phenomenon in human movement.

 

[Mike King]

It certainly can skid, but it's not a given it will if the pressures are managed correctly.

Do you have any evidence of that? Everything I have implies that even a slight adjustment fore or aft leads to a skidded ski.

Then again, there may be no such thing as a ski turn that is perfectly carved...

Try experimenting with a flat boot bed; no custom foot bed or orthotic ( assuming you have no podiatric issues that require an orthitic. I ditched mine 3 years ago and have not looked back. The full range of the foot and the entire superficial front line can be hampered by artificial arch support blockage. Pronation is a natural phenomenon in human movement.

Tom Gellie appears to be of the opinion that no orthotic or footbed is needed and that they may, in fact, hinder your ability to use the three arches of the foot. I'm not quite convinced yet, but his logic is persuasive...

 

[François Pugh]

Everything I have implies that even a slight adjustment fore or aft leads to a skidded ski.