Feet pullback physics

[John Mason]

clearly the legs are flexed at transition and then later the new stance leg is skeletally strong when the g-forces are strongest in the turn. The new stance leg goes from a flexed position to a straightened position. But this is done consistent to maintain the bodies momentum down the hill. You can easily push that top leg too soon and enter into the push off fallicy rather than allowing that lengthening to occur as a result of responding to the stronger g-forces of the turn.

The danger of using a term like - "this is where leg extension is needed", is that can put the cart before the horse and make leg extension the cause of something rather than a reaction to the turn's own development.

If you do any type of early leg extension that means you'll distrupt your bodies momentum down the hill and waste energy. But by maintaining your bodies momentum down the hill, you'll leg will extend to maintain the releative vertical position of your body over the slope as the turn occurs.

Here are visual attributes of a PMTS skier:

1. Legs most flexed at transition
2. stance leg most extended at the fall line (highest g-force section of the
turn.
3. Body does not bob up very much at transition, momentum of the body going down the hill is maximally conserved.
4. The high C part of the turn is carved and the skier is upside down with a bit of a 'faith' mode that the skis will carve and catch up with you as the turn progresses. Ski engagement at this part of the turn is from edge angles developed from Counter Balancing and Counter-rotation (hip counter). As the turn progesses inclination will also add to the edging, but right at transition inclination does not exist for edging which is why counter balancing and counter rotation are required.

Here are the visual attributes of most skiers on the hill:
1. Legs are straightest at transition accompanying a up movement at transition
2. Legs are shortest at the fall line of the turn
3. The top of the turn is not carved but the skier is using an active rotation and/or push off to get the turn started.
4. The skier is never upside down and basically is clueless at how to do the top of the turn in an efficient manner.

It's the difference in understanding of item's 4 in both lists that might make someone be tempted to do some leg extension rather than counter balance and counter rotation at the high C part of the turn.

Leg extension happens naturally in PMTS as the turn develops. No push off needed. The danger some people get in to in learning PMTS is when you release your old stance ski while the old turn is still occuring, the bent inside leg will then take the forces of the old turn. But because that's the uphill ski of the old turn and the old stance ski support is gone, you will use this shift in balance to maintain your body's momentum going down the hill, keep the leg short through transition and extend only as required as the new turn develops. Some skiers learning this super phantom type of transfer can react to the change in pressure on the inside ski before the old turn ends and push off. That is an error and prevents you from enjoying and properly using the 'float' phase of the turn.

[patprof]

Nice post John. Good to hear from you again

[milesb]

Good to see your posts again John. I'll just add that on steep stuff at slower speeds, the area of greatest pressure is going to be closer to the bottom of the turn. The same things you listed still apply, just keep both legs flexed longer because it is so easy to overpower the high C with any extension in those turns. I remember Rich M. yelling at me "stay flexed! stay flexed!" in the high C when we were skiing some steep stuff at the A-Basin camp last year. I still hear that whenever I'm on steeps, lol.

[quest]

John Mason:

Thanks so much for the explanation in detail.

milesb:

If for slower skiing the greatest pressure is to be closer to the bottom of the turn, at what point of the turn will we have the 'straighest' moment of our legs, and when to absorb the pressure build-up?

or you meant that although the greatest pressure is at the bottom of the turn, yet we stay flexed and flex further to deal with the pressure build up at the bottom of the turn?

[Max_501]

Keep in mind that the extension tends to be gradual with full extension at or right after the fall line (not before). Absorption happens when you are ready to release (or if you need to suck up a bump).

[milesb]

Quest*, depending on the speed and the steepness, it will be somewhere between the fall line and the finish of the turn. It really depends upon where and when when the stance ski is engaged enough. But the point is not to extend the stance leg, it's to flex and tip the free leg, the stance leg mostly extends in reaction to the forces of the turn. I think sometimes it's a good idea to absorb pressure by flexing the stance leg in the bottom of the turn so as not to overpower the snow or edge grip. But leave enough so that you can still actively flex to start the next turn. This has the usually unwanted effect of killing the energy of the turn, however. The general idea is to make the pressure build-up gradual enough so that the energy can be maintained. Turns with energy on double blacks= FUN!!

*Keep in mind what I'm talking about really only applies on some black and double black terrain, and a lower skill level. On most terrain, what John posted was right on and what we should strive for.

[milesb]

Ski engagement at this part of the turn is from edge angles developed from tipping, assisted by Counter Balancing and Counter-rotation (hip counter).

John sorry to nitpick, but is this more like what you meant?

[Max_501]

Another thought, full extension doesn't usually happen in very short radius turns like you'd typically use on very steep terrain as there isn't enough time to get the leg fully extended before the release.

[John Mason]

yes - I forgot to tip!!!!

all is useless unless you are tipping your free foot hard inside your boot

(I remember well the camp where Arc held the end of our skis flat to the ground and yelled to tip harder till we had him satisifed - none of us were tipping even close to as hard as we could or should)

Tipping the free foot- the primary movement

All the other stuff - secondary movements in support of the primary movement

Tipping is not pointing your knees someplace. That'll get you hurt and is skeletally weak. Tipping is done with the free foot inside your boot. You don't have to worry about your stance leg, it will follow by itself. (which is one of the reasons HH hates those solid orthtics somepeople get set up with and likes to build his with some give)

Thanks MilesB

[quest]

Thanks to everyone for the clarification.

However, John, your last comment got me baffled, "one of the reasons HH hates those solid orthtics somepeople get set up with and likes to build his with some give"

Since the tipping of the foot inside the boot is essentially tipping of the boot and the ski, what difference does it make whether the boot has solid orthtics or not?

[John Mason]

There is more of an ability to be progressive in your in boot pressure with an orthotic that is not ridgid. HH's are not 'soft' but they are not 'ridgid' either.

My first ones were ridgid not from HH. I much prefer the ones from HH.

I found this blurb from HH from back in 2005 that you might find helpful in understanding Harald's reasoning.

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#4 - Skiing Inside The Boot

At Harb Ski Systems we are always striving to put our customers and ourselves in the best products available in the ski industry. My staff and coaches are all professional skiers and have been for many decades. These people are not just instructors and coaches, but also boot fitters, footbed specialists and alignment experts. We feel that to teach skiing properly at the highest level you must understand the whole system: feet, ankles, boots and alignment. With this level of understanding, ski instruction becomes very precise and effective.
My staff and I are always looking to enhance our own experience on snow. Therefore I encourage them to try many products and to modify their own. Recently, we have been working on ski boot modifications.

Last summer, I modified many ski boots at Mt. Hood for FIS Junior US development racers with great success. We began this season modifying ski boots for many other racers including World Cup and US Ski Team racer, Erik Schlopy. This has become an ongoing relationship. We send modified boots to Europe for Erik and he sends his new boots to us from Europe to modify. Erik, remember, has access to the best boot technicians the World Cup can provide, but prefers to send his boots to us. We are working on two different modifications on Erik's boots. They increase the ability of the foot and ankle to produce edging power and the ability of the ankle to access the boot wall through medial wall and boot board modifications. These are the same movements of the ankle we try to provide for all our footbed and alignment customers. The functional articulation of the ankle and foot in the boot provides and enhances the skier's ability to make refined, fine-tuning movements to adjust the ski edge angle on the snow. If this articulation is not available, movements are made at the hip using the adductor muscles to lever the ski on edge. This is a very gross motor movement and does not allow for much adjustment once the movement to the edge begins. In high-end expert skiing or World Cup racing the combination of ankle, foot and leg edging adjustments is essential. So, why do so few recreational skiers have access to these movements? Because most industry footbeds are overposted and too rigid. This concept has been in my mind and I have applied it for generations as a ski racer, skier, coach and instructor. I have always felt that foot and ankle articulation in the boot are critical to skier performance, especially in the areas of ski edging, holding and controlling. But everywhere I investigated, even to this day, I find that the ski industry is trying to accomplish exactly the opposite. With hard footbeds and ski boot walls that are very tight on the medial (inside) ankle, most products reduce lateral movement of the ankle toward the boot wall - reducing or eliminating foot articulation. In some ways of thinking this can be justified and explained to seem like a benefit. For example, if rigid footbeds with dense material filling the arch stop any foot movement, one could think that you would get immediate edge and energy transfer. Yes, this does seem to make sense - until you begin to understand that you are now forced to use your upper leg muscles to achieve this immediate edging and transfer. The upper leg muscles (adductors) do not have the ability to fine-tune the edge, thus eliminating any presumed "benefit" of the rigid footbed/immediate-edge-power concept. Skiers whom we have converted from rigid footbeds to those that allow articulation become more balanced, smooth, and fluid. They also benefit from better foot circulation and therefore have warmer toes. Many overposted and rigid-footed skiers fight their edges. The lack of foot articulation creates chatter on hard snow and over-steering on soft snow. The skis are also super-reactive and feel nervous. Many skiers complain of arch pressure or even pain, but are afraid to mention it because they supposedly bought a "special upgrade". All these problems can be immediately relieved with a more compliant and accurately designed footbed. Now we must keep in mind that every body has different abilities and needs. Some skiers have excess foot movement that needs to be controlled, though not eliminated. A rigid foot and ankle demonstrate the opposite needs. The rigid foot and ankle are particularly interesting because increasing range of lateral movement in the ankle and foot is much more difficult than reducing range of motion. Hence every footbed needs to be carefully designed and built for the needs of the individual foot to optimize lateral edging power, allowing the range of articulation of the foot and ankle required to apply force to the boot wall. Applying force to the boot wall can only be achieved if the muscles that tip - evert - the foot can function. The peroneal muscles that run up along the outside of the tibia must be able to move the foot through some range of motion for this to occur. In our painstaking effort to evaluate a skier's balance on snow, we came across some interesting findings. We video all of the skiers who come to our camps while they perform on-snow balancing exercises. After careful analysis of the skiers before and after alignment, over a period of six years, we have determined that skiers with rigid feet and skiers with flexible feet both suffered similar consequences from rigid, inflexible footbeds. These skiers were not able to use their lower joints in the ski boot to help balance or edge the ski. They instead leaned or otherwise used the upper body in a contrived manner to lever the ski to an edge. Most of these skiers cannot engage the edge of the ski – make it slice into the snow. Instead, they demonstrate slipping of the ski. After a complete set of range-of-motion measurements are taken and a footbed made to allow for proper articulation of the ankle and foot, the skiers again perform the on-snow balance exercises. This second set of exercises yields very different results. Again, slow motion video analysis is used to determine differences in balancing and skiing abilities. One noticeable difference is a new, relaxed body position. The lower body acts as an adjuster of balance and the upper body a stable unit over the boots and feet. Some observers go so far as to say that, the skiers skied as if they had another joint to use in the boot to edge and balance over the ski. Another noticeable difference is an improvement in the skier's ability to engage the edge of the ski, eliminating the slipping that was previously evident. In this season alone we have assembled quantifiable evidence that the footbed and movements I am describing in this article are not only effective but also necessary for higher performance and comfort. We have documented major performance increases with ski racers the very next day after footbed changes. In one particular case, the ski racer improved by thirty FIS points on three different occasions. This occurred without further coaching or equipment changes. We can document such changes in recreational skiers by video and observing their improved edging and ski performance characteristics, but many objectors and detractors would claim that this is unscientific. When we have quantifiable results based on huge improvements in racing times, there is very little left to doubt. When the top ski racers in this country are noticing the performance benefits, and when our recreational skiers are noticeably skiing better and improving faster, that's all the proof they need.

[John Mason]

http://www.realskiers.com/pmtsforum/viewtopic.php?t=77

3rd entry down

[quest]

http://www.realskiers.com/pmtsforum/viewtopic.php?t=77

3rd entry down

Thank you all.