Flexing through transition (video)

[JESinstr]

Hmmmm, Where should I start....?
Let's try the KISS approach

1. A ski can only do 2 things. It can slide (straight line travel) or it can carve (circular travel). In between is a tenuous state we call "transition". Transition IMO, starts with release and continues until a controlled state is achieved, be it another circular path or straight line.

2. When a skier is creating circular (centripetal) travel, their mass is constantly trying to break the circular route and return to straight line travel. This feeling is what many call centrifugal force.

3. Once the skier begins the release of their mass from the circular path, where the COM seeks straight line travel is a function of the relationship to the fall line. It is also the source of velocity.

4. Blocking is a straight line activity. It is very useful in executing down the fall line short radius turns or pivot slips where the COM is pretty much traveling in a straight line and rotary is the primary force for ski directional change. When blocking is incorporated in larger carved turns, it is a sign that the skier has decided (either by choice or habit) to deal with velocity in a straight line manner.

Finally, Flexing is the key to skiing, It allows for the creation of angles. It allows us to center over and collapse the arch. And it allows us to manage the dynamic pressures (both positive and negative) that develop. Managing transition using flexing is fundamental to advanced skiing.

 

[BornToSki683]

Have to keep this short as I hope to ski tomorrow.

What 'flexing to release' does is change the trajectory of the com, release it from its former path if you will. What it doesn't do by itself is release the edges.

I can 'flex to release' then flex even more to allow my body to cross the path of my feet.

I can 'flex to release' then slow or stop the flexing and produce a "vault' that will accelerate my com up. Depending on the strength of the vault I may continue to flex or I might have to extend to maintain snow contact through the transition as the paths cross.

I can release the edge and the com at the same time by flattening the ski at the foot. Again with this move I can then flex or extend through the transition as necessary to achieve early edge engagement.

Hope that makes things clearer,

uke

I think you can add even further variation by how you relax/flex each leg independent of the other. Also... what would you say is the difference when you relax the outside leg earlier compared to later in the completion phase of the turn?

You eluded to some interesting aspects of the rate and intensity of how we relax our leg(s). you can relax one or both legs suddenly or gradually, with different results.

 

[Uke]

3. Once the skier begins the release of their mass from the circular path, where the COM seeks straight line travel is a function of the relationship to the fall line. It is also the source of velocity.

How is the path of the com related to the fall line after release? The path of the com after release is determined by the direction of movement of the com at the moment of release. Tangent to the arc.

uke

 

[JESinstr]

How is the path of the com related to the fall line after release? The path of the com after release is determined by the direction of movement of the com at the moment of release. Tangent to the arc.

uke

Uke, you are correct. My error. I was trying to bring velocity (derived from the fall line) into the equation and its effect on how quickly the mass can exit the arc, ergo the effect on direction. But you are right, direction is really a question of timing and the execution of the release.

 

[razie]

Since the thread is about flexing through transition, here's another view on direction: the lower we are, the quicker we can change direction and the more forward we are, the more direction we get:

note the ski bending under the toes so far above the fall line, we'd think he's hanging by an edge...

I personally like "gravity drop" it does match my thoughts, to some extent - how does that play into this sequence, to result in that massive ski bend? And how did he get forward in the first place, when he seemed sooo far back?

 

[BornToSki683]

Not sure what the "gravity drop" is you referred to, but I do want to make one point that gravity actually pulls the CoM towards the center of the earth, which on a ski slope is not down the fall line while completing a turn. While completing a turn, gravity will be pulling the CoM towards the inside of that old turn..there is your gravity drop there. In your photo above, you can see gravity drop happening AFTER the edge change in the second frame. Point is...gravity is not really directly providing a way to pull the CoM across the skis from the inside of the old turn down the fall line across into the inside of the other turn......aka....crossover. In fact something in the dynamics of everything needs to OVERCOME gravity in order to achieve the crossover.

Incidentally, we overcome gravity in a much easier way by flexing as we pass through transition, by providing the path of least resistance for the CoM.

Once you have released and the CoM is halfway through crossing over, then finally gravity can pull it towards the center of the earth in a way that can contribute to the second half of transition crossover, or actually its really post-transition....its the next turn and developing angles, when gravity can pull your CoM down into the turn, as you can see happening in the 2nd frame.

 

[Doby Man]

Oh my gosh those are certainly not the only bio mechanical things happening in skiing.... those are very broad categories. In some cases they are outcomes also...not bio mechanical instructions ........ its not a bad list of fundamentals in a broad sense, agree...but again...accomplishing them involves more specific information about body parts. So try to relate what I have said so far....and what the thread is about...flex to release...to the skill categories you embrace above ...... you really lost me there. Can you please elaborate? inclination to facilitate crossover? Angulation to facilitate crossunder? how? That is non sensical to me right now but maybe you can make sense out of it. Can you relate that to flexing through transition per the thread?

Great questions, BTS.

When the CoM crosses over the BoS we are “tipping” the CoM over the feet which is a function of inclination and why inclination is the primary fundamental movement input for a “cross over” turn. When the BoS crosses under the CoM it is doing so with lateral angular mobility for which the primary fundamental movement input is angulation of the hips, knees, ankles in varied combinations that is based on intent.

Flexing and/or extending through transition in a straight line is a function of decreasing fore/aft angles in the ankles, knees and hips which depicts vertical compression. Flexing and/or extending through transition in a curved path requires an additional function of decreasing lateral angles in the ankles, knees and hips which depicts angular compression (angulation).

There are, of course, more quantitative as well as qualitative nuances to skill blending and movement integration such as duration, intensity, rate and timing shared between these movements that can be more specifically and accurately described when traced through the physical anatomy, AKA the kinetic chain, and/or traced chronologically through the turn through the turn phases. While it is always fun to be conceptual, theoretical and even philosophical about ski technique, those elements do not go very far without any type of base of knowledge or academic foundation that is held true by all such as in any other professional discipline. The listed fundamental movements, kinetic chain and turn phase descriptions are not concepts, theories or philosophies with which to agree or disagree. They are “actual” descriptions of what, when and where something is happening in the body. Which body parts we use to apply that list of fundamentals is an obvious inclusion of joint flexion and is thoroughly covered through any kinetic chain description as a pattern rather than a simple list of body parts used. It covers movement from all degrees of flexion in all joints in all planes in more of a ski technique context rather than a strictly biomechanical one.

 

[Uke]

Have to keep this short as I hope to ski tomorrow.

What 'flexing to release' does is change the trajectory of the com, release it from its former path if you will. What it doesn't do by itself is release the edges.

I can 'flex to release' then flex even more to allow my body to cross the path of my feet.

I can 'flex to release' then slow or stop the flexing and produce a "vault' that will accelerate my com up. Depending on the strength of the vault I may continue to flex or I might have to extend to maintain snow contact through the transition as the paths cross.

I can release the edge and the com at the same time by flattening the ski at the foot. Again with this move I can then flex or extend through the transition as necessary to achieve early edge engagement.

Hope that makes things clearer,

uke

Strange to quote yourself.

I wanted to add one other common transition. I call it short leg, long leg. Step one, shorten (flex) the outside leg to release the com, continue to shorten it as necessary to clear com. Step two, begin making the inside leg long (extend) to maintain snow contact and engage the edge as soon as possible. This would be 'flex/extend through the transition'.

uke

 

[BornToSki683]

Which edges are engaged when you start to extend the uphill leg?

 

[Doby Man]

@Uke, The opposite of transition is turn phase two where long leg/short leg peaks. The actual center of transition is represented by "lateral angle neutral" where the legs are equally flexed over flat skis. I also think of long leg/short leg as the result of vertical separation from equal and high tipping so as the CoM movement is being generated by tipping the feet rather than from the top down as your flex to release paradigm suggests. Though, I can see how the inputs and outputs on each side of those movements are an integral part of entering and exiting transition.

"Strange to quote yourself"

... and even one step stranger to actually comment on it. You are having a three way conversation with yourself. Who are you now?

 

[LiquidFeet]

Strange to quote yourself.

I wanted to add one other common transition. I call it short leg, long leg. Step one, shorten (flex) the outside leg to release the com, continue to shorten it as necessary to clear com. Step two, begin making the inside leg long (extend) to maintain snow contact and engage the edge as soon as possible. This would be 'flex/extend through the transition'. uke

Sounds like a turn entry with weight staying a few nano-seconds on the downhill/new inside ski. If you lift the uphill/new outside shoulder as you do this, its momentum will make you topple faster onto the new edges. This shortens the top of the turn beyond just simply pulling that downhill/new inside knee up.

Ted does this in tight turns. He lifts that shoulder a bit and pulls the elbow back a little, then swims that whole arm forward through the turn. A little upper body english to help the turn along. Fun to watch.

 

[Uke]

Which edges are engaged when you start to extend the uphill leg?

The answer is the dreaded 'it depends'.

I can keep tipping the uphill foot and feel the uphill edge (little toe side) engage then roll over to the downhill new turning edge (big toe side) but its more common for it to feel like I'm reaching out behind me with tip of the new outside ski to engage the snow as soon as possible. Remember, I have already released the com so all this is taking place in a fraction of a second and I am reporting what I feel happening more than what I am doing. I never have a platform on the little toe edge of the uphill ski to push off of as you may be thinking.

uke

 

[Uke]

"Strange to quote yourself"

... and even one step stranger to actually comment on it. You are having a three way conversation with yourself. Who are you now?

Legion

 

[BornToSki683]

The answer is the dreaded 'it depends'.

I can keep tipping the uphill foot and feel the uphill edge (little toe side) engage then roll over to the downhill new turning edge (big toe side) but its more common for it to feel like I'm reaching out behind me with tip of the new outside ski to engage the snow as soon as possible. Remember, I have already released the com so all this is taking place in a fraction of a second and I am reporting what I feel happening more than what I am doing. I never have a platform on the little toe edge of the uphill ski to push off of as you may be thinking.

uke

Definitely not assuming anything. I more or less consider the transition over once the downhill edges are engaged enough to start to bend the ski, which ideally isn’t that long after flat. Extending that leg sooner or later is important. The only caution I have is that it’s easy to accidentally push enough to unweight or cause balance problems later if that leg extension is rushed. If early engagement and carving is desired then care is needed to avoid extending too soon. This is something I am constantly working on because it’s very easy to get a little excited and extend it a bit early or hard.

Recently helluva posted video on the tech model thread of Reilly doing medium radius turns. Those are a good example of using flex to release, in my view the transition is happening mostly flexed too but he doesn’t flex as deeply as he does for SRT and he does extend the uphill leg sooner then he does in his SRT while clearing through transition. This may be something similar to the variation you are talking about.

 

[François Pugh]

Uke, you are correct. My error. I was trying to bring velocity (derived from the fall line) into the equation and its effect on how quickly the mass can exit the arc, ergo the effect on direction. But you are right, direction is really a question of timing and the execution of the release.

As to gravity: Once you have fully (and completely) released your CoM from all forces acting through your CoM ski connection (legs) your CoM will follow along in its path acceleratig according to Newton's law F=ma, with F being gravity. It will follow a parabola, that will either resemble the path of a bullet or a dropped stone depending on its velocity. If you're traveling at 88 feet per second it will resemble the path of an off speed pitch in the major leagues or a fast ball in Tripple A baseball, and you will likely drop a small amount in the fraction of a second or so it takes you to go through the transition. If you're barely moving you will hit the snow before you get into the new turn.

As to instructions on what to do, that's a tough one. So many things to think about (or not at all if your lucky).

I never studied kiniseology (or spelling), but I'll give it a try just the same - self description from a non-instructor skier.

Starting at the apex of the old turn. I got there by tipping my feet/skis, while adjusting my balance so that most of my weight is on the inside edge of my outside ski (the part of the ski base that is in the snow) at the apex and a ground reaction force is pushing up perpendicular to the ski through my leg to my CoM. The inside ski has enough force on it, provided mostly by my inner lower leg's weight and inertia, to keep it carving in the turn dictated by its tipping angle, which I am consciously in control of. As my skis turn, I allow my legs to turn under the action of the snow acting upon their curved shape as they move forwards, or even better turn my legs in harmony with where the snow is forcing them to go. I also ride the skis (mostly the outside one, my inside leg rides the inside one) in the sense that I am allowing my leg bones (again mostly the outside ones) and muscles to transmit the force from the skis to my CoM, accelerating it around the turn my skis are making. All the while maintaining upper body alignment facing in my general direction of travel and close to vertical - in essence I am skiing my lower body into counter. I used to have less counter and more inclination, but it's safer (easier to recover from a slip) with more.

When I have turned far enough (as far as I want to), I relax the outside leg, and also my inside leg to disconnect my CoM from the forces being applied to it, wile maintaining a geometry and control to keep the skis tipping and turning - I control the angle my skis are tipped to the snow without allowing forces other than gravity to accelerate my CoM.

Depending on intent, I may hold onto the CoM turn longer (if I want to slow my decent speed down the hill), or release it at the apex as soon as I'm pointing down the hill (if I want to increase my decent speed down the hill). Typically I want to ski faster, so I will get most of my (CoM) turn done by the fall line, but on a bigger hill with SL skis, I need to stay about 40 mph for the skis to work best. As my skis cross under my CoM's path, which is usually down the hill (but it need not be), or shortly thereafter, I un-tip my skis to skis-flat and in a continuous movement, tip my skis in the other direction. A game I sometimes play is to delay this un-tipping as much as I dare. I've come close to tripping up, but haven't done so yet. On the way to the next apex, I make sure to keep that inside knee and hip from interfering with developing big edge angles, pressure the tips (pull back feet) and get turning fast down the hill, transferring my balance such that the reaction force through my CoM starts from the tips but as on its way to from-the-tails and past the heels at apex.

Variations, I can also untip the skis after apex, by a controlled amount and do the same thing as above, (same effect as more gradual release - but working from the other end) or tip them even more (after my CoM's Apex, but obviously moving the skis apex further ahead in time).

 

[Jamt]

Starting at the apex of the old turn. I got there by tipping my feet/skis, while adjusting my balance so that most of my weight is on the inside edge of my outside ski (the part of the ski base that is in the snow) at the apex and a ground reaction force is pushing up perpendicular to the ski through my leg to my CoM. The inside ski has enough force on it, provided mostly by my inner lower leg's weight and inertia, to keep it carving in the turn dictated by its tipping angle, which I am consciously in control of. As my skis turn, I allow my legs to turn under the action of the snow acting upon their curved shape as they move forwards, or even better turn my legs in harmony with where the snow is forcing them to go. I also ride the skis (mostly the outside one, my inside leg rides the inside one) in the sense that I am allowing my leg bones (again mostly the outside ones) and muscles to transmit the force from the skis to my CoM, accelerating it around the turn my skis are making. All the while maintaining upper body alignment facing in my general direction of travel and close to vertical - in essence I am skiing my lower body into counter. I used to have less counter and more inclination, but it's safer (easier to recover from a slip) with more.

When I have turned far enough (as far as I want to), I relax the outside leg, and also my inside leg to disconnect my CoM from the forces being applied to it, wile maintaining a geometry and control to keep the skis tipping and turning - I control the angle my skis are tipped to the snow without allowing forces other than gravity to accelerate my CoM.

Depending on intent, I may hold onto the CoM turn longer (if I want to slow my decent speed down the hill), or release it at the apex as soon as I'm pointing down the hill (if I want to increase my decent speed down the hill). Typically I want to ski faster, so I will get most of my (CoM) turn done by the fall line, but on a bigger hill with SL skis, I need to stay about 40 mph for the skis to work best. As my skis cross under my CoM's path, which is usually down the hill (but it need not be), or shortly thereafter, I un-tip my skis to skis-flat and in a continuous movement, tip my skis in the other direction. A game I sometimes play is to delay this un-tipping as much as I dare. I've come close to tripping up, but haven't done so yet. On the way to the next apex, I make sure to keep that inside knee and hip from interfering with developing big edge angles, pressure the tips (pull back feet) and get turning fast down the hill, transferring my balance such that the reaction force through my CoM starts from the tips but as on its way to from-the-tails and past the heels at apex.

Variations, I can also untip the skis after apex, by a controlled amount and do the same thing as above, (same effect as more gradual release - but working from the other end) or tip them even more (after my CoM's Apex, but obviously moving the skis apex further ahead in time).

Good description, but to make it complete I think a description of how the CoM is moving and being manipulated in the up down direction is missing.

 

[François Pugh]

Ah yes, the up and down. A flight plan must include altitude. As already said somewhere pure release lets the CoM fall, increasing the downwards component of velocity at 9.8 m/s per second. Pushing down with the feet decreases that rate (and may even change its direction to up). Timing is everything. Typically, you need to have more pressure at the apex and less at transition. The flex to release naturally fits that pattern. On average, over the run, your position above the snow is unchanging, your velocity vector must point parallel to the slope on average, so you can't constantly accelerate (changing the direction of your velocity vector) away from the snow. Pressure comes when you accelerate upwards, that is stop or slow going down, start or speed up going up.

You can play with a more gradual release, either by a gradual lessening of force transmission to the legs or un-tipping skis sooner. You can play with appling a little pressure with skis closer to flat as you go through (not something I recall doing, but I suppose it could work if your were going slow enough or did it slightly - I don't like the way it puts a hitch in things), applying more pressure at the beginning of the turn if you know you will need less at the end (that way you start the transition higher), In some cases you may even want to change to another transition, where you push yourself up with the old inside leg, vaulting over the old outside ski and then come down hard (with a lot of upward acceleration once you make contact) in the next turn.

Having altitude is like having pressure in the bank, because you can change it into downward velocity that you can then decrease with pressure. Too much of anything is a bad thing. You also need to be able to extend, and absorb, so you need to balance all your needs.

I hope that makes sense, I don't think too much when doing it.

 

[TDK]

Great video. One minor comment is that I agree with your final comment about never being in static balance and I think it is very important (hence the last part of my signature). However, it looks like the force diagram shows static balance ...

Yes, the diagram shows static balance. But the diagram is not made to show dynamic balance. Merely explain the forces at play. All forces except G are constantly changing. That was my intention at least. Is that wrong?

 

[Shawn]

I have a question about Guy Hetherington's movement here in a retraction turn. (Starting at 1:40)


Do you think there's something "off" about it? There's something about those knees thumping into his chest. Can't put my finger on it.

Compare to HeluvaSkier (the man, the myth, the legend):


Similar movement but much more controlled.

 

[Rod9301]

Looks pretty good, perhaps exaggerated so people can see the movement