[F]emoral rotation could be a key component of *un-edging* (aka flattening), for example.
It is. One direction, then the other.
[F]emoral rotation could be a key component of *un-edging* (aka flattening), for example.
[F]emur rotation is an active input for knee angulation and a passive output from the ski in an edge locked turn.
Starting from a straight run, the students only need to do one thing--rotate the femurs slightly into the hill.
Exactly how do you "only" rotate your femurs, what is the exact instruction to the student?
Knee edging is movement of the knee laterally. Since the Knee cannot move that way the movement happens primarily in the subtalar joint in the ankle and in the hip joint.
You can focus on tipping the feet or moving the knee or rotating the femur.
Of these my opinion is that tipping the feet is by far the best que, and rotating the femurs the worst. Moving the knee comes somewhere between.
How you move the femur is quite complex, you need to rotate it to flex the inside leg. You need to rotate it to counter. You need to rotate it to rotate the ski, you need to rotate it to hip angulate. How can you reliably separate the femur rotation that edges the ski from all these movements? Simple, focus on the foot tipping instead.
Focusing on femur rotation can easily lead to a passive ankle joint, which is very bad for balance and edge hold.
I do wonder about all the little wiggles in the colored lines.
Knee edging is movement of the knee laterally. Since the Knee cannot move that way the movement happens primarily in the subtalar joint in the ankle and in the hip joint.
You can focus on tipping the feet or moving the knee or rotating the femur.
Of these my opinion is that tipping the feet is by far the best que, and rotating the femurs the worst. Moving the knee comes somewhere between.
How you move the femur is quite complex, you need to rotate it to flex the inside leg. You need to rotate it to counter. You need to rotate it to rotate the ski, you need to rotate it to hip angulate. How can you reliably separate the femur rotation that edges the ski from all these movements? Simple, focus on the foot tipping instead.
Focusing on femur rotation can easily lead to a passive ankle joint, which is very bad for balance and edge hold.
Just to get the notion that femur rotation is the primary mechanism to edge the ski out of peoples heads. Here is a picture of what typically happens in a good SL type turn. @Zentune is right when he talked about de-edging the ski. That is the biggest movement of the knee angulation.
Off course you could angulate more with the knee, but the thing is that in general you don't want to in a high performance turn. The knee needs to be just inside the force line, otherwise the lateral bending moment in the knee would be anatomically bad. How do you find that amount? With proper aligned boots and foot tipping.
View attachment 37523
Doby Man said:[F]emur rotation is an active input for knee angulation and a passive output from the ski in an edge locked turn.
... because of the polygon of sustentation extended with the pole, he's not inclining ....
What fundamental movements would people here coach to produce a carved turn as opposed to steered turn?...
Knee edging is movement of the knee laterally. Since the Knee cannot move that way the movement happens primarily in the subtalar joint in the ankle and in the hip joint.
You can focus on tipping the feet or moving the knee or rotating the femur.
Of these my opinion is that tipping the feet is by far the best que, and rotating the femurs the worst. Moving the knee comes somewhere between.
How you move the femur is quite complex, you need to rotate it to flex the inside leg. You need to rotate it to counter. You need to rotate it to rotate the ski, you need to rotate it to hip angulate. How can you reliably separate the femur rotation that edges the ski from all these movements? Simple, focus on the foot tipping instead.
Focusing on femur rotation can easily lead to a passive ankle joint, which is very bad for balance and edge hold.
Just to get the notion that femur rotation is the primary mechanism to edge the ski out of peoples heads. Here is a picture of what typically happens in a good SL type turn. @Zentune is right when he talked about de-edging the ski. That is the biggest movement of the knee angulation.
Off course you could angulate more with the knee, but the thing is that in general you don't want to in a high performance turn. The knee needs to be just inside the force line, otherwise the lateral bending moment in the knee would be anatomically bad. How do you find that amount? With proper aligned boots and foot tipping.
View attachment 37523
Reid phD thesis is downloadable from here : https://brage.bibsys.no/xmlui/handle/11250/171325
In the image of the skier (action of the legs ), i would not call that knee angulation at all, it's flexing with femur rotation.View attachment 37534 I think that may illustrate an issue with Reid's measuring of knee angulation and his coordinate system. It's not what we commonly associate with it. He's measuring the offset between the knee and the hip. It maxes out at 5 degrees? Then the maximum is after the gate, finishing the turn/starting the new, but it's a negative value. So, the knee is now more to the outside of the turn than the hip, towards the new turn. Well, that would indicate femur rotation towards the new turn, no?
But, still trying to wrap my head around the coordinate system.
View attachment 37535
Reid Thesis. Measuring Definitions
View attachment 37536
Reid Thesis Knee Angulation
Note the large negative value. So, at transition, there's like -12 deg of knee angulation, yet at max in the turn there's less than 5deg positive.
View attachment 37541
I think most would consider that a lot of knee angulation. But, it's only about 5 degrees in the Reid measurement system. The most disappointing thing about the Reid phd thesis is there's no photos of the turns. All those digital images taken and we never get to see them? Odd. So, we can't compare his values with the images we are used to.
**If one gets anything out of this thread it should be where the actual anatomical hip is versus what people think of as "the hip".**
One interesting thing in Reid's images is a reminder of how inside the "hip" as it's commonly used the anatomical hip is. Commonly, it seems to be we think of the hips as very near the outside of the body. It's pretty far in. Shockingly far in when you see it marked on the speed suit of the skier.
View attachment 37551
Reid
The hip is at a large angle to the femur. It is not a ball merely at the end of the femur but extends medially, towards the inside of the body.
Hosptal for Special Surgery
https://www.hss.edu/conditions_femo...guide-to-hip-mobility-and-hip-arthroscopy.asp
https://bonesmart.org/hip/about-the-hip-joint/
View attachment 37550
Reid
These dots represent the measurement points for the hip. Look at the ones from the back and the front. Shockingly close together and far in from what we commonly refer to as "the hips".
Images taken from Reid phd thesis Appendices:
https://brage.bibsys.no/xmlui/handle/11250/171325
Originally posted by Jamt in the Inclination Angulation thread.
I don't think that is a lot more than 5 degrees, if even that. You have to consider that to see it properly you would have to imagine how it would look like if your point of view was straight in front of the ski, and in addition as you mention you'd have to compare it with a line going from the proper hip joint position and the ski.View attachment 37541
I think most would consider that a lot of knee angulation. But, it's only about 5 degrees in the Reid measurement system. The most disappointing thing about the Reid phd thesis is there's no photos of the turns. All those digital images taken and we never get to see them? Odd. So, we can't compare his values with the images we are used to.
**If one gets anything out of this thread it should be where the actual anatomical hip is versus what people think of as "the hip".**
One interesting thing in Reid's images is a reminder of how inside the "hip" as it's commonly used the anatomical hip is. Commonly, it seems to be we think of the hips as very near the outside of the body. It's pretty far in. Shockingly far in when you see it marked on the speed suit of the skier.
I think most would consider that a lot of knee angulation. But, it's only about 5 degrees in the Reid measurement system. The most disappointing thing about the Reid phd thesis is there's no photos of the turns. All those digital images taken and we never get to see them? Odd. So, we can't compare his values with the images we are used to.
I disagree with this advice. Edging is caused by rotating the femurs.
That picture is almost better than the real thing, because in the real thing you get different camera angles for the ski in every frame, whereas in this you always get a shot taken straight in front of the outside ski. Camera angles can really fool you into seeing things the wrong way.I agree that it would be very nice if they had included sample image series ala Lemaster or even video showing a typical 13m or 10m turn of the type quantified.
I disagree on the main focus being tipping the feet, because if given only this instruction students tend to do it by dumping the hips into the hill, with no rotation in the subtalar joint, so the the hip joints, knees, and feet remain in line.
It depends how you introduce it, those two tend to be completely opposite anyways (foot tipping and hip dumping). Most skiers hip dump because they can't tip.
Also, hip dumping is normally associated to extra-counter and delayed or non-existent tipping, so they wouldn't be square, because it's hard to dump the hips when you're square to the skis, the body is not that flexible laterally.
cheers
Exaclty, becauseIt depends how you introduce it, those two tend to be completely opposite anyways (foot tipping and hip dumping). Most skiers hip dump because they can't tip.
Also, hip dumping is normally associated to extra-counter and delayed or non-existent tipping, so they wouldn't be square, because it's hard to dump the hips when you're square to the skis, the body is not that flexible laterally.
cheers