Leg Motion in a Ski

6 years 2 months ago #21499 by robin.mousley
Replied by robin.mousley on topic Leg Motion in a Ski
I was focussing on this issue over the weekend and I came to the conclusion that I don't push against the footplate, I brace against it as I take the stroke. My knees go up and down naturally as I rotate.

I'm not saying that my technique is any good, just that I don't consciously thrust against the footplate - and it seems logical to me that it would be wasted energy to do so.

I remember being told by coaches not to worry about thrusting against the footplate. Just focus on rotation and the rest will come.

Rob

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6 years 2 months ago - 6 years 2 months ago #21500 by Watto
Replied by Watto on topic Leg Motion in a Ski
Yes, bracing it is. Into small river chop 15 knots on the nose tonight, not pushing, bracing. Good distinction.

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6 years 2 months ago - 6 years 2 months ago #21501 by Kocho
Replied by Kocho on topic Leg Motion in a Ski
I'm trying to visualize the following: imagine a bus driver turning the steering wheel with his arms. Busses have steering wheels that are quite horisontal, so to turn left, the driver needs to pull with the left hand and push with the right hand. He could do either or both at the same time.

Now, imagine that that bus does not have power steering (some of us remember cars with no power steering - we had to use both arms quite actively!). If he were to apply a significant force on the wheel, he would need to brace with his feet and butt against the bus - other wise he will rotate around the steering wheel instead of him rotating the steering wheel.

He needs to push with his left leg enough to counter the pull of his left arm. If he also pushes with his right arm, I think it would only make sense if he could also pull with his right leg to counter that arm's push. If he does not pull with his right leg, he is relying only on the push of his left leg, which means he cannot do that and remain centered - he will need to somehow counter the off-center forces that he is generating by unevenly bracing with his hands and arms.

If we say we can 100% counter the "pull" of the arm through the "push" of the same side leg, we are ignoring that the push-arm also needs something to counter its motion - having the push side leg pull would seem to be a natural way to do it.

On the bus, the steering wheel is symmetrical - you can pull as hard as you push if you like. On a paddle, the lever is not equal - the pull hand is the fulcrum point and the push hand needs to exert less effort than the push hand to counter the water's push.

Hope I'm making sense :)

Or try another exercise - standup with feet shoulder-widh apart and grab something big and heavy infront of you, like a big table. Try to rotate it conter-clockwise and observe what your legs are trying to do: the left one is pushing forward (towards the table), the right one is pulling back (away from the table). To exagerate the effect of your legs trying to rotate clocck-wise from underyou, step on an exercise disk that rotates or on a slippery area rug or put on some socks on a slippery floor (don't fall!). Next, repeat but now, deliberately try not to use your right leg - what happens? You may lose your balance and will have to lean away from your left leg towards and over your right leg to compensate. I think that's what folks who lean away from the paddle may be doing in a boat... What I can't tell for sure yet is if that leaning (e.g., pushing with one leg and *not* pulling with the other) is better than staying centered and pushing and pulling at the same time...

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6 years 2 months ago #21502 by Newbflat
Replied by Newbflat on topic Leg Motion in a Ski
This is topical for me as I just finished a clinic with the big O at the Wildside Relay in the Columbia river gorge, USA. He specifically told me you should be driving with your power side leg as hard as you can get away with but not pull with your other foot. I asked him why and he said your pulling the boat backwards negating much of your forward drive. Personally I don't think this is the case and don't think basic physics bare that out..... If you sit in a ski, don't use a paddle and drive with your leg as hard as you can your boat goes nowhere. Drive and pull with the other leg and it still goes nowhere. Paddle the ski to 10 kph, stop paddling and push or pull all you want and it's going to do nothing in terms of slowing you down quicker. You get zero actual energy or negative energy from pushing or pulling. But use a paddle and everything changes in terms of energy transfer to the boat but you can still pull all you want and it's not going to slow you down. Just like pulling on the handlebars on a bike doesn't slow you down ether. I thought about pointing this out to Oscar but life is fragile and I fear mine would have ended right then and there..... Such a humble man.

These 5 days in the gorge and clinics with The big O and Sean Rice did a lot for me. Mostly in the understanding how important the leg drive is. For the last few months I have been flat in any speed gains and have had this sense I can't get power down that I think I have and should be a bit faster than I am. This while paddling 5 days a week. Fast forward 5 days and I picked up .2-.3 kph and a feeling that I'm putting down more power mostly by using more muscles in my torso facilitated by much firmer leg drive.

Mostly I think my gains came from one sort of mental exercise. It was from Oscar and went something like ...." imagine on your left side there is 20 kilos with a handle on it on the ground next to your foot. How would you pick it up? Would you just bend over at the hip and pick it up with your arm putting a strain on your back and nearly pulling your self over, or would you bend at the knee, grab the handle, straiten your back and lift it driving with your leg and a straight arm and back.... This is how you should paddle, drive with your leg or there is nothing for your torso to pull / rotate against . The harder you pull the harder you need to drive"

I had been using what I thought was reasonable leg drive but when I really started to try and push hard after the clinic I realized I needed to move my foot plate closer a notch as my legs were bottoming out. Combine that with a little shorter stroke and some time working on the timing of the leg drive with stroke payed dividends. Nearly all of my gains I think came from the feeling that the better I time my foot drive and the harder I drive it the more muscles I engage in my back and can drive harder. Muscles I don't think were really engaging before or at least not in synch. There is a heart rate increase but my speed gains more than make up for it.

As for the pulling as well as driving with the leg, I pull a little but not much as it helps me rotate and seems to help my over all timing of the leg drive and helps me stay forward in the seat and resist driving myself back. When I do find myself self being driven back in the seat it's because my leg drive is out of time with the power phase of the stroke. They seem to cancel each other out if the timing is correct but the harder the stroke is the harder my leg drive needs to be. I don't buy the "pulling slows you down" line of thought from Oscar even if he sights a number of elite paddlers that don't use foot straps at all. You don't Need straps to get good drive but they help paddling hacks like me.

I'm not trying to suggest anything here other than talk about what really helped me over a long weekend. While much of this might be obvious to many of you, it was obvious to me as well. But just because you know something doesn't mean your doing it even when you think you are.... I gained more in a few days than months and months of paddling. I thought I was getting leg drive, but I wasn't really....... Technique, technique, technique.

Bill

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6 years 2 months ago #21504 by Kayaker Greg
Replied by Kayaker Greg on topic Leg Motion in a Ski
Some of the examples above are getting a bit out there and off the track with different dynamics and not really relevant in my opinion.

If you have ever been a decent MTB/BMX rider and pumped a bike around a pump track you will understand a little about weight transfer and creating power/speed without pedaling, you can get around a pump track without turning a pedal once under motion.

A better example for me is a decent skateboarder can pump his board using his weight and core/hip movement very subtlety to propel his board forward indefinitely without putting a foot on the ground or lifting a wheel(or foot), a beginner takes time to develop this skill. Pumping a board like this is very familiar in feel for me when paddling.

Lots of other sports probably use the same techniques, skiing comes to mind but I only have experience with the above two examples.
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6 years 2 months ago #21505 by Ric
Replied by Ric on topic Leg Motion in a Ski
Yes, Greg. I think a lot of us do the pumping to get onto a wave when downwinding.

I think that's a good analogy to get across what I was backing you up on.

Problem is I know Rob is faster then me downwind, and he seems to disagree with us... Darn!

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6 years 2 months ago - 6 years 2 months ago #21506 by Kocho
Replied by Kocho on topic Leg Motion in a Ski
Moving forward (or back) on skates or skateboard or surfing by zig-zagging relies on dynamic weight transfer and friction or buoyancy etc. counter forces. Very unlike pushing or pulling against the foot board on a ski, where the forces are fore-aft vs. sideways or up-down in the above examples.

The other poster is right: pushing or pulling the ski does not change materially what it does, until we get the paddle in the water. Without that paddle in the water, pushing or pulling the ski and expecting it to do something is like expecting something from nothing: there is no counter force external to the "system" that would transform our efforts into ski motion.

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6 years 2 months ago #21507 by Ric
Replied by Ric on topic Leg Motion in a Ski
But have you ever tried riding a skate board on a half pipe? There is no friction or side to side zig zag motion (if their was there would be instant wipeout). Its purely you against gravity, and it works... Just watch Tony Hawk.

By the same token, shifting weight forwards in the ski can help you get over the lip (or can help me at least) and is a very useful technique on downwinds.

At least in both cases, this has been my experience.
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6 years 2 months ago #21508 by Kocho
Replied by Kocho on topic Leg Motion in a Ski

Newbflat wrote: ... I had been using what I thought was reasonable leg drive but when I really started to try and push hard after the clinic I realized I needed to move my foot plate closer a notch as my legs were bottoming out...
Bill


Funny you should say that - I just moved back by a notch my footplate yesterday, as a result of experimenting with leg drive after reading this thread ;) Useful stuff, even though I'm still undecided on the "pull" part as my limited testing does not seem to be vey conclusive...

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6 years 2 months ago - 6 years 2 months ago #21509 by Kayaker Greg
Replied by Kayaker Greg on topic Leg Motion in a Ski
The external forces are the paddle in the water and the wall of water on the side of the ski opposite to the paddle side.

I notice that when I get onto the water everyday on my ski and run through my drills, before putting the paddle in the water, my ski always moves forward with my body movement.

I can move my seat with wheels that I'm sitting on right now with body movement, a child can move a swing, why is it so implausible to think we can't move a ski?

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6 years 2 months ago #21510 by Kocho
Replied by Kocho on topic Leg Motion in a Ski

Ric wrote: But have you ever tried riding a skate board on a half pipe? There is no friction or side to side zig zag motion (if their was there would be instant wipeout). Its purely you against gravity, and it works... Just watch Tony Hawk.

By the same token, shifting weight forwards in the ski can help you get over the lip (or can help me at least) and is a very useful technique on downwinds.

At least in both cases, this has been my experience.


There is a ton of friction on a half pipe. If there wasn't, your "pumping" action would result in a spectacular fail, with the tires of the bike sliding from under you sideways. Imagine doing that on slick ice with summer tires, that's what will happen.

Of course, assuming you do it absolutely perfectly and eliminate any sideways component (or zig-zagging) and somehow you push against the half pipe in such a way that no effort goes to waste sideways, you could do without friction. Yes. However, even kf you could do it (no one can be that perfect) in this case what propels you is the counter force that the half pipe exerts against you, combined with the pull down of gravity. Simple physics. Nothing like what we are talking about here pumping legs in forward paddling. Try it - sit in flat water and pump and see how far you go. Or sit on your skateboard and pus or pull against one of its ends forward or back - will you move???

As for going over the edge of a wave in a ski, that's entirely different from pumping on flat water: on the wave you shift your weight, using gravity, inertia, and rotational forces to trade your current position for one that is a foot or two away from it.

Also, you can push the ski past the finish line with a big lean back. Yes, you will gain a foot or two in forward motion, but as soon as you return to your upright position you will lose the same (or a bit less, assuming you managed to plane a bit over the line). You can't however do that effectively at each stroke when paddling forward on flat water over any reasonable distance - here, any forward momentum gained by pushing on one stroke will be lost on the next, and the net result will be zero speed difference but extra effort to do it.

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6 years 2 months ago #21511 by Kayaker Greg
Replied by Kayaker Greg on topic Leg Motion in a Ski
You and I will just have to disagree Kocho. I'm just going to start to cover old ground and I don't have the time. Thanks for the good discussion tho. :)

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6 years 2 months ago #21512 by Kocho
Replied by Kocho on topic Leg Motion in a Ski

Kayaker Greg wrote: The external forces are the paddle in the water and the wall of water on the side of the ski opposite to the paddle side.

I notice that when I get onto the water everyday on my ski and run through my drills, before putting the paddle in the water, my ski always moves forward with my body movement.

I can move my seat with wheels that I'm sitting on right now with body movement, a child can move a swing, why is it so implausible to think we can't move a ski?


We are talking different things here. What you describe relies on friction and some other principles. A swing moves because it is hung on the ceiling. A chair moves because the floor pushes back. Try to move through space in weightlessness without friction. E.g., swimming through space - can you do it?

I too can move my ski forward without a paddle or hand in the water. But not by pumping my legs only. What moves it in this case is similar to what let's you balance on one leg when you start falling and you wave your arms in a certain way. Do you not have a contact point? Afterall you are waving your arms in the air, right? Wrong - you push against the floor and transform the circular motion of your arms the right way against the resistance of gravity and friction.

Yes, you can use the "wall of water" concept, but that's similar to zig-zagging or squatting on a bike/skateboard over a half pipe or moguls.

Pumping legs fore and aft without a paddle in the water or waving your arms and torso can't move you forward, sorry.

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6 years 2 months ago #21513 by Kayaker Greg
Replied by Kayaker Greg on topic Leg Motion in a Ski
Can't move "you" forward. Not sure why my ski moves forward a good 20-30 metres during my warm up drills then (I do know why, its all in the hips). Like I said, we will just have to disagree.

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6 years 2 months ago - 6 years 2 months ago #21514 by Kocho
Replied by Kocho on topic Leg Motion in a Ski

Kayaker Greg wrote: Can't move "you" forward. Not sure why my ski moves forward a good 20-30 metres during my warm up drills then (I do know why, its all in the hips). Like I said, we will just have to disagree.


You move forward because you transfer the a special dynamic motion of your torso and arms through the leg and against the "wall of water". Yes, one can do that. No argument here.

I challenge you to move your ski forward if you sit in it perfectly upright, pump with your legs as usual, rotate in place, and don't swing your arms as if you are holding a paddle (just cross them in front of your chest). Try it on your wheeled chair if you are off the water now - sit backwards on it, legs on the base (not touching the floor) and push/pull the backrest with your arms. Don't lean back and forth, don't do funny motions with your head and arms, don't jump up and down, just pull/push and rotate with your torso. Tell me if it moves or just rotate.

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6 years 2 months ago - 6 years 2 months ago #21516 by Kayaker Greg
Replied by Kayaker Greg on topic Leg Motion in a Ski
Sorry, I don't see the point, that's not how I paddle. This is getting ridiculous. :pinch:

Paddling is a whole body exercise.
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6 years 2 months ago #21517 by Ric
Replied by Ric on topic Leg Motion in a Ski
I'm with Greg on this... will have to agree to disagree.

As long as we are all having fun on the water, right...

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6 years 2 months ago - 6 years 2 months ago #21519 by Kocho
Replied by Kocho on topic Leg Motion in a Ski
The only point I'm making is that leg drive (defined as fore/aft motion, pushing/pulling against the foot plate with your feet can't propel the ski forward, UNLESS you also do weight shifts. By the same token, just by pulling back on the foot strap will not move you backwards either.

One needs "something else" in addition to the push/pull/rotation motion to create forward movement.

We may as well be saying the same thing and I may have missed your point, but I understood your previous post as implying that you can move forward just by leg drive/rotation, which is impossible. Sorry if I misunderstood you.

If you share a video of how you move without a paddle, we should be able to tell what else you are doing, in addition to leg drive, that let's you move forward. My guess is that you are shifting your weight side-to-side and/or up-down and/or you are changing your balance fore-aft. That kind of added motion uses the dynamic interaction with the water to move you forward. Rotation/leg drive alone (without those extra motions) will not move you forward.

I can move the boat forward by shifting my weight forward and back and up and down in the right sequence. Or side to side. This creates a sort of brief "surfing" forward. The up-down/forward weight sift is like pumping a surf board up and down to move forward. The side to side weight shift is like zigzagging on a skateboard or on a surf to move forward.

Pumping up-down on a surf board, the surfer is not so much pushing forward with their feet, they are actually pushing down and to the rear. Yet, they move forward. So it is not the pushing forward that moves them forward - they are pushing backwards, if anything. What happens is that, because the board is at a downward angle when they push down and back relative to where they are, the board goes forward briefly, surfing down against the water behind it. They create their own wave, sort of. Then, the moment before the board would stop, they bend their knees, let the front of the board raise up (pushing rearwards and down with the rear leg and lifting up the front leg), then repeat the cycle - push down with the front leg to tilt the front of the board down, then push down and to the rear with both legs to propel themselves and the board forward. So, without pushing forward, they move forward. This example demonstrates that you can move forward without pushing forward with your legs, this showing that forward pushing with your legs is not what moves you forward when the paddle is not in the water.

Again, the only point I'm making is that, without a paddle in the water, and without shifting your weight, it is not possible to move forward.

Now, can a bit of a push forward at the right time help? Sure, but it only serves to transfer some other force to the ski (like the paddle in the water or the motion you created while shifting your weight). Pushing alone is not gonna move you forward. The explanation that Oscar and other give that "push forward = move forward" and "pull back = move back" is too simplistic and actually is wrong, unless the other things one is doing at the same time are explained as well.

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6 years 2 months ago - 6 years 2 months ago #21520 by Kocho
Replied by Kocho on topic Leg Motion in a Ski
And why am I "wasting" everyone's time with this? Because I hope it helps others figure out what's going on while paddling, separate fact from fiction, so they can try to feel it next time they are on the water ;)

You wouldn't believe how many people actually believe the hundreds of "free energy" (aka perpetual motion videos on YouTube). Folks that create them usually do it for laughs or just collect ad dollars from visits (very few are themselves so confused as to believe in the free energy experiments they are sharing). This thread was going in that direction a bit - folks apparently claiming they can move the ski forward by just kicking the foot board or experts advising novices that they will move back if they pull on the foot strap while sitting in the ski... So, the myth of free motion without an opposing force has to be dispelled :)

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6 years 2 months ago #21521 by Kayaker Greg
Replied by Kayaker Greg on topic Leg Motion in a Ski
I think you have been reading things that haven't been said, I also think we are getting closer to agreement. :laugh: We are talking about paddling, not just moving ones legs back and forward, not sure where you lost the plot. :P

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