Has anyone been learning/trying the "double push" technique on xc skis? I'm a sports med physician and only learned about it after coming across a few articles in some sports med journals. Since then I've been trying to find stuff on line about it. I haven't been able to see much world cup skiing this year but I'm going to be interested to watch the Olympics and see if any of the elite skiers are using it. I've tried to play with it a bit on snow but have mostly fallen my butt doing it. Ordinarily I'd be pretty skeptical except for the fact that a few scientific articles are touting increase speed especially at sprint distance.
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skate double push technique
(17 posts)-
Posted 2 years ago #
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for lots more info, look it up in reference to inline skating. they/we have been doing it for years. I have found it really only works for me at higher speeds where you are much more dynamic and explosive. you can not easily do it without having lots of body movement( as in skiing slow)
Posted 2 years ago # -
I'm not entirely sure what you are talking about, but i'm guessing your talking about the V2. check out this video and tell me if its what you're thinking about
http://www.youtube.com/watch?v=DS0cTEi4M7oor you might be talking about the V2 alternate
http://www.youtube.com/watch?v=eKhjtRepR_U&feature=relatedBoth are very common techniques. If you are talking about something else maybe you could post a link to the journal articles that describe it.
Posted 2 years ago # -
No, they aren't talking about standard skating techniques. This is another "alternate style" topic. I've seen people talking about this technique before, it involves a double push-off on each ski, something like what you can do on inline skates where you get a push off the outside edge and the inside edge. I'm not sure if it works, and I really doubt any World Cup skiers are using it. But at least its more legitimate than the Cat-1...
Posted 2 years ago # -
Another reason for the established elite skiers and posters to hate me.
I've read all I could find on this, and managed to do true double push on the extemely heavy Crosskates.
On Rollerskis, I've seen footage of racers performing it just like it were inline skating, just a bit more subtle. Rollerskis of course are so fast, that speed moves can be done more easily. DoPu requires swerving, and speed assists in getting some frequency into swerves.
On XC skis, Ken Roberts http://nordicskiracer.smugmug.com/gallery/2700429#143054756 was the first I am aware of to show it on camera. Recently, a Youtube video surfaced of a (Swedish?) skier who apparently find a speed edge when sprinting in DoPu.
On inlines, the skates can be landed pointing "inward", and then roll (be jerked into) a turn to skate outward. The leg uses each aim for propulsion.
On skis, at least as constructed today, this aim switch requires the ski to be taken of the snow. A little leap is needed. The often discussed swing weight of the ski finally gets a real-world appearance. In regular skating, IMHO, it barely exists, or is a result of inefficient push-off or binding response.On Youtube, http://www.youtube.com/watch?v=76vvqEqOIbE , it seems the aim switch isn't even complete. Ken Roberts showed the aim switch more complete on his first attempts.
BUt, apparently the ski which it landed dead stright on, as seen in WC starts V2 sprinting, CAN be used for propulsion by letting the center of mass be pushed a bit to the side and back.I failed to try DoPu when I was on snow a week ago. I bet it's not easy, for anyone, let alone get an advantage out of it.
To fuel the hate some more, I have been working on ski design specific to allowing DoPu cruising, while still allowing regular skating. A leading ski company showed interest, but we didn't really persue it further. Who knows, the increasing interest might change this. My design, if it works, would do away with the aim switch leap, making it more like inline skating.
When I performed DoPu on heavy big wheel skates, it felt like a smooth slalom. On those skates, it wasn't a speed gain, as much as being a very efficient cruise mode. Lots of meters, at a low effort.Posted 2 years ago # -
Yes, a version of this technique is used for sprinting. I know that it is taught be high level coaches and i've used it successfully in sprints. It is not however used for distance because it is very taxing aerobically.
The idea behind it is to maximize your forward glide without so much side to side motion. Once you've gotten up to speed, plant you gliding ski straight down the track, and after a little bit, hop up and move your ski so you can push off.
At 9 seconds into this video, Simi Hamilton demonstrates nearly perfectly what i'm talking about
http://www.youtube.com/watch?v=Q0y_PdOtiWAThe result of this technique is a more direct path down the trail, and the landing from the hop will load the leg, providing a more powerful kick.
The problem with this technique is that it can only be used on the flats and at a high speed. The speed gain is minimal, so it is not even worth it to use in any races but sprints where every tenth counts.
Thanks avpiv711 for bringing this up, could you perhaps post a link to the articles that reference this. They would be very interesting to read.
Cloxxki-
I can't hate you for trying to make a new ski, but i do because you mascaraed as a very knowledgeable skier when, by your own admission you aren't. Oh, and your ski. You're making a ski that only elite racers could use on 1/10th of the course- good luck!Posted 2 years ago # -
The hop skate is pretty standard. In fact, its not limited to just elite skiers. In some sprint and interval workouts I've done with teammates as young as 13-14, we work on that little hop in the v2 and v2 alternate. Even if it doesn't help you build a lot of speed unless you are an elite skier, it forces you to work on a quick explosive movement.
Also, Cloxxki-are youtube comments really the place to peddle the product of your engineering prowess?
Posted 2 years ago # -
Best video I know of double-push on snow is
http://www.youtube.com/watch?v=76vvqEqOIbEA key reason that double-push is more powerful than normal V2 or V2 Alternate in some sprinting situations is because it _increases_ sideways weight-shift (by the extra inward push thru the outside edge) which then gets converted into increased forward propulsion in the next outward push (thru the inside edge of the same ski).
As far as I can tell that Whistler USST rollerski Youtube video at time 0:08 is _not_ showing double-push -- because there's no pushing inward thru the outside edge, and no increase in sideways weight-shift. (But I remember Andy Newell in a Lake Placid rollerski training video from last fall showing off real d-p in a starting sprint)
Perhaps an early use of "half" d-p (= V2A with both outside-edge + inside-edge push by the same leg on one side only) was Bjorn Lind at Torino 2006, like for a few strokes in his starting sprint in gold-medal sprint final.
Origins: My suspicion is that Euro rollerski racers borrowed d-p from inline-skate racers. Then after d-p demonstrated success in rollerski races, people got the idea of seeing how to make it effective on snow. Perhaps the Swedish team was ahead in this, but before anyone talked publicly (me in 2005) about d-p on English-language forums, I heard that some Canadian ski racers were already working on transferring d-p to snow.
Perhaps it also helps to see a good video of double-push in it's original "pure" form on inline skates:
http://www.youtube.com/watch?v=QmFZxNEuJH8Ken
Posted 2 years ago # -
I'm really curious whether those studies avpiv711 mentioned were done with regard to skiing or rollerskating/rollerskiing. From watching that last video, it seems like this technique is very efficient on rollerblades, where the running surface is rounded and the skate can be rolled over from one side to the other with minimal effort. It seems to me that on skis, the transition requires a rather large vertical jump, thereby wasting a lot of energy that would be better spent on kicking outward explosively. Then again, maybe that's why I'm a terrible sprinter.
Posted 2 years ago # -
Actually the energy put into the vertical hop is not much "wasted" if you then put its landing impact directly into your double pole push. Any more than doing jump double poling in a Classic sprint is wasted.
(The extra muscular energy into lifting off the ground builds extra "potential" energy, and when you land the weight onto the poles (if you have strong arm muscles to transmit it effectively) that potential energy is converted into extra kinetic energy of forward propulsion. You put more in, but you also get more out.)
The bigger problem is that making the hop (to switch from outside to inside edge) is an explosive or "plyometric" use of the leg muscles. Explosive moves normally engage lots of "fast glycolytive" FG type muscle fibers. FG fibers normally can only fire a few times before they need to rest and "recharge" for a long time (before they can fire effectively again). Therefore it's not sustainable, so it only helps in short sprints.
d-p on inline skates, because there's no explosive hop needed, can be done with smoother muscle motions, thus with "slow oxidative" SO type muscle fibers. SO fibers when operated at an overall power output level in the aerobic range, can keep firing effectively for a long time. Indeed in inline skate racing, d-p is the main technique of elite marathoners (and not often seen in sprints).
So we get the odd result that d-p was borrowed from inline racing, but its appropriate race situations are completely different on skis.
Ken
(P.S. If you're having trouble with sprinting, maybe you just don't have a high percentage of Fast Glycolytive muscle fibers.
Or maybe you're trying too hard to be smooth and efficient. Lower speeds are generally more efficient than higher speeds. A race car burns more gas than a Honda Civic. Efficient skiing might be a good way to reduce the amount of money you spend on food, but it's not how to win sprints.)Posted 2 years ago # -
Here's are the two abstracts in the medical literature. I can try and get the article as a PDF but I'm not sure how to get it on here where people can read it. Interestingly, this article endorses it's use on an uphill but a short uphill (60 M). They don't really look at energy cost from what I can see
Med Sci Sports Exerc. 2010 Jan;42(1):187-96.
Double-push skating versus V2 and V1 skating on uphill terrain in cross-country skiing.
Stöggl T, Kampel W, Müller E, Lindinger S.Department of Sport Science and Kinesiology, University of Salzburg, Salzburg, Austria. thomas.stoeggl@sbg.ac.at
PURPOSE: The aims of the study were a) to compare the double-push skating technique with the V2 and the V1 skating techniques on an uphill terrain by a kinematic and kinetic analysis, b) to provide kinetic and kinematic data of the V1 technique at maximal skiing speeds, and c) to test the hypotheses that the double-push skating technique is faster compared with the V2 and the V1 skating techniques. METHODS: Six elite skiers performed maximum speed sprints over a 60-m uphill section (7 degrees -10 degrees) using the double-push, the V2, and the V1 techniques. Pole and plantar forces and cycle characteristics were analyzed. RESULTS: The double-push skating technique was approximately 4.3% faster (P < 0.05) compared with the V2 skating technique and equally fast compared with the V1 skating technique. The double-push and the V2 techniques demonstrated longer cycle lengths, lower cycle rates (both P < 0.05), and equal poling frequencies and pole forces compared with the V1 technique. Cycle length, peak foot force, and knee extension ranges of motion and velocities were higher in the double-push technique compared with the V2 technique (all P values <0.05). Center of pressure was located more laterally in the double-push technique compared with the other two techniques (P < 0.05). All measured skiing speeds were drastically higher compared with former studies. CONCLUSION: The higher skiing speeds of the V1 and the double-push techniques compared with the V2 technique stress the mechanical advantage of those techniques on uphill terrain. Because of larger cycle lengths, lower cycle rate, longer recovery times, and equal poling frequency, the double-push technique might be seen as more economic on steep uphills compared with the V1 technique. From a tactical point of view compared with the V1 technique, the double-push technique needs less space due to less lateral displacement, and no technique transitions are necessary when entering and leaving an uphill section.J Sports Sci. 2008 Sep;26(11):1225-33.
Biomechanical comparison of the double-push technique and the conventional skate skiing technique in cross-country sprint skiing.
Stöggl T, Müller E, Lindinger S.Department of Sport Science and Kinesiology, University of Salzburg, Salzburg, Austria. thomas.stoeggl@sbg.ac.at
The aims of the study were to: (1) adapt the "double-push" technique from inline skating to cross-country skiing; (2) compare this new skiing technique with the conventional skate skiing cross-country technique; and (3) test the hypothesis that the double-push technique improves skiing speed in a short sprint. 13 elite skiers performed maximum-speed sprints over 100 m using the double-push skate skiing technique and using the conventional "V2" skate skiing technique. Pole and plantar forces, knee angle, cycle characteristics, and electromyography of nine lower body muscles were analysed. We found that the double-push technique could be successfully transferred to cross-country skiing, and that this new technique is faster than the conventional skate skiing technique. The double-push technique was 2.9 +/- 2.2% faster (P < 0.001), which corresponds to a time advantage of 0.41 +/- 0.31 s over 100 m. The double-push technique had a longer cycle length and a lower cycle rate, and it was characterized by higher muscle activity, higher knee extension amplitudes and velocities, and higher peak foot forces, especially in the first phase of the push-off. Also, the foot was more loaded laterally in the double-push technique than in the conventional skate skiing technique.Posted 2 years ago # -
BTW, the first study was done on xc skis.
Posted 2 years ago # -
Thanks to avpiv711 -- those abstracts are helpful and interesting.
Somehow I never thought of using d-p up a steep hill -- but it makes it easier to measure and analyze, because the skiers' forward speed doesn't change much, and they can maintain the technique longer because they don't accelerate to "cruising" speed.
quote from abstract 1:
"peak foot force ... higher in the double-push technique ..."
I think that supports the point about greater engagement of Fast Glycolytive muscle fibers.quote from abstract 2:
"the foot was more loaded laterally in the double-push technique"
I think that supports the point that d-p adds more sideways-weight-shift energy.quote from abstract 1:
"knee extension ranges of motion and velocities were higher in the double-push ..."
I hadn't thought about that before, but I think the outward push by the previous leg and the inward push by the next leg overlap in time. So the new inward push helps the mass of the upper body (and attached hip joint) move away from the foot making previous outward push, and foot making outward push can continue pushing outward -- so the hip and foot end up farther apart, which by geometry implies larger range-of-motion for extension of the knee joint.avpiv711 wrote:
"They don't really look at energy cost from what I can see."I think measuring the energy (measured in Joules) or rate of energy (= Power measured in Watts) of skiing out on snow is kind of tricky.
For aerobic performance, a possible way to approximate it is by measure oxygen uptake (for energy) or rate of uptake (for power). But since this performance is anaerobic, that method doesn't help much.
For skiing on the flat, the major propulsive uses of energy are to overcome air resistance and gliding friction -- but it's hard to estimate what the forces of air resistance and friction are.
Another advantage of analyzing skating up a steep hill is that the main propulsive use of energy is to overcome gravity -- and it's pretty easy to know the force of gravity.
Roughly, the total propulsive energy (in Joules) used to climb a steep hill is proportional to the height of the hill. So all the skate techniques in abstract 1 (from 2010) applied roughly the same total propulsive energy for that performance.Power (in Watts) is roughly proportional to the rate of climbing. So if d-p technique got to the top of the hill 3% faster, then it was applying about 3% higher rate of propulsive Power.
Ken
Posted 2 years ago # -
KenR,
Great points. I've actually been dreaming of building some kind of ski with a sensor to measure the force/power transmitted through the ski but don't even have anything close to any concept of how it would really work.As the majority of masters skiers focus on longer races, it would be interesting to recreate these studies over a longer distance (1-2K) but have skiers ski below or near their threshold and look at their speed (or have them try to ski the same speed for each technique and see what their oxygen consumption is as a percentage of their VO2 Max). Hmm, I have access to a portable VO2 Max machine....
Posted 2 years ago # -
I think skis with some sort of force sensors have been used by some researchers (even American) since at least the 1990s.
Power (in Watts) is a trickier concept than Force (in Newtons): You can't really measure Power directly with a sensor on the skis.VO2 uptake comparison studies for different XC ski techniques are at least as old as the 1990s. Might be hard to find the results if they were before electronic publishing on the web.
Perhaps try Stephen Seiler's website for some clues -- he once had a paragraph summarizing some older results.
I vaguely recall that pure classic double poling had the highest speed output per unit of oxygen uptake.- (But even if it's true that pure classic Double Poling is more "efficient" in terms of speed per VO2 uptake than V2 skate, skiers who want a podium finish in a freestyle race are going to use V2.)
Ken
Posted 1 year ago # -
If I were intending to offend or mislead people, I would do so much better.
Also, I've posted sicker designs that others brought into reality (be it in cycling) with surprising results.My main aim would not be the last 10s of sprinting, but the V2-alt range, which is where most casual skaters spend their time anyway. Getting the double push without a hop, and just be all fluent and gracious. Imagine the inline skater morphed with a V2-alt skier. Once you've done it, you know it's beautiful. Downside is the mid-aim repositioning of the ski, although it's part of a slalom-like swing/stride.
I'll just clarify that I don't look to make money, just hope to one day have (share) a pair of skis as I envision, if only just to try it. It's not so complicated a design. Just an extreme outside sidecut similar to alpine skis for a natural turn during the initial gliding phase. Yes, the ski would be wider and thus automatically useless for some minds, and surely sub-standard or slow for straightline gliding. However, if you use it for DoPu specific cruising, you're nearly always on one edge or the other anyway. Staightline gliding, it would be slower. And it's not even sure the aim switch will work at all. No-one will know for sure until it's tried, and tried some more. On really hard snow, a (much) shorter ski with additional less width might make it happen. We'll not know for a few more decades most likely, unless someone is crazier than me and makes those skis, or something smarter.
Posted 1 year ago # -
But that would only be useful on a very flat course where you could cruise like that the whole time. Very little of cross-country skiing is done on dead flat. Most trails, at least the ones worth skiing, are mostly up and down, with some flats. Therefore, the ski would be almost useless, as it would slow you down more on uphills and downhills than it would help you in the flats.
Posted 1 year ago #
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