• If I lift my back and shoulders during my leg-push, I get extra grip. 

  • Then I drop them forward onto my poles for stronger push.

but this second part makes sense only if I'm using the "offset" timing of my pole-push.

  • Raising my arm recovering forward during my leg-push, gives more extra grip.

Key points for this arm-raise move are to (a) allow the hand to first drop low as it passes by the leg; and (b) not finish the raising of the arm until just after the leg-push is finished.

  • Extra leg-push down-force is the more obvious way to get extra grip, but it has a key flaw:

It pushes the hip joint up, which then shortens the length of the effective driving contact of the leg-push down and back against the snow surface.

Perhaps the mental image of pushing down with the leg could still be helpful for many skiers --  to activate neural patterns that better engage the big leg muscles in the leg-push.  Just check with video that the hips are not actually starting to rise until the leg-push is complete.

  • Reducing grip down-force during leg-push can add propulsive work.

But actually elite racers often allow the hip to drop down a little during the leg-push, then raise it up during the passive glide phase (using the knee-extension muscles). This tends to reduce grip force some, but the falling of the weight of the upper body adds some propulsive work to the leg-push. Apparently the reduction in grip force is worth it because it's the main (or only?) way that the big knee-extension muscles (e.g. quadriceps) can be engaged to add propulsive work in classic striding.

  • Climbing up a steep hill is completely different.

The back and shoulders stay bent forward through the whole stroke.  The pole-push is mainly with the arm muscles, not assisted much by upper-body crunch or forward-fall.  The big muscles do push the hips up and raise the weight of the upper body during the leg-push.  (see Climbing Up a Steep Hill)

what's here 

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Who is it for? 

for advanced skiers 

If the timing of the pole-push is synchronized with the leg-push, then the shoulders are trying to go forward and down to assist the pole-push.  But the back-lift move is taking the shoulders up and back -- so then the back-lift is working against the pole-push (in synchronized pole timing).  Not a helpful combination to be practicing.

  • Must already have enough back-muscle strength and endurance available.

This back-lift move is not a free lunch -- it takes real muscular work.  So if your back isn't prepared for it (or if you have a previous back injury), there's no point in trying to learn it.  You can get long-term injuries to your back if you make it do things it's not ready for.

And even if you have the strength in your back to do it, you also need endurance.  Doing it ten or twenty times in your living room or the gym or in a ski lesson is one thing.  But if make it a normal part of your classic striding motion, you'll be doing it like 80 to 120 times per minute.  For half an hour of skiing, that's around 3000 repetitions.  Often the pain and severity of the over-use injury does not hit until the next day.  So work into gradually over several weeks and months -- like start with just a few minutes, then add a few minutes each time you ski.  And lay off if you notice any pains or problems.

This move is not essential to having fun in cross country skiing.  It's not worth taking a chance on long-term back pain or injury.

  • Skiers who have not yet learned offset pole timing, but who need extra grip right now, might need to use the "stomp" of the extra down-push with the leg to actually raise the hips and upper body -- and just accept the disadvantage of the shorter leg-stroke.

In this situation, it's better to use only arm muscles for the pole-push, and not use "crunch" in the abdomen and chest to assist it.  And plant the tip of the pole further back behind the boot.  Planting the pole next to the boot and crunching the upper body down on it works against the "stomp" to raise the hips.

for serious racers 

  • Anything that might shorten the range-of-motion of the leg-push is of concern to a serious racer.

Not that range-of-motion should never be shortened (see comments about climbing up a steep hill) -- but a serious racer wants to be able to make choices about it.  Raising the hip takes away a choice.  Using the back muscles instead to raise some body weight gives more freedom of choice to the leg muscles.

If you're not convinced, find some videos of elite racers on a gentle uphill in side-view and analyze it in slow-motion and single-frame advance.  Also find some videos of elite racers climbing up a steep hill, and notice the difference in the motion of the hip (and the difference in the back and shoulders).  Make sure it's World Cup winners in actual race footage (not politically-correct demonstration videos to prove somebody's coaching theory).  The Norwegian Ski Federation 1997 Trondheim videos are excellent for this.

  • Serious racers can train the strength and endurance of their back muscles for months in advance in their summer dryland training, and also in their other skiing motions, especially double-poling and kick-double-pole.

Work into this move gradually.  It's not worth taking a chance on long-term back pain or injury.  At least one elite racer had his career cut short by a back injury.

  • Mental images are different from objective physical reality.

Just because you use a mental image of (or have a feeling of) extra down-force beyond what is needed to support your body weight, does not mean you're really using too much of it (or even enough of it).

Physics says that if you're really pushing down more than enough, your hip joint will rise vertically before your leg-push finishes.  That's the true test -- but it's not one that you can do by yourself.

The mental image of pushing down with the leg is helpful for many skiers -- but for a different reason:  that image can activate neural patterns that better engage the big leg muscles in the leg-push.

  • Check yourself on video. 

You might be doing it just the way you want already -- serious racers often have good instincts working in their neural controllers.

This is straightforward to observe in video.  Get someone to video your classic striding motion on gentle terrain from a side-view.  Wear clothing that makes it easy to see exactly where your hip joint is.  Then analyze the video in slow-motion and single-frame-advance, and look for the video frame where you complete the final toe-push in your leg-push. 

Your hip joint not rise at all before that frame. The hip should either be dropping lower or staying at roughly the same vertical level, until that toe-push frame.  After that frame your hip joint should start to rise. If your hip rises before then, then you're losing some range-of-motion in your leg-push.

Compare your video with side-view videos of elite racers in actual World Cup races.

Get video of yourself also climbing up a steep hill -- and check that your hip is rising during the second half of your leg-push -- because Climbing Up a Steep Hill is Completely Different.

  • Elite racers often actually soften the down-push by the leg.

They allow the hip to drop lower during the later phase of the leg-push in order to increase the length of the effective driving contact of the foot pushing down and back against the snow -- which delivers more foreward-propulsion power -- provided the ski doesn't slip near the end of the stroke.

This hip-lowering aspect somewhat reduces the down-force for effective grip. Playing with different compromises of effective grip is the price of winning advantage at the elite-racing level of classic striding. If you just prefer to make sure you get the best grip, better to keep the hip joint roughly at the same vertical level through the whole leg-push.

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My story 

I learned the leg-push down-force method back when I was casual about technique.  When I got serious about technique, I noticed the back-lift move in videos, saw the reactive-force benefit, and started to practice it. 

But then I heard the narrator of a classic striding video criticize too much vertical movement in the upper body.  And then I got into the idea of smoothing out my leg-push, to try to fight against the explosiveness of striding.  During 2001-2003 my goal was to find and practice an alternative to the "stomp" and glide style, to rely only on committed transfer of body weight to press down on the grip zone.  I analyzed and described some problems with the extra-leg-push down-force approach -- but I somehow forgot to consider the alternative of the back-lift move.  So I stopped paying attention to back-lift in my striding, but I was happy with my results in both racing and touring.

During 2003, I kept hearing about the importance of extra-leg-push down-force, and was starting to suspect it had some value that I had been missing out on.  So I looked at videos again and analyzed the physics -- and that's when I saw the bigger problem with it, that it shortens the leg-stroke.

But in the same videos I again saw the back-lift -- and that this move avoids the big problem of the leg-push method.  So this time I decided to keep it.

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How to do it

[ to be added ]


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How it improves grip

Reactive force.  Newton's Third Law:  Every action has an equal and opposite reaction.

The action force needed to raise the weight of the skier's shoulders and head upward must necessarily produce a reactive force downward through the leg and foot into the ski.  This extra downward force presses the ski more into the snow, and that makes it grip better.

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Leg-push down-force?

What's the difference?

What makes the back-lift and arm-raise moves better is:

  • The back-lift and arm-raise moves do not raise the hip joint, so they do not shorten the range-of-motion of the leg-push.

  • They do not move the weight of any body part any higher than where there is clear payback into forward-motion power.

Payback in the forward fall of the weight of the head+shoulder+chest onto the pole-push.  It's less clear how to get full payback from the elevation of the weight of the entire body, like when extra-leg-push down-force is used in hill-bounding.

  • The turnover frequency of the back-lift and arm-raise moves is more controllable, because both the upward lift and the downward crunch motion can be driven by muscles.

Once the weight of the most of the body is air-borne, there's no way to make it come back down again any faster than gravity works -- so extra-leg-push down-force can reduce the total average power rate by introducing a "dead spot" time gap, which reduces turnover frequency.

Why back-lift does not work on steep hills

  • Back-lift does not deliver enough extra grip to keep from slipping 

  • Big extra-leg-push down-force is the only way to get enough grip, and that leads into hill bounding technique  

  • The pole-push timing becomes less offset, more synchronized with leg-push in hill bounding technique. 

  • Back-lift does not fit as well with synchronized pole-push timing and hill bounding. 

  • Vertically raising the weight of the skier's body is a big part of the power expenditure in climbing up a steep hill.  Substantial use of back-lift moves -- together with crunching it down in between -- could result in raising the weight of the shoulders and head through the same range of vertical motion twice.  Usually that's inefficient in the physics, so optimal climbing technique usually tries to avoid most double-lifting of the same body parts.

Therefore, when bounding up a steep hill, it's usually better to

  • keep the back, abdominal, chest, neck muscles quiet in that situation, and use only the arms to help the legs.

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more . . . 

  • But climbing up a steep hill is different. 

The back-lift move tends to get in the way of climbing up a steep hill -- usually it's better to keep the back, abdominal, chest, neck muscles quiet in that situation, and use only the arms to help the legs.

Up a steep hill, the additional grip from this back-lift move is usually not enough to keep from slipping back, so most of us switch to herringbone. But strong racers can switch to hill-bounding strides, which make big use of extra leg-push down-force.  See Climbing Up a Steep Hill

see also

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