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see also 

 - - back to main Climbing Up a Steep Hill "secret" page 

 - - motion technique pages:  hill bound - herringbone 

 - - Learning program page 

 - - Is more glide good? 
 - - Double cost of extra down-force 
 - - more "Secrets"  

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Why is steep uphill so different? 

  • Since the skier's velocity is slower, the big leg muscles can be used more effectively. 

The big problem of classic stride is that the ski and the skier's foot must be in static contact with the snow surface while the skier's leg is pushing.  The distance over which a single leg-stroke can maintain ground contact and apply significant forward-push force is limited by the geometry of the skier's leg joints.  

Therefore at high speed on gentle terrain, the time duration of the leg-push becomes very short (around 0.1 second).  This implies that the intensity of the force much be large, in order to deliver significant power through that short moment.  Also this intensity must be delivered at high velocity.  This combination of high force intensity and velocity is "explosive" -- like "plyometric" exercises -- and it puts more stress on the leg muscles than would a longer or smoother leg-push. 

Therefore the leg muscles are not as effective at the high velocities attained by racers on flat terrain.  Since the distance of ground contact for the pole-push motion is much larger than for leg-push, elite racers rely mostly on their pole-push muscles on flat terrain.  This also helps them "save" the big leg muscles for the steep hills where they are most needed. 

  • It is good to increase leg-push cadence (or "turnover"), because the more times per minute the strongest muscles push with effective leverage in the strongest sub-range of their motion, the more power is delivered. 
  • Since the velocity is lower and the cadence is higher, the glide phase can be minimized. 

See the discussion how the combination of high velocity and low cadence makes a glide phase necessary, on the "Is more glide good" page

  • Applying extra down-force now helps -- because when the glide phase is minimized (and the leg-push is initiated as soon as the new ski lands), then the double-cost of extra down-force is rewarded with a double benefit of both "launch" down-force and "landing" down-force. 

See the discussion on the Double Cost of Extra Down-Force page.  The key difference is that in classic stride on gentle terrain the "landing" down-force hits in the glide phase -- but with hill bound the "landing" down-force hits in the leg-push phase. 

  • The extra grip from the extra down-force is often required -- to avoid slipping back down the steep slope. 

And the extra down-force resulting extra grip is also needed to mitigate the side-effects of some of the other changes in motions:  (a) synchronized pole timing; (b) lack of complete side-to-side weight transfer. 

Some instructors say to "straighten up", not bend forward 

One of the ideas on my main hill-climbing page is to "bend forward strongly".  

But some instructors say just the opposite:  Straighten up more as the hill gets steeper. 

Actually I believe that opposite advice works better for some people on hills -- which shows how complicated classic striding technique can get.  My guess is that what's behind this advice is an over-simplified "quasi-static" analysis of the basic physics.  The over-simplified analysis says that the only way to sustain the maximum down-force through the grip zone is to keep the skier's body's center of mass centered closely over the center of the grip zone.  Therefore they advise taking smaller steps with a straighter body. 

What a more dynamic analysis of the basic physics says is that I can temporarily allow my center-of-mass to fall behind the grip zone of the new leg-push ski -- provided that I use other dynamic tricks as described above.  Making this dynamic physics work requires that the skier has several things: 

  • knowledge of the "press the toe" trick
  • enough calf-muscle power to use that trick
  • enough pole-power to push the body up forward again
  • dynamic balance to coordinate it all

Elite racers have all of those, and so did I back when I was figuring out what really worked. 

But skiers who do not have at least three out of four of those may indeed find that the "straighten up" advice works better than the "bend forward strongly from the hips" idea. 

What is the slope grade number that divides between "steep" and "gentle"?

This depends on the skier and snow conditions: 

  • skier's velocity at different slope grades 
  • skier's leg-push cadence and force  
  • "effective static friction coefficient" for this wax on this ski with this skier's level of technique. 

Two key physics criteria for selecting hill bound over normal classic stride are: 

  • the slope grade at which this skier's velocity and cadence are such that the glide phase can be minimized to the point where most of the "landing" down-force now falls into the leg-push phase. 
  • the slope grade where the "effective static friction coefficient" of the grip can no longer hold against slipping back unless extra down-force is applied beyond skier's body-weight. 

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More . . . 

  • Getting the next leg-push ski air-borne together with my body sometimes goes naturally with applying large extra down-force to increase my grip -- but it is not necessary in order to get the extra benefit. 

If a large enough extra down-force is applied, then the reactive force can launch my body up into the air. I've seen videos of elite racers (and of myself) with both skis up in the air simultaneously.  But going air-borne is not necessary for this technique. 

Although I call this steep uphill technique "hill bound", there does not have to be a literal "bound" into the air.  What's important is not whether I get the next kick-ski into the air.  The important thing is to get the rhythm of the non-leg-push time gap matched with my body's upward-downward momentum, so that I get the double benefit in improved grip -- due to both the "landing" down-force and then the "launch" down-force fall during the time-period of the kick (rather than the "landing" down-force falling during the time-period of the glide, when it does no good -- see double cost of extra down-force).  

The weight of the ski is so small compared to my total body weight, that whether the ski slides on the snow or gets into the air a bit makes little difference to the desired result. 

because extra down-force is now available from up-and-down motion of the upper body; and because there is no benefit in getting into balance over a flat ski. 

Since complete side-to-side weight transfer has an energy cost, it is good to cut back on as much of it as is not needed. 

This is not the same as no weight transfer.  It just means that for going up a steep hill, side-to-side weight transfer is only one grip-enhancement trick among several available.  These other tricks are live options here because up a steep hill they no longer have the penalties associated with them on gentle terrain.  So I trade off the special costs and benefits of weight transfer against those of other grip-enhancement techniques -- and shift the "blend" as snow and slope and bodily conditions change. 

  • No benefit in getting into balance over a flat ski

because there is no glide phase.

Because focusing down-force to the snow through the small area of the edge of the ski deforms the snow surface, which increases grip friction -- friction is critical for not slipping back on a steep slope.  When the snow surface is harder, it is more difficult to deform it -- so it takes stronger edge pressure to achieve the same improvement in grip friction. 

This is one of the key physics principles behind herringbone, but it can also be used as another little grip-enhancement trick for hill bound (and for classic stride). 

  • Moving over outside the groomed set tracks for striding can give better grip sometimes. 

On some days the parallel tracks get "glazed" from previous skiers, while the snow outside is "fresher", so it can more easily attach to to the wax on your skis, especially if you land your ski into it with extra force and press into the snow.  So if the groomed set tracks aren't working so well for you, try stepping over into some snow with a different history.

see also 

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