what's here

• Strategies

• Specifics : Leg push | leg Recovery | Pole push | Forward fall

back to Top | more Ideas | Secrets | FAQ | Resources | more Classic

Strategies

Climbing skins are usually used with heavier skis and boots -- so there's more overhead to making each stride -- so it makes sense to take fewer strides per minute and get more out of each stride.

There's usually no problem getting good grip with climbing skins on moderate terrain unless its rather icy.

Usually don't get much glide, but when possible it helps to exploit it.

Specifics

Leg push

• can make the stride longer by stepping the foot further out in front -- get the ankle joint in front of the hip joint, even in front of the knee joint.

Skiers can sometimes get away with stepping the foot out further forward, because can use the pole-push to help the rest of the body catch up -- if the snow is dense and firm. But not if the snow is light and fluffy, so might not step so far forward in that situation.

• can also extend the stride further forward by advancing the next hip forward, ahead of the hip of the leg that is finishing the previous leg-push -- [ see more ]

• can also extend the stride further backward by pushing off with the toe at the end of the leg-push

Leg recovery

In some situations, the move of recovering the leg forward can itself add some power.

• If can get some glide with climbing skins, it adds power to drive the leg forward with maximum speed, and land the next foot out in front of the previous foot.

This adds power because accelerating the mass of the ski and foot and lower leg forward applies a backward force to the snow -- which helps push the skier's total body mass forward -- which adds propulsive work.

When the mass of the ski and foot and lower leg decelerates, there is a forward force against the snow -- which subtracts propulsive work. But since the friction of the ski and climbing skin against the snow is less when it is gliding forward, the propulsive work subtracted in deceleration of the leg-recovery move is less than propulsive work added -- so there is a net positive propulsive work added to help the skier move forward faster and farther.

The amount of this added propulsive work is roughly proportional to the velocity of the forward leg-recovery move just after the other leg comes off the ground at the end of its push.

So it helps to make the leg-recovery move quicker in the situation where there's some glide -- by holing it back a little, then doing it fast.

• In situations where there's no glide, there's no propulsive benefit to making the leg-recovery move quicker.

That's because if there's no glide, then the friction between the climbing skin and snow during the acceleration and the deceleration phases of the leg-recovery move is the same, the positive and negative propulsive work transmitted to the snow exactly cancel.

The other trick for arranging for the positive and negative work not to cancel each other out, would be to hop into the air a little in between the finish of one leg-push and the start of the next one. But if the skier had enough power capacity to repeat that for a significant duration of time, then the skier could get a little glide with each stroke.

Pole push

Pole-push doesn't help much in light soft snow, but in firm or dense snow it can add some significant propulsive push.

• can add a little more to pole-push by rotating the shoulders toward the pole-push side.

So the rotation of the shoulders helping the pole-push is opposite to rotation of the hips helping the leg-push. Which feels strange, and uses unexpected muscles in the abdomen. But it can add power as those unexpected muscles get developed through regular practice.

• ? Use upper-abdominal "chest crunch down" to add force to pole-push ?

Question perhaps a bit tricky.

While upper-abdominal "chest crunch down" can add force and power to a double-pole push -- I doubt the adding it to the stroke-cycle is going to add significant net overall propulsive work when striding with skins. Because the upper-abdomen + chest must get "un-crunched" upward before they can crunch down again. If the pole-push is continuing during this "un-crunch" recovery move, then propulsive work is subtracted from the pole-push -- which offsets most or all of the positive from the crunch.

They only way to get the positive without the negative is to end the pole-push before the finish of the un-crunch. This can be effective at high speeds with lots of glide (like on waxed racing skis with no skins on gentle terrain), because then the distance per stride is larger that the distance the pole can push through, so there's no choice but for the pole-push to end before the start of the next one -- so if the un-crunch is made during this time gap, it does not subtract much (or any) propulsive work.

But with skins there skier's forward speed is slower, there is usually little or no glide. Since the poles can usually push effectively through a longer distance than the leg-push, cutting short the pole-push to make an "un-crunch" move would reduce the distance through which the pole-push can contribute propulsive work. Better to simply finish the pole-push, in which case the "un-crunch" move will reduce its force -- but that's better than no force at all.

But if you're planning to "fall forward" with the torso and head anyway for other reasons, then Yes there is propulsive benefit to adding some muscular "crunch" to the fall -- and to making sure the shoulders and arms stay firm to transmit that force through the poles to the ground (instead of collapsing and absorbing the force)

Forward fall of torso + shoulders + head

Many skiers "fall forward" with their torso + shoulders as they are setting down the next ski. Does this help propulsion? Or is it just extra up-and-down motion that wastes energy?  "forward fall" versus "quiet upper body"?

?? not sure on this one -- here's some thoughts:

• With no poles, I think "forward fall" does not help, because it puts the hip joint further behind the ankle, a configuration where the leg-push is less powerful. Presumably the same point applies to deep fluffy snow, where the poles cannot help push anyway.

• With poles on firm snow, putting the hip joint behind the ankle-joint is not such a problem, because the poles can help the leg muscles bring them up forward again. So it can add length to the stride a helpful way.

• On gentle terrain, bringing the shoulders closer to the ground helps aim the pole-push more backward, so a higher percentage of its force goes into forward propulsion.

• On steep terrain, lowering the mass of the torso at the same time the leg is pushing up the hill, takes some load off the big leg muscles -- in situations where peak-force-intensity could put too much stress on those muscles. Then the mass of the torso is lifted vertically by help from the arms and back muscles, during the first phase of the pole-push when the push is aimed mostly downward, not yet backward.

So when the hill gets so steep that the goad is not speed, but "survival" of the big leg muscles so they're not thrashed for the remainder of the tour -- then the forward fall move might help by redistributing the peak force load to other parts of the stroke cycle -

Perhaps this approach works best when combined with slowing down the whole stroke-cycle, introducing a "rest gap" -- reducing the turnover frequency. If there is "rest gap", then using "chest crunch" can add net positive work to the pole-push.

So the sometimes desperate-looking forward-fall move might not be the inefficient cause of slower climbing, but a "survival" mechanism for dealing with insufficient leg-muscle capacity.

back to Top | more Ideas | Secrets | FAQ | Resources | more Classic