detail on Leg motion in ski Skating -- Roberts

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Focus of technique
Supporting Positions
Mental Images
Video checkpoints

Focus of technique

Feel and use the magic of pushing out to the side.

The magic in the physics of skating is that the gliding ski can convert sideways forces into forward-propulsive power.
Feel the magic.
Use the magic. Keep the side-glide going.

Actually the strongest leg-push is not literally directly out toward the side. It's at a 90-degree angle to the current line of the ski being pushed on. For high speeds on flat ground, the ski is pointed nearly straight forward, so the leg-push comes close to straight out to the side. At slow speeds climbing up a steep hill, the ski might be angled out like 45 degrees from the skier's overall direction of forward motion, so there is a substantial backward component to the leg-push force.

But the side-force is the component that the skier's conscious and unconscious muscle-control mechanisms tend to forget, so that's what needs to be emphasized here.

And once the glide out to the side is lost the "inclined plane" magic of in the physics of skating is lost, and we might as well just be skiing Classic-style. Not a big danger on flat terrain, but a definite possibility when climbing up a steep hill.

Key points

Forward ankle flex position is critical for several different reasons in ski skating --

much more so than it is for inline and ice speedskating.

Upper body motion side-to-side can help a lot (when it doesn't hinder).

Learn to feel exactly which upper body motions best add power to the legs. Try out all kinds of rotations, twists, tilts, and combinations. Practicing no-poles skating is very helpful for this.

Timing is critical: Getting the side-to-side rhythm wrongly synchronized can actually absorb power from the legs, instead of adding to it.

No-poles skating is the big key: practice, practice, practice.

Priority is engaging the big leg muscles.

There's lots of little muscles that can help in skating, and it's fascinating fun to play with using them. But there are big wins from (a) finding more effective supporting positions to leverage the big muscles like gluteus maximus and quadricips; (b) mental concepts and neural patterns to engage those big muscles; and (c) lots of training of those muscles for endurance and speed.

But watch out for using the big muscles in an inappropriate part of their range of motion, so they're working hard, but much of that work is not moving the skier forward.

Analysis of approach

[ to be added ]

Muscle moves used

see separate page on Muscle Moves in skating Leg motions

Sequence of Phases

see separate page on Phase sequence in skating Leg motions

The range-of-motion for the push of these big muscles is limited to how much the hips are flexed at the start of the leg-push. The hip joint is flexed when the torso is "hinged" forward and/or knee joint is out in front of the hip.

Torso forward -- how far the torso can hinge forward in a stable position depends on balance or on support from the poles.

One approach is to go for an unstable starting position, and "fall forward" beyond the range of static balance. Fall forward onto the ski poles -- or possibly onto the other leg, stepped out forward just in time to catch the weight of the upper body.

The "forward fall" move is not just for stronger pole-push. The surprise is that it's also good for fuller engagement of the big leg muscles in the skate-push. For V1 Skate up a steep hill, engagement of the Hip Extensors is indeed the primary benefit of forward fall.

Knee in front of hip -- there are two ways to achieve this.

The good way is by advancing the knee forward -- by flexing the ankle joint forward. That again.

The questionable way is by dropping the hips back and down. But that moves the skier's whole center of mass back and down -- not a good thing for climbing up a steep hill.

But it gets more complicated: because one part of the range-of-motion is much less useful for the actual requirements of cross-country skiing situations than the other.

So getting into position for bigger range-of-motion may result in a stroke which feels more powerful, and really does deliver more work -- but it's not power and work which is useful for the skater's current situation and goal.

Forward versus Upward

The Hip Extensor muscles can push the mass of the upper body both forward and upward (or sometimes backward). The ratio of forward to upward push delivered varies widely, depending on the skier's current body configuration.

In cross-country skiing, the skier's overall motion is much more forward than upward -- even going up hills. Now when climbing up a hill, the upward component is normally harder, because it's fighting against gravity. But then the tilted surface of the snow up a hill naturally converts forward motion into upward motion -- so the upward work does not need to come from direct upward pushing work. So the combination of the physics and biomechanics gets complicated.

Modern thinking about skating is that it's very easy to overdo the direct upward component of the leg-push work, and that most ski skaters will benefit from focusing more on the forward component of the Hip Extensor push.

Poling: But it gets more complicated, because while the forward component is more useful for the skate-push through the ski edge, the upward component can help add power to a double-pole-push. The problem is that the upward component from the Hip Extensors is not very effective for driving the pole-push. The Knee Extensors (and Knee Flexors) are much more effective for that. Anyway, for big double-pole-push focus (e.g. V2 and Open Field Skate) the upward component gets more important, for building "potential energy" to be delivered in the next pole-push. But in skate motions without big poling focus (e.g. V1 and No-Poles Skate), the upward component is down-played.

Controlling the Ratio: The ratio of forward to upward force delivered from the hip joint depends on: (a) the current angle of the torso in the forward-back-vertical plane; (b) the orientation and location of the knee joint and lower leg in the forward-back-vertical plane; and (c) the orientation of the leg in the side-vertical plane, underneath versus out.

when the leg is directly underneath in the side-vertical plane, the Hip Extensor force must go into pushing the torso upward. Also somewhat backward: the higher the vertical torso angle, the more backward the motion.

sounds like a good argument for keeping the torso leaning forward, and the shoulders forward and low -- and not "standing up straight and tall".

when the leg is out to the side in the side-vertical plane, the Hip Extensor force can push the ski edge down and out and back against the snow surface. The more the knee joint is low and forward, the more this force is forward and less upward.

another reason for strong forward ankle flex.

Which section of the gluteus muscles?

Various "gluteus" muscles go around the back and side of the human butt. The "hip abductors" are a section around the side of the hip ("gluteus medius"?), and push directly out to the side.

The "gluteus maximus" section is at the back of the butt, and pushes the leg straight back. This section is often well-developed from other sports like bicycling and mountaineering and backcountry ski climbing.

I think the section of major muscles that usually gets engaged in Phase 2a of the skating leg-push in somewhere in between those two sections, side and back.

Which section is best? Perhaps the point is rather to be able to switch sections, and learn to feel how to engage whichever sections are currently fresh, and avoid those currently fatigued.

Engaging the maximus section

Perhaps it would be advantageous to try to engage a section closer to straight back, including the "gluteus maximus" -- because this would better utilize the training from other sports.

(a) A possible way to do this would be to rotate the torso to the opposite side, and perhaps also tilt the hip joints away from the leg-push side, since this position helps "aim" the gluteus maximus section out to the side, more in the direction of the skate-push through the ski edge.

(b) The more the tip of the ski is aimed out toward the side, the more the skate-push is toward the back, and the more the gluteus sections toward the back can be engaged to push through the ski edge.

(d) Using the mental image of "stepping the next ski forward" on flatter terrain, can help engage gluteus sections more back closer to the gluteus maximus.

Knee Extensor muscles

These big muscles cannot be used to push unless the knee joint is first bent into a flexed position.

So the concept of the "high hips forward" position is in contradiction to effective use of this big powerful muscle mass in the leg.

If the big Knee Extensor muscles are to be used, the way to minimize moving the hip joint and butt back is to combine the required knee flex with strong forward ankle flex.

So it is critical to keep practicing that forward-ankle-flex position, for best ski-skating performance.

Note: Knee bend is so important to skating leg-power that elite inline and ice speedskaters do not attempt to get their hips high or forward. They just allow the hip joint and the butt to drop back.

Ski skating is different from ice and inlines in that regard, because:

(a) poles are used a lot in skiing: The best physical / biomechanical configuration to start the pole-push is with the shoulders high and forward. But the higher speeds of a skater on inlines or ice is usually too fast for pole-pushes to help much.

(b) steep hill climbs and/or slower glide in skiing means that each ski is often angled more out toward the side during the leg-push. So the leg-push force is aimed more forward, so it's easier to direct it through the ski skater's center of mass by keeping that center of mass more forward. Letting the hips and butt drop back is usually bad.

(c) aerodynamic position is less critical for skiing, because the speeds tend to be lower than for inlines or ice skates.

That's why expert ski-skaters usually give up some of the power of their Knee Extensor muscles by working to keep their hips and butt more forward.

Forward versus Upward

The Knee Extensor muscles can push the mass of the skier's butt and upper body both forward and upward. The ratio of forward to upward push delivered varies widely, depending on the skier's current body configuration.

Poling: But it gets more complicated, because while the forward component is more useful for the skate-push through the ski edge, the upward component of the Knee Extensors can help add power to a double-pole-push through the pole tip. So for motions with big double-pole-push focus (e.g. V2 and Open Field Skate) the upward component gets more important, for building "potential energy" to be delivered in the next pole-push. But in skate motions without big poling focus (e.g. V1 and No-Poles Skate), the upward component is down-played.

Modern thinking about skating up a steep hill is that it's very easy to overdo the direct upward component of the leg-push work, and that most ski skaters will benefit from focusing more on the forward component of their Knee Extensor push when climbing up a steep hill.

? Why should we believe that modern thinking ?

My current theories for non-elite skiers are that: (a) the real problem is how to go slow up steep hills and keep the power output low -- and direct vertical lifting delivers too much power too fast -- with too much lactate burden on the obvious big leg muscles; (b) there is more inefficiency loss in using vertical potential energy to drive the pole-push going up hills than on the flats; (c) some skiers mis-perceive the amount of direct upward pushing, and think they're only doing a little when really they're doing too much, perhaps more than they can efficiently "lock in"; and (d) focus on direct vertical motion is just more load on big muscles already burdened, and distracts away from side-to-side motion that can shift some lactate burden onto less obvious muscles.

Controlling the Ratio: The ratio of forward to upward force delivered from the knee joint depends on: (a) how far up or back the butt is in the forward-back-vertical plane; and (b) the orientation of the leg in the side-vertical plane, underneath versus out.

the further the ski is out to the side, the more the push from the Knee Extensor goes forward and inward.
the closer the ski is underneath, the more the push from the Knee Extensor goes forward.

if the ski is underneath, then the push goes more forward if the butt is already more forward (but in this configuration, some other part of the body must go backward at the same time, so there's no net gain to leg-power forward motion).
if the ski is underneath, then the push goes more upward if the butt is starting down and back. Good for building potential energy for the next double-pole-push, if that's the focus of the motion being performed (e.g. V2 or Open Field Skate).

So the key for using the Knee Extensors for leg-push power is to get the ski out to the side, rather than push it back more underneath.

That's a big reason why trying to "walk" or "stride" on skating skis is not effective: because it does not use the big Knee Extensor muscles.

Ankle Extensor muscles

Delay the toe-extension until the end of the leg-push. The main forces produced by the big Hip Extensor and Knee Extensor muscles are better transmitted to the ski thru the hard bones of the lower leg and heel, without the soft calf muscles getting "in the middle" any more than necessary.
The further forward my ankle is flexed at the start of the leg-push, the larger effective range-of-motion I get when I extend the ankle joint through the finish.

Another reason why it is so valuable to practice and practice the forward-ankle-flex position.

Mental images

Hip extensor muscles

The mental image of "stepping up the hill" can help engage the gluteus maximus muscles for pushing back and down.
Using the mental image of "stepping the next ski forward" on flatter terrain, can help engage gluteus sections more back closer to the gluteus maximus.

Ankle Extensor muscles

Danger is that consciously thinking of "toe-push" will result in losing that magical push out to the side -- fall into the novice trap of pushing backward.

Therefore many instructors tell learning skaters to focus the leg-push through the heel, at least until they have the "pushing directly out to the side" completely solid. Even then they would suggest conscious toe-push only if they observed that the skater had a definite problem with not doing it.

Think of extending the toe to push out to the side, not backward. It's only to extend the range of motion of the side-glide, not an independent push.