Central push phase 2 of normal-push skating -- Roberts

[ Print this | help ]

what's here

key points
definition of this phase
drivers of propulsion
details + hints
more

intro

This is one phase in a detailed analysis of the sequence of moves for Leg-push motions of "normal push" method of skating. For more context and an overview of all the phases of the sequence, see the summary of normal-push phases.

key points

Theme: Push with moves that do not extend the leg (because the leg-extension moves are most effective when the foot is out further away from the hip). Some of these moves are already effective if started earlier in Phase 1.

Here are moves which are effective from close to underneath the hip (and less effective further away): transverse-hip-abduction, inward-hip-leg-rotation (with bent knee), and ankle-pronation. Also forward-pelvis-rotation is effective either close or far.

?? inward-knee-roll ?? There's another propulsive move available: ankle-flexion -- ?? provided it has been prepared for by an inward-knee-roll move which includes some hip-adduction. The drawback is that the inward-knee-roll is counter-productive for other propulsive work in the phase (especially the hip-abduction move), so it's used mainly by ski-skaters, not much by inline or ice speedskaters.

definition of this phase

I call this the "central" push phase because:

(a) It's the obvious push that most people think this push with the big hip-extensor muscles as the main push move of skating;

(b) It comes in the center of this sequence of phases;

(c) The major leg muscles, especially the hip-extensors, perhaps also knee-extensors, are pushing through the central section of their range-of-motion;

(d) It avoids getting too specific about the overlaps with moves identified more closely with other Phases.

This phase goes from (roughly) the completion of three "contractive" side-push moves (inward-knee-roll, ankle-pronation, ankle-flexion), until (roughly) the start of the "full leg-extension" moves (outward-knee-roll, ankle-supination, ankle-extension).

This phase typically overlaps with either or both of Phase 1 and Phase 3. Perhaps some skaters just "reverse" immediately from the "non-extension" side-pushes to the "leg-extension" pushes, so they have no distinct Phase 2 at all.

But the biomechanical geometry of the leg-push and the physics of transmission to the snow combine to make the Phase 1 moves most effective when they are completed with the leg nearly vertical, close underneath the skater's pushing hip, and the Phase 3 moves most effective if started when the leg is more slanted down, way out to the side.

So there might be more propulsive power if those moves are shoved out from the center of the total leg-push, which leaves the center open to focus on the hip-extension push.

drivers of propulsion

[ physics and biomechanics parameters that drive the amount of added propulsion work -- and the additional time it takes to perform that work. ]

?? [ to be added ]

muscle moves

for forward propulsion:

hip extension - [ see more ]

also continuation of

forward hip rotation - [ see more ]

also perhaps initiation of

knee extension - [ see more ]

details + hints

Main push is with the hip-extension muscles. And some overlap with propulsive moves from other phases, such as the knee-extension push.

Main push is both sideways and backwards.

Some coaches say that we should only think about the sideways component of the push -- because the backward component feels so "natural" that we could never forget it -- But that consciously thinking about the backward component will make us forget the sideways component.

Push through the heel for maximum efficient transmission of force through the skate or ski to the ground..

Some coaches say should continue to think of driving the heel back during this phase.

Continue the forward-pelvis-rotation move.

Perhaps could continue the ankle-pronation move, though it gets less effective as the foot moves further out to the side, and at some leg-to-snow angle even becomes counter-productive.