Double push

Double push is an inline speed skating technique. Its major advantage over the previously practised "classic" technique is that it allows the skater to do useful work during the part of the stride that was "wasted", and therefore to go faster. Opinions differ on its usefulness for non-elite skaters as it requires much practice before a skater is faster using doublepush than without.

It is uncertain who first invented the doublepush. Chad Hedrick is generally acknowledged as having brought it to the public eye. Prior to Chad's arrival on the scene circa 1992, inline speed skaters used the classic speed skating technique derived from ice speed skating. Hedrick's alternative approach rapidly proved itself to be faster and was soon adopted by many elite skaters.

Wheels used in speed skating are usually round or elliptical in profile, and do not literally have edges. The terminology is carried over from ice skate blades, which have edges. In inline skating, being "on an inside edge" refers to skating with the wheel of the skate leaning inwards (i.e. medially: right skate leaning left, and vice versa). An outside edge is the opposite, and a center edge implies that the wheel is vertical.

The classic speedskating technique is an alternating cycle of inside-edge pushes and outer-edge glides. The cycle starts as the skater is gliding on one (let us suppose the right) leg with a bent knee. He then straightens (extends) the right knee and hip while leaning to the left. The direction of the push is therefore outwards (rightwards) from the center of mass. When the pushing leg reaches full extension he sets down the left (now support) leg and glides on it while picking up the right leg and bringing it back behind and underneath him (recovery) ready to be placed on the ground (set down) and become the new support leg. Once the pushing leg has been recovered, the support leg pushes out in the other direction and the cycle repeats. Note that the pushes are always in a lateral direction: the left leg pushes exclusively leftwards, and the right leg exclusively rightwards.

This will naturally result in a push that starts on the center edge or on a slight outside edge and "rolls over" onto the inside edge as the foot moves away from the skater's center of mass.

The double-push eliminates the "glide" phase from the above cycle, replacing it with a medially-directed "underpush" on the outside-edge. The recovery skate is placed on an outside edge and pushed underneath the body (right leg pushes leftward, and vice versa) while maintaining that outside edge, before being steered or pulled back across the centerline for the regular inside-edge push that follows. By its nature the double-push is less stable than classic technique, making it difficult to learn. If the skater should lose traction during an underpush there is no support leg to fall back on. The double-push also allows for the very brief application of force through both legs simultaneously. The skater does this by transferring his weight from the inside-edge foot to the outside-edge foot gradually, rather than transferring all of his weight to the outside-edge foot instantly. Some hold that this is essential to the DP, but this opinion is not universal.

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Wikipedia