ADELBODEN MEN’S SLALOM: GROSS VS. HIRSCHER


The Men’s World Cup Slalom held in Adelboden on January 11, 2015 saw Italy’s Stefano Gross edge out Germany’s Fritz Dopfer  by 2/100 of a second and Austria’s Marcel Hirscher by 3/100 of second. In my opinion, Italy’s Patrick Thaler looked better than the racers who made the podium. But he failed to finish the second run. Meantime, Ted Ligety was missing from the podium…… again, finishing a distant 22nd, over 2 second behind Gross.  Has he suffered a fate similar to what Shiffrin experienced at the beginning of this season? Did he make changes to his equipment before the season like Shiffrin?  Shiffrin has since recovered. Will Ligety?

If Shiffrin’s mantra is Get Over It and Stay Over It, it appears as if the mantra of the men is Get Behind It. The photos below compare Shiffrin on the left to Stefano Gross on the right. Both racers are in the fall line. Even though the inclination of the slope Shiffrin is on is much steeper than the inclination of the slope Gross is on, Shiffrin’s COM is Over It (as in over the head of her first metatarsal in both the long and transverse aspects) while Gross’ COM is Behind It.

Shiffrin v pitch

The alignment or lack of alignment becomes obvious when the slope is neutralized to level the playing field.

Shiffrin v

The following video clip compares the techniques of Gross and Hirscher.

 

Instead of moving forward in the hips as Shiffrin does (Up and Over), both Gross and Hirscher project their feet ahead of them as their COM moves into the new turn. It is not until the apex of the turn that their COM gets anywhere near being over their outside foot. This technique  works. In fact, a racer can win races using it. But it is only a winning technique so long as all racer’s are using it. The problem is that from a point of mechanics, biomechanics and physics, it doesn’t align the load W emanating from COM and the resultant force R with the proximate centre of the head of the first metatarsal of the outside foot which is, in turn aligned over the inside edge of the outside ski. If the men are using a learned technique then why is their stance at ski flat so different from the stance of Mikaela Shiffrin and even Ingemar Stenmark?

Screen Shot 2015-01-17 at 1.34.33 PM

Screen Shot 2015-01-17 at 1.34.59 PM

The most plausible reason why the Gross, Hirscher and others are skiing the technique seen in the videos is that their ski boots are preventing them from Getting Over It.

“The relationship between equipment and technique is fragile at best. In the chicken and egg scenario, equipment enables sound technique. At the same time, equipment can disable a sound technique once it has been established. Further, the effect of equipment tends to become apparent in competition where races are won or lost by hundredths of a second.  Here, seemingly minor changes can have major impacts on racer performance as reflected in results”. – TRENDS IN WORLD CUP EQUIPMENT AND SKI TECHNIQUE – 12-12-2014

 

6 comments

  1. In a typical SL retraction turn there is no weight on the skis when they are flat and hence the relation between metatarsels and CoM is irrelevant. There is no extension against the CoM here. That would effectively stop the CoM movement down into the turn and also put you immediately in an aft state. See e.g. this example where Mikaela is completely unweighted and floating. http://extras.mnginteractive.com/live/media/site36/2014/0222/20140222__BN20140222_Z00_BNSP23OLYSHIFFRIN~p2_300.jpg.
    The extension after this moment is primarily due to the crossing paths of the skis and CoM. When the skis are loaded again in the next turn, then we can talk about the alignment of metatarsels and COM.

    1. The skis are flat on the snow and there is no weight on them? Seriously? They must be fit with some sort of anti-gravity or levitation technology. The photo in the link you provided is a moment in time where Shiffrin’s skis are passing over a terrain change. The tails of both skis are on the snow. But there is no weight on them? This issue aside, given the maximum bit processing conscious rate of the human brain of 50 bps, retraction is nonsensical. If COM is within the limits of the feet, the CNS will take care of the load at 11 million BPS with postural responses. Principles of Neural Science describe this process.

      1. no SIGNIFICANT weight. If you measure the CoM to snow distance in a time sequence you can estimate the force between the skis and snow. You can also find lots and lots of clips where SL skiers are airborne in transition.

        You did not really address my statement “in an SL turn where you go from hip to snow in one turn to hip to snow in the next turn in less than a second you don’t have time to go up an over.”
        a pendulum of this size and angular magnitude simply takes too long. GS is a different story.

      2. There will be some situations in slalom where the interval between gates and terrain make it impossible for a racer to get COM positioned over the head of the first MT at ski flat. If a racer becomes airborne it is not possible to align COM at ski flat because the racer needs the contiguous source of reaction force at ski flat to execute this. But it is almost always possible to transfer load to the head of the first MT by aligning COM with it. As Ligety says in the NY Times video, he creates pressure by extending. What he doesn’t mention is that you have to align COM as the end game. In a future post, I will provide examples of stance that allow the achilles to transfer to load to the forefoot and align COM with very low body positions. Assuming a slalom course is set that makes it difficult for a racer to use the optimal technique, the racer who makes the most good turns still wins.

  2. David, in an SL turn where you go from hip to snow in one turn to hip to snow in the next turn in less than a second you don’t have time to go up an over.

    1. Matt, let’s think about that. The reason I say that slalom is the acid test of the ability of the foot and leg to function within the confines of a ski boot is that even a slight amount of interference will make it impossible for a racer (or skier) to get COM over the proximate center of the head of the 1st MT in both planes. At the start of the transition phase a racers’ COM is behind the inside foot and below where it needs to be in the most minimal correct skeletal position at ski flat. So the racer must get over it and up to some extend. But the full extension doesn’t happen until the apex of the turn. Instead, racers like Shiffrin get over it at ski flat as in over their new outside foot and wait for the pendulum to swing into the new turn. As it does, she extends and rotates her whole outside leg simultaneously while keeping her COM over the proximate center of the head of the 1st MT in both planes which is over the inside edge. She is exerting a vertical component of force over her outside ski BEFORE it changes edges and she maintains force on it throughout the entire turn. This is the key. I will explain the details in upcoming posts.

Comments are closed.