General comments 

"unexpected side effects" thread, April 2002 on rec.skiing.nordic

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Timo Salmi [website], April 2002 on rec.skiing.nordic: 

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"That is where the choice of the stiffness of the skis comes in. And also the length of waxing applied to the skis. A Sunday skier and even a more advanced hobbyist are well-advised to use softer skis than real competition level skier. Less sheer power is then needed.

It is all about the combinations of power, stamina, and the choice of the equipment. If one wants a good grip with less effort then one uses softer skis and does not have to kick and step downwards so hard. The price one pays is in the glide. If one thinks about it for a moment, it is easy to see that the best combination clearly is different for different kinds of skiers and situations such as for different distances to be skied (e.g. 5km vs. 50km)." 

Ken Roberts replies, April 2002 on rec.skiing.nordic:  

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"Yes. My first reaction to discovering the extra side-effects is that I should learn and use every other approach and trick for better grip -- and save extra down-force beyond committed body-weight as a last resort.  Certainly softer skis and more grip wax are the easiest.

It occurs to me that the "double payment" of leg-push energy can be reduced if the second "landing" down-force is taken transmitted partly to the pole, and then it can be re-directed into forward-force.

(But it seems to me that the transmission of down-force through a single arm in Classic stride is much less efficient than transmitting it through two arms in double-poling.)

Then the biggest penalty is on the skier who does not know about offset pole timing. First their pole push synchronized with kick reduces grip-friction, so they have more need to use more extra "launching" down-force to make up for that loss. But then they have no pole-push available during the glide phase to "catch" the second "landing" down-force. So they incur the full double cost of a greater concentration of extra down-force. 

It also occurs to me that the finding of a double cost for extra down-force does not mean that mental images of down-force are bad. It might well be that visualizing "drive the knee down" or "drive the heel down and back" is the best way for our complex human control systems to achieve the optimal physical down-force -- even if force-sensors in the binding measure the objective physical down-force as only barely larger than committed body-weight."