This barred scientists from using microplates in space, where researchers prize the absence of gravity for its insights into how crystals, bacteria and drug agents behave.

FORBES: Doing Science In Zero-G? You'll Have To Go Through Nanoracks

But the biggest challenge for those reared on downhill skiing and unused to the pulse-raising effects of working against gravity is the absence of any energy-saving tow-lifts.

BBC: Cross-country skiing in Washington��s Methow Valley

Let me start off by saying one of the nice things about where we physically are right now is that we remove the effects of gravity, so we're able to do experiments that involve the effect of gravity basically on Earth as we look at what happens with the absence of it.

WHITEHOUSE: President Obama's call to the International Space Station