Winter is here, but the snow is not. When the snow finally arrives, so will another opportunity for cross-training.
Pete Pfitzinger and Scott Douglas, in their book Advanced Marathoning (2001) wrote, "Cross-country skiing is the only form of exercise that provides cardiovascular benefits equal to, or even slightly better than, those associated with running. The whole-body nature of cross-country skiing really works the cardiovascular system, and some of the highest VO2 max values have been recorded in cross-country skiers."
Many of the top recorded VO2 max measurements among athletes have been found among cross country skiers. (A description of VO2 max can be found here.)
A study from the University of Minnesota analyzed upper body power during cross-country skiing compared to running. Runners, in their study, used 46% of the upper body power compared to cross-country skiers.
Running guru, Hal Higdon, has a website dedicated to teaching people how to cross-country ski.
So when the snow finally arrives, consider a trip to Spidahl Ski Gaard for an afternoon of cross-training.