From the papers:

"Skijoring is one of the newest niche sports in U.S. climes where there's so much winter that residents have to keep coming up with innovative ways to enjoy it. Explained simply, in skijoring, a dog (or two) pulls a cross-country skier." Sort of like dog-sledding without the sled.

"This poor man's dog-sledding [has] been a common mode of tronsportation in rural Scandinavia for centuries." You may consult websites "of the Alaska Skijoring and Pulk Association in Fairbanks (Pulking is a variant of skijoring.)" or of Idaho's Bogus Skijoring Club (named for the Bogus Basin Ski Resort) or of a club in Minneapolis, Minnesota.

Apparently in this sport one can, by ones own exertion as skier, greatly vary how much excerise is had by the dog and how much by the human.

I've never heard of either word before, so I tried looking them up. I couldn't find pulking in any dictionary, but I did find skijoring.

M-W defines it as "a winter sport in which a person wearing skis is drawn over snow or ice (as by a horse or vehicle)", and gives the etymology as "modification of Norwegian skikjøring, from ski + kjøring driving.

The OED Online defines it as "A winter sport in which a skier is pulled over the snow by a horse or horses (or by a motorized vehicle)". Its first quote is from 1920: "1920 Punch 17 Mar. 204/1 Skating, sliding, curling and yodelling in the intervals of ski-ing, skijoring, skilacking and skihandlung".

Now, what are slilacking and skihandlung?

Tinman