It's a cooperative effort with the dog pulling and the human skating or kick-gliding on skis.
Any breed of dog weighing thirty pounds or more is a suitable candidate.
Ideally the dog should like to run. The dog wears a harness just like a sled dog. The human wears cross country skis and boots plus a skijoring belt. The belt should be at least three inches wide where it goes across the back. A seven to twelve foot tow line connects the belt to the dog's harness.