Have you ever tried cross-country skiing?  I compete in the sport, there are actually quite a few formats for it.
I have actually never been skiing before but it sounds fun! What types of formats are there?
Well, for one thing there are races that happen on groomed tracks, and then there are freestyle events. 
Typically, how long are races? And how many people compete?
There are many different group sizes and lengths of races. There are even cross-country ski marathon events that are sanctioned by an organization called the Worldloppet Ski Federation. 
A ski marathon sounds intense. I've run a marathon before but skiing one sounds like a whole different beast. Have you ever done a ski marathon?
I have!  It's exhausting. My other favorite event is the biathlon, where  we stop to shoot at targets with rifles. There's also paralympic cross-country skiing.