Consistent running in the winter can be difficult: it's dark, it's snowy and icy, and it's just more fun to play in the snow. Integrating cross training into your running plan can be smart throughout the year, but especially so in the winter. Nordic skiing offers the best direct benefits to running compared to other cross training activities, so why not ski this winter?
As with most other cross training activities a large benefit of cross country skiing is the break from pounding. While skiing is still weight bearing, it does not have the same musculoskeletal impact as running. This makes it a good way to either reduce your running mileage yet maintain a high aerobic load, or to increase your aerobic loading without increasing impact.
For aerobic development it's hard to beat nordic skiing. Even well trained runners may find that getting out on skis leaves them gasping for breath after a few minutes. This increase in oxygen demand is because you use more than just your legs. While running your body gets used to recruiting your legs and core and maybe some flailing arms on a rocky descent, but while skiing you demand performance from your entire body. This dramatically increases your oxygen uptake and over a winter can lead to a greater aerobic capacity.
Additionally, cross country skiing demands more balance and coordination than trail running. The long glides on a single foot demand more focused balance than brief stints on one foot that comes with running, plus you have to balance on what amounts to a skinny stick! It also helps that the major muscle groups recruited in skiing are also the same used in running. Trail runners especially may notice a stronger feeling of confidence on rocky sections of trail immediately following a busier ski season.
Probably most importantly though, skiing is fun! While consistent year-round running is important to long term improvement as a runner, it is helpful to have focused relaxed times of the year. For most runners winter is a down time in terms of racing and is a good time to de-focus. Getting in running miles still keeps tendons used to the pounding, but substituting a few running days here-and-there for some time on the skis is mentally freeing.
So this winter don't stress about fighting the elements to get your miles in every day. Take some of those days to work with the season and pick up the skis and poles. Your aerobic capacity, balance, and mental health will thank you!