For something like a muni weekend, I’m thinking a nordic track won’t do you a whole lot of good, but my recommend–if you have limited conditioning time–is to focus your efforts on cardio, versus on endurance. Whether using the NT, walking the dog, or riding, try to work in some intervals training. If you’re not riding much, it may be the best way to avoid sucking major wind when you’re out on the trail. Or so my two-cents claims.
Do you have any paved hills near your house? Even though trail riding may not be convenient mid-week, if you have some decent short, steep hills in or near your neighborhood, you could get a good little interval training regimen going on your muni, which even without the dirt and boulders, will still have you closer to trail shape than a nordic track. I think the cross-over works. As an example, it’s now getting dark too early for me to do my traditional 15 mile climbing route on my 36-er after work. So how do I finish training for next week’s Bike MS tour? I toss my 29-er in the car, drive about 5 minutes away to a neighborhood that has a long steep uphill, and climb, descend, climb, descend, etc. until dark. The climb from bottom to top takes me about 4 minutes, but it’s 4 minutes of major cardio, heavy breathing. Then I beat it back down while my heart rate recovers, turn around, do it again. Even though I’m not logging the major miles on my coker, I’m building the strength and power, which will help when I hit the big hills out on the ride.
I’ve done this in the past to try to prep for Moab. Admittedly, that’s a bit closer a comparison…paved hill to slickrock hill…but I still think any time you can get on the muni pushing your cardio–dirt or not–will help.