If you're a cyclist who lives where it snows, you know that there's no sense in hating or complaining about it. No one likes shoveling a driveway, but the only way to survive in a winter climate as an athlete is, of course, to pray for snow, and play in it. The key is to make the best of the winter while it's here, and the best way to do that is on the "misery sticks". A bad winter for riding usually means a good winter for skiing.
Many of our clients and friends have either gotten serious about Nordic skiing, or come from a skiing background. In the early years, this was uncharted territory for us in terms of training properly if cycling was still your first priority, and some questions were put to me as a coach, particularly, how to cross over into another sport while applying the same methodology was used for cycling? Until this point, we hadn't worried too much about training for Nordic skiing other than emphasizing technique. We'd all been at the level with skiing that the biggest improvement we could make was technique first, since we could rely on cycling fitness otherwise. As the same time, some of my peers were beginning to take ski racing seriously, to the point of doing dry land training in the fall instead of racing cyclocross.
Ultimately, all of the same energy systems you focus on for road cycling are applicable for skiing, but sometimes for different reasons. For instance, you might not think sprint workouts would have any place on the skis. But they absolutely do. You need to have a place in your workouts where you're building explosive power. Not because you need to be worried about winning a sprint on the skis (though it happens), but because a) the movement of skating itself is essentially a repetition of explosive motions, and b) you need to be able to pop over small hills while still maintaining enough momentum to move forward. On the bike, you can shift into your smallest gear and keep your power output the same. The point at which you'd tip over is pretty low. On the skis, there's a minimum power you'll have to put out just to keep moving forward. So, neuromuscular power is an important aspect, and 15-second bursts, on the flats and on the hills, can be helpful.
Let me break it down into a) energy systems, and b) periods or phases, to show how they translate from cycling to skiing:
I personally find it difficult to ski at an endurance pace, because in order to simply move forward with my poor technique I have to go somewhat hard. If your technique is fair, you should be able to ski easy as warm up, recover between intervals, and perhaps on your recovery days if you're skiing classical. For skiing, endurance isn't a perfectly analagous training zone like it is on the bike, since skiing doesn't require the same kind of pure endurance as cycling. Your longest race ever would be 3 hours, whereas with cycling it can be more than twice that, and there are no stages races that require day to day recovery for performance over time.
Tempo is your first real interval or training zone for skiing. It's where you would do your endurance training, and you should be capable, at the end of your base period, of finishing 2.5 to 3 hours worth, to be consistent with what you'd have to finish in a 50K, and what sports science suggests is the maximal volume a human can finish. Not surprisingly, they're about the same length. Training in tempo also allows you the base level of fitness to be able to do high intensity training later and be able to recover from it quickly.
Threshold has the same application on the skis as it does on the bike. For any races that are an hour long or so, you'll find that those are the events where your average heart rate should hover around your threshold heart rate. 30-90 minutes in a single workout is what you should be capable of finishing. So here, you're talking about a 10-30K race, similar to a 1-hour criterium or cyclocross race.
Here's where we start to talk about VO2max training. Any random minutes you spend over your threshold heart rate you can value as VO2max, but more specifically, you're considering extended efforts of 2-5 minutes. So, in skiing, especially in a longer race, you know that you're going to be trying to stay right at threshold as much as possible. But when you hit the short, rolling hills, you're inevitably going to go over that tempo to get clear them quickly, and then settle back down at your threshold pace you've over the top. Intervals of 5 minutes on, with 50-100% recovery in between, will help with that.
Anaerobic work capacity (AWC) efforts are shorter efforts of 30 seconds - 2 minutes. Again, where they apply to skiing is when you're popping over short hills. Full on, 1-minute efforts with full recovery will help you attack those hills, and work on technique while under pressure..
I explained this above in the introduction.
This should give you a good starting point for considering the work you do on the skis, and how to quantify it in relation to the work you do on the bike. Even with these energy systems and training zones in mind, one important point to consider is that your threshold heart rate when skiing will be higher than your threshold heart rate for cycling, because you engage more muscles simultaneously while skiing. There are more muscles emptying the blood of oxygen, thus your heart must beat faster to transport that oxygen. Nordic skiers are known to have the highest threshold heart rates of any endurance athletes. That said, it may be difficult for many people to do a true threshold test on the skis. If you're skiing for fun, your heart rate zones on the bike will work well enough, as long as you're aware that you can go right up to and just a little bit over the zone, and rely heavily on perceived exertion. If you really want to estimate your true threshold heart rate while skiing, your best bet would be to evaluate some average heart rates for 30K races you were able to ski the distance strongly. Or, of course, just have a good time out there, and make the most of the snow while it lasts.