Hi,
I've been training with this setup for Nordic skiing on and off snow for about six months. Here are some things you should know before choosing to pursue a train by power approach to Nordic skiing.
1) Unlike cycling, there is no way to show either 5s power data or NP in a field. This is a severe training interface limitation when you're trying to stay in a power band because your meter jumps all over the place and sends constant annoying alerts (if you've chosen that setting.) Coupled with the fact that you must skip a pole stroke to lift and observe your watch, it's virtually a virtually useless training feature for Nordic skiing in its current configuration. This seems like a very very simple oversight and fix by Garmin, and I'm not sure why it didn't roll out as an inherent feature.
2) The HRM Pro is very challenged by conditions, most notably wind, and whether the snow is soft vs. hard. It's pretty easy to tell when you're dealing with this limitation because your HR zones might be dead on, but your NP will register exponentially lower or higher (seems like 5mph of wind will reduce your NP by about 30w, and soft snow can subtract as much as 50w while super hard snow will add as much as 50w.)
3) As a result, I think the XC ski power feature is still very much a good beta tool for post workout analysis, but useless as an actual real-time training metric like you'd find for cycling. NOTE: I believe that if Garmin can fix the field issue and enable NP or 5s power as a field, it *might* work as a real-time training tool. However, that's an unproven hypothesis until they do so. Until then, I still recommend HR as the most reliable real-time training metric for Nordic skiing on snow.
4) The caveat to all this is that on roller skis, the snow firmness variable is removed (the HRM Pro is not sensitive enough to know the difference between road surfaces). Therefore, I see power number veracity as much higher on rollers. I've still seen challenges with the data when there's any kind of ambient wind.
4) Unrelated, but I'd still like to see a roller-ski activity added, and a native interface with the Concept2 Ski Erg.
Matt Komatsu
