We use ME workouts for Xc skiers a lot. But we try to isolate the double pole or single pole muscle groups to achieve the localized effect we seek. With high level skiers I have used everything for 30 seconds to 5 min uphill double pole ME work and while the legs do come into play the arms/back/shoulder complex tends to be the limiter.
I was at a USST training camp where we used knee braces locked out on the men sprinters to isolate the upper body and reduce/virtually eliminate the leg input for just this reason. We used it for some of the top sprinters and it seems to be effective.