Ooweeohh wrote:
Overall, skate skiing is about 10-15% faster than classic. And depending on conditions classic is similar to running (note that they ski on tougher courses than XC or roads, like 100' to 150' of vertical per mile on average); nevertheless a world cup 10K classic race might be 25 to 27 minutes if conditions are decent (slower if it's on new snow or if it's super sloggy/slush). Note that classic is actually faster when it's very very cold (like below -15 F) but they don't allow racing below -4F (-20 C).
They stay in the tracks (usually) because it's more efficient (usually) and faster (usually). The more people that ski on a set of tracks, the faster the tracks get, and balance wise it's also easier/more efficient to be in the track. So in a classic race where you have to keep the skis parallel (no pushing off to the side, i.e., skating) it's easier to stay in the tracks most of the way. They'll remove the grooved tracks on sharp turns and steep downhills because they are a hazard there. If the uphill is steep you "herring bone" which is kind of a duck walk up the hill, fit athletes actually kind of herring bone run/bound on those sections--very demanding!
Like cycling you do get a recovery on the downhill, but those are usually short. 70 to 80% of the time you are climbing or on flats. You are working harder and heart rate is higher than running (it seems you can hold a high heart rate longer than you can with running), but overall in a 30 minute ski race your average heart rate would be similar to 30 minute running race.
Some time comparison at common distance for world class skiers (note they'd go even faster on super-flat courses like some road races)
10K freestyle - 22-25 minutes for world class men on an official course; 24-27 for women
10K classic - 25-28 minutes men; 27s-31 minutes women
15K freestyle - 35-42 minutes men, 39-46 minutes women
15K - classic - 40-45 minutes men, 44 - 49 minutes women
50K freestyle - 1:50 - 2:10 min men
50K classic - 2:00 - 2:30 men (really depends on conditions)
30K freestyle - 1:22 - 1:30 women (women ski only up to 30K on Olympics or World Championships)
30K classic - 1:30 - 1:40 women