Interesting, most competitive skiers lose muscle mass and strength in their legs during the ski season, unless they work out ( for legs) during the ski season.
I find the same, if I don't lift (squats primarily, and hamstrings) during the ski season, I end up weaker at the end.
Maybe because I lift a lot in the fall, so I start my ski season very strong.
Same with mountain biking.
I lift in May 3 times a week, and if I don't lift once a week during the summer, I end up weaker, even though I mountain bike 10 hours a week.
This makes sense actually. Competitive skiers enter the season in the best shape they can get themselves into then they get on snow and the time available for the gym is decreased, so their strength/muscle mass may decrease at least in terms of what they may have gained over the summer with a muscle specific exercise. I see that in my upper body as I don’t lift over the ski season.
It has been a few decades since I did any dry land training as part of a racing program pre season, so I’m probably a comparative weakling compared to someone doing an intensive pre-season regimen lol, with no where to go but to gain muscle mass just from skiing and being on skis so many hours per week.
In recent years I just went out and skied with no focused pre season program and usually pay for it the first week or so out. I changed that this year as my age (in my 50’s) and the fact that it seems like it takes a little longer every year to “get my ski legs.” It will be interesting to see if/how much it helps with early season stiffness and to see if I lose some of the leg muscles I’ve built up.
But back to the original point, if you have little body fat from being in great shape and get into a caloric deficit then you will loose muscle mass, no doubt competitive racers, particularly at the elite level, are burning a lot of calories skiing/training.