***Stop focusing on building stronger quads*** in your winter preparation.
These muscles are already strong and they will be triggered all winter long.
What you should be doing is training the antagonist muscles / posterior chain.
You can push the envelop even more by making them stronger than your quadriceps.
As long as the winter will go on, the balance of the agonist/antagonist muscles will come back.
This helps prevent many knee injuries due to super strong quads and weak hamstrings and glutes.
Squats are still a good off-season ski exercise, but maybe go for a 2 to 1 and even 3 to 1 post chain to quad training ratio.
Here’s a video featuring 4 bodyweight exercises (+ variations) that you can include in your weekly training routine.
1- Step and Russian Step up
2- Glute bridge (dual and single-leg + flat or heels on a step)
3- Glute bridge walkout
4- Superman hold
Training smart is less sexy sometimes …
But going thru the season without injury is way better than watching the show from the window!