Here is a 4-week at-home training plan that can help you get in shape for skiing at 4000 meters:
Warm up with 5-10 minutes of light cardio (such as jogging in place or jumping jacks) and then do 3 sets of 12-15 squats, 3 sets of 12-15 lunges (per leg), and 3 sets of 12-15 leg presses.
Warm up with 5-10 minutes of light cardio and then do 3 sets of 12-15 push-ups, 3 sets of 12-15 plank ups (from plank position, lift one hand and then the other, alternating sides), and 3 sets of 12-15 tricep dips.
Warm up with 5-10 minutes of light cardio and then do 3 sets of 12-15 jumping jacks, 3 sets of 12-15 mountain climbers (in plank position, alternate bringing each knee towards your chest), and 3 sets of 12-15 burpees.
Rest day
Warm up with 5-10 minutes of light cardio and then do 3 sets of 12-15 squats, 3 sets of 12-15 lunges (per leg), and 3 sets of 12-15 leg presses.
Warm up with 5-10 minutes of light cardio and then do 3 sets of 12-15 push-ups, 3 sets of 12-15 plank ups (from plank position, lift one hand and then the other, alternating sides), and 3 sets of 12-15 tricep dips.
Warm up with 5-10 minutes of light cardio and then do 3 sets of 12-15 jumping jacks, 3 sets of 12-15 mountain climbers (in plank position, alternate bringing each knee towards your chest), and 3 sets of 12-15 burpees.
Warm up with 5-10 minutes of light cardio and then do 3 sets of 15-20 squats, 3 sets of 15-20 lunges (per leg), and 3 sets of 15-20 leg presses.
Warm up with 5-10 minutes of light cardio and then do 3 sets of 15-20 push-ups, 3 sets of 15-20 plank ups (from plank position, lift one hand and then the other, alternating sides), and 3 sets of 15-20 tricep dips.
Warm up with 5-10 minutes of light cardio and then do 3 sets of 15-20 jumping jacks, 3 sets of 15-20 mountain climbers (in plank position, alternate bringing each knee towards your chest), and 3 sets of 15-20 burpees.
Rest day
Warm up with 5-10 minutes of light cardio and then do 3 sets of 15-20 squats, 3 sets of 15-20 lunges (per leg), and 3 sets of 15-20 leg presses.
Warm up with 5-10 minutes of light cardio and then do 3 sets of 15-20 push-ups, 3 sets of 15-20 plank ups (from plank position, lift one hand and then the other, alternating sides), and 3 sets of 15-20 tricep dips.
Warm up with 5-10 minutes of light cardio and then do 3 sets of 15-20 jumping jacks, 3 sets of 15-20 mountain climbers (in plank position, alternate bringing each knee towards your chest), and 3 sets of 15-20 burpees.
Warm up with 5-10 minutes of light cardio and then do 3 sets of 20-25 squats, 3 sets of 20-25 lunges (per leg), and 3 sets of 20-25 leg presses.
Warm up with 5-10 minutes of light cardio and then do 3 sets of 20-25 push-ups, 3 sets of 20-25 plank ups (from plank position, lift one hand and then the other, alternating sides), and 3 sets of 20-25 tricep dips.
Warm up with 5-10 minutes of light cardio and then do 3 sets of 20-25 jumping jacks, 3 sets of 20-25 mountain climbers (in plank position, alternate bringing each knee towards your chest), and 3 sets of 20-25 burpees.
Rest day
Warm up with 5-10 minutes of light cardio and then do 3 sets of 20-25 squats, 3 sets of 20-25 lunges (per leg), and 3 sets of 20-25 leg presses.
Warm up with 5-10 minutes of light cardio and then do 3 sets of 20-25 push-ups, 3 sets of 20-25 plank ups (from plank position, lift one hand and then the other, alternating sides), and 3 sets of 20-25 tricep dips.
Warm up with 5-10 minutes of light cardio and then do 3 sets of 20-25 jumping jacks, 3 sets of 20-25 mountain climbers (in plank position, alternate bringing each knee towards your chest), and 3 sets of 20-25 burpees.
Warm up with 5-10 minutes of light cardio and then do 3 sets of 25-30 squats, 3 sets of 25-30 lunges (per leg), and 3 sets of 25-30 leg presses.
Warm up with 5-10 minutes of light cardio and then do 3 sets of 25-30 push-ups, 3 sets of 25-30 plank ups (from plank position, lift one hand and then the other, alternating sides), and 3 sets of 25-30 tricep dips.
Warm up with 5-10 minutes of light cardio and then do 3 sets of 25-30 jumping jacks, 3 sets of 25-30 mountain climbers (in plank position, alternate bringing each knee towards your chest), and 3 sets of 25-30 burpees.
Rest day
Warm up with 5-10 minutes of light cardio and then do 3 sets of 25-30 squats, 3 sets of 25-30 lunges (per leg), and 3 sets of 25-30 leg presses.
Warm up with 5-10 minutes of light cardio and then do 3 sets of 25-30 push-ups, 3 sets of 25-30 plank ups (from plank position, lift one hand and then the other, alternating sides), and 3 sets of 25-30 tricep dips.
Warm up with 5-10 minutes of light cardio and then do 3 sets of 25-30 jumping jacks, 3 sets of 25-30 mountain climbers (in plank position, alternate bringing each knee towards your chest), and 3 sets of 25-30 burpees.
Remember to listen to your body and adjust the intensity and volume of your workouts as needed. It is also a good idea to incorporate some flexibility and balance work, such as yoga or Pilates, into your training plan to help improve your overall physical preparedness for skiing at high altitudes.