Winter often means that a lot of us are making the trek up the mountains in hopes to have that ultimate run back down.
Ski-lifts can often be more than 12,000 feet above sea level, which means you're getting a lot less oxygen than you're accustomed to on sea level. This lack of oxygen can leave you feeling sick (nausea and fatigue) but you're not alone, altitude sickness is fairly common. To help prevent it you may want to start slow the first day and work your way up the rest of your trip. Try a half day at first and if you're at a huge mountain, you may want to avoid going to the summit on day one. Also, avoid alcohol, it can contribute to altitude sickness.
Fit's Tip: If you start feeling symptoms coming on, drink a lot of fluids (non-alcoholic fluids that is) and get a lot of rest. After a few days, you should be back to normal and hitting the slopes like a pro.