One of the common misperceptions about jet lag is that it results from flying at high altitudes. In fact, jet lag is caused largely by crossing time zones on long-distance, east-west travel.
The body functions like clockwork. Our patterns of eating and sleeping, working and resting are scheduled by a clock in our heads, a rhythm in rough sync with the earth's cycles of night and day. When you travel by plane, you change the time of day without resetting the body's clock. Suddenly, it's 5 pm outside, but your body insists it's 11 pm and time to go to bed. Enter jet lag.
On a trip that requires a 5-8 hour time change, jet lag may keep you from feeling your best for 2 days to 2 weeks. How you're effected depends on many factors, including age, physical fitness and whether you're traveling from east to west or from west to east.
Why is traveling east to west more difficult for your internal time clock? The reason is that the human body cycle is about 25 hours long, rather than 24. When you travel west, you're required to stay up late, which is more acceptable to your body than going to bed early. Your heart rate, normally faster during the day than at night, may take up to 6 days to return to normal. Your bowels may not normalize for as much as 24 hours for every time zone you pass. Your body's ability to perform mathematical equations may stay out of whack for anywhere from 2 days to 2 weeks. If you're traveling from west to east, your recovery will usually take 30-50% less time.
So how should you cope with this? General tips include:
Drink lots of water before, during and after your flight.
Adopt the hour of the time zone you're traveling to, the minute you step into the plane.
Avoid overeating, alcohol and other depressants, such as motion-sickness drugs.
Exercise and sleep well for a few days before your trip.
When you arrive, DO NOT NAP or sleep longer than you normally would, trying to catch up. Instead go to bed at your normal bedtime (in your new time zone) and get up at your normal awake time (in your new time zone). If your European flight arrives mid morning or early afternoon, stay up through the day (DO NOT NAP) and go to bed in the evening and get up regular time the next day.