By Justin Bieber

Nowadays，it is possible to travel to distant parts of the globe in several hours.This can result in the traveler ending up in a part of the world where time is different from his or her own“body clock”,which controls our sleep patterns.

If we travel east or west by more than four time zones （hours） then we will usually be affected.

In the past when people traveled by sea,there was enough time for the body to adjust to the local time,but with the advent of modern high speed aircraft the body does not have time to adjust.Therefore,there is the term “jet lag(時差反應(yīng))”.It normally takes one day per time zone(hour)for the body to adjust to its new surroundings.

The effects of jet lag are usually tiredness and insomnia（失眠）but can also include:poor concentration,nausea（惡心）,vomiting(嘔吐)， constipation (便秘)and general malaise(不舒服).The effects are made worse by alcohol.

Sleeping while flying may help to reduce the symptoms(癥狀)of jet lag,but long periods of immobility aboard aircraft can make the traveler feel numb(麻木的)in the legs.The following are some other tips of reducing the symptoms of jet lag：

①Avoid traveling when you are already tired and rest before departure.

②Stopovers on long flights may be helpful.

③A relaxed flight is important.

④Sleeping tablets will help you to sleep and be correspondingly alert(相對警惕的)during the next day,but they do not speed up adjustment to the new time zone.

⑤Remember the actual traveling time will usually be at least twice the actual time spent in the air since it will include traveling to and from and hanging around in airports.

⑥Avoid heavy commitments on the first day after arrival.