Whether you're a "Road Warrior" who has piled up thousands of Frequent Flier Miles, or someone who is planning a vacation to a distant location, you are likely to experience the phenomenon of "jet lag," which can have a profound effect on your sleep and alertness. Every day, millions of travelers struggle against one of the most common sleep disorders — jet lag. For years, jet lag was considered merely a state of mind. Now, studies have shown that the condition actually results from an imbalance in our body's natural "biological clock" caused by traveling to different time zones. Basically, our bodies work on a 24-hour cycle called " circadian rhythms ." These rhythms are measured by the distinct rise and fall of body temperature, plasma levels of certain hormones and other biological conditions. All of these are influenced by our exposure to sunlight and help determine when we sleep and when we wake.

“Budging the circadian clock” after leaping several time zones is hard – but a sleep doctor says it can be done.

When he got to Yorkshire, England, on a recent trip, Robert Rosenberg began one of his standard routines: He laced up his sneakers and took an afternoon jog.

Rosenberg was, in reality, doing more than getting fresh air and exercise; he was adjusting his body to the local time zone, which was eight hours ahead of his home in Arizona. Rosenberg, a doctor of sleep medicine who runs the Sleep Disorders Center of Prescott Valley, in Prescott, Ariz., was beating jet lag with exercise and exposure to afternoon sunlight. Both are elemental to overcoming jet lag, he said.