Hamster jet lag: running it off.
Scientists have noted that people who become "jet lagged' after long trips adjust more quickly to their new sleep-and-wake schedule if, upon arrival, they engage in outdoor activity such as walking or running. But it is unclear whether this resetting of daily biological and behavioral rhythms is a result of the activity itself, exposure to light, the traveler's conviction that exercise is beneficial or some combination of these factors.
Researchers at the University of Toronto now report that hamsters with simulated jet lag quickly adjust to their new timetable with the help of exercise alone. The finding, say Nicholas Mrosovsky and Peggy A. Salmon in the Nov. 26 NATURE, suggests that it may be possible to design exercise schedules that diminish jet lag among humans.
The investigators housed 20 male hamsters in a room with a cycle of 14 hours of light and 10 hours of darkness. During the dark period, a dim red light was kept on. After the hamsters became accustomed to the light-dark cycle and to running wheels in their cages, their day was suddenly shifted forward by 8 hours so that darkness arrived prematurely. Half were left undisturbed, while the others were removed from their cages 1 hour after the new onset of darkness and placed on unfamiliar running wheels. Three hours later they were returned to their home cages.
The simple experimental procedure resulted in a rapid adjustment to the new light-dark cycle. Hamsters, which are nocturnal creatures, began normal wheel-running following the onset of darkness after an average of only 1.6 days when they had the initial 3-hour running session. Undisturbed animals took an average of 5.4 days to adjust.
When the experiment was repeated without a dim red light during the dark period, undisturbed hamsters required an average of 11.6 days to adjust, compared with 1.5 days for those forced into activity.
The results suggest that, at least among people who are physically fit, appropriately scheduled jogging might be a good way to fight off jet lag, according to the researchers. Other research has indicated that drugs such as melatonin and the tranquilizer triazolam reduce jet lag.
The observed effects of exercise on "jet lagged' hamsters is surprising, writes ecologist Arthur T. Winfree of the University of Arizona in Tucson, in an accompanying editorial. But he says it is not yet possible to make specific exercise suggestions for similarly afflicted humans. He notes that the hamster data "dramatize our ignorance' of daily biological rhythms.