On your marks, get ready--sleep.

Results of a new poll confirm what most Americans already know: we're really tired. Although experts recommend at least eight solid hours of sleep a night for optimum health, the majority of us get less than seven, and a third of the population sleeps six and a half hours a night or less. Nearly half of those polled say they will forfeit sleep in order to do more.

If you're among the sleepy, your missed sleep costs you plenty. The quality and quantity of your work is reduced, concentration is impaired as well as your ability to handle stress. With all these tired folks driving around, our roads are less safe, which has serious implications for runners sharing those roads. And, of course, your own running performance is reduced. It is also likely that your need for rest and recovery is increased, and your risk for injury may be higher. Numerous studies have examined the effects of sleep deprivation on athletic performance and the results are discouraging.

Studies have shown sleep deprivation to decrease weight lifting performance, decrease time to exhaustion in aerobic exercise, increase ratings of perceived exertion, increase insulin resistance and decrease glucose tolerance, alter the supply of energy to the muscles, increase the stress hormone cortisol, and reduce running economy. In a review of the sleep and performance literature, researchers have concluded that sleep deprivation strongly impairs human functioning overall. In another study, depriving your body of sleep causes hormonal changes that mimic the effects of aging.

If you routinely make tradeoffs of sleep for work or even sleep for training, consider making some lifestyle adjustments. In the poll mentioned above, about 85% say they would sleep more if they knew they would be healthier, avoid injuries, or improve their memory; more sleep can do those things. For more information about getting healthy sleep visit www.sleepfoundation.org.

(Lancet, 1999, Vol. 354, No. 9188, pp. 1435-1439; Sleep, 2001, Vol. 24, No. 4, pp. 392-400; Journal of Clinical Psychiatry, 2001, Vol. 62, suppl 10, pp. 33-38; Sleep, 1996, Vol. 19, No. 4, pp. 318-326; Journal of Sports Science, 1993, Vol. 11, No. 2, pp. 109-112; Sports Medicine, 1989, Vol. 7, No. 4, pp. 235-247)

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* Limit caffeine. Although individual responses vary, for some people caffeine can disturb sleep for as much as 12 hours later. Try avoiding caffeine in any form after lunch and see how it affects your sleep.

* Limit alcohol. A nightcap might allow you to fall asleep more quickly, but it impairs the quality of sleep.

* Watch your evening consumption. Foods that cause indigestion can disturb sleep and too many fluids can interrupt sleep.

* Exercise yes; overtraining no. While regular exercise promotes healthy sleep, overtraining impairs sleep significantly. You can monitor your morning pulse rate to check for overtraining. A higher than usual rate may indicate overtraining.

* Keep a regular schedule. Physiologically, circadian rhythms--the daily fluctuations of physiological phenomena--play a huge role in your functioning and performance. The more regular your habits, the better.

(National Sleep Foundation)