Good timing is crucial. If you don't believe that, just consider long-forgotten Clarence Chamberlin, who in 1927 flew the tiny plane Miss Columbia across the treacherous Atlantic--2 weeks after Charles Lindbergh.

Or look at your own body, which also has to be blessed with impeccable timing if it's going to look heroic. Perform the wrong activity at the wrong hour of the day, and your body will only sputter and wheeze like an aging prop plane. But get the timing right, and you'll improve not only your health but also your performance at work, in the gym, and even in the bedroom. So get ready to revise your daily planner. We've discovered the best time to ...

Father a child | 6 A.M. | "Men are most potent in the morning, and we know that stronger ejaculations are associated with higher sperm counts," says Marc Goldstein, M.D., professor of urology at Cornell University medical college. To improve your odds even more, focus on foreplay. High levels of arousal can improve the strength of your ejaculation and increase your chances of success.

Put on cologne |7:05 A.M. | You'll be less likely to splash on too much if you put on your Brut before breakfast. "Your sense of smell is most acute after you've fasted. It's evolutionary--your nose is better equipped to help you track down food when you're most hungry," explains Dr. Hirsch.

Take a multivitamin | 7:45 A.M. | The exact time you take it isn't as important as making sure you swallow it with a meal--preferably one that includes fat, says Elizabeth Somer, R.D., author of Age-Proof Your Body. You need a little fat--the amount in your cereal and milk is enough--to efficiently absorb fatsoluble vitamins, including A, D, E, and K.

Fly west for business | leave at 9 A.M. your time | If you're on a business trip and you're staying only one night, it might be wiser to trick your body into thinking you never left home. "If you don't want to reset your body clock, a daytime flight is best," says Dr. Moore-Ede. Keep the blinds drawn as late as possible the next morning. Your brain will think it's getting more night hours, and you'll have less of an adjustment to make when you fly home.

Eavesdrop on what your coworkers are saying about you | 9:15 A.M. | Your hearing may dull as the day progresses. The reason: To conduct sound efficiently, the tiny hairs in your inner ear need to wave like blades of grass in the wind. But daily exposure to noise that's loud and continuous batters those hairs like a hail-storm. "To rebound, the hair cells in your ear need protection and a period of quiet," explains Evelyn Cherow of the American Speech-Language-Hearing Association. Most of us have that quiet time during sleep, which is why our hearing may be sharpest in the morning.

Read the box scores in the newspaper | 10 A.M. | Read them any earlier and those tiny numbers will look even smaller. "Most men try to read the newspaper first thing in the morning, but their eyes need time to adjust before they can focus efficiently," says Anne Sumers, M.D., an ophthalmologist. Fluid builds up in your corneas while you sleep, and the swelling can cause blurred vision. It's not a sign you're going blind. "The problem resolves on its own within a few hours," says Dr. Sumers.

Do some actual work | 10 A.M. | Cortisol, a hormone that promotes mental alertness, starts to build up in your body 2 hours before you get up in the morning. "Cortisol helps you wake up and counters sleep inertia--that fuzzy period before you feel you're really wide-awake," says Dr. Moore-Ede. "By midmorning you're best prepared to handle both creative and analytical tasks."

Eat fat | noon | You probably thought you could burn off the fat in that sausage-and-cheese-omelette breakfast throughout the day. Unfortunately, your heart might not make it that far. "Recent studies indicate that eating fat can cause cellular changes that may trigger a heart attack within several hours," says Richard Stein, M.D., spokesman for the American Heart Association. "Since we know that early mornings and late nights are peak risk times for heart attacks, I wouldn't push my luck with a fatty breakfast or dinner." If you must, have your greasy cheeseburger at lunch.

Stretch | 12:15 | P.M. Stretching after your workout is beneficial, but if you're like most men you probably rush through it. So instead, use the time between sets to stretch. In a recent study, Wayne Westcott, Ph.D., of the South Shore YMCA near Boston, found that exercisers who stretched a worked muscle for a mere 20 seconds before moving on to the next machine in their workout gained more flexibility and strength than nonstretchers. After 10 weeks they performed an inch better on a sit-and-reach test and were 19 percent stronger on the leg curl than those who didn't stretch.

Do some heavy lifting |2 P.M. | To lift properly you need to rely on your legs, and a French study suggests that leg power is greatest in midafternoon. When researchers tested 23 men at 9 A.M., 2 P.M., and 6 P.M., they found that leg strength was as much as 7 percent higher during the 2 P.M. session. Keep this in mind when you're playing sports, too: The researchers concluded that such differences could have pronounced effects during competition.

Take a nap | 3 P.M. | Halfway between starting and ending your day is the ideal time to take a short snooze, says William Anthony, Ph.D., author of The Art of Napping. If you're up at 7 and down at II, your circadian rhythms are primed for sleep at 3. "A 15- to 20-minute nap will be enough to maximize your energy. You'll wake up better prepared for work, your workout will go better, and your evening will be smoother," he says. If your boss balks, tell him to take the half-hour out of your lunch. "And tell him that the facts are clear that napping increases productivity," says Anthony. "Science is on your side."

Eat carbohydrates |3:30 P.M. | That snapat-everyone feeling that hits in the afternoon is your body telling you it needs a serotonin fix, says Judith Wurtman, Ph.D., a nutritionist at MIT. Serotonin is a brain chemical that helps you feel calm and in control, and your body makes it with the help of carbohydrates. Give yourself what Wurtman calls "an emotional snack" of popcorn, pretzels, or even some fat-free candy. In 30 minutes you should feel calmer.

Go for a long, hard run | 4 P.M. | A recent study suggests that your aerobic power is greatest in the late afternoon. When 24 subjects were asked to exercise to exhaustion in tests given at 8 A.M. and 4 P.M., they lasted 9 percent longer and their oxygen intake was 7 percent higher in the afternoon test.

Fly west on vacation | arrive at 6 P.M.| their time I If you're flying west for an extended stay and the time difference is more than 5 hours, book your flight so you'll land at about 6 P.M. local time. Jet lag occurs when light hits you at the wrong time--your glandular watch says sundown, but the light outside says daytime. The combination throws off production of melatonin, a sleep inducer, and you may feel sleepy at midday and wide-awake at night. "To put yourself in sync, you want to see light in the early evening. That will help you reset your body clock," says Dr. Moore-Ede.

Visit a friend who has the flu | 9 P.M. | Lymphocytes, your immune system's soldier cells, swell their ranks as bedtime approaches. "There's a definite interaction between sleep and immune function," says Martin Moore-Ede, M.D., Ph.D., president of Circadian Technologies in Cambridge, Massachusetts. "Sleep-deprived people have lower immunity and experience more illness."

Pick up a hose | midnight | To minimize weeds in your garden, work by the light of the moon, says Mike McGrath, host of the public-radio show You Bet Your Garden. "When you turn over soil before planting, you're digging up thousands of weed seeds that have been lying dormant beneath the surface, maybe for 60 years," he says. If you hoe during the day, sunlight kicks those sleeping seeds into action so they can grow into big, healthy weeds. "If you work by moonlight, any weed seeds that are re-covered by soil won't get the initial sunlight they need, and they won't germinate."