According to detailed research, the body is perfectly primed for specific tasks at precise points during every 24 hours. "Our circadian rhythms, the peaks and troughs of hormones through our body each day, can work to our advantage if you know how to harness them," suggests Richard Ross, a professor of endocrinology at the University of Sheffield, in the UK. "A part of the brain called the suprachiasmatic nucleus controls these rhythms dictating when we get a surge of, say, the hormone testosterone or the sleep-inducing hormone melatonin."
As a result, experts studying everything from fertility and peak athletic performance to weight-loss and the complexities of jet-lag have discovered ways in which we can make the most of our body clock.
First, get up at the same time every day if you can. "Our body clock is slightly offset. It runs on a cycle of 24.2 hours," says Ross. "To reset it you need to expose yourself to natural light when waking up and, ideally, try to get up at the same time every day." The temptation to have a lie-in at weekends can result in the body clock misfiring so that come Sunday morning, you feel a lot less inclined to get up and out of bed than you do later in the week, when the clock's naturally recalibrated.
Everybody experiences a surge of adrenalin on waking, and Ross adds that "in men, testosterone levels rise during sleep".
Apparently, morning is also the best time for solving problems. "Overnight your levels of the natural hormone cortisol have risen," says Ross. "This helps kick-start your metabolism after a night spent fasting, but also helps you deal with stress a lot better. Often a problem you may have had on your mind the night before is easier to deal with the next morning, thanks to the influence of cortisol."
However, bear in mind that studies show most heart attacks and strokes also occur in the early morning as the blood pressure soars, too.
Definitely the best time of the day to deal with the toughest challenges you have or the hardest decisions to make. Not only because, as Ross points out, your melatonin (sleep) hormone levels are at their lowest so you're mentally at your sharpest, but also because your adrenalin and cortisol levels are still high enough to make difficult situations easier. Work presentations given at this point will not only reach a more alert audience, but your voice will be at its freshest and most confident sounding, researchers have discovered.
On the work front, an 11am meeting with the boss could be the best time to pitch your latest idea, request a sabbatical or seek a pay rise if you're after a positive response. "Not only are you at a peak when it comes to thinking on your feet, but you're also more likely to get what you're after than a late-afternoon meeting when energy levels have dropped," suggests Dr Lance Workman, a specialist in biological social sciences and the author of Evolutionary Psychology (Cambridge University Press). Later in the day you are more vulnerable to anxiety while your boss is more likely to be irritable.
Breaking for lunch at 1pm may have the disadvantage of joining like-minded hungry masses at the food counter, but as far as your body clock is concerned it's the perfect time to eat. "Your energy levels will have dipped since breakfast but also the body's digestive system is primed to tackle a hearty meal more efficiently than it would later in the day," suggests Workman. Even so, you can still experience a blood-sugar rush, especially if your lunch is too high in carbohydrates, which may lead to an energy dip immediately after lunch.
That's why a siesta or "power nap", if you can take one, is best done at around 2pm. With another shift in the circadian rhythm comes a natural dip in our energy levels, making us feel sluggish - especially if we've had a heavy lunch. If you're going to sneak in a nap make it a snappy one though. According to research from the University of Düsseldorf, Germany, a mere five-minute catnap is all one needs to jump-start the brain for the afternoon. The German studies, published in the Journal of Sleep Research, showed that short naps help to reboot the brain's memory-processing ability without disrupting night-time sleep.
By now, gravity has taken its toll on the body, and sportsmen and women in particular are advised not to buy shoes before around 3pm. "Shoes should always be bought in the late afternoon as feet tend to swell during the day and are at their largest around this time," explains Abid Hussain, podiatrist with drfoot.co.uk.
Our circadian rhythm also affects body temperature. "Most people are at their coolest maybe an hour or two before they wake up," explains Ross. So an early-morning jog could raise your risk of injury since your muscles may not have warmed-up enough. "If you want to exercise most effectively then you should do so when your body temperature is at its highest. For most of us that is late afternoon," says Ross. Research from California's San Jose University also shows that reaction time and hand-eye co-ordination are best at this time of day.
And if you're booking an appointment for anything that combines pain with gain - be it having a troublesome tooth removed or an hour with a personal trainer - then go for the 4pm slot, too. "Our pain threshold is at its highest mid to late afternoon," says Workman. And if you're trying to sneak in a favourite snack or particularly calorific food, then eating it within two hours of an afternoon workout is the ideal time for that, too. US research shows that during this post-exercise window, the sugar in that food will help replenish the glycogen stores in your muscles and not necessarily go straight to your hips.
During the working week it pays to start getting ready for bed around 9-10pm. "At this time the brain begins to produce the sleep and relaxation hormone, melatonin," says Ross. Taking a shower before bed will cool your body temperature, which in turn will spike your melatonin levels. "Your growth hormones are increasing to a peak through the night, so most muscle repair and bone development occurs at this time - making a good night's rest vital." But if you're trying to tap into the creative caverns of your mind, then setting your alarm to wake you around four to five hours after you've gone to bed - say at 3am - could spur the great ideas you're looking for. According to research by the Body Rhythms and Shiftwork Centre at the University of Wales, we are at our most mentally inventive in the early hours, which may explain why our dreams are often so weird, too.