What is beneficial to do in the morning, what about daytime and how do we best end our day in the evening? This is all related to our internal day clock.
Want to lose those last few kilos, perform at your peak physically and mentally, or simply recover better from illness? The secret could be to tap into your body's hidden rhythms.
"Did you know that our bodies are so finely tuned into a circadian rhythm that there are better times of day to break an athletics record, schedule a painful medical procedure, sit an exam, or even conceive?"
Chronobiologists study why and how our bodies react to time. They say we all have an internal ''master clock'' - a nucleus in the brain that is responsible for the synchronisation of the body's essential processes. Dr. Gerard Kennedy of Victoria University in Melbourne says:
''Each cell has its own little clock which ticks away but without the master clock they quickly lose synchronicity. It's a bit like the maestro of the orchestra conducting all the other instruments, which are the other cells in the body.''
It all starts when you go to bed. Kennedy says there is no set ''best'' sleep and waking time and that it's important to tune into your body's clues. There are two extreme ends of people's body clocks.
''At the one end we've got the larks and at the other the owls but most of us are in the middle,'' he says. ''For the average person, bedtime is around 10.30pm and getting-up time is around seven to eight in the morning.''
Waking and sleeping times also depend on how much sleep you need. Some people are short sleepers, needing less than six hours a night whereas others need more than nine, so this affects when you need to go to bed.
A leading researcher in body clock function, Dr Michael Smolensky, a professor of environmental physiology at the University of Texas School of Public Health, says that for peak health it's important to get in sync with your body clock. How do you do this?
- Wake up at the same time every day to ensure all-day energy.
''Your internal clock controls your production of the sleep-triggering hormone melatonin,'' Smolensky says. ''Keeping the gap between your wake-up time and bedtime constant ensures that melatonin peaks in the evening hours when you really need it.''
- The body's ability to control blood sugar is also ruled by our body clock and changes throughout the day. Eating a protein-rich breakfast and lunch will help keep blood sugar steady during waking hours.
- Get a half-hour dose of sunlight first thing.
''Morning light exposure sets your internal clock, so your body temperature, energy level and alertness stay high during the day.''
And if you need to solve a tricky problem or do some high-level thinking, plan to strain your brain in the morning.
By the clock
According to research there are ideal times for different activities:
7am Try for a baby. Hormone levels are highest and sperm counts peak. Blood pressure also rises, making it easier for you to get out of bed and walk around.
9am Schedule a surgical procedure. Medical staff are likely to be less fatigued!
10am Study for or sit an exam. You're most alert from 10-11am; the brain is most rested. Get your blood pressure and cholesterol checked. Their levels can vary throughout the day but high-morning readings are more likely to indicate a health problem.
Noon Take medication. Joint pain, such as osteoarthritis, peaks in the afternoon and evening. Take medication about lunchtime to give it time to work. Negotiate a tricky deal. It also is apparently the best time for an argument because verbal reasoning skills peak about noon!
1-2pm Visit the dentist. Research shows that local anaesthetics last three times longer if given between 1pm and 3pm, and our pain threshold is at its highest.
2-3pm Take a nap. Your metabolism slows between 2pm and 3pm and this is when our bodies are programmed for a short sleep.
4-6pm Exercise. More Olympic records have been broken in the late afternoon than at other times. Lung capacity is at its maximum and core temperature is raised, speeding nerve impulses and improving co-ordination. Research shows that strength and endurance climb about 5 per cent between 4pm and 8pm, compared with morning hours, so you can push yourself harder. Your muscles are warmer, too, which will help you avoid injury.
5-7pm Eat carbohydrates. Refuel energy stores up to two hours after exercising and your muscles will thank you. Your muscles can best take up energy consumed and your body is less likely to store kilojoules as fat. This is also the ideal time to enjoy a glass of wine because your liver is more able to metabolise the alcohol.
10pm Enjoy some horizontal dancing! Libidos hit their peak in the late evening.