The body clock determines almost all of the body's daily behaviours. In addition to driving our 24-hour sleep-wake cycle, it regulates hormone levels, body temperature, blood pressure, alertness and performance.
Getting in sync with your body clock offers the ability to make the most of your day by planning tasks for times when your body is naturally better equipped to handle them.
"Understanding circadian rhythms is critical to maintaining optimal levels of performance and health, as any disturbance to the natural cycle can result in impairments in almost all the functions of the body," explains Shantha Rajaratnam, president of the Australasian Sleep Association.
Even though circadian rhythms are typically an internally driven process, a number of environmental or behavioural responses can have an impact on this 24-hour time profile.
By setting your clocks for better health and vitality, he says you can get an insight into the secret life of your body.
6am Wake up, but try to do so without the aid of an alarm clock. "The best time to wake up is when you feel well rested and your body physiology promotes wakefulness," says Rajaratnam.
7am Go for an (easy) stroll. A rise in adrenaline and cortisol mean blood pressure is at its highest within the first few hours of waking. While any exercise is better than none, some experts believe a morning run could place extra pressure on a vulnerable heart. Check with your doctor if you have concerns.
10am Get stuck in! You might think it's just your morning coffee kicking in, but a distinct spike in concentration and alertness can be enjoyed mid-morning. Rajaratnam says well-rested individuals can expect to have a fairly consistent level of performance for the rest of the day, so make the most of this period of increased performance.
Noon Head outdoors. At least 15 minutes' exposure to sunlight will help keep your circadian clock on track and encourage production of melatonin later in the evening, as you prepare for sleep.
12.30pm Choose aqua. Rethink that second drink if you enjoy a tipple with lunch, especially if you're planning to drive. The body's ability to metabolise alcohol isn't as effective at this time.
2pm Make a phone call to distract the sweet cravings, or have healthy nuts ready. It might be tempting to curl up under the desk for a nap, as the body experiences another small dip in alertness. This also explains why we're more tempted to reach for something sweet to dunk in our afternoon cuppa for a short-term energy boost.
5pm Hit the gym. Your body is experiencing a peak in core body temperature and it's a great time to make the most of your best cardio efficiency and muscle strength.
8pm Wind down. Dimming the lights helps your body prepare for a good night's sleep. Studies have shown that exposure to even low-level light can substantially affect this phase of the human circadian rhythm. "Exposure to too much light before bed can result in a major delay to the circadian clock and shift the sleep wake time to later, which will then affect sleep quality and alertness the next day," says Rajaratnam.
10pm Your body's secretion of the melatonin hormone started about an hour ago, so now is the perfect time to go to bed. But while you're dreaming, your body is still hard at work. Rajaratnam says one of the significant areas of growth during sleep is in memory consolidation, which means all the experiences and learning you have had throughout the day get filed away in your memory for later recollection.
Midnight The body's ability to metabolise fats is poorest at this time, and may explain why shift workers have a higher rate of cardiovascular disease.
2am It's called beauty sleep for a reason. A nana nap is no match for the deep restful sleep of night when it comes to skin repair. The skin's metabolic rate is much faster during deep sleep, which hastens the repair of skin damage such as that from ultraviolet rays.
3am Shift workers and night owls beware - a decline in alertness and increased reaction time make this the peak risk period for accidents.
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