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As we continue to look at fatigue this month, one helpful tactic in reducing the effects of fatigue is power naps. So, how do power naps help and why do they work?
Naps, especially short naps, have garnered attention for decades as they show immediate benefits and improvements in our cognitive systems after waking. Some benefits are improved memory, greater learning skills, motor skills and alertness.
To begin with, let’s talk about the sleep cycle.
Non-REM 1: You start to loosen up as your electrical brain activity and breathing slows down. Your brain produces theta waves which induce a state of relaxation.
Non-REM 2: Your heart rate slows, brain activity in areas associated with thought, reasoning, language, problem solving and body temperature lowers. The theta waves are joined by brief bursts of electrical activity known as spindles and k complexes which help block out internal and external stimuli.
The first two stages of the sleep cycle generally last 20 minutes and are known as ‘light sleep’.
Non-REM 3: Your body is now fully relaxed. Much slower delta waves turn up and brain activity is reduced to a minimum. You are now in ‘deep sleep’ and the brain is almost exclusively producing delta waves. There is almost no eye movement or muscle activity and it becomes more difficult to wake up, which is why people feel very groggy if woken.
Stage 3 is known as ‘slow wave sleep’ or ‘deep sleep’ and can last 30-40 minutes.
REM: Involves REM (rapid eye movement) sleep where dreaming is most intense. Your brain activity is nearly as active as when you are awake, your heart starts to race, your breathing becomes shallow and your eyes dart back and forth.
While the amount of time you spend in each stage of the cycle differs throughout the night, REM sleep can last up to an hour.
This full cycle takes around 90 minutes and generally repeats until you wake up. A full cycle will likely ensure you wake up refreshed, however, if you are woken up during ‘deep sleep’ chances are that you’ll be left feeling groggy and not well rested. This happens because of sleep inertia – the drowsiness a person experiences after waking from deep sleep. This can cause disorientation and significantly impair cognitive performance and motor dexterity throughout the day.
Sleep inertia can be fatal for those who need to drive right after waking up.
To avoid sleep inertia, most experts agree that the optimal length for a power nap is no longer than 20 minutes.
One study showed that while a 30 minute nap left people with a period of impaired alertness and performance (i.e. sleep inertia), a 10-20 minute nap produced immediate improvements in sleep latency, subjective sleepiness, fatigue, vigour and cognitive performance. These benefits lasted for over two hours after the nap.
Drinking a cup of tea or coffee right before you take a nap can also help to amplify the benefits of a nap. As it takes 15-20 minutes for the caffeine to kick in, you’ll feel extra refreshed and alert when you wake up.
While it’s best to get at least seven hours of sleep every night, a 20 minute power nap can help reduce the effects of fatigue, dramatically decreasing the odds of a fatigue-related crash.
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