How much sleep do you need?
It’s become part of British folklore that Margaret Thatcher survived on only 4 hours sleep a night. According to a BBC news article those around her who needed more sleep were thought of as weak. Throughout history there have been countless examples of military and business leaders who’ve claimed to survive on 4 hours a night.
So is it true that of us who need a solid 8 hours sleep are just wimps?
Sleep researchers suggest that most people need 7-9 hours sleep every night, which is where the magic figure of 8 hours comes from. What’s often missed, though, is that this is a minimum!
The average person needs at least 8 hours sleep a night. Every night. Otherwise we build up what’s called a sleep deficit.
But what’s an average person? If you take part in regular physical exercise: running, gym, football, netball, cycling and so on, then you’re not an average person. If your job is physically demanding such as being a scaffolder, a mechanic, etc., then you’re not an average person. The average person is office-based these days and doesn’t do much exercise; if you’re doing more than the average person, then you need more sleep - in other words, more than 8 hours each night.
Why does a physically active person need more than 8 hours sleep?
We all know that sleep restores the body, but believe it or not it’s really only been during these early years of the 21st century that science has caught up and proven it.
Research from the University of Stanford in the US from 2007 onwards has demonstrated that:
- Glucose is metabolised during sleep. This replenishes the stock of in-muscle ATP which fuels the bodies for the first 90 seconds or so of intense activity (see the previous blog post on carbohydrates)
- Growth hormone is only released into the body when it’s at rest, and given that sleep is maximal rest, this is when muscle grows & repairs the most. For men, between 60-70% of muscle mass growth occurs during deep sleep.
Even now, though, nobody fully understands the complexities of sleep or can account for how it fully restores the body.
Sleep and athletic performance
Most of the research into sleep and the performance of amateur athletes has been done at the Stanford School of Medicine’s Sleep Center. In 2011 researchers there asked 6 basketball players to continue their normal sleep pattern for 2-4 weeks to establish a baseline. Their sprint time and shooting accuracy were then measured.
Next, the basketball players were asked to extend their nightly sleep to a minimum of 10 hours each night for 5-7 weeks. Most of the players found that after a few nights of catch-up, they were waking up naturally before the 10 hours were up… sometime just after 9 hours.
After 6 weeks of this sleep extension the amateur athletes performance was re-measured. It’s the results that matter:
- the players’ sprint time was faster by an average of 0.7 seconds, and
- their free-throw accuracy in shooting increased on average by 9%.
In another Stanford experiment back in 2008, 5 competitive swimmers were similarly asked to undergo sleep extension for 6-7 weeks, with their performance again measured before and after. The researchers found that:
- the swimmers’ sprint time was 0.51 seconds faster on average,
- their turn time was 0.1 seconds faster on average, and
- they increased kick strokes by 5.0 kicks.
It seems that sleep is the secret advantage.
Whether we run, swim, play or compete, we often obsess over our training schedule, our diet, our kit, or the latest electronic toy to help us be better. But we’re missing out on the one thing that can help us make real improvements: sleep
The sleep deficit
Let’s face it, most of us find it hard enough to fit in 8 hours sleep a day, let alone have 9 or more.
So it’s worth looking at the effect of building up a sleep deficit - that is having less than 8 hours a day if you’re a “normal” person, or less than 9-ish hours if you’re active.
Sleep deprivation can mean that glucose is metabolised less efficiently, so that less fuel is available to your muscles for exercise.
Its also been shown that the risk of injury in teenagers is 2.3 times greater if they suffer from lack of sleep (American Academy of Pediatrics, 2012). If you think about it, there’s no reason why that shouldn’t apply to adults as well - when we haven’t slept enough our reactions are dulled and our coordination is a bit slower.
So having too little sleep definitely makes us perform worse. Having enough sleep makes us perform better.
The last word on sleep
Sleep - it’s the simpler, cheaper way to improve your performance.