If you're an athlete, sleep is especially important. Rigorous exercise takes a toll on the body and nervous system, and studies suggest sleeping is key to the healing and recovery process.
Some athletes refer to something called sleep hygiene, a set of behaviours designed to gradually prepare the body for sleep. Sleep hygiene may include things like limiting screen time at night and cutting back on how many alcoholic beverages you drink close to bedtime.
But it turns out that aside from making sure you're getting the right amount of sleep, there's another factor to consider: Your biological clock.
Depending on whether you're an early bird or a night owl, you might have better athletic performance at a certain time of day.
Elise Facer-Childs is a doctoral researcher working at the University of Birmingham in the field of chronobiology, who studies what times of day people perform their best, depending on their sleep cycles and biological rhythms. Everything we do, she says, affects the time of day that we're at our optimum level.
"The main thing that we're interested in in terms of sleep patterns and body clocks is the different types of people that we have," Facer-Childs told Business Insider. "We like to generalise and say we all need 8 hours sleep, or you should go to bed then and wake up then, but actually we're all different. We've got different genetics, different lifestyles, different behaviours, and that's reflected in the body clock type."
In simple terms, there are morning people and evening people; those who get up first thing without needing an alarm, and those who struggle to get out of bed but stay up late into the evening to burn the midnight oil. And this can have an impact on how we perform athletically.
Early birds performed best at midday, and night owls peaked at about 8 p.m.
In previous literature, athletes have been grouped together to study the optimum time to perform. In these cases, research shows that peak performance tends to occur in the early evening, between 6 and 8 p.m.
However, Facer-Childs explained that her research group wanted to divide the athletes up into morning and evening people and test them separately and see if this result differed.
They tested individuals at six times throughout the day, from 7 a.m. to 10 p.m., by making them run to exhaustion. What they found was that early birds were performing best at about midday, and night owls peaked at about 8 p.m.
"We automatically see these differences in performance linked to their peak," Facer-Childs said. "But also the early birds weren't physically at their best as soon as they woke up at 6 o'clock in the morning - it still took them a bit of time to wake up."
Many different factors can affect the quality of our sleep, but the biggest one is light exposure. Our brains are affected by light, which is what resets our biological clocks every day. That's why looking at your phone late at night can hinder you in drifting off.
In fact, all of our organs have their own clocks, and respond to different stimuli. The liver, for example, responds when we eat. So if you have a meal at 1 a.m., your liver thinks that you should be awake for a few more hours, whereas your brain knows it's dark outside and wants you to go to sleep. This imbalance can affect both physical and cognitive performance.
Caffeine and alcohol intake also have an effect. For example, drinking coffee to wake yourself up might feel like a quick fix, but ultimately if you drink too much, then you're going to be impacting your ability to sleep later on in the evening. If that happens, and you can't sleep until very late, then you may be more likely to repeat that behaviour the next day, and the next, and so on.
Sleep deprivation in general can also be dangerous. One study from 2000 showed that if someone is kept awake longer than usual, at around 3 or 4 in the morning their cognitive performance is actually lower than it would be if they were over the alcohol limit to drive.
"Someone driving at 5 in the morning or you know performing surgery, they might as well be drunk," Facer-Childs said. "Which is pretty crazy when you think of it that way."
The biological clock vs. the social clock
According to Bleacher Report, at least a dozen NFL teams have recently explored some kind of sleep monitoring program, with the use of wearable devices like Fitbits and apps. They also report that many NFL veterans have strict sleep routines, including Tom Brady, who goes to bed at 9 p.m.
Unfortunately, sleep can be overlooked, especially when our biological clocks are competing with the social one. Ideally, Facer-Childs says, these clocks should be in time, but this rarely happens when we're so easily governed by the 9-5 schedule.
Maybe we should take a leaf out of Usain Bolt's book and try and get a few more hours a night. Nobody's expecting you to suddenly run 100 meters in less than 10 seconds, but you might be surprised at the benefits you feel.
"We tend to think of sleep as more of a luxury in our day and age with our 24 hour lifestyle, when it's probably the most important behavioural and physiological process that we go through," Facer-Childs said. "Actually understanding and having more awareness of this research area could help psychologically, not just physically, by understanding your athletes or your employees and knowing what fits them."