We all know sleep deprivation does a number on the body, but there’s a good chance we’re underestimating just how much. Here’s what a lack of sleep has to do with sports injuries, and how much sleep regular exercisers actually need.
Sleep is one of the most basic things our bodies do, and it takes up a big chunk of our lives. The average person sleeps about 6.8 hours a day, which adds up to roughly a third of their life. When you think about it, that’s a lot of time.
Beyond the awful tired feeling that follows a bad night, poor sleep has plenty of other effects, and most of us have felt them first-hand: irritability, low energy, slow thinking, trouble concentrating and even depression.
But what about the less obvious consequences? Specifically, how does sleep affect exercise and injuries?
What does sleep have to do with injuries?
Sleep is when your body recovers from everything it went through during the day and gets ready for the next one. After a hard session or a big day of physical effort, your body needs enough time to rest and repair. Much of that repair happens while you sleep, and like most processes in the body, it’s driven by hormones. If your sleep is cut short or poor quality, the release of the hormones that help your muscles recover (growth hormones, for example) takes a hit as well.
Your immune system also does most of its work while you sleep, including keeping inflammation in check. Inflammation is a necessary part of healing tissue, so getting enough sleep matters.
Does missing out on sleep make you more injury-prone?
Since the immune system is mostly active during sleep, it makes sense that skimping on sleep causes problems. Research shows sleep deprivation disrupts the endocrine system, protein synthesis and other things your body relies on to recover from exercise. Over the long term, this can raise the risk of overuse injuries.
There’s a mental side too. Sleep loss significantly affects cognitive function, including reaction time and neuromuscular control. That matters a lot in reactive sports like soccer and tennis, where a dip in these skills can lower your game and also leave you more exposed to injury.
A common example is a torn anterior cruciate ligament (ACL), which is linked to poor cognitive performance during play and often happens without any contact at all.
How does sleep affect sporting performance?
There hasn’t been a lot of high-quality research on this, but what exists suggests it takes around 36 hours without sleep before maximal efforts take a real hit. Maximal efforts are things that need peak force in a short burst, like lifting heavy weights at the gym. Surprisingly, performance in sports built on sub-maximal efforts, such as distance running, did suffer.
When it comes to cognitive function, a single sleepless night is enough to notice a drop. Put simply, one night without sleep probably won’t change how high you can jump, but it will likely affect how well you play across the whole game. Think of the number of times you’d lose the ball in a footy or soccer match.
Studies looking at several nights of short sleep in a row found the same results.
Will sleeping more improve your performance?
In one study, participants slept 10 hours a night for six to seven weeks, and the extra sleep had a positive effect on performance across the measures tested. Let’s be realistic, though. With busy lives, most people can’t manage 10 hours every night.
Luckily, another study looked at whether a nap could make up for a night of only four hours’ sleep. It found that even a quick 30-minute nap (a “power nap”) had positive effects on the measures tested, compared with the control group.