Bad Night's Sleep? This Much Exercise Needed To Reset Your Brain—Study

If you've suffered from a bad night's sleep, a day of brain fog, sluggishness and distractions is often on the cards. But you're in luck: scientists have revealed a simple way to banish the brain fog and boost cognitive function in as little as 20 minutes.

Sleep is essential for our mental and physical wellbeing. And yet, one in three adults in the U.S. report not getting enough of it, according to the U.S. Centers for Disease Control and Prevention. The CDC recommends that adults sleep for seven to nine hours every night, but work, family and other commitments often get in the way of achieving these targets.

In the long term, chronic sleep deprivation can contribute to heart disease, obesity, neurodegenerative disorders and depression. But even in the short term, a lack of sleep can take a toll on our attention span, judgment, emotions and general cognitive function. A new study from the University of Portsmouth in the U.K. offers a glimmer of hope to anyone struggling with sleep-induced brain fog.

"We know from existing research that exercise improves or maintains our cognitive performance, even when oxygen levels are reduced," Joe Costello, a researcher at the university's School of Sport, Health and Exercise Science and senior author on the study, said in a statement. "But this is the first study to suggest it also improves cognitive performance after both full and partial sleep deprivation, and when combined with [oxygen deprivation.]"

Their study, published in the journal Physiology and Behavior, involved two experiments, each with 12 participants. The first looked at the impact of partial sleep deprivation (three consecutive days of five hours sleep a night) on the participants' cognitive performance; the second looked at the impact of total sleep deprivation (no sleep) in combination with oxygen deprivation. In both experiments, all participants saw a significant improvement in cognitive performance after just 20 minutes of moderate intensity activity on an exercise bike.

"If the exercise was any longer or harder it may have amplified the negative results and became a stressor itself," Costello said.

But how does 20 minutes of cycling actually impact the brain?

"One potential hypothesis for why exercise improves cognitive performance is related to the increase in cerebral blood flow and oxygenation," Costello said. "However, our findings suggest that even when exercise is performed in an environment with low levels of oxygen, participants were still able to perform cognitive tasks better than when at rest in the same conditions."

In their paper, the researchers speculate that this improved cognitive function could actually be down to changes in hormones in the brain—like dopamine and adrenaline—as well as cerebral blood flow, arousal and motivation.

"The findings significantly add to what we know about the relationship between exercise and these stressors, and helps to reinforce the message that movement is medicine for the body and the brain," Costello said.