A little afternoon recess could help schoolchildren remember what they learned during their morning lessons. New research suggests exercise fours after the acquisition of new information boosts memory and retention.

Exercise immediately after learning does no good. A good workout roughly four hours later is the key, according to researchers at the Radboud University Medical Center in the Netherlands.

"It shows that we can improve memory consolidation by doing sports after learning," Guillén Fernández, a researcher at Radboud's Donders Institute, explained in a news release.

Researchers showed 72 study participants 90 pairs of picture-location associations. One group of participants was made to exercise immediately after the memorization exercise, while another exercised four hours later. A third group, the control, didn't exercise at all.

The workout included interval training on a stationary bike, with participants pushed to a peak of 80 percent of their max heart rate.

Two days later, participants returned to take a test on the picture-location associations. Scientists used magnetic resonance imaging to monitor the participants' brain activity while they took the test.

Those who exercised four hours after learning retained the picture-location associations better than the other two groups.

Scientists published their findings in the journal Current Biology.

"Our results suggest that appropriately timed physical exercise can improve long-term memory and highlight the potential of exercise as an intervention in educational and clinical settings," researchers wrote in their newly published paper.

It's not clear how exercise boosts memory, but previous studies have highlighted the importance of organic compounds called catecholamines, such as dopamine and norepinephrine, in memory consolidation and retention. Exercise has been shown to enhance the production of catecholamines in the body.

Scientists hope further study will explain why learners must wait four hours to gain the memory-boosting powers of exercise.