Regular exercise could be the key to improving your memory, a new study suggests.
Researchers from the National Institute on Ageing found that exercise such as running triggers a protein that enhances brain cell growth.
They found that levels of the protein, called cathepsin B, increased in the blood and muscle cells of mice after they'd used their exercise wheels daily for several weeks.
Researchers said upping fitness levels could also be beneficial to human memory.
"We did a screen for proteins that could be secreted by muscle tissue and transported to the brain, and among the most interesting candidates was cathepsin B," senior author Dr Henriette van Praag commented.
"Moreover, in humans who exercise consistently for four months, better performance on complex recall tasks, such as drawing from memory, is correlated with increased cathepsin B levels."
The scientists also found that mice that had been genetically modified so they no longer produced cathepsin B didn't perform as well in memory tests than their unmodified counterparts.
To test memory function, a mouse was placed in a small pool and had to learn to swim to a platform that was hidden just below the surface of the water.
After doing this task for a few days, normal mice eventually learned where to find the platform.
However, when both groups ran before their swim test, the normal mice were better able to recall the location of the platform, while the mice unable to make cathepsin B could not remember its location.
"Overall, the message is that a consistently healthy lifestyle pays off," Dr van Praag concluded.
"People often ask us, how long do you have to exercise, how many hours? The study supports that the more substantial changes occur with the maintenance of a long-term exercise regimen."
The study, which is published in the journal Cell Metabolism, isn't the first to link exercise to memory.
Earlier this month a study from Radboud University Medical Center in the Netherlands found that exercising four hours after learning something new could help you remember it.