An intense workout for as little as 20 minutes can enhance episodic or long term memory about previous events by about 10 percent in healthy young adults, say researchers.

Many existing studies have shown that long aerobic exercises like running can boost memory but the present study had participants lift weights just once every two days before testing them.

"Even without doing expensive MRI scans, our results give us an idea of what areas of the brain might be supporting these exercise-induced memory benefits," said Audrey Duarte, an associate professor from the Georgia Institute of Technology' school of psychology in the US.

For the study, the team showed 90 photos to the participants on a computer screen before they started stretching their legs.

The participants returned to the lab 48 hours later and saw a series of 180 pictures - the 90 originals were mixed in with 90 new photos.

Those who exercised remembered about 60 percent of the photos.

"Our study indicates that people do not have to dedicate large amounts of time to give their brain a boost," said Lisa Weinberg, a Georgia Tech graduate student who led the project.

Although the study used weight exercises, resistance activities such as squats or knee bends would likely produce the same results, noted Weinberg.

"The findings are encouraging because they are consistent with rodent literature that pinpoints exactly the parts of the brain that play a role in memory benefits caused by exercise," concluded Lisa Weinberg.

The study appeared in the journal Acta Psychologica.