The participants were randomized into "active" and "passive" groups and seated at leg extension resistance exercise machines.
Previous studies have shown that memory may be improved by several months of aerobic exercises, such as running, cycling or swimming. However, the findings of the new study - published in the journal Acta Psychologica - demonstrate that a similar memory boost can be achieved in a much shorter period.
"Our study indicates that people don't have to dedicate large amounts of time to give their brain a boost," says Lisa Weinberg, the Georgia Tech graduate student who led the project.
As well as looking at aerobic exercise, Weinberg's team also examined how resistance exercise - weightlifting, push-ups and sit-ups - might affect memory.
The team recruited 46 participants (29 women and 17 men), who were randomly assigned into two groups. For the first part of the experiment, all participants viewed a series of 90 images on a computer screen.
These images were split evenly been photographs that had been classed "positive," "neutral," and "negative." These ranged from pictures of children playing on a waterslide, to photographs of clocks, to images of mutilated bodies. The participants were asked to try and remember as many of them as they could.
Next, the participants were randomized into "active" and "passive" groups and seated at leg extension resistance exercise machines.
The active group were told to extend and contract each leg 50 times, at their personal maximum effort. The passive group were told to simply sit in the chair and allow the machine to move their legs.
The blood pressure and heart rate of the participants were monitored, and saliva samples were collected.
'Active' group showed improved recall of images
Two days later, the participants were again shown the original 90 images they had seen previously, but this time they were mixed in with 90 new photos that the participants had not seen before.
The researchers found about 50% of the original photos were recalled by the passive group, while the active group remembered about 60% of the images.
All of the participants were better at recalling the positive and negative images than the neutral images, but this was even more true for the active participants. The researchers suggest that this is because people are more likely to remember emotional experiences following short-term stress.
The team believes their results are consistent with previous research in a rodent model that found stress responses result in releases of norepinephrine - a hormone that may improve memory.
Analyzing the saliva from the participants, the team found that the active group showed increased levels of alpha amylase in their saliva - a marker of norepinephrine.
Audrey Duarte, an associate professor in the School of Psychology at Georgia Tech, describes the results:
"Even without doing expensive fMRI scans, our results give us an idea of what areas of the brain might be supporting these exercise-induced memory benefits. The findings are encouraging because they are consistent with rodent literature that pinpoints exactly the parts of the brain that play a role in stress-induced memory benefits caused by exercise."
The Georgia Tech study looked at weight exercises, but Weinberg says that other forms of resistance exercise - such as squats or knee bends - would most likely produce similar results. She explains the study in the video below.