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Does High-Intensity Exercise Improve Memory?

A recent study explores the cognitive effects of working out.

Source: Rido/Shutterstock

By Cameron Evans

Exercise helps us stay fit and makes us feel more energized, but if you crave further motivation, a new study adds to the evidence that working out is useful for even more than that.

Researchers at McMaster University in Canada found that young adults who undertook six weeks of high-intensity exercise significantly improved on a measure of what they call high-interference memory, which is used to distinguish visual patterns. “Faces are very similar,” says Jennifer Heisz, a cognitive neuroscientist and assistant professor of kinesiology at McMaster University. “You have two eyes, a nose, and a mouth, and being able to distinguish that it’s your face and not my face in a big crowd relies on this high-interference memory.”

For the study, which was published in the Journal of Cognitive Neuroscience, researchers recruited 95 healthy participants (58 women, 37 men, with an average age of 21). Each was assigned to one of three groups: an exercise training group, a group that received combined exercise and cognitive training, or a control group that did not complete either form of training.

The exercise and cognitive training sessions were conducted three times a week. The exercise protocols, completed on stationary cycle machines, were individualized based on pre-testing of each participant, and each session included alternating, minute-long high-intensity and recovery intervals. Each week, the researchers increased the resistance for the high-intensity intervals to maintain a desired target heart rate. Those who also participated in cognitive training sessions played an increasingly challenging computer game in which they learned the locations of similar, grayscale faces that were hidden by cards, then attempted to match them.

To assess memory improvements following the intervention period, participants were shown computer images of everyday objects, such as apples and lawn mowers, and asked to place the objects in one of three categories: an image they had seen before, one they had never seen, or an image similar to one that they had seen. The images that were similar, but not exactly the same (for example, two versions of an apple) tested high-interference memory.

The results showed that, unlike the control group, participants who underwent the cognitive and exercise training sessions improved on the high-interference memory task. So did those who only received exercise training.

“It’s pretty amazing to show that exercise can improve memory, especially in young adults,” Heisz says. “We typically think of young adults as being at the prime of brain functioning, but we can still improve this very important aspect of memory in these individuals over a short period of time.”

The researchers also measured physiological changes over the course of the study. Compared to participants whose aerobic fitness gains fell below the median, those who saw greater fitness advances (or "high responders") ended the study with higher levels of brain-derived neurotrophic factor (BDNF) and insulin-like growth factor-1 (IGF-1), proteins that increase the functionality of brain cells. “When (brain cells) function better, especially in the hippocampus, it improves memory,” Heisz says. (The "high responders" also showed additional memory improvement in the cognitive-and-exercise condition relative to the exercise-only condition.) Yet the levels of BDNF and IGF-1 did not differ between the control and intervention groups. "Our results point to individual differences in response to exercise training that may mask an effect at the group level," the researchers write.

Andrew Whiteman, a Boston University graduate student who has researched memory at the Center for Memory and Brain, says he thinks the study is well-designed and that the authors’ use of the mnemonic similarity task (MST) is fitting. “The MST is thought to recruit the hippocampus and supporting structures and so makes a good choice for probing memory in this type of paradigm,” he explains.

“Doctors don’t really need more reasons to recommend aerobic exercise to their patients beyond the long-known cardiovascular and metabolic benefits, but the body and mind are tied together,” Whiteman says. “We now think that exercise improves health in nearly all major organ systems, including the brain, and this study lends more support to that hypothesis.”

One way to incorporate high-intensity exercise into an exercise routine, Heisz says, is to switch up the patterns with which you use a workout machine, such as an elliptical: “Instead of just going constantly at one intensity, ramp up the wattage or ramp up your speed. Either one of those would work. It’s intermittently getting your heart up.”

The findings could have implications for older adults who are grappling with diseases that impact memory, such as Alzheimer's. Heisz is currently working on a similar study with adults aged 65 and up. It's still in the works, but Heisz speculates that there could be comparable effects across the lifespan.

Dementia is scary. There’s no cure, and if exercise is going to boost their memory and protect them against developing dementia, it’s a strong motivator, I think, for people to be active,” Heisz says. “What I hope is that by teaching people that there are brain benefits that really matter to us, that will help them to be more committed to staying physically active.”

Cameron Evans is a former Psychology Today editorial intern.

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