Exercising in morning might make it harder to remember things that evening, study suggests

Exercising first thing in the morning makes long-term memory recall increasingly hard as the day continues, according to surprising results from an undergraduate student-led study that challenges conventional wisdom about the positive role physical activity plays in making new memories.

“If you’re going to exercise in the morning, you might have a little trouble remembering things you learn later in the day,” said Arth Pahwa, medical student in the Faculty of Medicine & Dentistry and lead author on the study.

The idea for the study originated with Pahwa, who was an undergrad student in the Faculty of Science in 2015 when he started up an early-morning exercise routine.

“I lost a bunch of weight and noticed that I started doing significantly better in school,” he said. “It seemed much easier to remember things … and I didn’t have to study as much at night.”

U of A medical student Arth Pahwa
U of A medical student Arth Pahwa conducted his study on how exercise affects memory as an undergraduate science student, with help from two professors. “It is very much an open community. People are trying to push you towards figuring out the answers to life’s questions.” (Photo: Supplied)

Pahwa, whose neuroscience undergrad included a “mini-thesis” component, said he began to wonder about how much exercise helped people in terms of their cognitive abilities.

He undertook a literature review and turned up research that showed the ability to encode and retrieve new information gets a boost in the hour following exercise. He also found a number of studies that showed exercise comes with significant long-term cognitive benefits for improving all aspects of memory.

“But no one had done a study looking at how your ability to learn and remember new information changes throughout the day after exercise,” said Pahwa.

After a little more digging, the upstart researcher found himself reaching out for help from David Collins, a professor in the Faculty of Kinesiology, Sport, and Recreation.

“He wanted to use this idea as the basis for a project,” said Collins. “He’s an impressive guy; he had already done a literature review, so I said, ‘Sure, let’s give it a go.'”

The pair then enlisted U of A memory expert Jeremy Caplan, professor in the Department of Psychology, to design the memory task, which saw 106 test subjects complete a baseline memory test before either running on a treadmill for 20 minutes or solving Sudoku puzzles.

The subjects would return to the lab at two, five and eight hours after their respective early-morning sessions to complete a different memory task involving the recall of 30 pairs of completely unrelated words.

What they found was that exercise had no impact on memory at two and five hours. However, scores on tests taken eight hours after exercise fell by 8.6 per cent below baseline and 9.8 per cent below the Sudoku-solving control group. 

“We hypothesized that memory was going to be up for eight hours,” said Collins. “But we found that any memory boost from exercise is short-lived.”

Although there may be several reasons for this phenomenon, Collins said this study didn’t address the mechanism. He did suggest, however, that it may be worth considering the timing of exercise programs and other vigorous activities to enhance, and not hinder, learning. 

“You don’t want to exercise a long time before you’re trying to learn things,” said Collins, who added there are also implications for shift workers who exercise in the evening before going to work.

Since the study, which was finally published in 2020 in the Journal of Sport and Exercise Psychology, Pahwa has graduated and is now in his final year in medical school at the U of A.

“Obviously, the biggest overall message is that exercise in the long run helps memory, just not later in the day,” said Pahwa.

With an eye on becoming a neurologist, Pahwa hopes he can do his residency training at the U of A. If it doesn’t work out, he said what he will remember about his time at the U of A was the openness towards research.

“I can’t say enough good things about the U of A,” he said. “It is very much an open community. People are trying to push you towards figuring out the answers to life’s questions.”

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