Relax at the gym: Intense workouts can affect your memory performance

HANOVER, NH — Studies continue to conclude that exercise is good for the body, brain and overall well-being. However, Dartmouth College researchers are showing the true complexity of the relationship between exercise, memory and mental health. Their study finds that the impact of exercise is much more nuanced; differences in exercise intensity over a long period appear to result in different outcomes for memory and mental health.

“Mental health and memory are central to almost everything we do in our daily lives,” lead study author Jeremy Manning, assistant professor of psychological and brain sciences at Dartmouth, said in a news release . “Our study is trying to build a foundation for understanding how different intensities of physical exercise affect different aspects of mental and cognitive health.”

No two workouts are exactly alike; some people train at a particularly intense pace, while others take a low-key, less intense approach. The study authors gathered a group of 113 Fitbit users and asked each person to take a series of memory tests, answer some questions about their mental health and share their fitness data from the previous year . The researchers expected that the more active participants would have stronger memory performance and show better mental health, but the results were not so simple.

Taking it easy may be better for your brain

Participants who regularly exercised at a low intensity actually performed better on some memory tasks compared to the more intense athletes. Those who exercised at higher intensity also reported higher stress levels, while the lower-intensity athletes showed lower rates of anxiety and depression.

Previous research projects focusing on exercise and memory have mostly lasted only a few days or weeks. The Dartmouth team wanted to look at the effects over a much longer period of time. Data collected included daily step count, average heart rate, time spent exercising in different FitBit-defined “heart rate zones” (resting, out of range, fat burning, cardio or peak), as well as additional information collected during a full calendar year period.

The team used a total of four specific memory tasks for this project, all designed to assess a different vital aspect of memory at different time scales. A couple of the tasks focused on testing “episodic” memory, or the memory we use to remember events from our past. Another task focused on testing “spatial” memory, or the kind of memory people use to remember locations on a map. The final task tested “associative” memory, or the ability to remember connections between concepts or other memories.

The results show that athletes who were more active in the previous year tended to do better on memory tasks overall, but the specific areas they could improve varied depending on the person’s typical exercise routine .

Those who exercised at moderate intensities tended to perform better on episodic memory tasks, while participants who typically exercised at high intensities scored higher on spatial memory tasks. Meanwhile, people who didn’t exercise very often generally performed worse on spatial memory tasks.

Mental health disorders affect memory

Notably, the team also found connections between participants’ mental health and memory scores. Those who reported dealing with depression or anxiety typically performed better on spatial and associative memory tasks. However, participants with self-reported bipolar disorder scored higher on episodic memory tasks. People under stress tend to perform worse on associative memory tasks.

“When it comes to physical activity, memory and mental health, there are really complicated dynamics at play that can’t be summed up in simple phrases like ‘walking improves memory’ or ‘stress hurts memory,'” Professor Manning explains. “In contrast, specific forms of physical activity and specific aspects of mental health appear to affect each aspect of memory differently.”

More work is needed, but the study authors are optimistic that their research will one day lead to interesting future applications.

“For example,” concludes Professor Manning, “to help students prepare for an exam or reduce their symptoms of depression, specific exercise regimens could be designed to help improve their cognitive performance and mental health.”

The study is published in Scientific reports.

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