Ease up at the gym: Intense workouts can impact your memory performance

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

“Mental health and memory are central to nearly everything we do in our everyday lives,” lead study author Jeremy Manning, an assistant professor of psychological and brain sciences at Dartmouth, says in a media 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 the same; some people work out at a particularly intense pace, while others take a low-key, less intense approach. Study authors gathered a group of 113 Fitbit users and asked each person to perform series of memory tests, answer some questions about their mental health, and share their fitness data from the prior year. Researchers expected more active participants to have a stronger memory performance and display better mental health, but the results weren’t that simple.

Taking it easy may be better for your brain

Participants who usually exercised at a low intensity actually performed better at some memory tasks in comparison to more intense exercisers. Those who were working out more intensely also reported higher stress levels, while lower-intensity exercisers showed lower rates of anxiety and depression.

Prior research projects focusing on exercise and memory have predominantly only lasted for several days or weeks. The team at Dartmouth wanted to analyze the effects over a much larger timeframe. Collected data included daily step counts, average heart rates, time spent exercising in different “heart rate zones” defined by FitBit (rest, out-of-range, fat burn, cardio, or peak), as well as additional information collected over a full calendar year.

The team used a total of four specific memory tasks for this project, all designed to gauge a different vital aspect of memory over varying timescales. A pair of the tasks focused on testing “episodic” memory, or the memory we use to recall events from our past. Another task centered on testing “spatial” memory, or the type 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.

Results show exercisers who were more active over the prior year tended to do better on the memory tasks in general, but specific areas that could use improvement varied depending on the person’s typical exercise routine.

Those exercising at moderate intensities usually performed better on the episodic memory tasks, while participants who typically exercised at high intensities scored higher on the spatial memory tasks. Meanwhile, people who didn’t exercise very often in general usually performed worse on the spatial memory tasks.

Mental health disorders impact memory

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

“When it comes to physical activity, memory, and mental health, there’s a really complicated dynamic at play that cannot be summarized in single sentences like ‘walking improves your memory’ or ‘stress hurts your memory,’” Prof. Manning explains. “Instead, specific forms of physical activity and specific aspects of mental health seem to affect each aspect of memory differently.”

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

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

The study is published in Scientific Reports.