Optimize Exercise: Specific Links Between Exercise, Memory, and Mental Health Revealed by Fitness Trackers

Exercise can improve your mental and cognitive health, but not all forms and intensities of exercise affect the brain equally. In fact, according to a new Dartmouth study, the effects of exercise are much more nuanced. It found that specific intensities of exercise over a long period of time are associated with different aspects of memory and mental health. The findings were recently published in the journal scientific reports and provide information on how exercise could be optimised.

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

For the study, the researchers enrolled 113 Fitbit users. They were asked to take a series of memory tests, answer some questions about their mental health, and share their fitness data from the previous year. Scientists expected that more active people would have better memory performance and mental health, but the results were more nuanced. Participants who tended to exercise at low intensity performed better on some memory tasks, while people who exercised at high intensity did better on other memory tasks. People who were more intensely active also reported higher levels of stress, while those who exercised regularly at lower intensities showed lower rates of depression and anxiety.

Previous research has generally focused on the effects of exercise on memory over a relatively short period of time, such as several days or weeks. However, the Dartmouth scientists wanted to analyze the effects on a much longer time scale. The data collected included average heart rates, daily step counts, how long you spent exercising in different FitBit-defined “heart rate zones” (resting, out of range, fat burning, cardio, or peak), and other information collected during a full calendar year. Study participants were recruited online from Amazon’s Mechanical Turk, a collaborative workforce.

Four types of memory tasks were used in the study, which were designed to test different aspects of the participants’ abilities, on different time scales. Two sets of tasks focused on testing “episodic” memory, the same type of memory used to recall autobiographical events, such as what you did yesterday. Another set of tasks was developed to test “spatial” memory, the same type of memory used to remember locations, such as where you parked your car. The final set of tasks was aimed at testing “associative” memory, the ability to recall connections between concepts or other memories.

Participants who had been more active in the previous year tended to show better memory performance overall. However, the specific areas for improvement depended on the type of activity people were doing. The researchers found that participants who often exercised at moderate intensities tended to perform better on episodic memory tasks, while those who often exercised at high intensities did better on spatial memory tasks. Sedentary participants who rarely exercised typically performed worse on spatial memory tasks.

The research team also identified connections between the participants’ mental health and their memory performance. Participants with self-reported anxiety or depression tended to perform better on spatial and associative memory tasks. People with self-reported bipolar disorder tended to perform better on episodic memory tasks. Those who reported higher levels of stress tended to perform worse on associative memory tasks.

All data and code have been made freely available by the research team at github to anyone who wants to explore or better understand the dataset.

“When it comes to physical activity, memory and mental health, there’s a really complicated dynamic at play that can’t be summed up in simple sentences like ‘walking improves your memory’ or ‘stress damages your memory,'” says Manning. “Instead, specific forms of physical activity and specific aspects of mental health appear to affect each aspect of memory differently.”

With further investigation, the researchers say their findings could have some interesting applications. “For example,” says 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.”

Reference: “Fitness Tracking Reveals Task-Specific Associations Between Memory, Mental Health, and Physical Activity” by Jeremy R. Manning, Gina M. Notaro, Esme Chen, and Paxton C. Fitzpatrick, Aug 15, 2022, scientific reports.
DOI: 10.1038/s41598-022-17781-0