Exercise can improve your cognitive and mental health -; but not all forms and intensities of exercise affect the brain in the same way. The effects of exercise are much more nuanced, as specific intensities of exercise over a long period of time are associated with different aspects of memory and mental health, according to a new study from Dartmouth. The findings are published in Scientific reports and provide insight into how the exercise could be optimized.
Mental health and memory are central to almost everything we do in our daily lives. Our study attempts to lay the groundwork for understanding how different exercise intensities affect different aspects of mental and cognitive health.”
Jeremy Manning, lead author, assistant professor of psychological and brain sciences, Dartmouth College
The researchers asked 113 Fitbit users to complete a series of memory tests, answer a few questions about their mental health, and share their fitness data from the previous year. They expected more active individuals to have better memory performance and mental health, but the results were more nuanced. People who tended to exercise at low intensity did better on some memory tasks while those who exercised at high intensity did better on other memory tasks. Participants who were more intensely active also reported higher levels of stress, while people who exercised regularly at lower intensities had lower levels of anxiety and depression.
Previous research has often focused on the effects of exercise on memory over a relatively short period of days or weeks, but the Dartmouth researchers wanted to examine the effects on a much longer time scale. Data included daily step counts, average heart rates, time spent exercising in different “heart rate zones” as defined by FitBit (resting, out of range, fat burn, cardio or peak) and other information collected. over a full calendar year. Study participants were recruited online from Amazon’s Mechanical Turk, an outsourced workforce.
The four types of memory tasks used in the study were designed to probe different aspects of participants’ abilities, over different time scales. Two sets of tasks aimed to test “episodic” memory -; the same kind of memory used to remember autobiographical events, like what you did yesterday. Another set of tasks was designed to test “spatial” memory -; the same kind of memory used to remember locations, like where you parked your car. The final set of tasks tested “associative” memory -; the ability to remember connections between concepts or other memories.
Participants who had been more active in the previous year tended to show better memory performance overall, but the specific areas of improvement depended on the types of activity people engaged in. The researchers found that participants who often trained at moderate intensities tended to do better on episodic memory tasks, while participants who often trained at high intensities did better on spatial memory tasks. Sedentary participants who rarely exercised tended to perform worse on spatial memory tasks.
The researchers also identified links between the participants’ mental health and their memory performance. Participants with self-reported anxiety or depression tended to do better on spatial and associative memory tasks, while those with self-reported bipolar disorder tended to do better on episodic memory tasks. Participants who reported higher stress levels tended to perform worse on associative memory tasks.
The team has made all of its data and code freely available on Github for anyone who wants to explore or better understand the dataset.
“When it comes to physical activity, memory and mental health, there’s a very complicated dynamic at play that can’t be summed up in simple phrases like ‘walking improves your memory’ or ‘stress hurts your memory,'” Manning explains. “Instead, specific forms of physical activity and specific aspects of mental health appear to affect each aspect of memory differently.”
With further research, the team says their findings could have interesting applications. “For example,” Manning explains, “to help students prepare for an exam or reduce their symptoms of depression, specific exercise programs could be designed to help improve their cognitive performance and mental health.”
Manning, JR. et al. (2022) Fitness tracking reveals task-specific associations between memory, mental health, and physical activity. Scientific reports. doi.org/10.1038/s41598-022-17781-0.