Washington: Exercise can improve your cognitive and mental health, but not all forms and intensities of exercise have the same effect on the brain. According to a new Dartmouth study, the effects of exercise are much more nuanced, with specific intensity levels of exercise over a long period of time associated with different aspects of memory and mental health.
The findings are published in Scientific Reports and provide insights into how exercise could be optimized.
“Mental health and memory are central to almost everything we do in our daily lives,” says lead author Jeremy Manning, 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.”
The researchers asked 113 Fitbit users to take a series of memory tests, answer a few questions about their mental health, and share their fitness data from the previous year. They expected that more active people would have better memory performance and mental health, but the results were more nuanced. People who tended to exercise at low intensity performed 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 stress levels, while people who exercised regularly at lower intensities showed lower rates of anxiety and depression.
Previous research has often focused on the effects of exercise on memory over a relatively short period of time over several days or weeks, but the Dartmouth researchers wanted to examine the effects over a much longer period of time. The data included daily step counts, average heart rate, how long you spent exercising in different FitBit-defined “heart rate zones” (rest, out of range, fat burning, cardio, or peak), and other information collected. for a full calendar year. Study participants were recruited online from Amazon’s Mechanical Turk, a collaborative workforce.
The four types of memory tasks used in the study were designed to test different aspects of the participants’ abilities, on different time scales. Two sets of tasks aimed to test “episodic” memory, the same type of memory used to recall autobiographical events, such as what you did yesterday.
Another set of tasks was designed 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 tested “associative” memory, the ability to remember connections between concepts or other memories.
Participants who had been more active in the past year tended to show better memory performance overall, but the specific areas of 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 participants who often exercised 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 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, while those with self-reported bipolar disorder tended to perform better on episodic memory tasks. Participants who reported higher levels of stress tended to perform worse on associative memory tasks.
The team has made all of their 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 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 team says 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 and mental performance.
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