Exercise can boost 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 insight into how exercise could be optimized.
“Mental health and memory are central to nearly everything we do in our everyday 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 perform a series of memory tests, answer some questions about their mental health, and share their fitness data from the previous year. The scientists expected that more active individuals would have better memory performance and mental health, but the results were more nuanced. Participants who tended to exercise at low intensities performed better at some memory tasks while people who exercised at high intensities did better on other memory tasks. People who were more intensely active also reported higher stress levels, whereas those who regularly exercised at lower intensities showed lower rates of depression and anxiety.
Prior research has usually focused on the effects of exercise on memory over a relatively short timeframe, such as over several days or weeks. However, Dartmouth scientists wanted to analyze the effects over a much longer timescale. The data collected included average heart rates, daily step counts, how much time was spent exercising in different “heart rate zones” as defined by FitBit (rest, out-of-range, fat burn, cardio, or peak), and other information collected over a full calendar year. Participants in the study were recruited online from Amazon’s Mechanical Turk, a crowdsourced workforce.
There were four types of memory tasks used in the study, which were designed to probe different aspects of participants’ abilities, over different timescales. Two sets of tasks were focused on testing “episodic” memory — the same type of memory used to remember autobiographical events, like what you did yesterday. Another set of tasks was developed to test “spatial” memory — the same type of memory used to remember locations, like where you parked your car. The final set of tasks was aimed at testing “associative” memory — the ability to remember connections between concepts or other memories.
Participants who had been more active over the prior year tended to show better memory performance overall. However, the specific areas of improvement depended on which types of activity people did. The researchers discovered that participants who often exercised at moderate intensities tended to perform better on the episodic memory tasks while those who often exercised at high intensities did better on the spatial memory tasks. Sedentary participants who seldom exercised typically performed worse on the spatial memory tasks.
The research team also identified connections between participants’ mental health and their memory performance. Participants with self-reported anxiety or depression tended to perform better on the spatial and associative memory tasks. People with self-reported bipolar disorder tended to perform better on the episodic memory tasks. Those who reported higher levels of stress tended to perform worse on the associative memory tasks.
All of the data and code has been made freely available by the research team on 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 cannot be summarized in single sentences like ‘walking improves your memory’ or ‘stress hurts your memory,’” says Manning. “Instead, specific forms of physical activity and specific aspects of mental health seem to affect each aspect of memory differently.”
With additional research, the scientists say that their findings could have some exciting applications. “For example,” Manning says, “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.”
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, 15 August 2022, Scientific Reports.
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