A new study from researchers at Dartmouth College found that when it comes to intense gym workouts and mental health, less may be more. Participants in the study who exercised at a low intensity performed better at some memory tasks than those who worked out intensely. And men and women who performed intense workouts, as measured by their Fitbits, reported higher stress levels than those who exercised less intensely.

According to Study Finds, researchers expected the more active participants to have stronger memory and display better mental health, but the results were more complicated.

“Mental health and memory are central to nearly everything we do in our everyday lives,” said lead study author Jeremy R. Manning, 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 growth.”

According to a Dartmouth College news release, previous research has studied the effects on memory over a short period of time, but the Dartmouth team wanted to examine the effects over a much longer time period. They analyzed data on daily step counts, how much time was spent in different heart rate zones as measured by Fitbits, and other information gathered over a year.

The more active participants tended to show better overall memory. But those who worked out moderately tended to perform better on episodic memory tasks, remembering autobiographical events, such as what they ate yesterday. The intense exercisers scored higher on spatial memory tasks, the type of memory you use to remember location, like where you parked your car.

Participants who self-reported anxiety and depression tended to perform better on the spatial and associated memory tasks, the ability to remember connections between concepts and other memories. Participants who reported higher levels of stress tended to perform worse on the associative memory tests.

In addition to high intensity exercisers reporting higher stress levels, men and women who regularly exercised at lower intensities were found to have lower rates of depression and anxiety.

‘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,” said Manning. “Instead, specific forms of physical activity and specific aspects of mental health seem to affect each aspect of memory differently.”

According to Study Finds, the researchers acknowledge that more work is needed to understand how their findings can be applied to real life issues.

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