Exercise Is Great for Mental Health, But How Much Is Too Much?

It's common knowledge that exercise has lots of psychological benefits, but how much is too much? A recent study has suggested that intense workouts could be detrimental to mental health and memory. 

Researchers at Dartmouth University found that, while exercise can have a positive effect on mental health, not all forms and intensities of exercise will be equally effective.

They asked 113 Fitbit users to undertake a series of memory tests and answer questions about their mental health, as well as share exercise data from the previous year.

Understanding the Research

While the researchers expected that higher levels of activity would correlate to better mental health and memory performance, the results weren’t quite so simple.

In fact, those exercising at lower intensities did better on some memory tests, while those exercising at higher intensities did better on others. In terms of mental health, those exercising at higher intensities reported higher levels of stress, while those exercising at lower intensities reported lower levels of anxiety and depression.

Whereas previous research in this area has focused on exercise and memory over shorter timeframes, this research looked at the effects of exercise on memory over the longer term. The data the researchers focused on included daily step counts, average heart rates, and the time spent exercising in different ‘heart rate zones.’

Exercise and Memory

Researchers also saw connections between mental health and memory. Participants who reported anxiety or depression generally performed better on the spatial and associative memory tasks, the types of memory associated with locations, and the ability to remember connections between concepts or other memories respectively.

In comparison, participants who reported bipolar disorder performed better on the episodic memory tasks—this is the type of memory associated with autobiographical events, like what you did yesterday or last weekend. Participants who reported high-stress levels tended to do poorly on the associative memory tasks.

“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 lead author Jeremy Manning, an assistant professor of psychological and brain sciences at Dartmouth University, in a press release. “Instead, specific forms of physical activity and specific aspects of mental health seem to affect each aspect of memory differently.”

In comparison, participants who reported bipolar disorder performed better on the episodic memory tasks – this is the type of memory associated with autobiographical events, like what you did yesterday or last weekend. Participants who reported high stress levels tended to do poorer at the associative memory tasks.

“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 lead author Jeremy Manning, an assistant professor of psychological and brain sciences at Dartmouth University, in a press release.

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

Take These Findings With a Grain of Salt

Of course, exercise does bring a number of mental health benefits. Running reduces the risk of depression, for example.

As Elena Touroni, PhD, a consultant psychologist and co-founder of The Chelsea Psychology Clinic comments, “When you exercise, your body releases feel-good hormones, endorphins, and serotonin, which give you a natural energy boost and promote positive feelings in the body. Your body and mind also become better at managing the stress hormone, cortisol.”

She goes on to explain that people often find that exercise is a good release of pent-up energy, helping them break cyclical thoughts and give them a clear head, and that exercising can boost self-esteem too: “The increase in energy can help you feel stronger in yourself and more confident to take on any challenges in your life.” 

Can We Exercise Too Much?

“You don’t have to push yourself or ‘feel the burn’ to get benefits from exercise, for either physical or mental wellbeing,” says Smriti Joshi, lead psychologist at Wysa. 

She explains that there are all sorts of factors that may impact decisions on the type and amount of exercise we do, from our age to our general health. 

“What is important is to try and be a little more physically active than you are now, and it could mean just doing stretches or going for walks with friends or loved ones regularly. You could choose to build on this and increase the duration or bring in more variety and make it fun,” she says.

“You don’t have to exercise rigorously every day to reap the benefits of exercise,” says Daniela Beivide, PhD, Director of Content, Research, and UX at Holly Health. “Even more accessible movements like walking or gardening cause improvements in mood. Some of the possible mechanisms of this relationship include reduced inflammation, better regulation of the stress response, and increased production of some neurotransmitters such as serotonin.” 

Taking exercising to excess can be harmful too—exercise addiction is a very real issue, and as Joshi explains it can lead to physical complications like injuries, fractures, and amenorrhea, the absence of menstruation. 

Personalized Exercise is Best

While the findings are interesting and pose various questions, there were limitations to the study. For example, the research doesn't answer whether different forms of exercise actively cause changes in memory and mental health, or whether people who partake in certain forms of exercise might have similar memory or mental health profiles.

For example, the fact that people who did higher intensity exercises reported higher levels of stress may indicate nothing more than people who are more stressed trying to release more energy through higher-intensity exercise. 

Manning went on to say that additional research could be beneficial: “For example, 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.”

“It might not be that the actual quantity or intensity of the exercise isn’t right, but the ‘why’ behind it. If it’s to punish yourself for eating something, to keep up with that person you saw on Instagram, or because you’re addicted to it, those are negative signs.”

Beivide agrees, explaining that intense physical activity is a form of stress in itself. “While exposing ourselves to some physical stress during exercise is a good thing, prolonged high-intensity activity can actually keep our nervous system in a 'fight-or-flight' state, which is what happens when we are going through a stressful situation.”

She stresses the importance of a balance between physical challenges and resting, the latter calming our nervous system and helping us go back to “a state of ‘rest and digest,’ which helps calm the mind and improve cognitive function.”