Exercise typically has positive impacts on mental health outcomes. But a new study suggests that engaging in physical activity might have a surprising side effect. The findings indicate that exercise can exacerbate the tendency to recall negative as opposed to positive material among those who engage in high levels of rumination.
The study has been published in Cognitive Behaviour Therapy.
“It is well known that exercise is good for one’s mental health and even as effective as antidepressants or psychological treatment in reducing depressive symptoms,” said study author Michele Schmitter, a PhD student at Pro Persona mental health care and the Radboud University Nijmegen.
“Yet, we still do not know how exercise relieves depression. This information is important to improve the match between patient characteristics and treatment and ultimately, to improve treatment response. According to cognitive theories of depression (e.g. Beck, 1960), maladaptive cognitive processes such as negatively biased memories or rumination are key mechanism is the development and maintenance of depression.”
“Accordingly, modifying these processes is a key target in depression treatment,” Schmitter explained. “Because exercise improves brain health in the areas related to higher-order cognitions and memory, it may be that altered depressotypic cognitions may act as the mechanisms of the antidepressant effect of exercise which has not been tested previously. Therefore, our study investigated in the lab whether exercise indeed affects negative memory bias and rumination.”
For their study, Schmitter and her colleagues used the Radboud University’s research participant system to recruit a sample of 100 individuals who reported engaging in exercise no more than once a week. The participants were roughly 25 years of age on average and a little more than half (58%) were students.
The participants first completed baseline assessments, including measures of rumination, depressive symptoms, and general activity level.
To induce a negative mood, the participants were then instructed to watch a segment from the drama film “Sophie’s Choice.” After viewing the segment, the participants were randomly assigned to either exercise or rest for 24 minutes. Those in the exercise condition performed 2 minutes of slow-cycling, then 20 minutes of moderate-intensity cycling, followed by a 2 minute cooldown.
The participants then completed another set of assessments, including measures of rumination, negative memory bias, overgeneral memory, and positive and negative affect.
In addition, positive and negative mood were assessed eight times throughout the study. As expected, the participants reported increases in negative mood and decreases in positive mood after watching the film segment. But the researchers found no difference between the two conditions throughout the study. They also observed no differences in overgeneral memory or state rumination.
In other words, exercise did not appear to improve (or worsen) one’s general mood, the ability to retrieve specific autobiographical memories, or ruminative self-focus (e.g. “Right now, I am thinking about how happy or sad I feel”).
However, there were some differences between the two groups.
The researchers found that those in the exercise condition reported more positive affect — emotions such as excitement, alertness, and enthusiasm — compared to those in the rest condition. But among those with higher levels of rumination, those who had exercised scored higher on the measure of negative memory bias compared to those who had rested.
“Our study showed that a single bout of exercise is not sufficient to relieve memory bias or rumination, rather it may even aggravate these depressotypic cognitive processes in some individuals,” Schmitter told PsyPost.
While the link between exercise and positive affect was expected, the link between exercise and negative memory bias was not.
“It was surprising that exercise actually resulted in more negative memory bias for people who ruminate a lot, even though boosting positive affect at the same time. One explanation for this finding is that individuals prone to ruminate may have experienced the exercise session in the laboratory as stressful,” Schmitter explained.
But the findings have an important caveat.
“Exercising was not voluntarily initiated and may be very different from usual exercise activities such as going for a run in nature or listening to great music while running on a treadmill at the gym,” Schmitter told PsyPost. “Especially being monitored during the session and being required to keep the right intensity level might have been experienced as stressful. Future studies are warranted that investigate exercise and depressotypic cognitions in naturalistic settings.”
The study, “Working it out: can an acute exercise bout alleviate memory bias, rumination and negative mood?“, was authored by Michèle Schmitter, Marie-Anne Vanderhasselt, Jan Spijker, Jasper A. J. Smits, and Janna N. Vrijsen.