I have written previously about the link between exercise and mood, including the consistent research finding that aerobic exercise is just as effective in treating depression as either psychotherapy or medication. This week, I'm excited to share a new multi-national research collaboration that I was able to participate in, looking at the mood-exercise linkage in a different way.
In this just-published article, a German research team conducted a within-person meta-analysis, meaning that they merged raw data from 69 different studies across 14 countries to draw overall conclusions. Each of these studies (including one of mine) measured exercise parameters using an accelerometer -- either a research-grade device like Actigraph, or a commercial-grade tracker such as a Fitbit, AppleWatch, or Garmin wristband. Each of the studies also collected daily survey data on a measure of mood or subjective well-being. The combination of daily exercise tracking with daily survey data allowed for tests of the relationship between mood and exercise in two different directions:
1. Mood before exercising -> more or less subsequent exercise
2. Amount of exercise -> score on a subsequent measure of mood
Although direction #2 is the one that we are often most interested in, suggesting that exercising makes you happier, there's an important confound when direction #1 is not also considered. For example, people who are happier to start with might be more likely to go out for a run. Or people who have already exercised might remember their initial mood to have been worse when a retrospective study design is used. In some of the foundational work for Two Minds Theory, I have shown that people are particularly bad at retrospectively reporting their previous emotional states.
My colleagues' analysis found that direction #2 was the best-supported by evidence. Exercising does indeed lead to better mood later on, including feelings of contentment ("valence," r = .06), happiness or good cheer ("positive affect," r = .07), and feeling more energetic and awake ("energetic arousal," r = .14). These aren't very strong relationships, but they are noteworthy because they show a consistently positive effect across many studies, despite extremely high levels of variability in the types of people studied, international contexts of the studies, and measurement tools utilized. The particularly strong relationship between exercise and subsequent energy levels makes sense in terms of improved physical fitness, but it's the opposite of what many people say is their reason for not exercising: That if they do, they will feel tired. In fact, the research overall suggests that they would feel more energized later on instead of less. In contrast to these findings, there was no evidence for direction #1 in the relationship between mood and exercise: So you can start exercising no matter how you currently feel, and reasonably expect to feel better. The findings were consistent across participants of different genders, ages, body mass index, and other demographic characteristics.
One surprising finding was that exercise did not necessarily reduce participants' level of Negative Affect (i.e., feeling sad, anxious, or angry). It is known that Positive and Negative Affect are at least somewhat independent of one another, with people able to truthfully say that they feel both sad and happy at the same time. The lack of a consistent effect of exercise on Negative Affect (in either direction) suggests that positive feelings are more strongly related to physical activity than negative ones. Exercising might not make negative feelings go away, then -- but it might still make them feel more bearable.
I'm delighted to have been able to contribute to this massive analysis, which provides the best evidence to date about the nature of the relationship between physical activity and emotional well-being.

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