The premise: You already know that there are many positive biological effects of exercise, such as the release of endorphins and the stimulation of serotonin, which may have a positive effect on mood.
"In addition, many people report that engaging in exercise makes them feel better about themselves and, in the case of team sports, is a good way to increase their social contact," says researcher Dr. Samuel Harvey.
Harvey teamed up with colleagues at Institute of Psychiatry, King's College London and other researchers from the Norwegian Institute of Public Health and the University of Bergen in Norway to explore the relationship between exercise and mood. While they expected physical activity to have positive psychological benefits, the team was surprised to find that the context of the activity seemed to be vital in terms of predicting mood boosts.
The set-up: The researchers asked 40,401 Norwegian residents how often they engaged in both light and intense physical activity during their leisure time. Light activity was defined as anything that did not lead to being sweaty or out of breath, while intense activity was anything that resulted in either side effect. The subjects were also asked about their physical activity at work, underwent a physical examination and answered questions regarding symptoms of depression and anxiety.
"We had to rely on the participants' own estimate of how much time they spent engaging in leisure time physical activity each week," says Harvey. For more exact results, the team is currently at work on a new study where they'll record the precise amount of time spent exercising.
The results: As predicted, "Those who participated in leisure time physical activity were less likely to be suffering from symptoms of depression," begins Harvey. However, there was no such effect seen with activity that took place in the workplace, indicating that the activity is more beneficial when it's something that's done for recreation. People who were not active in their leisure time were almost twice as likely to have symptoms of depression compared to the most active individuals. And yet even the people who participated in very light exercise were still less likely to show symptoms of depression. "We were surprised, though, that the apparent benefits of exercise were limited to depression symptoms, with very little impact seen in regard to anxiety."
The takeaway: "Around 15 percent of men will suffer from depression at some point in their lives," warns Harvey. Although they don't fully understand the relationship between physical activity and depression, the researchers do know that the intensity of activity doesn't seem to matter too much. "What is most important is spending part of your leisure time doing something active, which you enjoy and that makes you feel good about yourself," suggests Harvey.