Want to be happier? If you're really serious about it, you could take this Yale's wildly popular course on how to be happy. The free online course takes six weeks, and walks you through the science of happiness and strategies to put into practice. Happiness guru Gretchen Rubin just opened registration to a happiness course, too.  

But there might be a simpler way to improve your happiness that doesn't require watching lectures and doing homework.

Plain old exercise.

Sure, you've heard this advice before before. Countless studies celebrate the mood-boosting benefits of physical activity. We're supposed log 150 minutes a week, according to Department of Health and Human Services. It turns out that even less than that -- just a few minutes -- could be beneficial to boosting your mood.

1x a week is enough

Exercising once a week or 10 minutes a day might increase your happiness. And really any kind will suffice, as long as it gets you moving. Running, biking, walking and stretching are all fair game.

These are the results from research published in the Journal of Happiness Studies. The researchers dug through previous studies done about physical activity and happiness -- 23 in total since 1980 -- and synthesized the results. According to New York Times Phys Ed columnist Gretchen Reynolds, in total these studies covered 500,000 participants. They were all observational, meaning that researchers examined the existing exercise habits and happiness levels of all participants. (The opposite would have been an experimental study, where researchers would assign one group to exercise and a control group to do nothing, then compare the results.)

"Every one of the observational studies showed a beneficial relationship between being physically active and being happy," Weiyun Chen, an associate professor of health and fitness at University of Michigan's School of Kinesiology, told Reynolds.

Some of the people in the studies only worked out once a week. Still they reported better moods than the non-exercisers. Since these were not controlled experiments, the researchers could not determine cause and effect between exercise and happiness. Perhaps people who are happier are more likely to exercise. Indeed, people who already have better mental health are more likely to remain physically active later in life.