2. You'll get more exercise (especially if you're a child)
You don't need to be outside to be active: millions of people exercise indoors in gyms or at home on treadmills and elliptical trainers. Nor is being outside a guarantee of activity. At the beach on a summer day most people are in various angles of repose.
Still, there's no question that indoor living is associated with being sedentary, particularly for children, while being outdoors is associated with activity. According to some surveys, American children spend an average of 6 hours a day with electronic media (video games, television, and so on), time that is spent mainly indoors and sitting down. British researchers used Global Positioning System devices and accelerometers, which sense movement, to track the activity of 1,000 children. They found that the children were more than doubly active when they were outside.
Adults can go to the gym. Many prefer the controlled environment there. But if you make getting outside a goal, that should mean less time in front of the television and computer and more time walking, biking, gardening, cleaning up the yard, and doing other things that put the body in motion.
3. You'll be happier (especially if your exercise is 'green')
Light tends to elevate people's mood, and unless you live in a glass house or are using a light box to treat seasonal affective disorder, there's usually more light available outside than in. Physical activity has been shown to relax and cheer people up, so if being outside replaces inactive pursuits with active ones, it might also mean more smiles and laughter.
Researchers at the University of Essex in England are advancing the notion that exercising in the presence of nature has added benefit, particularly for mental health. Their investigations into "green exercise," as they are calling it, dovetails with research showing benefits from living in proximity to green, open spaces.
In 2010 the English scientists reported results from a meta-analysis of their own studies that showed just five minutes of green exercise resulted in improvements in self-esteem and mood.
Mind you, none of the studies were randomized controlled trials. The intuitive appeal of green exercise is its strength, not the methodological rigor of the research supporting it. It's hard to imagine how a stroll in a pretty park wouldn't make us feel better than a walk in a drab setting.