Americans don't get out much anymore. We're indoors for 90 percent of each day, according to the Environmental Protection Agency.
For a big chunk of that time, many of us are behind a desk. One study found that just one-quarter of office workers spent more than an hour outside each day.
Research shows that people who are cooped up all day have less energy and worse moods. That's bad news not just for them but for their employers. After all, a happy, energetic worker is more productive.