Many of us associate exercise with the monotony of running in circles on a track or riding a stationary bicycle to nowhere, or with the stress of competitive sports. But some of the other activities we do just for fun can also improve fitness levels, according to experts who emphasize that playtime shouldn't be just for kids.

Dancing, hiking and rock climbing all come with health benefits...

Dancing, hiking and rock climbing all come with health benefits that have been documented by researchers. Even tossing a Frisbee or whirling a hula hoop offer outlets not just for physical activity but also for creativity, spontaneity, and stress release.

"The 'power of play' for adults lies in simply focusing on the joy of moving, having a little fun with it, and not taking ourselves too seriously," said Carol Torgan, PhD, a Washington, D.C.-based health scientist and spokesperson for the American College of Sports Medicine. Torgan spoke last month at the ACSM's annual Health & Fitness Summit & Exposition. "Play has no obvious goal, and has no winners or losers. It's the perfect antidote for when your exercise routine starts to feel more like a chore than an activity of enjoyment."

Research supports the fitness benefits of non-traditional exercise. A 2007 study of hiking patterns at Rocky Mountain National Park suggested that even the easiest hikes involve energy expenditure levels equal to walking at a very brisk pace, with the added benefit of scenic views. A March 2008 study categorized the exercise intensity of noncompetitive rock climbing as appropriate for maintaining good cardiorespiratory fitness. Another 2007 study found no difference in caloric output between walking and folk dancing.

These types of activities also include a social component, which Torgan said may be as important as the physical element.

"Whether it's shooting hoops or even playing on a teeter-totter with a friend, these unstructured activities can create a sense of belonging and community," she said. "The need for play may be hard-wired in our brains and appears to be as basic as sleep. We never outgrow it."