Scientist Craig Venter begins his memoir, A Life Decoded, with his recollections of outdoor playtime after school and during the summers. Although a "C" student during his early school years, Venter believes all those unsupervised hours of play and exploration were key not only to his physical development but also his intellectual maturity.

Most doctors agree, while the World Health Organization recommends children get at least 60 minutes of moderate to vigorous physical activity each day. Yet in an era of play groups, after school programs, and helicopter parents, many kids don’t get the chance at vigorous activity. However, a new study brings hope. Time spent outdoors after school, researchers found, is linked to a positive increase in moderate to vigorous physical activity (MVPA).

Playtime Is Health Time

Generally, physical activity for kids includes games, play, sports, chores, recreation, and gym class. “Children and youth aged 5-17 should accumulate at least 60 minutes of moderate- to vigorous-intensity physical activity daily,” the World Health Organization (WHO) notes on its website. Further recommending most of the physical activity be aerobic, WHO suggests it will improve a child's muscular fitness and bone health, while boosting his or her cardiorespiratory condition. Considering school is the only time many children play, Drs. Lee Schaefer and Jonathan McGavock of the University of Alberta wondered if increasing outdoor time after school might increase MVPA.

Working with their colleagues, the two doctors studied 306 children between the ages of 9 and 17 who were enrolled in the Healthy Hearts Prospective Cohort Study of Physical Activity and Cardiometabolic Health. During the winter and spring of the 2008/2009 academic year, participants wore an accelerometer and completed an online survey that included a self-report of time spent outdoors after school, including free play as well as organized sports. When the study concluded, the researchers set to work examining the data.

As any former kid would predict, the results showed the 17 percent of children who did not spend time outdoors after school achieved 21 fewer minutes of MVPA each day. Worse, they logged an additional 70 minutes of sedentary behavior compared with the 39 percent of respondents who spent most of their time outdoors after school. In general, the more outdoorsy kids were three times more likely to meet the WHO guidelines for daily physical activity while also showing significantly higher cardiorespiratory fitness levels compared to indoor peers. Even in the winter months, the positive effects of more outdoor activity held true.

In the end, this study disappointingly proved only a third (34 percent) of children achieved the recommended 60 minutes of MVPA each day. Much more work, then, is needed. "Schools and parents should consider structured time outdoors for children in an effort to boost physical activity levels and enhance [cardiorespiratory] fitness,” Dr. Schaefer said. Better yet, parents might consider un-structured time outdoors for their children. It worked out well enough for Craig Venter.

Source: Schaefer L, Plotnikoff RC, Majumdar SR, et al. Outdoor Time Is Associated with Physical Activity, Sedentary Time, and Cardiorespiratory Fitness in Youth. The Journal of Pediatrics. 2014.