Green exercise may be good for your head.

Have you had a bad day at work? If so, going for a long walk in the park will almost certainly help you de-stress. But it turns out that even small doses of outdoor exercise can have remarkable effects on mental health, report Jules Pretty and Jo Barton of the University of Essex (U.K.) in this issue of ES&T (Environ. Sci. Technol. DOI 10.1021/es903183r). In a meta-analysis of 10 studies, they found that getting outsidesand movingsfor as little as five minutes at a time improved both mood and self-esteem. Exercise near a body of water had the biggest effect. “It shows that green exercise benefits pretty much everybody and that the effect sizes are pretty substantial,” says William C. Sullivan, the president of the Environmental Council at the University of Illinois at Urbana-Champaign, who was not involved in the study. It’s well established that both exercise and exposure to nature can improve and protect mental health. Several years ago, Pretty and his colleagues at the University of Essex wanted to find out whether there was any synergy between the two treatments, so they had volunteers exercise on a treadmill while watching scenes projected on a wall. They found that those who watched “pleasant scenes” of rural and urban environments showed a stronger improvement in blood pressure and mood than those who just exercised (and watching “unpleasant scenes” correlated with reduced health benefits). Therefore, a positive nature experience seemed to increase the positive effects of exercise. Since then, the group has studied the effects of different types of green exercise on a variety of populations, from gardening by visitors to university farms to walking and sailing activities for young offender groups, as well as walking by members of urban flower shows. This new analysis reviewed 10 of these studies, which involved