Psychological benefits of outdoor physical activity in natural versus urban environments: A systematic review and meta-analysis of experimental studies.

The impact of environmental context on the psychological benefits derived from physical activity has attracted research attention in recent years. Previous reviews have compared effects of indoor versus outdoor exercise. This review compares the effects of physical activity undertaken in outdoor green natural environments versus outdoor urban environments on psychological health outcomes in adult general populations. An electronic literature search identified 24 experimental studies meeting the inclusion criteria. Results were analysed via narrative synthesis (n = 24) and meta-analysis (n = 9) of effect on six outcomes. Narrative synthesis found in favour of the natural environment for anxiety, anger/hostility, energy, affect and positive engagement. Post-intervention effect sizes suggested duration and social context as potential moderators. The meta-analyses revealed large or moderate effects in favour of the natural environment for anxiety, fatigue, positive affect and vigour, and a small effect for depression. Results were subject to high risk of bias and heterogeneity. Physical activity undertaken outdoors in natural environments is more beneficial for a range of psychological outcomes compared with urban environments. The various effect sizes evident in the meta-analyses may be explained by differing mechanisms through which psychological gains are experienced during physical activity in nature.