Zhang and colleagues learned that “Physical activity performed in a natural environment, especially among green spaces, is associated with mental health benefits. . . . [study participants] engaged in incremental cycling exercise at a moderate intensity while viewing an image in front of them on a large screen. Participants were randomly assigned to one of four groups in which the image they viewed was a green tree, an achromatic tree, a formless color green, or a formless achromatic color. .…