IFNG and chronic obstructive pulmonary disease: In a study that used 90 min of walking intervention for patients with chronic obstructive pulmonary disease, in the morning and afternoon, respectively, for four days in the forest [29], IL-6, IL-8, IFN-γ, IL-1β, and TNF-α were measured; significant changes were reported in each of these outcome measures apart from TNF-α.