IANAB (biochemist) but based on the article, methylation of a gene generally reduces its activity. In this case, exercising, forcing contractions in cultured cells, or near lethal does of caffeine in cell cultures resulted in less methylation on some genes involved in energy metabolism, presumably increasing how much they are expressed. The article does note that these genes may still be expressed when methylated.
Or if that's still unreadable, exercise changes how much some genes are active in muscle cells.