By Tanner Garrity For years, the NFL has sponsored an initiative with the American Heart Association called PLAY 60, which has a pretty straightforward mission statement: encourage kids to get 60 minutes of physical activity each day. While the project has reached millions of children, that number has also long felt a bit meager — just one hour of running around for an entire day? But believe it or not, the goal is actually pretty robust. According to research from the Child Mind Institute, the average American child averages less than seven minutes of play outside a day, compared to seven hou…