iGreenMill is the worldâs first and only outdoor curved treadmill. iGreenMill has a revolutionary roller system that provides an amazing running experience for people of all ages â from children to adults and seniors. The principle of the treadmill is simple: You want to go faster â go faster. You want to slow down â slow down. You want to stop â stop. Just like in life â you are the powerhouse of the iGreenMill treadmill.