Thatsbthe first machine i go on in the gym,i set it on undulating hills,i normally stay on it for 3 miles at around 8-9 km an hour,just nice and gentle as a warm up,i had an op on my knee 2 years ago so i dont really do any other leg excercises apart from calf raises,health is wealth,but when i used to really run at times i used to push it so my lungs felt on fire.