Hi Paul. Without knowing what it is you’d like to accomplish through your work with a treadmill, it’s hard to give a specific answer here. However, with that being said, generally speaking I’d say that a person gets their best results from treadmill workouts by adding VARIETY. Inclines, as mentioned before, speed (vary the speed of your training), and duration (how long you are on the treadmill) are all variables that you can adjust to get the ‘best’ out of your treadmill workout.
I hope that this helps.