Unless you’re using treadmill for sprints, hill walks or changing it up at least every 10 minutes, then just walking on it is a waste of time. This is because you’re building up your appetite for later. You’ll burn calories for sure, but now you’ll be hungrier and want to replace those calories later. Instead use treadmill for intense running or workouts like sprints. Use them for hill runs or for warm up and cool downs. Your focus should be on weight lifting exercises , like total body exercises and isolation workouts.