[Lost Dog]

Running is overrated for the most part. AND, so many people just shouldn't run. Me, for one. If you're a bad (raises hand) runner, then you end up taking it in the knees, feet, or ankles or all of the above.

I like the stair/step mills (they are like going up a down escalator), both style of bike, and rowing machines. If you need some time on the treadmill, bump up the incline and walk harder, rather than getting up to a full run.

As to your body getting used to one thing, that really takes a long time. It's been exaggerated, so it's not like it's suddenly innefective. It's more like a veeeery gradual shift toward being more efficient at the activity. Hardly noticeable unless you're doing a ton of mileage every week and don't have any room for improvement. As long as you can up the speed, incline, time, or tension, you've got some room to grow.

For combatting boredom, I'm partial to 15-30 minutes on 2-3 machines, depending on the length of time you're going for. Plus, a podcast of the thefitcast to pass the time.