Shout out here for the inclined treadmill workout. If you have a heart rate monitor that the machine can read, you should be able to set a target heart rate and the machine will adjust the incline to keep you at your target heart rate. I love that feature. You control the speed and the machine goes up and down as needed. Set it low to get warmed up, then higher as you get your second wind. I even do High Intensity Intervals with this technique. Using a target heart rate is much better for long-term training fitness. Some days you're feeling strong and some you're not. A heart rate monitor compensates for that. My wife is a personal trainer so I get exposed to this stuff.
Another tidbit I've learned is to use an elliptical machine pedaling backwards. This will strengthen your leg stabilizer muscles which really helps with the knees.
