The elliptical will help you with your cardio, but really will not help you with your running at all. It might help your endurance with the run, because of the cardio, but they are no where close to the same thing as far as work outs go. I thought the same thing, and after a month off of running, ok maybe 2 months, using elliptical in its place, I was not able to run as far or as fast as before the time off.
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2007 Jamis Ventura Comp
2006 Jamis Explorer 2.0
2000 Specialized Hardrock (bought used)
Swim, Bike, Run and sounds like fun