I'm a discus thrower on the track and field team. My coach doesn't want us to do any running outside of practice. He says it's too hard on the knees and that all the throwing we do already puts enough stress of the knees since we're jumping around, landing and turing on weird angles and bent knees. I used to run quiet a bit back in high school. I do miss it; especially on the trails through the forests.

It doesn't get much better than running; but is an elliptical a good substitute for running?

If you mean will using an elliptical make me a better runner the answer is, yes, but not as much as running will make you a better runner. If you mean will using an elliptical burn calories like running, the answer is yes, but probably not quite as fast. If you mean will using an elliptical provide other benefits of running, such as improving bone density, the answer is no. If you mean will using an elliptical reduce joint stress, as your coach thinks, the answer is probably yes.