Is a former runner who has not run for two years the same as an untrained person?

I think that the former runner is way ahead, at least initially. Running is a skill, like playing the piano. Neurologically, there's a significant difference between the former runner and the never-was runner.

i would expect the former runner to be much more efficient

Former runner is much better off. Muscle memory, better form, knowing what to expect all helps.

Think of how much easier it is to get back to a level of fitness after you have been there once before.

This is a no brainer. The former runner will be way ahead. I believe Noakes and a whole bunch of other people discuss this.

i just happen to be an identical twin and we focused on different events in track. now this year he will be focusing on the same events as me in indoor 800 and mile.

so my answer, from personal experience, is that i think the former trained one will definately be better. we will see if he ends up with similar prs as me by the end of the season.

I would imagine that the former runner would have a mental advantage as well as a physical one. Knowing you have done something before (for example breaking a certain time) will make it easier to do for the second time (even if woefully out of shape). The untrained person has to wonder, "am I really capable of this?" while the former runner knows it is in there somewhere.

I'm two years out of running and can say that if I got back into it I could get into shape pretty quickly, alot faster than an untrained person could at least.

The former runner has the mental advantage of experience and knowing what he's really capable of, but this could work against him. An untrained guy might take it easy building up mileage, but the former has-been could be too aggressive in building up mileage and end up getting injured.

The former runner is way ahead, unless he was in a coma for those two years.

Don't forget that much of that running through middle and high school would have been done during times of growth and devleopment - puberty and the growth that follows, too. Putting in mileage during that time of rapid remodeling of the body will cause the runner to physically develop differently than the nonrunner. There would be long-lasting anatomical differences, as well as physiological.