I would think that anything that helps with cardiovascular endurance can help, somewhat.
As for straight improvement on cycling...probably only as much as Cardio goes.
Kind of like running on a tread mill as opposed to putting in actual miles on the road.
The regular exercise bikes at the gym actually bother my knees a lot, so I hit the elliptical machines.
Maybe a spinning class can help since you can get into a more conventional cycling position.
Hey, I'm just this GUY...you know?
>>>Team Critical Mess<<< (You mean it's not SUPPOSE to hurt?)
My nice new Nashbar Touring Build AKA "The Flying Avocadooooooooo!"
1998(?) Trek 700 Multitrack
1995 Trek 1220 AKA "Jimi"
Older Non-suspension Specialized Hardrock