In Reply To:
Let's suppose...if a person plateaus...and let's face it, we all do...then why not mix up your training to see what might happen? Lifting will not kill you or give you some adaption you can't back out of later. It has always seemed to me that there are enough good riders out there who lift regularly (maybe a mesocycle per year or even all year) that it's worth a shot against a fitness stalemate. I already decided to give it a try this winter. If it doesn't work, so what? If it does, awesome.
I think this is a great approach, my question would be - is it better to address a plateau with more volume in that specific sport, or with non-specific exercise?
The latter is firmly at odds with the principle of specificity.
Additionally - for every GOOD rider you can find me who lifts regularly, I bet I can find a GREAT rider who does nothing but ride his bike.