Definitely extending the usefulness of the analogy, but when I am riding my bike a lot and then take a break for repairs and walk more instead, I quickly get sore. Even after walking distances that I dont normally get sore from if I am bike free for a while and walking more regularly.

Was your use of this example a reference to Steve Job's referring of the computer as the "Bicycle of the mind"? I think he might have been quoting Stewart Brand.

More zeppelins than bikes.