For a given walking speed, yes.
but not many people cycle at 3 miles an hour. It's not strictly because it's more efficient. It's because it's non-weight bearing, so you are only accelerating your mass horizontally, not vertically against gravity.

cycling at 12 miles an hour requires 16 times as much energy, more or less, than cycling at 3 miles an hour. And 12 miles an hour is still a pretty slow cycling speed, even for someone unfit. And 16 times would easily cancel out the "non-vertical accleration" thing.
( the mighty badger Aphrodite, on a bar stool, by your side, Tue 25 Jan 2011, 11:55, Reply)