Sprinted for an Entire Level!
They don't actually expect you to finish a level only by sprinting, and nothing else. The trophy simply requires you to have (or any of the trigger buttons) held down for an entire level.
This trophy can easily be done on any of the rainbow road levels, such as the level "Over the Rainbow" in the first world. Note that you cannot die, and you must have sprint held down the entire time, including cutscenes until you get to the results screen where your Lums are tallied up. Otherwise, the trophy will not unlock.