Everything is measurable.
Significant?
Not at all to anyone who is not putting food on the table by riding a bike. Messengers don't count as they are paid to deliver packages. How they do it is irrelevant.
Well if I could just borrow your legs I could beat my riding partner on a 20 inch Huffy.
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My bikes: 1970`s Roberts - 1981 Miyata 912 - 1980`s Ocshner (Chrome) - 1987 Schwinn Circuit - 1987 Schwinn Prologue - 1992 Schwinn Crosspoint - 1999 Schwinn Circuit - 2014 Cannondale Super Six EVO