Beginners Guide to riding Fixed/Single Speed in London

Running bags are designed to resist bounce, but not big changes in direction. They are also designed to sit nicely on your back when standing, not leaning over in a cycling position.
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Again though.....running bags aren't designed to carry big loads...if a running bag was carrying the same weight as a messenger bag is capable of (which it can't) it would bounce when leaned over on a bike.
As i said....two different things completely.