that's the same ratio (we) runners maintain it takes to call up yer endorphins runnin' vs. bikin'. so fixed is to gears as runnin' is to bikin' in general. but, as ol' shants and others have pointed out, there's too many more variables involved for there to be a hard and fast formula. if ya do both pretty hard day in ad day out though, your runnin' gets better and so does your bikin'. but ya'll prolly knew that.