Cycling versus running
I did a great deal of bicycling when I lived in India in my youth. For at least two and a half hours every day I used to cycle as I did errands around the Ashram. Cycling does not increase running speed at all, but something is better than nothing. Sometimes cycling can actually be a hindrance to running speed because it develops special kinds of muscles which do not complement the speed muscles. Bicycling does help for endurance, but if you want to increase your running speed, then I do not advise it.
Sri Chinmoy, My cycling experiences, Agni Press, 2007