work - Why can we cycle faster than we can run?

This seems obvious: faster long-distance runners hit ~20 km/h (marathon records) while fastest cyclists can do ~40 km/h (Tour de France stats).

But on the physical/biological level this doesn't seem obvious for me. To move we need to perform work on our mass. And for cycling there is an additional mass of the bike which should make it even slower.

So what causes the difference?

• different cardiac activity?


• different power output during these activities?


• more energy loss for running?


• friction?


• impact of the bike gearing?



• something else?

Of course I would like to discuss running/cycling on a flat terrain, as downslopes would be a something completely different.