Dear Daniel
What the Talmud actually says is: "One who walks a distance of four cubits (approximately 6 - 8 feet) in the Land of Israel is assured of being a ben olam haba - heir to the World to Come." Because of the intrinsic Holiness of the Land of Israel, a person gains spiritual merit by merely walking here.
So, each step is a step towards "walking four cubits" in the Land of Israel, but unless you have a really big stride, you can't do it all in one step.
Sources:
- Ketuvot 111a
- Maharal Chidushei Aggadot 1:168