Difference between "running up" and "walking up"?

[bully3000]

A person runs up several flights of stairs and is exhausted when they get to the top. Later, when they have recovered, the same person walks up the same stairs and does not feel as tired. Why is this? Ignoring air resistance, does it take more work or energy to run up the stairs than to walk up? Why is this so?

Any help would be appreciated!

[mark_alec]

Look at the definitions of both work and power.