I only have to outrun you

Two hikers are out hiking. All of a sudden, a bear starts chasing them. They climb a tree, but the bear starts climbing up the tree after them.

The first hiker gets his sneakers out of his knapsack and starts putting them on.

The second hiker says, "What are you doing?"

The first responds, "I figure when the bear gets close to us, we'll have to jump down and make a run for it."

The second says, "Are you crazy? Don't you know you can't outrun a bear?"

The first guy says, "I don't have to outrun the bear... I only have to outrun you!"