Could you accompany me, please?

A friend of mine told me funny story. She was asked to accompany a marathon runner. She would be a great help, if she carries all the nutrition on her bike and motivates him to stand the marathon distance. She was nice and said: "Yes, no problem.".

After twenty kilometers she asks exhausted the runner: "How many kilometers are remaining.".

He said: "Oh, up to now it is just the half distance we want to go".

She was upset: "Are you crazy? I am tired right now on my bike and you want to run the full distance we have done so far again?".

He said: "Yes, I said I want to run a marathon. It has 42 kilometers".

She: "42 Kilometers? Never gone so far by bike! You are kidding me?"

From now on he needs to motivates her till they finally achieved the full distance.

After the tour she was groggy and the runner was smiling.