The phrase "spur of the moment" adds to the tone of the passage because it emphasizes the hard work that is required when you train for a marathon
Explanation:
This little reading called Marathon gives a full description of how people train for this kind of competition and all the hard work that people have to do to be able to take the challenge, it is not only about the time or preparation but also about the long term project this represents being the mining of spur something that is made without any preparation the phrase shows that it is all the opposite.
