Huifeng wrote:How does this develop the perfections and bring one closer to anuttara samyak sambodhi?
How can polishing a tile make a mirror?
I often think that one's motivation and view are as important as one's practice. Some ancient Buddhist masters, such as Naropa, went through many arduous trials. When Tilopa hit Naropa over the head with his sandal, Naropa became enlightened. If Tilopa had hit someone else with his sandal, the result may have been different. Similarly, some Buddhists might benefit from strenuous exercise and see it as a stimulus to look deeper into their own true nature, although it's certainly not for everybody.
Personally, I think that other practices would be more effective, but physical practices are easy for other people to observe and can inspire other people by giving them a glimpse of what the human mind and body can do. Many people are inspired by elite athletes for this reason. They show people how much can be achieved through intense dedication and training. Maybe this is the first glimmer of belief in the power of the human mind, which can be harnessed to do even more incredible things for the sake of all beings through Buddhist spiritual practices.
The other aspect is marketing. For example, many people (including myself) first became interested in Asian culture through martial arts. The exciting physical actions draw people in and then some of the people start looking more deeply into the cultures from which they came. A similar thing may happen with the marathon monks. People might think, "Oh, hey, look at these extreme things these monks do. Hmm...I wonder what religion they are? Aha, they're Tendai Buddhists. Hmm...I don't know anything about Tendai. I'd like to read a bit about it." That's how things often begin.
In short, marathon monks may be good marketing for Buddhism. Sometimes it's best to be hidden in retreat Sometimes it's best to show oneself to the world.