In my opinion, the infinity icon doesn't stand good for the meaning of endurance. Endurance is something like "last one standing wins"..It doesn't go forever.It is limited by the total energy of the competitor.
That's why i think we could look wider.There are some good examples in the nature ready for usage as icons.
For ex. the longest distance migrating animal..What is that animal? An arctic bird? might be used in the logo with some well done typography.
Or a horse, which is not a longest distance winner but it has a good place as a strong icon in human culture...
Or take a microscobe and check out the blood running in weins of living creatures.What is the factor that makes the difference in an long distance athlete? Those red cells that carry oxygen to the body? Why not use those cells well illustrated.
Even, think about popular culture.What makes one to stand longer? Determination? Hard training? Does that remind you something? Who is the character which is like a piece of iron in popular culture? I'd use gloves of "Rocky" as a reminder of strength in the logo.
The examples will go on and on for pages. But what i want to tell is not to stick with one icon because it is there for infinity. Think different.
I used a burning match in my design and posted with e-mail. It might be discussed about the layout and typography but at least i think i made a new offering.