You've done the long runs. You've stacked back-to-back days. Your VO2 max is solid and your race-day nutrition is dialed. But somewhere past mile 60, when the wheels start to wobble and your form degrades into something resembling a very determined zombie shuffle — that's when fitness stops being the whole story. That's when durability takes over.
Durability Is the Ultrarunner's Most Underrated Superpower
Finishing a 100-miler isn't just about fitness — it's about who holds together when everything starts to fall apart. Here's what separates the runners who make it to the finish line from those who don't.
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